A Guide to the Orthognath Spiders with Opisthosomal Tergites
Liphistiidae Thorell, 1869
Pronunciation: Lih-fiss-tee-ih-dee.
Type Species: Liphistius desultor Schiødte, 1849; gender masculine.
Genera: Liphistius; about 70 species.
Common Names: Segmented trapdoor spiders, basal trapdoor spiders, armored trapdoor spiders, primitive spiders.
Taxonomy: They are closest to the Heptathelidae. Some less recent authors place atypoids with these spiders due to their opisthosomal tergites. Liphistiidae is considered a senior synonym of Heptathelidae, and heptathelids could probably be reunited with liphistiids as a subfamily. Whether or not they should be requires further study.
Similar Families: Antrodiaetidae, Atypidae, Heptathelidae, Hexurellidae, Mecicobothriidae, Megahexuridae. All of these families have one or more sclerites on the dorsal opisthosoma.
Related Families: Heptathelidae. This family has similar genitalia and spinnerets.
Diagnosis: Liphistiids can be distinguished from all similar and related families minus Heptathelidae by the ten dorsal tergites on the opisthosoma and eight spinnerets, the laterals being the largest. They can be distinguished from heptathelids by the presence of a male tibial apophysis and lack of a conductor, and by the female unpaired sac in the receptacula. They also have six to eight tripwire threads radiating from the entrance of the burrow.
Body Length: 9.0-37.0 mm.
Carapace: The carapace has almost no setae and is very smooth. The cephalic region is elevated above the thoracic region. There are conspicuous radial lines radiating from the fovea to the coxae. The clypeus is short and slants forward, and there are macrosetae in the lower middle area. The fovea is a deep pit and has no distinct shape.
Sternum: The sternum is much longer than it is wide, and its posterior end is very elongate. The end of the elongate tip has a few macrosetae. The central area of the sternum is flat and has strong macrosetae. The margins steeply slope, and they have a few, weak macrosetae. The labium is fused to the sternum.
Opisthosoma: The opisthosoma is globular and is as wide as it is long. It has ten dorsal tergites resembling segments, and the tergites bear strong macrosetae at the posterior margins. The opisthosoma is made of soft cuticle with long setae.
Mouthparts: The endites are longer than they are wide, and in front of them are thick scopulae. The area where the serrula lies is roughened. The labium is wider than it is long, and it is fused to the sternum.
Chelicerae: The chelicerae are glabrous and porrect, but they can move up and down and side to side. They can even make a right angle when stretched apart. The condyles are very conspicuous, and they look as if they occupy the entire proximal paturon. The promargin of the chelicera has a single row of teeth between rows of pro- and retromarginal setae. The distal area of the paturons is covered in macrosetae. It is argued whether or not they possess venom glands, but research shows they do not possess any venom. Their fangs support these studies as they have no venom openings (i.e., no venom can pass through the fangs). The fangs are directed backward, pointing towards the labium, and form an acute angle, almost a right angle.
Walking Legs: The leg formula is 4321, so the largest of the legs are legs IV, and they gradually decrease in size anterior to leg IV. Tibiae I-III have a single pair each of distal spurs. The legs are very numerous with macrosetae and setae, especially on the femora and distal leg segments. These macrosetae are stouter ventrally. There are trichobothria in paramedian rows on the tibiae, metatarsi, and tarsi. Clavate trichobothria are present in a single median row on the metatarsi and tarsi. The leg scopulae are absent, and so is the onychium. The tarsal organ is a rounded protrusion. The tarsi have three claws each, none with claw tufts. The paired claws have a few smaller teeth and are curved. The unpaired claw lacks teeth and is shaped sort of like a boomerang.
Palpi: The female palps have a single dentate claw each. The palps have trichobothria and macrosetae. The male palp subdistally has a swollen retrolateral tibial apophysis with strong macrosetae. The cymbium is rather large with numerous macrosetae, especially on the paracymbium. The cumulus has closely grouped setae. The bulbous has three sclerites. The embolus is leaf-like. The conductor is absent.
Epigastric Region: The genitalia are haplogyne. The female epigynum has an internal posterior stalk. There is also a poreplate anterodorsally and a receptacular cluster anteroventrally. The receptacula has an unpaired ventral sac.
Respiratory System: The respiratory system consists of two pairs of book lungs, one pair each under a distinct sclerite. There are claims of tracheae, however, it has been discovered that these are false claims.
Spinnerets: There are eight spinnerets near the middle of the venter rather than the posterior venter as in most spiders. The anal tubercle, however, is still at the posterior venter. The four lateral spinnerets are large and segmented. They have numerous spigots laterally. The four median spinnerets are small and unisegmented. They have a single spigot each at the tip. There is a colulus in front of the spinnerets that bears several setae.
Eyes: There are eight eyes on a distinct ocular tubercle. The median eyes are on the top of the tubercle and are circular. The lateral eyes are on the sides and are ovular. The anterior lateral eyes are the largest of the eyes. The anterior median eyes are the smallest of the eyes.
Coloration: They are usually tan to black, but some are bright orange. Many species have several colors such as orange and black. The species Liphistius desultor is a great example and has an orange prosoma, coxae, trochanters, and femora, and the opisthosomal and remaining appendage segments are black. The clypeus and eyes have black as well.
Distribution: They are known from Myanmar (Burma), Thailand, Loas, Malaysia, and Sumatra.
Lifestyle: These spiders live in forests and caves in silk-lined burrows, with or without a thin trapdoor. There are six to eight tripwire threads radiating from the entrance for sensory purposes, and the legs placed on these tripwires.
Lifecycle: The male drums to signal to his mate, sometimes even opening the trapdoor of the female's burrow. He approaches the female and places his leg I on her chelicerae. The male deposits sperm into her epigynum. Fertilized eggs deposited in a sac and are protected. Ecdysis is preformed whilst lying dorsally, but sometimes also ventrally.
Diet: These spiders primarily prey on ground or cave insects and spiders, but they are also known to hunt centipedes.
Threats: Liphistiids are poached by humans who sell them for great payment. Natural predators include small mammals, birds, herptiles, wasps, and other arthropods. Many species are considered endangered.
Venom: The venom is absent in these spiders, so they are not dangerous. Their bites just cause mild pain.
Remarks: Despite their common names, liphistiids lack true segments and are only internally segmented like all other spiders. Like heptathelids, they have twelve opisthosomal "segments" including the pedicel. Because they lack venom, they rely on sheer force to overpower their prey. The strong teeth and ventral macrosetae help them overpower their prey. When waiting for prey, liphistiids place all their appendages minus legs IV on the tripwire threads. Liphistiids are known to flip over and fake death.
Heptathelidae Kishida, 1923
Pronunciation: Hep-tuh-thee-lih-dee.
Type Species: Heptathela kimurai Kishida, 1920; gender feminine
Genera: Ganthela, Heptathela, Luthela, Qiongthela, Ryuthela, Songthela, Vinathela; about 110 species.
Common Names: Segmented trapdoor spiders, armored trapdoor spiders, primitive spiders.
Taxonomy: They are closest to the Liphistiidae. Some less recent authors place atypoids with these spiders due to their opisthosomal tergites. Liphistiidae is considered a senior synonym of Heptathelidae, and heptathelids could probably be reunited with liphistiids as a subfamily. Whether or not they should be requires further study.
Similar Families: Antrodiaetidae, Atypidae, Hexurellidae, Liphistiidae, Mecicobothriidae, Megahexuridae. All of these families have one or more sclerites on the dorsal opisthosoma.
Related Families: Liphistiidae. This family has similar genitalia and spinnerets.
Diagnosis: Heptathelids can be distinguished from all similar and related families minus Liphistiidae by the ten dorsal tergites on the opisthosoma and eight spinnerets, the laterals being the largest. They can be distinguished from liphistiids by the lack of a male tibial apophysis and presence of a conductor, and by the female paired sac in the receptacula. They also lack tripwire threads radiating from the entrance of the burrow.
Body Length: 7.0-17.0 mm.
Carapace: The carapace has almost no setae and is very smooth. The cephalic region is elevated above the thoracic region. There are conspicuous radial lines radiating from the fovea to the coxae. The clypeus is short and slants forward, and there are macrosetae in the lower middle area. The fovea is a deep pit and has no distinct shape.
Sternum: The sternum is much longer than it is wide, and its posterior end is only slightly elongate. The end of the tip lacks macrosetae. The central area of the sternum is flat and has strong macrosetae. The margins steeply slope, and they have a few, weak macrosetae. The labium is fused to the sternum.
Opisthosoma: The opisthosoma is globular and is as wide as it is long. It has ten dorsal tergites resembling segments, and the tergites bear strong macrosetae at the posterior margins. The opisthosoma is made of soft cuticle with long setae.
Mouthparts: The endites are longer than they are wide, and in front of them are thick scopulae. The area where the serrula lies is roughened. The labium is wider than it is long, and it is fused to the sternum.
Chelicerae: The chelicerae are glabrous and porrect, but they can move up and down and side to side. They can even make a right angle when stretched apart. The condyles are very conspicuous, and they look as if they occupy the entire proximal paturon. The promargin of the chelicera has a single row of teeth between rows of pro- and retromarginal setae. The distal area of the paturons is covered in macrosetae. It is argued whether or not they possess venom glands, but research shows they do not possess any venom. Their fangs support these studies as they have no venom openings (i.e., no venom can pass through the fangs). The fangs are directed backward, pointing towards the labium, and form an acute angle, almost a right angle.
Walking Legs: The leg formula is 4321, so the largest of the legs are legs IV, and they gradually decrease in size anterior to leg IV. Tibiae I-III have a single pair each of distal spurs. The legs are very numerous with macrosetae and setae, especially on the femora and distal leg segments. These macrosetae are stouter ventrally. There are trichobothria in paramedian rows on the tibiae, metatarsi, and tarsi. Clavate trichobothria are present in a single median row on the metatarsi and tarsi. The leg scopulae are absent, and so is the onychium. The tarsal organ is a rounded protrusion. The tarsi have three claws each, none with claw tufts. The paired claws have a few smaller teeth and are curved. The unpaired claw lacks teeth and is shaped like a fang.
Palpi: The female palps have a single dentate claw each. The palps have trichobothria and macrosetae. The male palp lacks a tibial apophysis. The cymbium is rather large with numerous macrosetae, especially on the paracymbium. The cumulus has closely grouped setae. The bulbous has three sclerites. The embolus is leaf-like. The conductor is present.
Epigastric Region: The genitalia are haplogyne. The female epigynum has an internal posterior stalk. There is also a poreplate anterodorsally and a receptacular cluster anteroventrally. The receptacula has a paired ventral sac.
Respiratory System: The respiratory system consists of two pairs of book lungs, one pair each under a distinct sclerite. There are claims of tracheae, however, it has been discovered that these are false claims.
Spinnerets: There are seven or eight spinnerets near the middle of the venter rather than the posterior venter as in most spiders. The anal tubercle, however, is still at the posterior venter. The four lateral spinnerets are large and segmented. They have numerous spigots laterally. The four median spinnerets are small and unisegmented. They have a single spigot each at the tip. There is a colulus in front of the spinnerets that bears several setae.
Eyes: There are six or eight eyes on a distinct ocular tubercle. The median eyes are on the top of the tubercle and are circular. The lateral eyes are on the sides and are ovular. The anterior lateral eyes are the largest of the eyes. The anterior median eyes are the smallest of the eyes when present.
Coloration: They are usually tan to gray. Many species have bands on the appendages.
Distribution: They are known from China, Vietnam, and Japan.
Lifestyle: These spiders live in forests and caves in silk-lined burrows, with a thin trapdoor. The burrow lacks tripwires radiating from the entrance of the burrow.
Lifecycle: The male drums to signal to his mate, sometimes even opening the trapdoor of the female's burrow. He approaches the female and places his leg I on her chelicerae. The male deposits sperm into her epigynum. Fertilized eggs deposited in a sac and are protected. Ecdysis is preformed whilst lying dorsally, but sometimes also ventrally.
Diet: These spiders primarily prey on ground or cave insects and spiders.
Threats: Heptathelids are poached by humans who sell them for great payment, but not quite as often as liphistiids are poached. Natural predators include small mammals, birds, herptiles, wasps, and other arthropods.
Venom: The venom is absent in these spiders, so they are not dangerous. Their bites just cause mild pain.
Remarks: Despite their common names, heptathelids lack true segments and are only internally segmented like all other spiders. Heptathelidae is named after the genus Heptathele of which means "seven spinnerets", referring to the genus including members that bear seven ventral spinnerets. Other members of the family may have eight spinnerets.
Atypidae
Pronunciation: Ah-tye-pih-dee.
Type Species: Aranea subterranea Roemer, 1789; gender masculine.
Genera: Atypus, Calommata, Sphodros; about 60 species.
Common Names: Purse-web spiders, atypical tarantulas, sock-web spiders.
Taxonomy: They are closest to the Antrodiaetidae, but also close to the Mecicobothriidae, Megahexuridae, and Hexurellidae. They belong to the superfamily Atypoidea and are sometimes placed near liphistiomorphs because of their dorsal sclerites on the opisthosoma.
Similar Families: Antrodiaetidae, Heptathelidae, Hexurellidae, Liphistiidae, Mecicobothriidae, Megahexuridae. All of these families have one or more sclerites on the dorsal opisthosoma.
Related Families: Antrodiaetidae, Hexurellidae, Mecicobothriidae, Megahexuridae. All of these families have one or more dorsal sclerites on the opisthosoma, somewhat similar genitalia, and similar spinnerets.
Diagnosis: Atypids can be distinguished from heptathelids and liphistiids by the four or less dorsal sclerites on the opisthosoma and six spinnerets, the posterior laterals being the largest. They are distinguished from the remaining families by the truncated posterior median spinnerets, the elongate anterior lobe on the endites, and the parallel, backward-pointing fangs.
Body Length: 7.0-30.0 mm.
Carapace: The carapace is as wide as it is long or longer than wide. It is glabrous and quadrangular. The cephalic region is elevated and strongly arched, and the thoracic region is lower. The fovea is deep, broad, and transverse and is subovular to quadrangular (Atypus, Sphodros, Calommata part), or it is a longitudinal groove (Calommata part).
Sternum: The sternum is subquadrangular and around as wide as it is long (Atypus), round and similar length (Sphodros), or ovular and longer than it is wide (Calommata). The labiosternal junction is a narrow groove. On the sternum are three (Calommata) or four (Atypus, Sphodros) pairs of sigilla. The posterior pair of sigilla is the largest. The labium is fused to the sternum.
Opisthosoma: The opisthosoma is ovular (Calommata) or subquadrangular (Atypus, Sphodros). It has one to four anterodorsal sclerotized patches known as tergites, and the second patch is the most heavily sclerotized and is always present. They are sometimes fused, and the females usually just have the second tergite.
Mouthparts: The endites are rotated forward and are broad. They can be longer than they are wide (Calommata) or wider than they are long (Atypus, Sphodros). The endites are with (Atypus, Sphodros) or without (Calommata) cuspules, and the serrula is always absent. The anterior lobe of the endites is very elongate and bears scopulae. The labium is wider than it is long, and it has cuspules but lacks serrula. The labium is fused to the sternum and has no visible separation aside from the color in some (Calommata with a pale sternum and brown labium).
Chelicerae: The chelicerae are extremely large, about the length of the entire carapace. They are glabrous and porrect and can move up and down. The posterdorsal paturon is slightly (Atypus, Sphodros) or greatly (Calommata) depressed. They don't have a rastellum, but they do have a single row of teeth on each cheliceral furrow. The fangs are very long and point almost completely backwards. The fangs have two teeth each (Atypus, Sphodros) or a transverse ridge (Calommata). The lower and inner margins of the chelicerae are serrate.
Walking Legs: The leg formula is 4321, so the largest of the legs are legs IV, and they gradually decrease in size anterior to leg IV. Legs I in females are with (Atypus, Sphodros) or without (Calommata) macrosetae. Males have longer, more slender legs. These spiders have ventral metatarsal preening combs. The posterior legs have macrosetae that are mostly dorsal. The tibiae and metatarsi have trichobothria. The males have pseudosegmented tarsi that are flexible, and on these tarsi are thin scopulae. In the females, there are no scopulae. An onychium isn't present in these spiders, but there is a small process with the claws. The tarsal organ is low and domed, and it doesn't have concentric ridges. All tarsi have three claws each without claw tufts. All of the claws have a single row each of long teeth. The claws are very small.
Palpi: The female palps have a single claw. Each of these claws has a single row of long teeth. The claws are very small. The tibiae and tarsi of the female palps are flattened. The male palp, however, has a swollen tibia. The male palp has two basal sclerites and a bulbous with a distinct third haematodocha. The embolus is short and straight. The embolus and conductor are not fused, one or both are hinged, or are rarely fused.
Epigastric Region: The genitalia are haplogyne. The female epigynum has spermathecae with two or more paired receptacula, two open into each copulatory organ. The receptacula have coiled (Sphodros) or uncoiled (Atypus, Calommata) lobes.
Respiratory System: The respiratory system consists of two pairs of book lungs.
Spinnerets: There are six spinnerets on the posterior venter, just below the anal tubercle. The anterior lateral spinnerets are widely separated and very small. Between them are the posterior medians of which are larger and truncated. The posterior lateral spinnerets are longer than the others combined, and each has a digitiform apical segment. The posterior laterals are three-segmented, the posterior medians are one-segmented, and the anterior laterals are one-segmented. The anterior laterals have nubbins and can thus not produce any silk, but the posterior medians and laterals have spigots that allow them to construct silk. The colulus is absent.
Eyes: There are eight eyes in two rows at the anterior prosoma (Atypus, Sphodros) or near the fovea with two triads widely separated with two eyes in between (Calommata).
Coloration: These spiders range from tan to black, but some can have interesting colors (e.g., Sphodros rufipes with its red legs, only the coxae and trochanters of the legs with black; the rest of the body, including the palps, chelicerae, and body tagmata, is black).
Distribution: They are known from the eastern United States and northeastern Mexico, southeastern Canada, Europe, Africa, and all of Asia but northcentral Asia.
Lifestyle: These spiders live in forests and fields in burrows that they excavate. In these burrows, they construct a sock-like tube that exits the burrow, usually to the side of the burrow or straight up a tree. Ground tubes are broad whilst tree tubes are longer and thinner. In Calommata, the tube that extends to the side is at a lower elevation so that they lump looks no different from the surrounding soil. All tubes are covered in debris.
Lifecycle: The male drums on the sock-like web with his appendages and then secretes digestive enzymes on the web. This weakens the silk so the male can enter. In the web, the male mates with the female and may continue to live with her for several months, and he usually dies of exhaustion from mating or of old age rather than leaving. The eggs are deposited in a sac that is carried by the female in the web or is hidden in a chamber at the bottom of the burrow. These spiders undergo ecdysis whilst hanging from the ceiling of the web.
Diet: These spiders primarily prey on ground insects and spiders.
Threats: Wasps are the biggest threats for these spiders as they will rip open the tube and sting the spider when it is enclosed. Other predators include small vertebrates.
Venom: The venom is somewhat weak in these spiders. They are unable to cause necrosis and cannot kill humans.
Remarks: The family name means "ugly in appearance", referring to the very large chelicerae and smaller legs. In the genus Calommata, the paturons have proximal depressions dorsally, and this allows them to easily rise into a threat posture without raising the entire body which is a vulnerability in mygalomorphs. With their sock-like webs, these spiders hang on the underside of the ceiling. When prey passes by, the spiders spear their fangs through the web and pull their prey inside. Thereafter, the spiders repair their webs so they can ambush their next meal.
Antrodiaetidae Gertsch, 1940
Pronunciation: An-troh-dye-eeh-tih-dee.
Type Species: Mygale unicolor Hentz, 1842; gender masculine.
Genera: Aliatypus, Antrodiaetus, Atypoides, Hexura; about 40 species.
Common Names: Folding-door trapdoor spiders, turret spiders, collar-door trapdoor spiders, folding-door spiders, folding-door and sheet-web trapdoor spiders, trapdoor spiders.
Taxonomy: They are closest to the Atypidae, but also close to the Megahexuridae, Mecicobothriidae, and Hexurellidae. They belong to the superfamily Atypoidea and are sometimes placed near liphistiomorphs because of their dorsal sclerites on the opisthosoma. The genus Hexura has long been placed with mecicobothriids, but despite their many similarities, their characters seem to remove them from their prior parent taxon and closer to the antrodiaetids. The genus Aliatypus, could well form a family of its own, and so could Hexura. Both would be based on the spigots in the spinnerets as well as a few other characters.
Similar Families: Atypidae, Ctenizidae, Cyrtaucheniidae, Dipluridae, Euagridae, Euctenizidae, Halonoproctidae, Heptathelidae, Hexathelidae, Hexurellidae, Ischnothelidae, Liphistiidae, Macrothelidae, Megahexuridae, Microhexuridae, Porrhothelidae, Rhytidicolidae. All of these families have one or more sclerites on the dorsal opisthosoma, elongate posterior lateral spinnerets, and/or are shaped similarly.
Related Families: Atypidae, Hexurellidae, Mecicobothriidae, Megahexuridae. All of these families have one or more dorsal sclerites on the opisthosoma, somewhat similar genitalia, and similar spinnerets.
Diagnosis: Antrodiaetids can be distinguished from ctenizids, cyrtaucheniids, diplurids, euagrids, euctenizids, halonoproctids, hexathelids, ischnothelids, macrothelids, microhexurids, porrhothelids, and rhytidicolids by the presence of tergites on the dorsal opisthosoma, and from heptathelids and liphistiids by the four or less tergites on the dorsal opisthosoma. They can be distinguished from atypids by the smaller anterior lobes on the endites and smaller chelicerae. All antrodiaetids minus Hexura can be distinguished from hexurellids, mecicobothriids, and megahexurids by the shorter apical segment of the posterior lateral spinnerets. In antrodiaetids minus Hexura, the apical segment is about two to three times as long as it is wide, but in the other families, it is about five times as long as it is wide. Hexura can be distinguished from the families by the dorsal opisthosomal tergites being fused into a single tergite, and by the anterior median spinnerets present as a single segment or absent. They are distinguished from all the families by the branched conductor in the males, and by the four separate receptacula in the females.
Body Length: 4.0-25.0 mm.
Carapace: The carapace is glabrous and is longer than it is wide. The cephalic region is strongly arched and is greatly elevated (Aliatypus, Antrodiaetus, Atypoides), or it is slightly elevated (Hexura). The thoracic region is much lower. The clypeus is low (Hexura) or high (Aliatypus, Antrodiaetus, Atypoides). The tegument is smooth. The fovea may be a longitudinal groove, a deep pit, a shallow rounded depression, or it is absent.
Sternum: The sternum is ovular and is longer than it is wide. It has sinuous sides. There are four pairs of sigilla. The anterior pair of sigilla is indistinct (Aliatypus, Antrodiaetus, Atypoides) or is the largest and moderately distinct (Hexura). The labium is fused to the sternum (Aliatypus, Antrodiaetus, Atypoides) or not (Hexura).
Opisthosoma: The opisthosoma is ovular and longer than it is wide. It has one to four anterodorsal sclerotized patches known as tergites, and the second patch is the most heavily sclerotized and is always present. They are sometimes fused, and the females usually just have the second tergite.
Mouthparts: The endites are slightly longer than they are wide and have smaller anterior lobes that are distinct and have scopulae, and the endites don't have any cuspules. The endites are with (Hexura) or without (Aliatypus, Antrodiaetus, Atypoides) a surrula. They are slightly converging and truncate. The labium is around as long as it is wide (Aliatypus, Antrodiaetus, Atypoides) or almost twice as wide as it is long (Hexura), always without cuspules. It is (Aliatypus, Antrodiaetus, Atypoides) or is not (Hexura) fused to the sternum.
Chelicerae: The chelicerae are glabrous and porrect and can move up and down. The chelicerae are with small (Antrodiaetus part), elongate (Atypoides), or are without (Aliatypus, Antrodiaetus part, Hexura) cheliceral apophyses. Some are with distal macrosetae dorsally on the chelicerae in both genders (Hexura). The cheliceral furrow has one (Antrodiaetus, Atypoides, Hexura) or two (Aliatypus) rows of teeth. Females have (Aliatypus, Antrodiaetus, Atypoides) or lack (Hexura) a rastellum.
Walking Legs: The leg formula is 4312. These spiders have ventral metatarsal preening combs. In males, tibia I is sometimes moderately incrassate (Hexura), and it also sometimes has clasping macrosetae (e.g., Antrodiaetus, Hexura). The legs have macrosetae, but the tarsi usually don't (Antrodiaetus, Atypoides, Hexura). The male femora are not swollen and lack any brushes of macrosetae. Males may (Antrodiaetus, Atypoides, Hexura) or may not (Aliatypus) have pseudosegmented tarsi, and the tarsi III and IV may (Aliatypus, Antrodiaetus, Atypoides) or may not (Hexura) have scopulae. The onychium isn't present in these spiders. The tarsal organ is low with (Hexura) or without (Aliatypus, Antrodiaetus, Atypoides) concentric ridges. The base of the tarsal organ is low and ovular (Hexura) or domed (Aliatypus, Antrodiaetus, Atypoides). All tarsi have three claws each without claw tufts. The paired claws each have a single row of teeth, and the unpaired claw usually lacks teeth (Aliatypus, Antrodiaetus, Atypoides, Hexura part), but it sometimes bears a single tooth (Hexura part).
Palpi: The female palps have a single claw each with a single row of teeth. The male palp has a swollen (Aliatypus, Antrodiaetus, Atypoides) or moderately incrassate (Hexura) tibia, all with a simple bulbous. The patella is sometimes elongate (Aliatypus). The cymbium bears or lacks macrosetae. The conductor is branched, well-developed, and consists of two sclerites. The conductor is fused with the embolus to make a common basal sclerite (Aliatypus, Antrodiaetus, Atypoides), or the conductor is stout and covers a thin embolus (Hexura). The third haematodocha of the male palp is distinct.
Epigastric Region: The genitalia are haplogyne. The female spermathecae have four separate receptacula.
Respiratory System: The respiratory system consists of two pairs of book lungs.
Spinnerets: There are four (Antrodiaetus, Hexura part) or six (Aliatypus, Atypoides, Hexura part) spinnerets on the posterior venter, just below the anal tubercle. The anterior median spinnerets are small and only one- or two-segmented if they are even present. The posterior median spinnerets are always present but only consist of one segment. The posterior laterals are obviously the longest of the spinnerets and consist of three segments. The distal segment of the posterior laterals is digitiform, and it is sometimes pseudosegmented (Hexura). The colulus is absent.
Eyes: There are eight eyes in an anterior procurved row and a posterior recurved (Antrodiaetus, Atypoides, Hexura) or straight (Aliatypus) row. The four median eyes are the smallest, either the anterior medians (Hexura) or the posterior medians (Aliatypus, Antrodiaetus, Atypoides). The anterior lateral eyes are the largest.
Coloration: These spiders range from tan to black. They don't have any patterns, but most have dark cephalic regions (Aliatypus, Antrodiaetus, Atypoides).
Distribution: They are known from western North America (Aliatypus, Antrodiaetus part, Atypoides, Hexura), central and eastcentral United States (Antrodiaetus part), and Japan (Antrodiaetus roretzi, A. yesoensis).
Lifestyle: These spiders live in forests in burrows with (Aliatypus, Antrodiaetus) or without (Atypoides) a trapdoor, or they construct sheet-webs underneath logs, stones, and leaf litter (Hexura).
Lifecycle: Courtship hasn't been studied much in these spiders, but we do know in Antrodiaetus, the cheliceral apophyses and tibial clasping macrosetae are used for grasping the female's chelicerae and legs. Some females may attach their egg sacs (round or lens-shaped) to the sides or near bottom of the burrow, but in Hexura, the sacs are lens-shaped, hold around 80 eggs, and are carried via the chelicerae.
Diet: These spiders primarily prey on ground insects and spiders.
Threats: Wasps are the major predators for most antrodiaetids (Aliatypus, Antrodiaetus, Atypoides). The remaining (Hexura) are probably hunted by wasps as well, but it isn't completely known.
Venom: The venom is somewhat weak in these spiders. They are unable to cause necrosis and cannot kill humans.
Remarks: The family name means "cave-dweller"; however, these spiders don't burrow in caves. The name probably refers to the fact that the inside of the burrow is like a small cave. Members of the genus Hexura don't construct burrows and lack a rastellum, rather spinning sheet-webs with their whip-like spinnerets. There are two species in this genus. The species Hexura picea is easily distinguished from H. rothi by the presence of six spinnerets rather than four, the presence of a single tooth on the palpal claw, and the absence of macrosetae on the cymbium. The genus Hexura means "six tails", but really, Hexura species can have four or six spinnerets or "tails". Antrodiaetids are some of the most well-studied mygalomorphs in North America. It is weird how only two antrodiaetids live in Japan whilst the remaining approximately 35 species are found in North America.
Megahexuridae Hedin & Bond, 2019
Pronunciation: Meh-guh-hex-urr-ih-dee.
Type Species: Hexura fulva Chamberlin, 1919; gender feminine.
Genera: Megahexura; exactly 1 species.
Common Names: Ravine funnel-web spiders, giant dwarf tarantulas, ravine funnel-web tarantulas, ravine dwarf tarantulas.
Taxonomy: They are closest to the Mecicobothriidae and Hexurellidae, and pretty close to Hexura from Antrodiaetidae, but also close to the rest of Antrodiaetidae and Atypidae. They belong to the superfamily Atypoidea and are sometimes placed near liphistiomorphs because of their dorsal sclerites on the opisthosoma. Due to their elongate spinnerets and teeth on the endites, they are also placed near diplurids and their kin. They are in the Mecicobothrioidea group. The families Mecicobothriidae and Hexurellidae along with the genus Hexura were formerly included with Megahexuridae in the family Mecicobothriidae, and the recent separation seems quite reasonable.
Similar Families: Antrodiaetidae, Atypidae, Dipluridae, Euagridae, Heptathelidae, Hexathelidae, Hexurellidae, Ischnothelidae, Liphistiidae, Macrothelidae, Mecicobothriidae, Microhexuridae, Porrhothelidae, Rhytidicolidae. All of these families have one or more sclerites on the dorsal opisthosoma and/or elongate spinnerets.
Related Families: Antrodiaetidae, Atypidae, Dipluridae, Euagridae, Heptathelidae, Hexathelidae, Hexurellidae, Ischnothelidae, Liphistiidae, Macrothelidae, Mecicobothriidae, Microhexuridae, Porrhothelidae, Rhytidicolidae. All of these families have one or more dorsal sclerites on the opisthosoma, somewhat similar genitalia, similar mouthparts, and/or similar spinnerets.
Diagnosis: Megahexurids can be distinguished from diplurids, euagrids, hexathelids, ischnothelids, macrothelids, microhexurids, porrhothelids, and rhytidicolids by the presence of tergites on the anterodorsal opisthosoma. They are distinguished from heptathelids and liphistiids by the single tergite on the dorsal opisthosoma rather than ten. They can be distinguished from atypids by the smaller anterior lobes on the endites, smaller chelicerae, and the very long, pseudosegmented spinnerets, and from antrodiaetids minus Hexura by the distal segment of the posterior lateral spinnerets. Antrodiaetids minus Hexura have an apical segment that is about two or three times as long as it is wide whilst megahexurids have an apical segment about five times as long as it is wide. They are distinguished from Hexura by the two-segmented anterior lateral spinnerets. They are distinguished from mecicobothriids by the presence of pronounced, chitinous extensions on the posterior carapace, and from hexurellids by the three-segmented posterior lateral spinnerets. Hexurellids have four-segmented posterior laterals. They are distinguished from the families by the females with four elongate receptacles, and two separate receptacula that are bilobed, the males with a distinct third haematodocha, an integral cymbium, the lack of a prolateral lobe, and a conductor is recessed behind a thin embolus.
Body Length: 8.0-18.0 mm.
Carapace: The carapace is glabrous and is longer than it is wide. The cephalic region is only slightly elevated over the thoracic region. The tegument of the carapace is smooth. There are expanded pleurites at the posterolateral corners of the carapace. These expansions are pronounced, chitinous extensions. The clypeus is short, less than the anterior median eye diameter. The fovea is short and longitudinal.
Sternum: The sternum is ovular and is longer than it is wide. There are four pairs of sigilla, and the anterior pair is the only pair that is conspicuous, more so in males. The labium is not fused to the sternum.
Opisthosoma: The opisthosoma is ovular and longer than it is wide. It has a single anterodorsal sclerotized patch known as a tergite. The tergites bear long, black setae.
Mouthparts: The endites are longer than they are wide and are slightly converging. They have distinct anterior lobes with scopulae, and they lack cuspules but have a serrula with several rows of small teeth. The labium is wider than it is long and has a few black setae. The labiosternal junction is a transverse groove in these spiders. The labium is not fused to the sternum and lacks cuspules.
Chelicerae: The chelicerae are glabrous and porrect. They are somewhat large, half the length of the carapace, and they can move up and down. The lateral edges of the paturons are compressed. Males lack a ridge of macrosetae on each paturon and lack an apophysis on each paturon. The rastellum is absent in these spiders. Above the inner margin, there is a thin row of black setae. The promargin of the cheliceral furrow has 14 stout teeth in a single row, and the retromargin has a cluster of 14 small denticles.
Walking Legs: The leg formula is 4123. These spiders have ventral metatarsal preening combs. The legs are coated in fine black setae, and they have ventral paired or single macrosetae. Leg IV has numerous macrosetae, but the other legs are scarce with macrosetae. There are trichobothria in two rows on each tibia, and the metatarsi and tarsi each have a single trichobothrium. Leg I of the males is not incrassate and is unmodified, and all leg tarsi of males are pseudosegmented. The femora of males are swollen, and each has a single brush of heavy macrosetae. The legs lack scopulae, and the onychium is absent. The tarsal organ is slightly elevated and ovular with concentric ridges. All the tarsi have three claws each and lack claw tufts. The paired claws each have a sinuous row of slender teeth, and each unpaired claw sometimes bears a single tooth.
Palpi: The female palps have a single claw each with a single row of teeth. The male palp has an elongate tibia with four large ventral macrosetae. The tibia is moderately incrassate. The tarsus has a retrolateral invagination, but there is no prolateral lobe. The cymbium lacks macrosetae and is elongate, integral, and spoon-shaped, and it has a bulb proximally. The long, straight conductor is recessed behind a thin embolus. The third haematodocha is distinct.
Epigastric Region: The genitalia are haplogyne. The female epigynum has a pair of long receptacles on each side. There are four elongate receptacles total. There are two separated bilobed receptacula.
Respiratory System: The respiratory system consists of two pairs of book lungs.
Spinnerets: There are six spinnerets on the posterior venter, just below the anal tubercle. The anterior lateral spinnerets consist of two segments. The posterior median spinnerets consist of a single segment each, and they are separated from each other by about twice their basal diameter. The posterior lateral spinnerets are obviously the longest and consist of three segments, the apical of which is digitiform and pseudosegmented. The two basal segments of the posterior laterals are of subequal length. The colulus is absent.
Eyes: There are eight eyes in a procurved anterior row and a slightly recurved posterior row. The anterior lateral eyes are the largest of the eyes, and the remaining eyes are of subequal size. The eyes are on a tubercle.
Coloration: These spiders range from lighter brown to dark brown, without any patterns.
Distribution: They are known from California (United States).
Lifestyle: These spiders live in forests in funnel-webs underneath logs, leaf litter, and stones. Their webs are large and commonly compared to araneomorph agelenids.
Lifecycle: These spiders are virtually unstudied when it comes to their lifecycle. Like most mygalomorphs, they probably live for more than a year based on the sizes and ages of juveniles found in the wild. After undergoing ecdysis, these spiders are completely colorless aside from their opisthosomata.
Diet: These spiders primarily prey on ground insects and spiders.
Threats: Albeit their threats are just their natural predators which are probably wasps and small vertebrates.
Venom: The venom is somewhat weak in these spiders. They are unable to cause necrosis and cannot kill humans.
Remarks: The family name means "large Hexura", referring to their very large size for a "mecicobothriid". Unlike Hexura which can have four or six spinnerets or "tails", megahexurids, the "large six-tailed" spiders, have a total of six spinnerets, no more, no less. Megahexurids construct webs that are compared to the araneomorph agelenid spiders, especially because of the web's size. Some photographers favor megahexurids over other mecicobothrioids due to their large size.
Mecicobothriidae Holmberg, 1882
Pronunciation: Meh-sih-koh-boh-three-ih-dee.
Type Species: Mecicobothrium thorelli Holmberg, 1882; gender neuter.
Genera: Mecicobothrium; exactly 2 species.
Common Names: Midget funnel-web spiders, sheet funnel-web spiders, midget funnel-web tarantulas, dwarf tarantulas.
Taxonomy: They are closest to the Hexurellidae and very close to Megahexuridae, and pretty close to Hexura from Antrodiaetidae, but also close to the rest of Antrodiaetidae and Atypidae. They belong to the superfamily Atypoidea and are sometimes placed near liphistiomorphs because of their dorsal sclerites on the opisthosoma. Due to their elongate spinnerets and teeth on the endites, they are also placed near diplurids and their kin. They are in the Mecicobothrioidea group. The families Megahexuridae and Hexurellidae along with the genus Hexura were formerly included in the family Mecicobothriidae, and the recent separation seems quite reasonable.
Similar Families: Antrodiaetidae, Atypidae, Dipluridae, Euagridae, Heptathelidae, Hexathelidae, Hexurellidae, Ischnothelidae, Liphistiidae, Macrothelidae, Megahexuridae, Microhexuridae, Porrhothelidae, Rhytidicolidae. All of these families have one or more sclerites on the dorsal opisthosoma and/or elongate spinnerets.
Related Families: Antrodiaetidae, Atypidae, Dipluridae, Euagridae, Heptathelidae, Hexathelidae, Hexurellidae, Ischnothelidae, Liphistiidae, Macrothelidae, Megahexuridae, Microhexuridae, Porrhothelidae, Rhytidicolidae. All of these families have one or more dorsal sclerites on the opisthosoma, somewhat similar genitalia, similar mouthparts, and/or similar spinnerets.
Diagnosis: Mecicobothriids can be distinguished from diplurids, euagrids, hexathelids, ischnothelids, macrothelids, microhexurids, porrhothelids, and rhytidicolids by the presence of tergites on the anterodorsal opisthosoma. They are distinguished from heptathelids and liphistiids by the two tergites on the dorsal opisthosoma rather than ten. They can be distinguished from atypids by the smaller anterior lobes on the endites, smaller chelicerae, and the very long, pseudosegmented spinnerets, and from antrodiaetids minus Hexura by the distal segment of the posterior lateral spinnerets. Antrodiaetids minus Hexura have an apical segment that is about two or three times as long as it is wide whilst mecicobothriids have an apical segment about five times as long as it is wide. They are distinguished from Hexura by the two-segmented anterior lateral spinnerets and the two separate tergites on the anterodorsal opisthosoma. They are distinguished from megahexurids by lacking pronounced, chitinous extensions on the posterior carapace, and from hexurellids by the three-segmented posterior lateral spinnerets. Hexurellids have four-segmented posterior laterals. They are distinguished from the families by the females with shortened and rounded outer pair of receptacles, and the two separate receptacula that are bilobed, the males with cheliceral apophyses, a small and concealed third haematodocha, the presence of a distinct prolateral lobe, and the screw-shaped embolus.
Body Length: 6.0-11.0 mm.
Carapace: The carapace is glabrous and is longer than it is wide. The cephalic region is only slightly elevated over the thoracic region. The tegument of the carapace is smooth. There are unexpanded pleurites at the posterolateral corners of the carapace. The posterior carapace lacks pronounced, chitinous extensions. The clypeus is narrow, equal at the middle to the anterior median eye diameter. The fovea is short and longitudinal.
Sternum: The sternum is ovular and is longer than it is wide. There are four pairs of sigilla, and the anterior pair is the only pair that is conspicuous, more so in males. The labium is not fused to the sternum.
Opisthosoma: The opisthosoma is ovular and longer than it is wide. It has two anterodorsal sclerotized patches known as tergites, and the second patch is the most heavily sclerotized.
Mouthparts: The endites are longer than they are wide and are slightly converging. They have distinct anterior lobes with scopulae, and they lack cuspules but have a serrula with several rows of small teeth. The labium is wider than it is long and also lacks cuspules. The labiosternal junction is a transverse groove in these spiders. The labium is not fused to the sternum.
Chelicerae: The chelicerae are glabrous and porrect. They are somewhat large, half the length of the carapace, and they can move up and down. The lateral edges of the paturons are compressed. In males, there is a ridge of macrosetae or an apophysis on each paturon. The rastellum is absent in these spiders. The promargin of the cheliceral furrow has a single row of teeth, and the retromargin has a group of denticles.
Walking Legs: The leg formula is 4132. These spiders have ventral metatarsal preening combs. Leg IV has numerous macrosetae, but the other legs are scarce with macrosetae. There are trichobothria in two rows on each tibia, and the metatarsi and tarsi each have a single trichobothrium. Leg I of the males is not incrassate and is unmodified, and all leg tarsi of males are pseudosegmented. The femora of males are swollen, and each has a single brush of heavy macrosetae. The legs lack scopulae, and the onychium is absent. The tarsal organ is slightly elevated and ovular with concentric ridges. All the tarsi have three claws each and lack claw tufts. The paired claws each have a sinuous row of slender teeth, and each unpaired claw has two or three teeth.
Palpi: The female palps have a single claw each with a single row of teeth. The male palp has a tibia that is elongate and not incrassate. The tarsus has a distinct prolateral lobe and a retrolateral invagination, forming a cymbium distally. The cymbium lacks macrosetae and is elongate, bilobed, and spoon-shaped, and it has a bulb proximally. The conductor is shielding a screw-shaped embolus. The third haematodocha is small and concealed.
Epigastric Region: The genitalia are haplogyne. The female epigynum has four receptacles, and the outer pair of receptacles is shortened and rounded. The spermathecae have two separated receptacula that are bilobed.
Respiratory System: The respiratory system consists of two pairs of book lungs.
Spinnerets: There are six spinnerets on the posterior venter, just below the anal tubercle. The anterior lateral spinnerets consist of two segments. The posterior median spinnerets consist of a single segment each, and they are separated from each other by about twice their basal diameter. The posterior lateral spinnerets are obviously the longest and consist of three segments, the apical of which is digitiform and pseudosegmented. The two basal segments of the posterior laterals are of subequal length. The colulus is absent.
Eyes: There are eight eyes in a straight anterior row and a slightly recurved posterior row. The anterior lateral eyes are the largest of the eyes, and the remaining eyes are of subequal size. The eyes are on a tubercle.
Coloration: These spiders range from tan to brown, without any patterns.
Distribution: They are known from eastcentral Argentina, Uruguay, and southeastern Brazil.
Lifestyle: These spiders live in forests in funnel-webs underneath logs, leaf litter, and stones. Some compare the webs to those of the araneomorph, agelenid genus Tegenaria.
Lifecycle: These spiders are not very well-studied, but the females probably carry their eggs in a spherical sac via the chelicerae. Albeit the males grasp the females' chelicerae with their cheliceral apophyses.
Diet: These spiders primarily prey on ground insects and spiders.
Threats: Albeit their threats are just their natural predators which are probably wasps and small vertebrates.
Venom: The venom is somewhat weak in these spiders. They are unable to cause necrosis and cannot kill humans.
Remarks: Mecicobothriids previously included a handful of species found in the western United States and Canada, but recent taxonomic revisions separated them from their kin. One extinct mecicobothrioid from central Mongolia is named after American arachnologist Norman I. Platnick. This species name is Cretomegahexura platnicki. Another extinct mecicobothrioid is Cretohexura coylei from Transbaikalia. Both species were described by the same authors (Eskov & Zonstein) in the same year (1990). When examined alone, one could very easily mistake mecicobothriid genitalia for araneomorph genitalia.
Hexurellidae Hedin & Bond, 2019
Pronunciation: Hex-urr-ell-ih-dee.
Type Species: Hexurella pinea Gertsch & Platnick, 1979; gender feminine
Genera: Hexurella; exactly 4 species.
Common Names: Micro dwarf tarantulas, micro funnel-web spiders.
Taxonomy: They are closest to the Mecicobothriidae and very close to Megahexuridae, and pretty close to Hexura from Antrodiaetidae, but also close to the rest of Antrodiaetidae and Atypidae. They belong to the superfamily Atypoidea and are sometimes placed near liphistiomorphs because of their dorsal sclerites on the opisthosoma. Due to their elongate spinnerets and teeth on the endites, they are also placed near diplurids and their kin. They are in the Mecicobothrioidea group. The families Mecicobothriidae and Megahexuridae along with the genus Hexura were formerly included in the family Mecicobothriidae, and the recent separation seems quite reasonable.
Similar Families: Antrodiaetidae, Atypidae, Dipluridae, Euagridae, Heptathelidae, Hexathelidae, Ischnothelidae, Liphistiidae, Macrothelidae, Mecicobothriidae, Megahexuridae, Microhexuridae, Porrhothelidae, Rhytidicolidae. All of these families have one or more dorsal sclerites on the opisthosoma, somewhat similar genitalia, similar mouthparts, and/or similar spinnerets.
Related Families: Antrodiaetidae, Atypidae, Dipluridae, Euagridae, Heptathelidae, Hexathelidae, Ischnothelidae, Liphistiidae, Macrothelidae, Mecicobothriidae, Megahexuridae, Microhexuridae, Porrhothelidae, Rhytidicolidae. All of these families have one or more dorsal sclerites on the opisthosoma, somewhat similar genitalia, similar mouthparts, and/or similar spinnerets.
Diagnosis: Hexurellids can be distinguished from diplurids, euagrids, hexathelids, ischnothelids, macrothelids, microhexurids, porrhothelids, and rhytidicolids by the presence of tergites on the anterodorsal opisthosoma. They are distinguished from heptathelids and liphistiids by the two tergites on the dorsal opisthosoma rather than ten. They can be distinguished from atypids by the smaller anterior lobes on the endites, smaller chelicerae, and the very long, pseudosegmented spinnerets, and from antrodiaetids minus Hexura by the two distal segments of the posterior median spinnerets being pseudosegmented. They are distinguished from Hexura by the two-segmented anterior lateral spinnerets and the two separate tergites on the anterodorsal opisthosoma. They are distinguished from mecicobothriids and megahexurids by the four-segmented posterior lateral spinnerets and the high clypeus, and from megahexurids by lacking chitinous posterior extensions on the carapace. They are distinguished from the families by the females with four, short receptacles, and the presence of a single copulatory duct, the males with a coiled embolus, an integral cymbium, the lack of a prolateral lobe, and the third haematodocha being very reduced if present.
Body Length: 2.3-5.0 mm.
Carapace: The carapace is glabrous and is longer than it is wide. The cephalic region is only slightly elevated over the thoracic region. The tegument of the carapace is smooth. There are unexpanded pleurites at the posterolateral corners of the carapace. The posterior carapace lacks pronounced, chitinous extensions. The clypeus is high, three or four times the anterior median eye diameter. The fovea is short and longitudinal.
Sternum: The sternum is ovular and is longer than it is wide. There are four pairs of sigilla, and the anterior pair is the only pair that is conspicuous, more so in males. The labium is not fused to the sternum.
Opisthosoma: The opisthosoma is ovular and longer than it is wide. It has two anterodorsal sclerotized patches known as tergites, and the first patch is much wider than it is long.
Mouthparts: The endites are longer than they are wide and are slightly converging. They have distinct anterior lobes with scopulae, and they lack cuspules but have a serrula with several rows of small teeth. The endites lack spinules, but they have scattered pale setae. The labium is wider than it is long and also lacks cuspules. The labiosternal junction is a transverse groove in these spiders. The labium is not fused to the sternum.
Chelicerae: The chelicerae are glabrous and porrect. They are smaller, a third of the length of the carapace, and they can move up and down. The lateral edges of the paturons are compressed. Males lack a ridge of macrosetae on each paturon and lack an apophysis on each paturon. The rastellum is absent in these spiders. The promargin of the cheliceral furrow has a single row of teeth and sometimes denticles, and the retromargin has one or two teeth and/or denticles.
Walking Legs: The leg formula is 4132. These spiders have ventral metatarsal preening combs. Leg IV has numerous macrosetae, but the other legs are scarce with macrosetae. There are trichobothria in two rows on each tibia, and the metatarsi and tarsi each have a single trichobothrium. Leg I of the males is moderately incrassate and is with or without clasping macrosetae. All leg tarsi of males are not pseudosegmented. The femora of males are swollen, and each has a single brush of heavy macrosetae. The legs lack scopulae, and the onychium is absent. The tarsal organ is slightly elevated and ovular with concentric ridges. All the tarsi have three claws each and lack claw tufts. The paired claws each have a sinuous row of slender teeth, and each unpaired claw has only a few teeth.
Palpi: The female palps have a single claw each with a single row of teeth. The male palp has a tibia that is elongate and incrassate. The tarsus has a shallow retrolateral invagination, but there is no prolateral lobe. The cymbium lacks macrosetae and is elongate, integral, and spoon-shaped, and it has a bulb proximally. The conductor and embolus are coiled. The third haematodocha is very reduced if present.
Epigastric Region: The genitalia are haplogyne. The female epigynum has a pair of thin receptacles on each side, and each receptacle is short. The spermathecae have a single quadrilobate receptaculum. There is a single copulatory duct.
Respiratory System: The respiratory system consists of two pairs of book lungs.
Spinnerets: There are six spinnerets on the posterior venter, just below the anal tubercle. The anterior lateral spinnerets consist of two segments. The posterior median spinnerets consist of a single segment each, and they are separated from each other by about twice their basal diameter. The posterior lateral spinnerets are obviously the longest and consist of four segments, the apical of which is digitiform and consisting of two pseudosegments. The two apical segments are pseudosegmented. The two basal segments of the posterior laterals are of subequal length. The colulus is absent.
Eyes: There are eight eyes in a straight to procurved anterior row and a slightly recurved posterior row. The anterior lateral eyes are the largest of the eyes, and the remaining eyes are of subequal size. The eyes are on a tubercle.
Coloration: These spiders range from tan to brown, without any patterns. The body, especially the opisthosoma, has a rainbow-colored sheen.
Distribution: They are known from California and Arizona (United States), and northeastern Mexico.
Lifestyle: These spiders live in forests in funnel-webs underneath logs, leaf litter, and stones.
Lifecycle: These spiders are not very well-studied, but the females carry small, spherical egg sacs with about seven eggs via their chelicerae.
Diet: These spiders primarily prey on ground insects and spiders.
Threats: Albeit their threats are just their natural predators which are probably wasps and small vertebrates.
Venom: The venom is somewhat weak in these spiders. They are unable to cause necrosis and cannot kill humans.
Remarks: The family name means "little Hexura", obviously referring to the minute size of these tiny spiders. In fact, these are amongst the smallest of all mygalomorphs in the United States and are amongst the smallest mygalomorphs worldwide minus the mygalomorph microstigmatids. When excluding microstigmatids, only the mygalomorph microhexurids rival their size. With their shorter legs and smaller chelicerae, hexurellids are considered chunky and cute (and the author doesn't beg to differ).
RESOURCES
- World Spider Catalog (2023). World Spider Catalog. Version 24. Natural History Museum Bern, online at http://wsc.nmbe.ch, accessed on March 16, 2023, to March 19, 2023. doi: 10.24436/2
- Gertsch, W. J. & Platnick, N. I. (1979). A revision of the spider family Mecicobothriidae (Araneae, Mygalomorphae). American Museum Novitates 2687: 1-32.
- Haupt, J. (2003). The Mesothelae -- a monograph of an exceptional group of spiders (Aaneae: Mesothelae): (Morphology, behaviour, ecology, taxonomy, distribution and phylogeny). Zoologica 154: 1-102.
- Hedin, M., Derkarabetian, S., Alfaro, A., Ramírez, M. J. & Bond, J. E. (2019). Phylogenomic analysis and revised classification of atypoid mygalomorph spiders (Araneae, Mygalomorphae), with notes on arachnid ultraconserved element loci. PeerJ 7(e6864): 1-24. doi:10.7717/peerj.6864
- Jocqué, R. & Dippenaar-Schoeman, A. S. (2006). Spider families of the world. Musée Royal de l'Afrique Central Tervuren, 336 pp.
- Murphy, J. A. & Roberts, M. J. (2015). Spider families of the world and their spinnerets. British Arachnological Society, York, volume 1 & 2, pp. i-xii, 1-189; xiii-xvi, 191-553.
- Platnick, N. I. Spiders of the World: A Natural History. 1st ed., Princeton University Press, 2020. 256 pp.
- Raven, R. J. (1985a). The spider infraorder Mygalomorphae (Araneae): cladistics and systematics. Bulletin of the American Museum of Natural History 182: 1-180.
- Ubick, D., Paquin, P., Cushing, P.E. and Roth, V. (eds). 2017. Spiders of North America: an identification manual, 2nd edition. American Arachnological Society, Keene, New Hampshire, USA. 425 pp.
- Xu, X., Ono, H., Kuntner, M., Liu, F. X. & Li, D. Q. (2019b). A taxonomic monograph of the liphistiid spider genus Heptathela, endemic to Japanese islands. ZooKeys 888: 1-50. doi:10.3897/zookeys.888.34494
If one is to find any mistakes or errors, please contact Matthew Lindsey (@huttonia) or comment below stating what the mistake/error is and how it can be corrected.
