StayiNatHome: it's bumble time!

A common find in Kiwi gardens is the bumblebee. If you've got some pretty flowers in your garden, and it's a nice sunny day, or even an overcast mild day, there's a good chance you'll see a visiting bumblebee or three. Look again though, as there's more to bumblebees than fluffy neighbourhood pollinators.

Bumblebee 1, bumblebee 2, bumblebee 3, bumblebee 4

For a start, New Zealand has more than just one bumblebee species. There are four! Telling them apart takes a closer look at the colour bands. Check our the below illustrations by iNat NZ user @tony_wills.

Buff-tailed Bumblebee, Bombus terrestris

Large Garden Bumblebee, Bombus ruderatus

Garden Bumblebee, Bombus hortorum

Short-haired Bumblebee, Bombus subterraneus

New Zealand's four bumblebee species, from the iNaturalist NZ Guide Bumblebees of NZ by @tony_wills.

Remember that you don't need to do the identifying yourself. Just take a good photo of a bumblebee showing the colour bands and upload it with the free iNaturalist app. The insect experts there will do the rest.

Which bumblebee is the most common?

By far the most abundant of the bumbled four is the buff-tailed bumblebee, Bombus terrestris. It's the only species with a black back at the back of its thorax. This band is yellow on the others. Currently on iNaturalist NZ–Mātaki Taiao, there are 2,111 observations of bumblebees in NZ and 73% of those are buff-tailed bumblebees. The buff-tail is so abundant that it's even managed to spread across the Tasman from New Zealand to Tasmania.

The two big fluffy bumblebees with a yellow band at the back of the thorax are Bombus ruderatus and Bombus hortorum. These have longer tongues than the buff-tailed bumblebee and are better at pollinating deeper flowers. The two species are pretty tricky to tell apart. Luckily, they're in their own subgenus from the other bumblebees and that subgenus is called Megabombus (which is a pretty spectactular name). You'll often find that your bumblebees will get identified by iNat NZ's insect experts to Megabombus, but they cannot confirm which Megabombus species from your photo.

(If you've got kids in your bubble with you during the Covid19 lockdown, see if they can invent some stories or drawings of Buff-tail and Megabombus the Bumblebees. Make sure that they remember that most bumblebees they'll see are females.)

@agoranomos's son found this Megabombus dead on their driveway in Christchurch this week. Note the yellow band at the back of the thorax.

There are no native bumblebees

Like the honeybee, all of NZ's bumblebees are northern hemisphere native species, introduced into New Zealand to provide pollination for our crop plants. Many of our fruit trees and vegetables depend on honeybees and bumblebees for pollination.

Despite New Zealanders' affection for honeybees and bumblebees, it's worth remembering that native plants don't need bumblebees and they don't need honeybees. Also, many of our weeds are also dependent on honeybees and bumblebees to set seed (for example, gorse and Scotch broom, two of our worst woody weeds). A bumblebee in your garden can be a great thing for your fruit trees and vege garden but it's not necessarily a good thing in a national park. (The answer to most questions in ecology is "it depends".)

Which bumblebees are in your garden?

There's still a lot we don't know about bumblebees in NZ, including why some species are more abundant than others, and how this differs through the country. For example, so far on iNaturalist NZ 84% of the 541 bumblebee observations in Wellington are buff-tailed bumblees, but only 61% of the 684 bumblebee observations in Canterbury are buff-tails. Why? We don't know.

Also, there's a great deal of alarm overseas about the decline of pollinators like honeybees and bumblebees, especially in Europe and North America. As far as we can tell, there's no equivalent decline happening in New Zealand. Having said that, there's also not a lot of good data here.

You can help, by spending a little time in your garden watching the bumblebees.

Posted on April 2, 2020 10:22 AM by