Ericameria laricifolia apical gall
(For lack of a given term)
I've been interested in these galls on Ericameria laricifolia for some time, and recently found great numbers at the Sears Kay ruin on the Tonto National Forest. I returned later and collected a couple of dozen to observe.
Galls are apical, teardrop-shaped and are derived from leaf tissue widening and forming a gall with a chamber of overlapping bracts. The bracts are weakly and incompletely fused, occasionally leaving small gaps. It appears that the gall is abandoned by the caterpillar before pupating; apparently they drop and pupate in the soil below.
The galls are only occupied for a short period; field dissections of the galls showed them mostly empty with remnant frass at the distal end of the gall. Occupied gall here:
Of the galls collected, half a dozen larvae were collected in the bottom of a jar with loose peat. Most of these died, but one was removed and raised in a petri dish; it developed into a pupa:
The pupa matured and the adult emerged overnight and measures about 7 mm in length. It had difficulty in escaping the exuviae - took a bit of work to help it escape. Material from the exuviae remained on its left side after the struggle. It is interfering with its attempts to fly.
A second larva built a chamber using the peat material in the bottom of the jar. A check of the jar last week revealed a couple of dozen tiny wasps. Most were released but attempts to photograph a living adult weren't successful. Photos here are of one the wasps post-mortem. Length about 2 mm.
(Photos link to the observations with additional photos.)
Comments
Extremely interesting! Thanks so much for sharing your detective work :-)
(Marianne J.)
Interesting!
Fascinating! A whole, tiny world in each turpentine bush. The more we look, the less we know.
Were the wasps parasitizing a catepillar larva/pupa?
Well done. I'll start looking at turpentine bush more closely.
Probably, Perry. I didn't see the larva or pupa; it was embedded in a clump of peat in a corner of the jar. I removed everything but the clump a week before the wasps emerged.
When I noticed the larvae were leaving the galls and dropping to the bottom of the jar, I placed the larvae and some remaining galls in a jar of loose peat. The galls had some leaves attached, so it's possible some other critter was introduced, or the wasps themselves came from another part of the plant (unlikely). I took apart the clump after removing it, but couldn't find anything distinctive, just mess.
Interesting.
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