Download high resolution image here.
I retrieved this pupa from the interior chamber of a midge gall on a
Atriplex canescens (fourwing saltbush) described here:
Images and descriptions of other stages of development are linked on that page. The bush was located at
35°08'10.4"N 106°28'48.9"W, 6128 ft,
Sandia Crest 7.5’ quadrangle, near the trailhead of Embudito Trl (192) in the
Sandia Mountains, Bernalillo Co, NM.
Most pupae are relatively immobile, and fully eclose interior to any protective enclosure they've made. This one, however, burrows its way out, eclosing at the surface. Molts left behind from two such midges can be seen here:
The bottom molt shown in that image is as found at the surface of the gall. The top one (middle gall) had its orientation disturbed during the process of tearing open the gall. The pupa burrows out head first. I have not witnessed the process myself, but its two anterior horns are undoubtedly used to cut and/or tear away gall tissue (which is rather soft). Numerous backward-pointing spines on its dorsal abdomen prevent backsliding. Beyond that, it's not clear whether locomotion is accomplished by elongation/contraction or wriggling. Or, perhaps, the legs eclose first and the midge crawls forward.
This image is from a
Helicon Focus processed stack of 166 images with a 7.7 µm step taken with a
Mitutoyo M Plan APO 10×/0.28 ∞/0 mm microscope objective + Nikon 135 mm F2.8 AIS telephoto lens + Nikon D810 camera (magnification 6.75×; technique described
here).