Over in the macro forum, I have been posting some pictures of the relatively large head capsule shed by a mature (5th instar?) larva of a fritillary butterfly (genus Speyeria).
What's shown here is the relatively small head capsule shed by a 1st instar larva of the same brood. This capsule formed inside the butterfly's egg and was used by the freshly hatched caterpillar until its first molt, at which time the caterpillar simply grew a new head capsule and cast off this one along with its old too-small skin.
What you see here is roughly what you'd see through a 100X microscope. On a typical monitor, the image is actually reproduced at about 250X.
I was interested to notice that the bristles of this 1st instar larva are obviously barbed. The much larger bristles of the 5th instar head capsule appear to be smooth when viewed at correspondingly lower magnification. However, when examined at the same magnification as shown here, the 5th instar bristles appear to be barbed also, with the size and number of barbs apparently not much changed from 1st instar. (This is a casual observation; I have not studied carefully.) Many bristles on insects have a sensory function. I do not know what function the barbs serve.
Two large light spots on the left side of the head capsule are thin membranes that used to cover lateral ocelli. Similar membranes appear over all the other ocelli (on both sides), but they are shadowed and appear dark in this particular orientation.
The light halos around some bristles are artifacts of the stacking procedure. Often I do some manual stacking to remove artifacts like these, but in this case they struck me as helpful by delineating bristles that would otherwise be almost invisible.
--Rik
Technical: Canon SD700IS point-and-shoot through 10X eyepiece, 10X NA 0.25 achromat objective, brightfield illumination, background pushed to uniform light gray in Photoshop postprocessing. 73 frames stacked by Helicon Focus, total depth about 0.2 mm, subject just barely restrained under cover slip elevated by vaseline on corners.
