The addition of Pythidae as one of the cucujid look-alike larvae has necessitated another comparison shot showing the four families involved: Pyrochroidae; Pythidae; Cucujidae; and Boridae.

At top is the very common pyrochroid Dendroides canadensis followed (literally) by a pythid of similar coloration, Pytho niger. The reddish one is our old cucujid friend Cucujus clavipes and the dark olive one on the bottom is a borid, Boros unicolor.

I would have thrown in the dark green-brown pyrochroid Schi*zotus cervi*calis as well, but one of my two S. cervi*calis larvae died while the other pupated.

As to why these four families have larvae so alike in form, may I offer the evolutionary dictum, "Form follows function." In other words, because these larvae all make their living under bark, they must be shaped optimally for roving around under the just-loose-enough bark of trees and logs. The lower their side profile, the safer they are from larger predators also. So their shape helps them eat and avoid being eaten.