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, Boris 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 eating not wood or cambium but other small underbark invertebrates, 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.