The Piedpiper opined some time ago - though I'm not sure how serious he was - that the June bug or June beetle surely undermines Darwin's theory of natural selection. To us it seems so vulnerable to prey, so ill-adapted to its conditions, so aberrant, that it may fancifully be called a living fossil, or so he says ("the junebug should have gone the way of the dodo centuries ago."). Yet, like Michael Jackson, it's still around.
Its existence may tell us much about ancient forms of life, but it surely is not consistent with the ordinary view of special creation theories in which species are supposed to have been created (as a cell? egg? seed? baby? adult?) out of thin air and perfectly adapted for their environment. If anything, the existence of a bug with parts useless to its existence serves as a grave objection to the assumptions of creationists and their ilk.
Not so for Darwin and his "theory of descent with modification" (as he likes to call it). He too was captivated by the existence of ill-fitted organisms like the June bug. Rather than undermining his theory of natural history, such specimens only strengthened his conviction that species are mutable. He said,
"Nor ought we to marvel if all the contrivances in nature be not, as far as we can judge, absolutely perfect; and if some of them be abhorrent to our ideas of fitness. We need not marvel at the sting of the bee causing the bee's own death; at drones being produced in such vast numbers for one single act, and being then slaughtered by their sterile sisters; at the astonishing waste of pollen by our fir-trees; at the instinctive hatred of the queen bee for her own fertile daughters; at ichneumonidae feeding within the live bodies of caterpillars; and at other such cases. The wonder indeed is, on the theory of natural selection, that more cases of the want of absolute perfection have not been observed." (Darwin, The Origin of Species, Chapter XIV)