I found this mantidfly at a friend’s house yesterday and took it home to photograph because it was much, much smaller than any that I’ve seen before. Looking at it this morning, it looks the same as others I’ve seen, just smaller. I went looking online today to see if males and females are different sizes, but I don’t think they necessarily are. Apparently, after mating, either one may eat the other, so probably they are about the same size.
My small mantidfly wasn’t going to grow any bigger, because they don’t grow as adults. Mantidflies undergo hypermetamorphosis, which is like complete metamorphosis (egg, larva, pupa, adult) but with an additional stage. In their case, there are two different larval forms. The first one is mobile and needs to find a host, but after doing so they transform into a more grub-like form. Many species parasitize spider egg sacs, and the early larvae latch onto a spider in order to get access to an egg sac. If need be, they will remain attached to the spider until she lays eggs.
Also, although their front legs look like praying mantis front legs, they are not closely related, and each one developed these legs independently. When a similar form is developed by unrelated groups of animals, this is known as convergent evolution. On St. Martin, there are also several true bugs that have developed similarly shaped forelegs.
