Okay, technically, this is a shore fly, and it’s definitely a fly, not a mantis, but what else can you call this little dude? Meet Ochthera tuberculata, one of about 13 North American species, and 40 species worldwide, of “shore flies with raptorial forelegs”. (They’re not technically “mantis flies”, because that’s an entirely separate family of insects which look more like actual preying mantises.)
Flies in the genus Ochthera are not closely related to mantids, but they have evolved, on their own, some very mantis-like forelegs (a process called convergent evolution). They use these forelegs just like mantids do: to reach for, grab, and hold prey. Multiple lines of insects have adapted their forelimbs in this way, actually. It’s clearly useful!
Even as larvae, these guys are heavy duty predators. The maggots live in the water, eating other insect larvae, such as those of midges and mosquitoes. As adults, they live along the shore (as you might imagine), eating adult midges and mosquitoes. Go, little flies, go! (I hate mosquitoes.)
Unlike most flies, who have only sucking mouthparts, Ochthera flies have a hard, sharp proboscis which sort of resembles a serrated dagger; this is used to break through the exoskeletons of its prey. Once the prey is pierced, Ochthera eats like most flies, by regurgitating digestive juices into the prey’s body and sucking up the results.
Ochthera have even been observed to dig for food in sand or mud, inserting their proboscis into the ground to try to locate the meal before digging with those huge front legs.
As they walk along surfaces, Ochthera flies carefully reach out with their forelegs, one after the other, tilting them this way and that. They may be signaling to each other with UV-reflective patches that we can’t see, or perhaps using movement to attract prey — we don’t know yet. We have seen that, during mating displays, the male performs his little foreleg dance along with rhythmic tapping of his hind legs against his belly.