Illinois Natural History Survey - University of Illinois



Susan Post


My front legs resemble a preying mantis, my prothorax a giraffe, my wings a green lacewing, and my larvae have never met a spider egg sac they didn’t like. What am I?

Does this seem like some bizarre creature from the land of Dr. Seuss or a real insect? The answer is—a mantispid from the insect order Neuroptera, family Mantispidae, and subfamily Mantispinae.


      Mantispids, or false mantids, resemble miniature preying mantids. Their two front legs are enlarged, equipped with spines, and are raptorial (folded) just like the mantis. In a recent nature center newsletter, a lengthy article was devoted to the preying mantis only to show a photo of a mantispid! Even early taxonomists confused the two as they described new species of mantispids as mantids. The mantispid/preying mantis confusion is an example of convergent evolution, e.g., insects that are not closely related but have evolved similar adult structures due to similar selective pressures. 

      While the two species may have similar front legs, they differ in their wing structure, size, and life cycle. Mantispids have two pairs of membranous wings crisscrossed by a network of nervelike veins that they hold tentlike over the body. The Order name “Neuroptera” is Greek and means “nerve wing.” Mantids, on the other hand, have forewings that are leathery in appearance and the hind wings are folded underneath the fore-wings. Both sets lie flat on the insect’s body. Mantispids are small, 20–35 mm, while preying manitids are larger, 70–120 mm. Perhaps the greatest difference is in their life cycle. Mantispids undergo complete metamorphosis—egg, larva, pupa, and adult—while a mantis has incomplete metamorphosis—egg, nymph (that looks like a miniature adult), and adult.

      A female mantispid will lay numerous stalked eggs randomly on leaves and wooden structures. The newly hatched larvae, less than a millimeter in size, are very active and begin the search for spiders. They find their spider hosts via one of two ways. Either they actively seek a previously constructed spider egg sac that they enter through direct penetration, or they climb onto a female spider and enter the egg sac as the female builds it.  While the mantispid is waiting for the female spider to build an egg sac, it will enter the spider’s book lungs and feed on the spider’s blood. The mantispids will not molt until they enter an egg sac. If the larva happens to board a male instead of a female, it will eventually die or it can transfer to the female during mating. The mantispid will enter the egg sac before the female spider can finish spinning the silken protective case. Once in the egg sac, the mantispid will dine on spider eggs and undergo three molts.  After two to three weeks, the mantispid spins a cocoon inside the egg case and emerges as an adult one to two weeks later.

      There are 300 species of mantispids worldwide, with approximately 10 species found in North America. In Illinois, they are generally found in weedy fields, brushy areas, and woodland openings and are usually ignored by the casual observer. The next time you think you’ve found a miniature preying mantis, take a closer look, it could just be the strange but equally fascinating mantispid.


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