Mantidfly

Mantidflies belong to the family Mantispidae within the order Neuroptera, the same broad group as lacewings and antlions, despite their uncanny resemblance to praying mantises. The similarity is a striking example of convergent evolution: unrelated insects independently evolved the same raptorial front-leg design for grabbing prey.

What sets mantidflies apart from true mantises is easy to spot once you know what to look for: mantidflies have two pairs of membranous, net-veined wings folded flat or tent-like over the body, versus the leathery forewings of mantises, and they are generally much smaller.

Perhaps the most remarkable aspect of mantidfly biology is the larval stage in many species, which begins as a tiny, mobile hunter that seeks out spider egg sacs, burrows in, and develops by consuming the spider eggs within, a highly specialized parasitic strategy unlike anything seen in true mantises.

• Raptorial front legs held folded in a mantis-like praying posture, used to grab small prey
• Two pairs of clear, net-veined, membranous wings, usually held roof-like over the body at rest
• Elongated, mobile neck-like prothorax similar to a mantis, but body overall smaller and more delicate
• Compound eyes proportionally large; antennae relatively short and thread-like (unlike a mantis's)
• Coloration ranges from pale green or yellow to brown, often mimicking wasps in some species
• Lookalikes: true praying mantises (larger, leathery forewings, no true metamorphosis) and some wasps (mimicked by certain mantidfly species)

Mantidflies are found on most continents in warm temperate to tropical regions, typically in gardens, meadows, shrubby areas, and woodland edges with abundant flowers and small insect prey. They are most often noticed visiting flowers or resting on foliage in summer. Larvae of species that parasitize spiders begin their search near ground level or on vegetation where spider egg sacs are likely to be found.

Adult mantidflies are ambush predators that use their raptorial front legs to snatch small insects such as flies, aphids, and other soft-bodied prey, much as a mantis would, though on a smaller scale. Some species are also attracted to flowers, where they hunt visiting insects. Larvae of many species have an unusual life history, actively searching out spider egg sacs to enter and feed on the eggs within, a specialized predatory-parasitic role that ties mantidflies closely into spider population dynamics within their ecosystems.

Females lay large numbers of tiny stalked eggs on leaves or bark. In species that parasitize spiders, the newly hatched larva is a highly mobile, long-legged form that seeks out a spider or its egg sac; once inside an egg sac, it transforms into a grub-like form and feeds on the eggs before pupating within the sac. Other mantidfly species develop more like typical predatory neuropteran larvae, hunting small insects directly. After pupation, adults emerge to mate and continue the cycle, generally producing one generation per year in temperate regions.