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How to identify it
- Adults are 3/4 to 1 1/4 inches long with threadlike, toothed or feathery antennae that are never clubbed. The raptorial front legs are attached at the front of the elongated prothorax, just behind the head, and are held up rather than used for walking; a large claw at the tip closes against a wide, spiny tibia. Only the middle and hind legs walk.[1]
- All four wings are alike and lacewing-like, with an intricate net of veins. Most species are green, brown, tan, gray or yellowish: the green mantidfly (Zeugomantispa minuta) is pale lime green with iridescently patterned eyes, while Say's mantidfly (Dicromantispa sayi), D. interrupta and Leptomantispa pulchella are nondescript tan to brown and widespread in the eastern United States.[1]
- The brown wasp mantidfly (Climaciella brunnea) is banded in yellow, brown, rust or black, with wings colored and patterned to resemble a wasp's; across its broad North American range its coloration varies to match whichever wasps are locally abundant.[1]
- Adult size within a species varies enormously: in Say's mantidfly it depends largely on how many eggs were in the spider egg sac the larva grew up in, and either the male or the female in a mating pair may be the larger one.[4][1]
Look-alikes
| Look-alike | How to tell them apart |
|---|---|
| Praying mantids | True mantises are much larger, with chewing mouthparts on a mobile head and leathery forewings; mantidflies are only an inch long, have four clear net-veined wings, and are far more closely related to lacewings than to mantises.[1] |
| Green lacewings | The same delicate net-veined wings and often the same pale green color, but without the long prothorax and spiny raptorial forelegs.[1] |
| Dustywings | Tiny lacewing relatives no more than about 3 mm long, looking like miniature lacewings covered in dust; their larvae eat aphids, mites and scale insects.[1] |
| Snakeflies | Western insects with a long neck-like prothorax and a wide head held up and bobbing like a cobra's, but without raptorial forelegs; not found in Missouri.[1] |
Where it lives
Statewide in Missouri and most common in the southern parts of the United States; Say's mantidfly, D. interrupta and L. pulchella are widespread in the eastern United States, and the brown wasp mantidfly has a broad North American range in grasslands and open habitats. The University of Florida studies collected Say's mantidflies at blacklights in north-central Florida from May through September.[1][3]
Biology and life cycle
Adults capture prey the way a mantis does, snatching a smaller insect, mite or other arthropod with the spiny forelegs and chewing it; they are generalist predators, and the brown wasp mantidfly hunts insects visiting flowers. Many species, especially at blacklights, come to lights at night. Adults appear from late April through June and may persist until hard frosts in October.[1][3]
The larvae are predators in spider egg sacs, draining the eggs through a piercing and sucking tube formed from the modified mandibles and maxillae. First-instar larvae reach the eggs in two ways: by burrowing straight through the silk of an egg sac they find, or by boarding a female spider and riding her, often near the pedicel and sometimes inside her book lungs, feeding on her blood until she builds a sac, which the larva enters as it is constructed. A larva that boards a male can transfer to a female during mating or cannibalism.[2][1]
Boarding mantidflies attack all the major groups of hunting spiders, while egg-sac penetrators also enter the sacs of web builders. The brown wasp mantidfly specializes in wolf spiders. Florida experiments showed that first-instar Say's mantidflies detect spider silk and excreta left on a surface, spend more time on it than on clean paper, follow dragline silk, and prefer cues from adult spiders of either sex over juveniles; field surveys have found larvae on male and female spiders in about equal numbers.[2][1][3]
The life cycle is a hypermetamorphosis. Stalked eggs are laid in large clusters; the slender, agile first larva molts inside the sac into a chubby, grub-like feeder; the full-grown larva spins a cocoon and pupates; an active second-phase pupa crawls about on the cocoon and spent egg sac before the final molt to a winged adult. In some mantidfly groups the larvae are instead ordinary predators of other insects' larvae.[1]
A female Say's mantidfly has been documented eating a male before copulation, and because body size in both sexes varies so widely, either partner may be at risk.[4]
Damage and signs
- Mantidflies damage nothing. They eat small insects and spider eggs, but the Missouri Department of Conservation judges them too uncommon to have a large effect on prey populations by themselves; they are one more member of the predator community alongside spiders, assassin bugs, lady beetles and mantises.[1]
Health risk
Harmless to people: the sources describe only predation on small arthropods and spider eggs, and the Missouri Department of Conservation calls them friendly from a human point of view.[1]
Control
Prevention
No control is needed or appropriate. A mantidfly at a porch light or on a flower is a predator passing through; most people would consider them friendly since they feed on spiders, insects and other small arthropods. Many species come to lights at night, which is where most people meet them.[1]
Common questions
- Is this a baby praying mantis with wings?
- No. A winged insect is an adult, and an inch-long mantis-like insect with four clear, lacewing-style wings and raptorial forelegs attached right behind the head is a mantidfly, a relative of lacewings. Mantids have leathery forewings and are much larger.[1]
- Does it bite or sting?
- The sources record no bite or sting; the forelegs are for grabbing small insects, and the wasp-banded brown wasp mantidfly is a mimic that gains protection by looking like a wasp.[1]
- Why would a mantidfly larva ride around on a spider?
- To reach the eggs. A first-instar larva that boards a female spider feeds on her blood until she spins an egg sac, then slips inside as the sac is built and eats the eggs through its piercing mouthparts; others simply burrow into sacs they find.[2]
Sources
- Missouri Department of Conservation, “Mantidflies (Mantis Flies) field guide.” mdc.mo.gov/discover-nature/field-guide/mantidflies-mantis-flies (accessed 2026-11-10)
- Annual Review of Entomology (Annual Reviews), “Redborg (Coe College). Biology of the Mantispidae. Annual Review of Entomology 43: 175-194 (1998), PMID 15012388.” pubmed.ncbi.nlm.nih.gov/15012388/ (accessed 2026-11-10)
- Scientific Reports (Nature Portfolio), “Lietzenmayer and colleagues (University of Florida). Mantidfly larvae use cues on substrate to locate and distinguish different sexes and life stages of potential spider hosts. Scientific Reports 14 (2024), PMC11551181.” pmc.ncbi.nlm.nih.gov/articles/PMC11551181/ (accessed 2026-11-10)
- Royal Society Open Science, “Lietzenmayer, Clark and Taylor (University of Florida and Michigan State University). Extreme natural size variation in both sexes of a sexually cannibalistic mantidfly. Royal Society Open Science 9: 220544 (2022), PMC9382211.” pmc.ncbi.nlm.nih.gov/articles/PMC9382211/ (accessed 2026-11-10)
- iNaturalist, “Mantispidae taxon page (order and family).” www.inaturalist.org/taxa/52955 (accessed 2026-11-10)