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Insect Identification Key
Order Strepsiptera: the twisted-wings

Twisted-winged parasite
This illustration of a male twisted-winged parasite (family Halictophagidae) shows the characteristic branching antennae, large eyes and large hind wings. In addition, it shows the small knob-like structures in front of the hind wings. Illustration credit: Halvard Hatlen.

Elenchus koebelei
This species, Elenchus koebelei, (family Elenchidae) is just 2 mm long. It infects planthoppers, insects which are in the suborder Auchenorrhyncha (formerly in the order Hemiptera). Photo by Marisano James.

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Based on your answers to the questions, you have identified your insect as being in the order Strepsiptera!

Members of this order include: twisted-winged parasites (sometimes shortened to simple “twisted-wings” in colloquial usage).

Etymology: Strepsiptera comes from the Greek words strepsos, which means twisted, and ptera, which means wings. This refers to the large, fan-like, hind wings present in the males. The males hold their hind wings in a turned or twisted fashion.

General characteristics:
• most adult females are wingless, legless, eyeless, and look much like grubs. (Exceptions are females in the family Mengenillidae. Adult females in this family have very simple eyes, as well as legs.)
• males have two hind wings, but instead front wings, they have two, small, knobbed, stalk-like structures. Note: Flies (order Diptera) have similar structures, but they are located behind their wings. In both the flies and the twisted-wings, the structures are known as halteres.
• the hind wings in males are large and fan-like
• females are rarely seen (see Basic Ecology below)
• males have tiny heads with large eyes
• males have branched antennae
holometabolous metamorphosis (egg — larvapupa — adult)
• the larvae are hypermetamorphic, which means that a larva goes through several changes in form and structure as it grows. The newly hatched (first instar) larva has both eyes and legs, although most adult females usually have neither legs nor eyes.

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Number of species worldwide: about 550-600

Basic ecology: Twisted-winged parasites have a rather unusual life history. The larva hatches from its egg inside the mother’s body, moves around within her “blood,” or hemolymph, and feeds on her stored fat reserves. When the larva is ready, it crawls out of the mother through a so-called “brood canal” on her protothorax, which is the part of the thorax just behind the head. It then begins scouting for a suitable host, typically a bee, wasp, leafhopper or other insect. Once it finds a good candidate, the larva burrows into the host’s body, where it survives by eating the host’s blood and other tissues. Unusually, the larva molts then and loses its legs and antennae. The larva changes into a pupa inside the host’s body. If the twisted-winged parasite is a male, it emerges from the host and uses its large wings to fly off in search of a female with which it can mate. The adult males only live a few hours, so they need to find a mate quickly. If the twisted-winged parasite is a female, she remains inside the host from the time she is a newly hatched (first instar) larva to pupa to adult. How do the adult males and females connect? She sticks just enough of her body (actually her front end, which is where the brood canal is located!) out of the host’s body so the male can mate with her.

Classification:
Kingdom Animalia
   Phylum Arthropoda
      Class Insecta
         Order Strepsiptera

For a list of all of the orders in this key, click here: List of Orders.

Oops! If this doesn't appear to be the order for your insect, go back through the key and look more carefully at your insect while answering the questions again. Your perseverance will reward you!

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Photos at the top of this website are (from left to right): potato beetle (Leptinotarsa decemlineata) — photo credit: Scott Bauer, U.S. Department of Agriculture; ebony jewelwing (Calopteryx maculata)— photo credit: U.S. Fish and Wildlife Service; sweat bee (Agapostemon splendens) — photo credit: Natalie Allen and Stephanie Kolski, U.S. Geological Survey; preying mantis, monarch butterfly (Danaus plexippus), hellgrammite (aka toe biter) larva and eyed click beetle (Alaus oculatus) — photo credit: Leslie Mertz, DailyGraceCards.com; Halloween pennant (Celithemis eponina) — photo credit: Kay Meng, U.S. Fish and Wildlife Service.

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