Volume 48, Number 1,
May 2002:
Scorpionflies, Hangingflies, and other Mecoptera

Text-only version

ISSUE HOME PAGE

ABOUT THIS ISSUE
- about KSN
- about the author

IN THIS ISSUE
- The Order Mecoptera
- Fossils
- Modern Species
- Family Panorpidae
- Family Bittacidae
- Family Meropeidae
- Family Panorpodidae
- Family Boreidae
- Key to the Families of North American Mecoptera (Adults)
- References

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Scorpionflies, Hangingflies, and other Mecoptera
by Geroge W. Byers

FAMILY BITTACIDAE

Hangingflies have a single, large claw at the end of each tarsus; they are unable to stand on a surface but suspend themselves from edges of leaves or from twigs.  Their wings are elongate, slender toward the base, and usually held down alongside the abdomen except in flight.  Some bittacids may be found in shaded habitats together with scorpionflies, but others occur at edges of woodlands or in unshaded places, such as in tall grasses.

Adult hangingflies are predators, feeding on other insects, which are usually captured by the raptorial hind tarsi and held up to the mouth. Bittacids may fly upward along a plant stem and pluck off unwary prey.  Only soft parts are eaten. Larvae of Bittacidae feed on dead insects.

Mating behavior of hangingflies has similarities to that of scorpionflies. A male first captures a suitable food item (and may feed on it briefly himself), then emits a pheromone from vesicles everted between sclerites 6–7 and 7–8 on the back of the abdomen. When a female is attracted to the pheromone and appears to judge the food offering adequate, mating ensues, with both partners hanging from overhead support and the female feeding (Figure 3).

Figure 3. A mating pair of Hylobitticus apicalis hang from overhead support while the female feeds.

Female bittacids show no particular concern for the welfare of their young.  When ready to oviposit, the female suspends herself above probably suitable habitat and drops here eggs, one by one. The eggs fall among dead leaves and other debris on the ground, there to lie until hatching. Eggs of most bittacids are unusual in being nearly cuboidal, with each surface slightly impressed. Near the time of hatching, the egg enlarges somewhat and becomes roughly spherical. Duration of the egg stage varies greatly according to the species (Setty 1940).

Larvae of Bittacus (and other bittacids) have compound eyes but with only seven ommatidia each; they also have one ocellus at the top of the frons (front of the head). They are eruciform (that is, they resemble caterpillars), with the head sclerotized but most of the body except the dorsum of the first thoracic segment, virtually membranous, with a pair of branched, fleshy projections on the back of the hind two thoracic segments and abdominal segments 1–9, with smaller appendages at the sides.  Bittacid larvae do not burrow into the soil but remain at the surface, concealed by vegetational debris; they may excrete fluid containing soil and deposit this on their dorsal projections, where it adheres and hardens. Setty (1940) has described and illustrated the morphology of adults, larvae of various instars, pupae and many other details, based on his many careful studies of Bittacidae.

Figure 4. A species of Apterobittacus from California lacks wings.