Mecoptera (Scorpionflies and Hangingflies)

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Mecoptera

(Scorpionflies and hangingflies)

Class Insecta

Order Mecoptera

Number of families 9

Evolution and systematics

Classified within the order Mecoptera are perhaps the most primitive insects with complete metamorphosis. The fossil record of Mecoptera is rich, dating back to the lower Permian, when they were one of the most abundant insect groups. The modern orders Trichoptera, Lepidoptera, Siphonaptera, Strepsiptera, and Diptera are believed to have descended from a mecopteran ancestor. The order today is made up of remnants of this former diversity, containing about 600 species in nine families: Apteropanorpidae (1 genus, 1 species); Bittacidae (16 genera, 172 species); Boreidae (3 genera, 27 species); Choristidae (3 genera; 8 species); Eomeropidae (1 genus, 1 species); Meropeidae (2 genera, 2 species); Nannochoristidae (2 genera, 7 species); Panorpidae (3 genera, 360 species); and Panorpodidae (2 genera, 9 species). Living examples of Mecoptera vary widely in form and biology. Because of this extreme diversity, the status of the order as a single evolutionary unit is under debate, and it eventually may be divided into several new orders.

Physical characteristics

No single feature unifies the order. Fully winged species share wing structure, having four long, membranous wings,

with both the front and hind pairs similar in shape and venation (number and shape of veins in an insect's wings). The order name Mecoptera means "long wings." Mecoptera generally have hyaline (clear) wing membranes with dark veins. When a color pattern exists, it is typically a transparent amber coloration or dark brown banding and striping on the wing membranes. Another common feature is the elongation of the mouthparts and lower portions of the head into a rostrum, a useful character for placing short-winged or wingless species within the order. The mandibles are located at the tip of the rostrum.

Many adult body types exist. Males of Panorpidae and Panorpodidae commonly are called scorpionflies. They have enlarged, bulbous genitalia, carried curled above the body, resembling the tail of a scorpion. The hangingflies, family Bittacidae, look like crane flies (order Diptera), in that they have narrow bodies and long, thin legs. Meropeids and eomeropids are cockroach-like, with flattened bodies and tough, densely veined wings. There are three body types of mecopteran larvae: eruciform (caterpillar-like, with false legs on the abdomen), campodeiform (long and cylindrical, lacking false legs), and scarabaeiform (grublike).

Distribution

Mecoptera are distributed worldwide, including the northern polar regions. Some families are very restricted in distribution. The highest species diversity occurs in the Indomalayan biogeographical region, which encompasses Southeast Asia and Indonesia.

Habitat

Mecoptera are found chiefly in cool, moist habitats. Forests with plentiful shade support the greatest diversity of species. Most larvae develop beneath soil or litter. Nannochoristid larvae, however, are completely aquatic. Adults of Boreidae, called snow scorpionflies, are found on rocks, snow, and ice in the vicinity of moss clumps, within which their larvae develop.

Behavior

Adult Mecoptera tend to be rather secretive, inactive insects, most frequently found resting on the surface of leaves in dense shade. Flight in most species is feeble and brief. Predaceous species typically feed during the day, while opportunistic species have flexible foraging schedules. Reproductive activity in most species takes place only at night.

Feeding ecology and diet

Mecopterans are carnivorous, herbivorous, or omnivorous. Hangingflies are adapted to a predaceous lifestyle. Their hind legs are raptorial, with a single large tarsal claw, used to capture small insect prey. Prey is pierced with the rostrum, and fluids are withdrawn. Snow scorpionflies apparently are an entirely herbivorous group, feeding on mosses as adults and larvae. Most panorpid scorpionflies are omnivores, feeding opportunistically on dead or dying insects but also on plant secretions such as pollen, fruit juice, and nectar. Mecopteran larvae are mostly omnivorous, an exception being the aquatic larvae of Nannochoristidae, which are predaceous on the larvae of midges (order Diptera).

Reproductive biology

Males court nearby females with displays of wing and body movements, and many offer females a nuptial meal.

Common nuptial meals are prey items and salivary secretions. Competition among males often is fierce, and males that are competitively unsuccessful may attempt to force copulation. Females have been shown to prefer males that offer nuptial meals, and feeding on the meal stimulates egg laying and increases fecundity. Mating may last for several hours. Development progresses through four larval instars, a prepupal stage and a pupal stage. Larval development can be as rapid as one month. Adult life span is of similar duration.

Conservation status

No species of Mecoptera is listed by the IUCN. A decline of mecopteran populations in North America, Mexico, and Java has been noted and is attributable to human activity.

Significance to humans

Mecoptera are not known to affect humans in any way. The common name scorpionfly implies that they are in some way dangerous, but no species stings or bites.

Species accounts

List of Species

Black-tipped hangingfly
Snow scorpionfly
Panorpa nuptialis

Black-tipped hangingfly

Hylobittacus apicalis

family

Bittacidae

taxonomy

Bittacus apicalis Hagen, 1861, southern Illinois, United States.

other common names

None known.

physical characteristics

Body and appendages glossy yellow to brown. Wings clear with black tips, held outstretched when at rest.

distribution

Eastern United States.

habitat

Understory vegetation of moist, shaded woodlands.

behavior

This species hangs from low-growing vegetation by the front legs, which are useless for walking. Movement on vegetation is accomplished through a monkey-like swinging motion. Flight is weak and undulating.

feeding ecology and diet

Adults are generalized predators, hunting small insects during the daytime. Prey is captured with the long raptorial hind legs, either from a hanging position or while flying. Draining prey of fluids may take up to one hour.

reproductive biology

The male captures or steals a prey item and emits pheromones while in flight. He offers the prey to attracted females, who reject the male or terminate copulation early if the prey is small or poor in quality. Females feed on the prey while mating, which takes 20–30 minutes. After mating, the male usually retains the prey and may use it in subsequent courtship attempts (females are not able to entirely drain the prey within the time spent in copulation). Females scatter eggs over the ground from a hanging position.

conservation status

Not threatened.

significance to humans

None known.

Snow scorpionfly

Boreus brumalis

family

Boreidae

taxonomy

Boreus brumalis Fitch, 1847, eastern New York, United States.

other common names

None known.

physical characteristics

Small, dark brown, and compactly built. Males have narrow wings, about half as long as the abdomen, hooked downward and with many spines. Female wings are reduced to tiny pads.

distribution

Northeastern North America.

habitat

Larvae live inside clumps of moss growing among rocks or on loamy soil. Adults are found on rocks, soil, snow, and ice near the larval habitat.

behavior

Adults are active in fall and winter. Activity at low temperatures is made possible by a substance in the blood that acts like antifreeze. Larvae are scarabaeiform and can be found any time of year within mosses.

feeding ecology and diet

Larvae and adults feed on mosses.

reproductive biology

The male leaps, grasping an appendage of the female with the claspers at the tip of his abdomen. The male then maneuvers the female onto his back and holds her in place with his hook-like wings. Copulation lasts from one to 12 hours. The female deposits eggs into moss singly or in small clutches. The life cycle probably takes two years.

conservation status

Not threatened.

significance to humans

None known.

No common name

Panorpa nuptialis

family

Panorpidae

taxonomy

Panorpa nuptialis Gerstaecker, 1863, Texas, United States.

other common names

None known.

physical characteristics

Adult body is reddish brown. Wings are amber in color, with striking bands of dark brown. Larva are caterpillar-like, pale, and encircled with rings of dark spots and setae.

distribution

South-central United States and northern Mexico.

habitat

Dense vegetation in open fields and pastureland. Larvae are found beneath the soil in these habitats.

behavior

Adults are active only during the day and rest vertically on vegetation at night.

feeding ecology and diet

Adults and larvae feed primarily on feeble or dead soft-bodied insects.

reproductive biology

Males infrequently offer a salivary secretion to the female. Females lay eggs in existing cracks in the soil, probing with the ovipositor until a suitable site is found. Larvae develop in about a month. Winter is passed in the pupal stage. Adults emerge in late fall and live nearly a month. This species may have two generations per year.

conservation status

Not threatened.

significance to humans

None known.

Resources

Books

Byers, G. W. "Mecoptera." In The Insects of Australia: A Textbook for Students and Research Workers, edited by CSIRO. 2nd edition. 2 vols. Carlton, Australia: Melbourne University Press, 1991.

——. "Order Mecoptera." In An Introduction to the Study of Insects, edited by D. J. Borror, C. A. Triplehorn, and N. F. Johnson. 6th edition. Philadelphia: Saunders College Publishing, 1989.