Scorpionflies and Hangingflies: Mecoptera
SCORPIONFLIES AND HANGINGFLIES: MecopteraNO COMMON NAME (Panorpa nuptialis): SPECIES ACCOUNT
Mecopterans measure 0.08 to 0.86 inches (2 to 22 millimeters) in length. They are small to medium sized insects that vary considerably in shape. The common name "scorpionfly" refers to male mecopterans with swollen, stinger-like reproductive organs on the tip of their abdomens. These organs are sometimes held over the back just like a scorpion. However, scorpionflies are unable to sting. Hangingflies have long slender bodies and resemble crane flies with four slender wings. Other species known as earwigflies are flat with finely veined wings. Their abdomens are tipped with long pincher-like projections. Snow scorpionflies are small insects measuring only 0.08 to 0.29 inches (2 to 7.4 millimeters) long. The males use their slender, hook-like wings to grasp the nearly wingless females while mating.
Most mecopterans have downward projecting beaks with chewing mouthparts at the tip. The antennae are long and threadlike. They have both compound eyes, or eyes with multiple lenses, and simple eyes, or eyes with only one lens. The four narrow wings, if present, are clear and often banded, spotted, or have darkened patterns along the veins. The forewings and hind wings are similar in size and appearance. In some species the wings are either very narrow, almost as wide as they are long, very short, or absent. All mecopterans have relatively long and slender legs. Unable to support themselves with their thin legs, hangingflies prefer to hang from twigs and leaves by their front legs. The abdomen has nine visible segments and is usually slender and narrow toward the rear. Male abdomens are sometimes tipped with special reproductive organs or claspers.
The larvae (LAR-vee), or young, do not resemble the adults at all. There are three distinctive body types. Many resemble caterpillars and have distinct heads with downward projecting mouthparts and eight pairs of fleshy false legs on their abdomens. Others are c-shaped and grub-like, lacking false legs. A few species have slender bodies without false legs. Some species do not have eyes, while others have seven simple eyes on each side of the head. Many other species have compound eyes with 30 or more lenses on each eye. This is unique among insects whose larvae do not resemble the adults, since most others have only simple eyes.
The legs, wings, antennae (an-TEH-nee) or sense organs, and mouthparts of all mecopteran pupae (PYU-pee), the life stage between larvae and adults, are distinct. These appendages are not attached to the pupa along their entire length. The pupae are not enclosed in a cocoon.
Mecopterans are found on all continents except Antarctica. Some species even live in the northern polar regions of North America and Eurasia. Most species are found in Southeast Asia and Indonesia. There are about 550 species of mecopterans worldwide, with 81 species in the United States and Canada.
Mecopterans live mostly in cool, moist habitats, especially in shady forests near springs, streams, and rivers. Adults are usually found resting on leaves and other vegetation. The larvae usually live in the soil or leaf litter, although a few species are aquatic and live in streams. Adult snow scorpionflies are found on ice, snow, and stones near clumps of moss. Their larvae develop in moss.
Mecopterans eat both plant and animal tissues. The adults and larvae of scorpionflies scavenge mostly dead insects. The adults are known to steal insects trapped in spider webs. They also feed on pollen, nectar, and fruit juice. Adult hangingflies are predators (PREH-duh-ters) or hunters and seize aphids, caterpillars, flies, moths, and sometimes spiders with their hind feet. Their larvae eat mostly dead insects and some decaying parts of plants. Adults and larvae of snow scorpionflies eat mosses. Short-faced scorpionfly adults graze the surfaces of leaves, but it is not known what their larvae eat. Aquatic scorpionfly larvae feed on the aquatic larvae of flies (Diptera) known as midges, but the diet of the adults is unknown.
BEHAVIOR AND REPRODUCTION
Mecopterans are secretive animals and are usually active during the day. Scorpionflies and hanging scorpionflies spend their time resting on or hanging from leaves. They are weak flyers and take to the air for only short distances. Earwigflies sometimes hide under logs and rocks and are often attracted to lights at night.
Courtship and mating usually occurs early in the evening or after dark. The males of many species offer a dead insect as food to females during courtship. They will sometimes steal insects caught in spider webs. If a suitable dead insect is not available, the male may try to steal one from another courting male, or he may spit up a blob of saliva and offer it to the female instead. Once he has a gift he flaps his wings and releases a pheromone (FEH-re-moan), which is a scent to attract females. The pheromones also attract other males who may try to steal his gift. Females select mates on the basis of the size and quality of their gift. In some species, males pretend to be females and then steal the gift of males attempting to court them. The thief then mates with a female while she eats his gift of stolen food. In some species of scorpionflies (Panorpa) the males use a special clamp on their abdomens to grab the edges of the female's wings to prevent her from flying away. Mating sometimes lasts for several hours. The gift of food provides the female with nourishment and helps to stimulate egg production. At times a male will simply seize the female's wings with his abdominal clamp and mate with her without offering her anything to eat.
ESCAPING STICKY SITUATIONS
When male scorpionflies invade webs to steal dead insects, they run the risk of becoming food themselves. If attacked, some species produce a brown fluid from the tip of their abdomen and attempt to put it on the spider. If the scorpionfly is successful, the spider will suddenly stop its attack and immediately begin to clean itself. This fluid apparently not only repels several kinds of spiders but also some ants as well.
The life cycle of mecopterans includes four very distinct stages: egg, larva, pupa, and adult. Eggs are laid in the ground, rotten wood, or leaf litter. The eggs hatch in a week or two. In some species, the eggs are laid in the fall and do not hatch until the following spring. The larvae molt, or shed their exoskeletons or hard outer coverings four times, reaching the pupal stage in anywhere from a month to two years. Mature larvae dig a small chamber in the soil in which they undergo the change. Adults live for about a month in the wild and two months or longer in captivity.
MECOPTERANS AND PEOPLE
Scoropionflies, hangingflies, and their relatives are seldom noticed by most people. They do not sting or bite.
No species of Mecoptera is considered endangered or threatened. However, studies have shown that populations in North America, Mexico, and Java are getting smaller as a result of habitat destruction caused by human activity.
Physical characteristics: The bodies of the adults are reddish brown. The yellow wings are marked with broad black or brown bands. The larvae are ringed with dark spots and short bristles and resemble caterpillars.
Geographic range: Panorpa nuptialis is found in the south-central United States and northern Mexico.
Habitat: The adults rest on dense vegetation in open fields and pastureland. The larvae live in the soil of these habitats.
Diet: Both adults and larvae scavenge dead or dying soft-bodied insects.
Behavior and reproduction: Courting males occasionally offer saliva secretions to the female. Females lay their eggs in cracks in the soil. The larvae reach the pupal stage in about a month. They overwinter as pupae. Adults emerge in late fall and live nearly a month.
Panorpa nuptialis and people: This species does not impact people or their activities.
Conservation status: This species is not considered endangered or threatened. ∎
FOR MORE INFORMATION
Tavolacci, J., ed. Insects and Spiders of the World. Volume 8: Scorpion Fly-Stink Bug. New York: Marshall Cavendish, 2003.
Byers, G. W., and R. Thornhill. "Biology of the Mecoptera." Annual Review of Entomology 28 (1983): 203–228.
"Mecoptera. Scorpionflies." Ecowatch. http://www.ento.csiro.au/Ecowatch/Insects_Invertebrates/mecoptera.htm (accessed on October 21, 2004).
Mecoptera. Scorpionflies/Hangingflies. http://www.cals.ncsu.edu/course/ent425/compendium/mecopt1.html (accessed on October 21, 2004).
Mecoptera Page. http://members.tripod.com/buggyrose/ipm/81mecoptera.html (accessed on October 21, 2004).