SNAKEFLIES: Raphidioptera

PHYSICAL CHARACTERISTICS

Adult snakeflies have slender bodies that range from 0.20 to 0.79 inches (5 to 20 millimeters) in length. The head is flat and has chewing mouthparts that are directed forward. The antennae (an-TEH-nee), or sense organs, are long and threadlike. Some species also have three simple eyes, or eyes with one lens, in between the large compound eyes, or eyes with multiple lenses. The first section of the three-segmented thorax, or midsection, is long and slender. The four wings are similar to one another in size and shape. They are clear, with a network of dark veins, and are held like a roof over the body when at rest. Each wing has a distinct yellow, white, or black spot on the leading edge near the tip. All six legs are similar in appearance and are adapted or built for walking. The abdomen is ten-segmented. The abdomen of the female is tipped with a long egg-laying tube, called an ovipositor, while the abdomen of the male ends with the reproductive organs. These organs sometimes have very complicated shapes.

The larvae (LAR-vee), or young of an animal, are long and flat. The head has chewing mouthparts that are directed forward, short antennae, and four to seven simple eyes on each side. The head and the first segment of the thorax are hard, while the rest of the thorax and abdomen are soft. The abdomen is ten-segmented.

GEOGRAPHIC RANGE

Snakeflies are found in North America, Eurasia, and parts of North Africa. In North America they are found only in the southern United States and extend south to southern Mexico. Their range in Eurasia includes nearly all forested regions. In the Old World, their distributions range as far south as the mountainous regions of Morocco, northern Algeria, northern Tunisia, Israel, Syria, northern Iraq, northern Iran, northern Pakistan, northern India, Bhutan, Myanmar, northern Thailand, and Taiwan. There are 206 species of snakeflies worldwide, 21 of which occur in the United States and Canada.

HABITAT

Snakeflies prefer habitats where there is a winter period and lots of woody shrubs. They are found from sea level up to more than 9,840 feet (3,000 meters). Adults are found resting on vegetation. The larvae live under the bark of trees or shrubs or in the top layer of soil. The larvae of a few species are found in rock crevices.

DIET

Both larval and adult snakeflies eat soft-bodied insects and spiders. Some adults are known to eat pollen.

BEHAVIOR AND REPRODUCTION

Snakeflies are active during the day and spend most of their time cleaning themselves. They use their front legs like a comb over their head and pull their antennae through their leg segments. The legs are then pulled to their mouthparts for cleaning. As adults, snakeflies are weak flyers and are not able to move very far from where they grew up as larvae. Like most animals that hunt other animals for food, adult snakeflies live alone and come together only to mate. Courtship in some species involves movements of the antennae, wings, and abdomens. The male places sperm directly into the reproductive organs of the female. Mating lasts up to three hours.

WHY NOT PUT SNAKEFLIES TO WORK?

Both adult and larval snakeflies are potentially valuable predators. After all, the adults eat soft-bodied arthropods, like aphids that are considered crop pests. There have been several attempts to use snakeflies as biological controls. Biological controls are natural enemies of pests that can be used instead of pesticides or poisons. Unfortunately, snakeflies are picky eaters and their long development stages prevent them from being effective predators of pests that only live short-term in agricultural fields.

The life cycle of snakeflies includes four very distinct stages: egg, larva, pupa, and adult. The eggs are laid in the crevices (KREH-vuh-ses) of tree bark or under leaf litter. The eggs may take just a few days or up to three weeks to hatch. Snakefly larvae do not resemble the adults at all. The larval stage usually lasts one to three years. During this time they will molt, or shed their exoskeletons or hard outer coverings, ten to fifteen times or more before reaching the pupal stage. The pupa is the stage that separates the larva from the adult. The pupal stage may last up to ten months. In most insects with a pupal stage, the pupae move very little. However, the pupae of snakeflies are incredibly active and resemble adults with short wing pads.

SNAKEFLIES AND PEOPLE

Images of snakeflies were carved on wood blocks that were then used to print their likenesses as illustrations in books as early as the seventeenth century. However, scientists did not begin to study them until 1735.

CONSERVATION STATUS

No snakeflies are listed as endangered or threatened. Many species might be threatened by extinction someday due to habitat destruction. This is because they are found only in very small geographic areas.

SCHUMMEL'S INOCELLIID SNAKEFLY (Inocellia crassicornis): SPECIES ACCOUNT

Physical characteristics: The males of this small to medium-sized insect including wings measure 0.31 to 0.43 inches (8 to 11 millimeters), while females are 0.41 to 0.59 inches (10.5 to 15.0 millimeters). The wing spots are dark brown. The head lacks simple eyes.

Geographic range: This species is found from central and northern Europe to eastern Asia.

Habitat: This species lives in pine, in forests up to elevations of 3,280 feet (1,000 meters). The larvae are found underneath the bark of cone-bearing trees, especially pines.

Diet: The larvae eat soft-bodied arthropods, such as insects and spiders. It is not known what the adults eat, but their diets probably include pollen.

Behavior and reproduction: Very little is known about their behavior, other than the fact that they are very clumsy flyers. The life cycle, from egg to adult, usually takes about two to three years.

Schummel's inocelliid snakeflies and people: This species is not known to impact people or their activities.

Conservation status: This species is not listed as endangered or threatened. It is rare, but it does not appear to be threatened with extinction. ∎

FOR MORE INFORMATION

Books:

Tauber, Catherine A. "Order Raphidioptera." In Immature Insects, edited by Frederick W. Stehr. 2 vols. Dubuque, IA: Kendull/Hunt Publishing Company, 1991.

Tavolacci, J., ed. Insects and Spiders of the World. Volume 8: Scorpionfly-Stinkbug. New York: Marshall Cavendish, 2003.

Periodicals:

Acker, Thomas S. "Courtship and Mating Behavior in Agulla species (Neuroptera: Raphidiidae)." Annals of the Entomological Society of America 59 (1966): 1–6.

Web sites:

"Rhaphidioptera. Snakeflies." Tree of Life Web Project. http://tolweb.org/tree?group=Raphidioptera&contgroup=Endopterygota (accessed on October 12, 2004).