ANGEL INSECTS OR ZORAPTERANS: Zoraptera

PHYSICAL CHARACTERISTICS

Angel insects are small, ranging from 0.08 to 0.16 inches (2 to 4 millimeters) in length. They are long, somewhat flattened brown or black insects resembling termites. Their distinctive and triangular heads have chewing mouthparts with toothed jaws that are directed downward. The antennae (an-TEH-nee), or sense organs, have nine beadlike segments. All three segments of the thorax, or midsection, are distinctive.

Both males and females of each species have winged and wingless forms. Wingless angel insects are the most common form. They are pale and blind. Winged forms are darker and have compound eyes, or eyes with many lenses, and three simple eyes, or eyes with only one lens each. Winged females are usually more common than winged males. When present, the wings are long, broad, and have very few veins. The hind wings are shorter than the forewings and have fewer veins. At rest they fold their four wings flat over their backs. Like termites, they shed their wings easily, leaving four small stubs behind.

The front and middle legs of angel insects are similar to one another. The thighs of the back legs are slightly enlarged and have a row of thick spines underneath. The feet have two segments and are tipped with a pair of claws. The abdomen of all angle insects is broadly attached to the thorax, giving them a thick-waisted appearance. The short abdomen is oval in shape and ten-segmented. The tip has a pair of projections, each made up of a single segment. Each of these projections has a single, long bristle.

The larvae (LAR-vee), or young form of the animal that must change in form before becoming adults, are pale creamy brown and resemble wingless adults. Unlike the adults, the larvae have eight-segmented antennae. There are two different kinds of larvae that develop into winged or wingless adults.

GEOGRAPHIC RANGE

There are thirty-three species of angel insects worldwide. Angel insects are found on all continents, except Australia and Antarctica. Most species live in the New World tropics, but other species are known from North America, Southeast Asia, Africa, or the Pacific islands. Three species are found in the United States, including Hawaii.

HABITAT

Angel insects are found in warm, moist habitats, usually under the bark of dead, rotten logs. In the eastern United States, they also have been found in piles of sawdust in lumber mills. They are sometimes found with termites. Winged individuals are sometimes attracted to lights at night.

DIET

They feed on various parts of funguses or scavenge small, dead worms, insects, and mites. In captivity they will eat crushed yeast, rat chow, and sometimes each other.

BEHAVIOR AND REPRODUCTION

Angel insects live in groups that are probably founded by a single female. They may have a well-defined social structure. Larger, older males dominate these colonies. They will either avoid other males or engage in head butting, grappling, chasing, and kicking. Angel insects spend a great deal of time grooming themselves and each other.

Winged angel insects are carried over wide distances by wind currents. This explains the presence of some species on isolated islands out in the ocean. After finding a suitable habitat, winged individuals seek the shelter of a rotten log and soon shed their wings. Adults with wing stumps are frequently found in young colonies.

Zorapterans usually reproduce by mating, but males are sometimes very rare. Females of a Panamanian species usually reproduce by parthenogenesis (PAR-thuh-no-JEH-nuh-sihs), a process where the young develop from unfertilized eggs. However, they will also mate with males on those occasions when they meet. Males are larger than females and sometimes fight each other before they can mate with nearby females. Females may mate every few days, either with the same male or with a variety of partners.

In another Central American species, males do not dominate the colonies. During courtship the male presents the female with a drop of liquid produced from a gland on his head. Males and females touch each other with their antennae before mating. Mating is brief but may occur several times, one right after the other.

Angel insects guard their eggs and cover them with chewed bits of food. Eggs take several weeks to hatch. The larvae closely resemble the adults but lack wings and are not capable of reproduction. They develop gradually and molt, or shed their exoskeletons or hard outer coverings, four or five times before reaching adulthood. Adults live for about three months.

ANGEL INSECTS AND PEOPLE

Angel insects do not impact people or their activities.

HARD TO FIND

The order Zoraptera is one of the smallest and least known orders of insects. In fact, many entomologists (EHN-tih-MA-luh-jists), scientists who study insects, have never seen one alive. The order was originally created in 1913 for wingless individuals collected in West Africa. Since then scientists have discovered only 37 species of angel insects, including five fossil species. All of the known fossils are preserved in amber, or hardened tree sap.

CONSERVATION STATUS

No species of angel insects are endangered or threatened. The entire order is poorly known and many species are known only from single individuals. There has been some concern expressed for the Hawaiian species because of the loss of habitat. Unfortunately, there are no estimates of the population size of this or any other species, and it is impossible to say whether or not their populations are shrinking or growing in size.

HUBBARD'S ANGEL INSECT (Zorotypus hubbardi): SPECIES ACCOUNTS

Physical characteristics: This species resembles a leggy, medium to dark brown termite. They are small, ranging in size from 0.10 to 0.11 inches (2.6 to 2.9 millimeters) in length.

Geographic range: This species is found in the Eastern United States, from Pennsylvania and Maryland, south to Florida, and west to Iowa and Texas. Its wide distribution in North America is thought to be, at least partially, the result of accidental introductions by humans.

Habitat: They are found under the bark of moist logs and old sawdust piles in lumber mills.

Diet: They eat bits of funguses and scavenge pieces of dead small insects and mites.

Behavior and reproduction: They live in colonies numbering 15 to 120 individuals. Some colonies may live for several years.

This species reproduces either by mating or by parthenogenesis.

Hubbard's angel insects and people: This species is small, secretive, and seldom if ever noticed by people.

Conservation status: This species is not endangered or threatened. ∎

FOR MORE INFORMATION

Books:

Tavolacci, J., ed. Insects and Spiders of the World. Volume 10: Wandering spider-Zorapteran. New York: Marshall Cavendish, 2003.

Periodicals:

Gurney, A. B. "A Synopsis of the Order Zoraptera, with Notes on the Biology of Zorotypus hubbardi Caudell." Proceedings of the Entomological Society of Washington 40 (1938): 57–87.

Valentine, B. D. "Grooming Behavior in Embioptera and Zoraptera (Insecta)." Ohio Journal of Science 86, no. 4 (1986): 150–152.

Web sites:

Zoraptera.http://www.cals.ncsu.edu/course/ent425/compendium/zorapt.html (accessed on October 4, 2004).

The Zoraptera Data Base.http://www.famu.org/zoraptera/links.html (accessed on October 4, 2004).