SPRINGTAILS: CollembolaLUCERNE FLEA (Sminthurus viridis): SPECIES ACCOUNT
Springtails have three distinct body regions (head; thorax, or midsection; and abdomen), no wings, and six legs, but they are not considered true insects. They form a group closely related to insects that includes proturans (order Protura) and diplurans (order Diplura). All of these animals have mouthparts located inside a special pocket in their head.
Springtails range in length from 0.008 to 0.4 inches (0.2 to 10 millimeters). Species living in caves, deep in leaf litter, or soil are whitish or grayish, while those living out in the open are usually darker or brighter in color. Their bodies are covered in flattened hairlike structures called scales. These insects might have no eyes at all, or they might have small groups of simple eyes, each with single lenses. The mouthparts are needlelike for sucking fluids or have grinding surfaces for chewing.
On the underside of the abdomen is a special organ that absorbs moisture from the surrounding habitat, to maintain the body's water balance. Farther back on the abdomen is a forklike structure that inspired the common name "springtail." The six-segmented abdomen does not have pinchers or a tail at the tip.
Springtails are found worldwide, from the tropics to the edges of the polar ice caps.
Springtails live in warm, damp places. They are especially common in leaf litter and soil. Some species are found in caves, the burrows of small mammals, or the nests of ants and termites. They also live in moss, under stones, on the surfaces of ponds and lakes, and along rocky seashores. Others are found high in the trees of tropical rainforests or on the surface of snowbanks. Springtails are sometimes so common in grasslands that there are more than 596,000 individuals per square yard (500,000 per square meter).
Most springtails feed on funguses, organisms that include mushrooms, mold, and yeast. All funguses depend other plants or animals for their food. They also feed on bacteria, tiny living things that are made up of only one cell. Species living in trees or those living in the soil also eat plant material and algae (AL-jee), living things that resemble plants but do not have roots, stems, or leaves. A few species are carnivorous (KAR-nih-vuh-rus), or meat eating, feeding on tiny worms and other springtails and their eggs.
BEHAVIOR AND REPRODUCTION
Springtails "jump" not with their legs but by the springlike release of the forklike structure underneath the abdomen. When released, the "fork" snaps down against the ground and flips the springtail into the air, sometimes as high as 8 inches (20.3 centimeters). This device, present in all but a few springtails, seems to be an effective method to avoid predators, or animals that hunt the springtail for food.
Adults are capable of reproduction only every other time they molt, or shed their external skeleton. Reproduction usually requires a male and female, but some females can produce eggs without a male. Some springtails have elaborate courtship behavior, with males dancing and butting heads with females. Many males leave a sperm packet on the ground that is later picked up by the female. Others place sperm with their hind legs directly into the female's reproductive organs.
Eggs are laid singly or in large masses by several females. Some females cover their eggs with a mixture of chewed-up soil and their own waste, to protect them from mold or from becoming dried out. The eggs hatch into larvae that resemble small adults. They usually molt four or five times before reaching adulthood and continue to grow and molt for the rest of their lives. Some species, especially those living in the tropics, produce several generations every year, and others have only one generation per year. Some Antarctic species may take as long as four years to become adults.
SPRINGTAILS AND PEOPLE
Springtails found in homes are often considered pests, but they do not cause any harm. A few plant-feeding or fungus-feeding species may become pests, damaging alfalfa crops and commercially grown mushrooms. Many springtails play an important role in the environment by breaking down and recycling dead plant materials. They are most commonly encountered in the garden under stones or in compost. Springtails swarming on snow are called "snow fleas."
WALKING ON WATER
Some springtails live on the surfaces of still ponds, lakes, and tide pools. Their dark blue or reddish brown bodies are covered with a waxy, waterproof coating that allows them to live on the surface of the water without getting wet or sinking. Sometimes they gather by the hundreds or thousands, and, in such a group, they resemble velvety mats on the water's surface. However, they do not lay their eggs on the water and must return to land to reproduce.
No springtails are endangered or threatened.
Physical characteristics: Lucerne fleas, also known as varied-springtails, are round and have a distinct and well-developed "fork." They grow up to 0.1 inches (2.5 millimeters) in length. They have long, elbowed antennae (an-TEH-nee) and an irregular pattern of green, brown, and yellow coloring over the body.
Geographic range: Originally from Europe, springtails have spread worldwide.
Habitat: Lucerne fleas live in agricultural fields planted with alfalfa.
Diet: The larvae eat patches of leaves, while adults eat all of the leaf except the veins.
Behavior and reproduction: When disturbed or threatened, Lucerne fleas can jump as far as 12 inches (30.5 centimeters). The male leaves a sperm packet on the soil or attaches it to low vegetation to be picked up later by the female. The female typically lays clusters of up to forty eggs in the soil during winter. Up to three generations are produced each winter. Eggs that are laid in spring are capable of surviving hot, dry conditions. These eggs hatch the following autumn.
Lucerne fleas and people: Lucerne fleas are considered pests in fields of lupine flowers, lentils, beans, and field peas. Predatory mites are used to keep these pests under control.
Conservation status: This species is not endangered or threatened. ∎
FOR MORE INFORMATION
Tavolacci, J., ed. Insects and Spiders of the World. Vol. 7, Owlet Moth–Scorpion. New York: Marshall Cavendish, 2003.
"Critter Catalog: Springtails." BioKids. http://www.biokids.umich.edu/critters/information/Collembola.html (accessed on September 1, 2004).