Antlions are a family of insects given the zoological classification Myrmeleontidae. The name is rooted in the Greek words myrmex (ant) and leon (lion). The family Myrmeleontidae is part of the order Neuroptera, translated variously as "nerve wings," "net wings," or "sinew wings." All Neuroptera have four wings marked by a netlike pattern of veins. The order Neuroptera, which includes dobsonflies and lacewings, is the most primitive order of insects with complete metamorphosis
The name antlion is really applicable only to the larvae, voracious predators that eat ants and other insects. Some species hide under bits of debris or wood and attack passing insects. In sandy regions, some species dig a shallow cone-shaped pit and wait at the bottom for an ant or other insect to slip on the loose sand and fall in, only to be immediately devoured. These pit-digging antlions are called "doodlebugs" in the United States because of the designs they make in the sand. As a doodlebug seeks an ideal location to dig its pit, it leaves meandering trails that resemble the random "doodles" of a preoccupied artist. When it finally finds the right place to dig, the doodlebug "draws" a series of concentric spirals, each deeper than the last, until the pit is excavated.
Adult antlions resemble dragonflies or damselflies (order Odonata) and, like damselflies, they are feeble flyers. Antlions are easily distinguished from Odonata by their longer, prominent, clubbed antennae and different type of wing venation. Compared to other Neuroptera (e.g., lacewings), an antlion's antennae are shorter. The adult is seldom seen in the wild because it is active only in the evening; during the day it rests, motionless, well-camouflaged by its transparent wings and dusk body.
For most North American species, fully developed larvae are as long as a human fingernail—about 1.5 cm (0.6 in.). Adults are approximately 4 cm (1.5 in.) long and have a wingspan of 8 cm (3.2 in.).
The largest forms are found in the predominately African genus Palpares; these have a wingspan of 16 cm (6.3 in.). A very small form in Arabia has a wingspan of only 2 cm (0.8 in.). The largest European species is Acanthaclisis occitanica, with a wingspan of 11 cm (4.3 in.). The other ten or so species native to central Europe are about a third smaller, and only half build sand traps.
Interrelationships with other animals
Of the documented relationships between antlions and other animals, perhaps the most interesting is the relationship in which antlion larvae serve as hosts to parasitic insects. For example, the larvae of the Australian horsefly Scaptia muscula live inside antlion larvae pits, where they share the spoils of the antlions' trapping abilities.
A species of chalcid wasp, Lasiochalcidia igiliensis, is also an antlion parasite. The wasp provokes a host antlion larva into grabbing the parasite's legs in its mandibles, at which time the parasite oviposits into the membrane between the larva's head and thorax (Systematic Entomology Laboratory).
Antlions are often included in lists of beneficial insects, no doubt because they prey upon ants, a common pest to humans.
Antlions can be found in sheltered, sandy areas such as wooded dunes, open forest floors, and dry, tree-lined river banks. They can also be found in the sandy soil of flower beds, under hedges or eaves, in undeveloped city lots, and under buildings set on piers. Antlions have even adapted to the ancient volcanic habitat of Crater Lake in Oregon (USA). Pit-digging antlions are easiest to find because of their distinctive, cone-shaped pits, which often occur in clusters.
Antlions are typically most active during late spring and summer, although they may remain active during winter in warmer climates. Antlions have been observed in Yosemite National Park (USA) even during January, when temperatures dip below 0° C (32° F).
The approximately 2,000 species of antlions are distributed throughout the world, primarily in the warmer regions. In North America, the greatest number of genera and species are found in the southwestern states of the U.S. One of the most common North American species is Myrmeleon obsoletus. The main European species are Myrmeleon formicarius and Euroleon nostras.
After emerging from their cocoons and allowing their wings to expand and harden, adult antlions fly into nearby trees. Nocturnal creatures, adult antlions rest on dry twigs during the day. At night they hang on the twigs, with raised wings.
Mating is a rather acrobatic affair. As the female clings to a twig, the male attaches his tail to hers. He then hangs below her, suspended only by his genital apparatus. Copulation lasts nearly two hours. After separation the female cleans up by feeding on the remaining spermataphore.
Laboratory studies have detected volatile compounds produced by the adult male Euroleon nostras. Researchers hypothesize that these compounds may function as "aggregation" pheromones in antlion mating behavior.
Egg laying, or "oviposition," occurs in the sand. When a female finds a suitable place, she repeatedly taps the sand surface with the tip of the abdomen. She then inserts the abdomen into the sand and lays an egg. This procedure is repeated several times if she remains on a particular patch of sand. During egg laying the wings are raised and move very fast with short wing strokes. In captivity females lay an average of 20 eggs and show a preference for warm sand. After a successful oviposition, fit females return to the tree, where mating possibly occurrs again.
Adult Life Span
A wide range in longevity has been observed in adult antlions. The average life span is 20 to 25 days, but some adults have lived for more than 45 days. Ironically, because they emerge and lay eggs in the sand near active larvae pits, adults may occasionally be captured and eaten by their younger relatives.