Lacewings Antlions and Relatives: Neuroptera

Many adult neuropterans are active at dusk or in the evening and are attracted to lights. During the day they remain inactive and hidden among vegetation. Some species rely on camouflage to avoid detection by predators. Some brown and green lacewings will pretend to be dead when threatened. Others produce a bad odor to discourage predators. Some mantidflies not only mimic the color and appearance of paper wasps but will also adopt their movements and postures when disturbed.

Larvae engage in a variety of behaviors to capture prey. The larvae of owlflies are "sit-and-wait" predators, ambushing hapless prey as they walk into their open jaws. Some antlions hide at the bottom of cone-shaped pits they construct to trap crawling insects. Green lacewings, brown lacewings, and dustywings actively hunt for prey, as do larvae living in freshwater habitats. Spongilla flies eat only freshwater sponges and moss animals and use their incredibly long and slender jaws to pierce individual cells. Some species living along the shore use their long jaws to probe wet sand and mud for fly larvae. Pleasing and silky lacewings hunt in crevices and under bark for arthropods (AR-thruh-pads), or animals with hard outer skeletons and several pairs of jointed limbs, such as insects and spiders. The first and third stages of beaded lacewing larvae burrow in the soil in search of termites, while the second state is inactive and does not feed.

The larvae of mantidflies feed in spider egg sacs or in the nests of social wasps. Immediately after hatching, the larvae that prey on spider eggs actively seek a suitable host spider and climb up on its body. Eventually the larvae enter the egg sac to feed. The second and third larval stages look very different from the first stage and have very large, bloated abdomens. Scientists think that these larvae might produce chemicals that slow down the development of the spider eggs to give them plenty of time to feed. Mantidfly larvae are specialists and attack only a single species or several closely related species of spiders.

Only two groups of neuropteran larvae are not predators. Moth lacewings eat sap from the roots of trees and shrubs as they burrow through the soil. It is not known what the larvae of giant lacewings eat, but their mouthparts are blunt and unsuitable for stabbing insect prey.

Many neuropterans use chemicals to communicate with potential mates during courtship. Males have special organs on their abdomen or wings that produce pheromones, chemicals that are attractive to females. Green lacewing males use sound to attract mates, vibrating their abdomens to communicate with females.

Males and females must mate to produce eggs that will develop into larvae. Males deposit sperm directly into the reproductive organs of the female. Mating is either brief or lasts up to several hours. Mating usually occurs when a male and female meet, but swarms of mating moth lacewings have been observed in Australia and the United States.

The life cycle of neuropterans includes four very distinct stages: egg, larva, pupa, and adult. Eggs are laid one at a time or in batches on rocks, bark, or in crevices of bark. Some species of green lacewings, mantidflies, and split-footed lacewings lay a single egg on top of a silk stalk. This keeps them out of the reach of hungry predators, especially other lacewing larvae. There is little or no parental care of the eggs. The larvae look nothing like the adults and do not live in the same habitat. The larvae usually molt, or shed their exoskeletons or hard outer coverings, three times over several months or years before transforming into a pupa. The pupa is formed inside a silk cocoon. Neuropteran larvae produce silk with special organs inside their abdomen. These same organs work like kidneys in other insects, filtering out waste in the blood. The legs and wings of the pupa are not completely attached to the body and the abdomen is capable of some movement.