All the members of this order are predatory in either the immature or adult stage or both. The adults lack anal cerci and many have elongated sickle-shaped mandibles. Many of the larval stages also possess sickle-shaped mandibles.
Right. A Dobsonfly with Greatly Exaggerated Sickle-shaped Mandibles. Image Courtesy of Bugbios, Dexter Sear.
The family Corydalidae contains the dobsonflies and fishflies. They typically are large insects with a body usually longer than one inch Or larger. They often have long filamentous antennae; though in male fishflies, they are characteristically feathered. The four large wings are translucent, smoky grey, or mixed, and the front pair is slightly longer than the posterior pair.
The eastern dobsonfly is the most well-known North American species. The males have distinctly elongated mandibles. The genera in which the males have normal mandibles are the fishflies. The summer fishfly is perhaps the best-known of these in North America. Summer night skies in the Upper Mississippi River region are populated with massive mating swarms every year. These flights are similar to those of the mayflies in many areas worldwide. Eventually, millions of carcasses remain to be cleaned up the next day. The larvae are aquatic, active, armed with strong sharp mandibles and breathe by means of abdominal brachial filaments. When full sized — which can take several years — they leave the water and spend an inactive pupal stage in chambers near streams and under stones or logs.
Right Typical Dobsonfly Male Adult. Image Dr. Kaae. Right Dobsonfly Larva. Image Courtesy Dellaray923 CC BY- SA 2.5 International
Snakeflies. Snakeflies are usually found in temperate coniferous forest. They are distributed widely around the globe: Europe and Asia, and can be found in certain regions of Africa, and western North America and Central America. In Africa they are only found in the mountains north of the Sahara desert. In North America they are found west of the rocky mountains, and range from south west Canada all the way to the Mexican-Guatemalan Border which is the farthest south they have been found on the western hemisphere. In the eastern hemisphere, they can be found from Spain to Japan. Many species are found all throughout Europe and Asia with the southern edge of their range in northern Thailand and northern India. Even though there is a large distribution of this insect order, individual species distribution is often very limited and some species are confined to a single mountain range. It was once thought that larvae were only found in the bark of trees, in part due to females' long ovipositor. Besides tree bark, larvae have also been found in soil, detritus, and around the roots of trees or smaller shrubs. The eggs can absorb the nutrients through the soil or detritus before larvae hatch.
Snakefly. Image Courtesy Beentree/foto/insect CC BY-SA 3.0
Green Lacewings. These are a much better known group of insects than the brown lacewings. They are typically much larger (0.6 to 0.8 inch body length) and lack the hairy appearance of the body and wings of their brown relatives. As their name implies, most are green, although shades of yellow are also common. The adults are chiefly nocturnal, while the larvae may be active during the day.
Green Lacewing Adult. Image Courtesy of entomart.
The eggs are deposited on a thin elongated stalk that serves for protection against predatory insects such as ants or even their own hatching siblings. This engineering feat is accomplished by the use of a quick drying material that is produced by a gland at the tip of the abdomen. A drop of this material is placed on a leaf and then the abdomen is quickly raised, drawing it into the thin stalk. Subsequently the egg is deposited on the stalk. The eggs of green lacewing are commercially available and are used as source of biological control of a number of pests.
Some species of ants have developed the ability to climb the stalk, cut it and carry off the egg. There are a few species of green lacewings that place small droplets of oils along the length of the stalk. This oil is repulsive to ants and also makes the stalk more difficult for the ants to climb. Of course this also makes it more difficult for the newly hatched lacewing larvae to climb down the stalk. This feat is easily accomplished as the larva simply consumes the oil as it descends.
The adult green lacewings have a variety of defensive mechanisms. When disturbed they emit a defensive stench from a pair of glands located in the thorax. One of the chemicals in this secretion is skatole, one of the main components that give mammalian feces its smell. Put more simply, they smell like poop.
As with some moths they can detect echo-locating pulses from a hunting bat and therefore are able to take defensive maneuvers when pursued. They are also frequently capable of avoiding detection of a spider once caught in its web. They are relatively light bodied and initially may not be detected by a spider once hitting its web. Subsequently, they do not flutter frantically in the spider’s web (as with many insects), but proceed to slowly and precisely work their way out. Initially the lacewing uses its mouthparts to cut any strands that have entangled its body, legs and/or antennae. If its wings are entangled, the lacewing relies on gravity as it very slowly slides down the web to freedom. The veins of the wings of a green lacewing are covered by very fine erect hairs which prevent the web strands from reaching the flat membranous wing surface. It may take up to an hour for this whole process to work, but this is certainly better than the alternative-becoming dinner!
The Eggs of a Green Lacewing on Thin Stalks. Image Courtesy of Whitney Cranshaw, Colorado State Univ., Bugwood.
The larval stage is predatory and feeds on aphids, mealybugs, other homopterous insects and mites. Frequently they are referred to as “aphid lions.” They are easily recognized by the sickle-shaped mandibles and by the presence of prominent body tubercles ending in tufts of hairs. Some species camouflage themselves by heaping bits of litter and even the dead remains of their prey on their back. A common name for these species is the “trash carriers.” The entire life cycle generally takes 5 to 6 weeks with the larvae passing through 3 instars. These insects overwinter as pupae, generally in leaf litter on the ground.
Larval Stages of a Green Lacewing. Left-Larvae with Remains of Its Prey on Back. Image Courtesy Peter Chew. Right Image Dr.
Brown Lacewings. Species of brown lacewings are similar in overall body shape and biology to the green lacewings. Most brown lacewings are yellow to dark brown, a few green species. They are typically smaller than green lacewing and have the typically net-like veination in the wings. Brown lacewings differ from green lacewings in having forked costal cross veins as opposed to straight parallel costal veins. As with green lacewings, their larvae and adults are predatory on aphids and other soft bodies insects.
Brown Lacewing. Image Courtesy entomart.
Antlions. This is the largest group of Neuropteran in North America, occurring most commonly in the south and west. The adults are not as commonly recognized as the larval stage. Adults resemble damselflies with their stalk-like abdomens, but possess elongate club-shaped antennae that are frequently hooked at the tip. They are rather weak fliers and attracted to lights, especially in summer months. Their eggs are deposited in sand. There are about 2,000 species. Strictly speaking, the term "antlion" applies to the larval form of the members of this family, but while several languages have their own terms for the adult, there is no widely used word for them in English. Very rarely, the adults are called "antlion lacewings."
The antlion larva is often called "doodlebug" because of the odd winding, spiraling trails it leaves in the sand while looking for a good location to build its trap, as these trails look like someone has doodled in the sand.
Antlions are worldwide in distribution and are most commonly found in arid and sandy habitats. A few species occur in cold-temperate places. They can be fairly small to very large Neuroptera (wingspan range of 2–15 cm). The antlion larvae eat small arthropods - mainly ants - while the adults of some species eat pollen and nectar and others are predators of small arthropods. In certain species the larva, although resembling that of the genus Myrmeleon structurally, do not make pitfalls, but seize passing prey from any nook or crevice in which it shelters.
They are very feeble fliers and are normally found fluttering about in the night in search of a mate. The adult is thus rarely seen unless attracted to light. They are highly active in desert regions and can be a nuisance. They are capable of delivering a small, mildly painful bite.
The life cycle of the antlion begins with oviposition (egg-laying). The female repeatedly taps the sand surface with the tip of her abdomen. She then inserts her abdomen into the sand and lays an egg. The antlion larva is a ferocious-appearing creature with a robust body, a very plump abdomen and the thorax bears three pairs of walking legs. Depending on species and where it lives, the larvae will either hide under leaves or pieces of wood, in cracks of rocks, or dig pits in sandy areas. Ant lion larvae are unusual among the insects as they lack an anus. All the metabolic waste that is generated during the larval stage is stored and is eventually emitted as meconium near the end of its pupal stage.
The Adult of Antlion-Note the Hooked-Clubbed Antennae, Image Courtesy entomart.
Antlion larvae (doodlebugs) are strange looking insects with elongated sickle-shaped mandibles and fringed lateral projections on the abdomen. Some larvae remain motionless on the surface of the soil or buried just beneath the surface waiting for passing prey. When aroused, they give chase and quickly subdue the victim with their piercing jaws.
Antlion Larvae or Doodlebugs. Left. Dr. Kaae. Right. Courtesy entomart.
In more notorious species, the larvae capture their prey by means of a pitfall. They construct a small cone-shaped pit in the soil and remain buried at the bottom. When a passing ant or other potential prey falls in, the larva will begin to jerk its flattened head upward, throwing sand in an attempt to undercut the sloping walls of the pit. If the ant does not fall to the bottom of the pit due to the quickly eroding walls, it may be knocked down by the catapulting sand particles. Once captured, the ant is quickly pulled below the soil and consumed.
Antlion Larval Pits. Image Dr. Kaae.
Mantispids. Although possessing many of the characteristics of other Neuroptera, mantispids look more like mantids than lacewings. They are smaller (more or less 1 inch in length), but possess the large raptorial front legs and a similar body of a mantid.
Mantispids. Image Courtesy of entomart.
The adults of these bizarre insects are obviously free-living predators (equipped with raptorial front legs), while the larvae of some species exhibit a very unusual existence. These feed on the eggs of spiders. Because spider eggs are not that easy to find and, when found, can be a dangerous commodity (some spiders guard their egg sacs and are capable of eating adult mantispids). These insects have developed a rather ingenious means of reaching their prey. The adults deposit their eggs on the ends of short stalks that are attached to leaves (much like those of the green lacewings). Once hatched, some of the very active tiny larvae seek out a spider and hop on. They ride on the spider until she lays her eggs (if they are lucky enough to find a female). If not, they presumably wait for the male to find a mate and subsequently transfer to the female during mating. This would be the case particularly in spiders where the female eats the male after mating. While riding on the spider the larvae may feed by crawling into the spider’s book-lungs and snack on her blood. When the spider molts in preparation for egg laying, the larvae will leave the book-lungs and sit on top of the spider’s petiole (the thin stalk (waist) that attaches the cephalothorax to the abdomen) until the eggs are deposited. Once deposited, the tiny larvae quickly crawls into the egg mass before the spider coats it with a protective silk covering. The larvae feed and complete their life cycle (except the adults) within the egg mass.
Owlfly Adults, Eggs, and Larvae of Owlflies. Left Image Courtesy Brand Haynold. CC BY-SA 3.0. Right Courtesy Peter Chen Brisbane Insects.
Owlflies are readily distinguished from dragonflies by the antennal and wing shape. The former has an elongated thread shaped antenna terminating in a ball shaped club while the latter is bristle lik and not readily visible. Adults and larvae are predatory with the latter either chasing down their prey or are ambush predators and lie on the ground or in vegetation covered with debris, waiting for next meal. When disturbed, some species produce a strong, musk-like chemicals to deter enemies. Many species are most active at sunset and dawn and during the day rest on stems and twigs with the body, legs, and antennae pressed to the stem. The abdomen in a few species is held up, projecting into the air, to look like a broken twig.