The insect order Neuroptera contains a diverse group of around 6,000 species. The name comes from the Greek words “neuron” (nerve) and “ptera” (wing), translating to “net-winged insects.” This name is a direct reference to the intricate pattern of veins that cover their two pairs of wings, giving them a delicate, lace-like appearance. This order includes widely recognized insects such as lacewings and antlions.
Defining Characteristics of Neuroptera
Adult neuropterans are identified by their two pairs of membranous wings, which are roughly equal in size. When not in flight, these insects hold their wings in a tent-like fashion over their soft bodies. Their heads are equipped with large compound eyes and a pair of long, slender antennae. They possess chewing mouthparts with strong mandibles designed for predation.
The size of these insects can vary considerably. Their generalized body plan, with few specialized features beyond their wings and mouthparts, has proven to be a successful evolutionary model.
The Complete Metamorphosis
All members of Neuroptera undergo a complete metamorphosis, involving four distinct life stages: egg, larva, pupa, and adult. This process means the immature and adult forms look vastly different and often occupy separate ecological niches. Some species, like green lacewings, lay eggs on slender silk stalks, elevating them from surfaces and potential predators.
From the egg hatches a larva, a stage dedicated to feeding and growth. Neuropteran larvae are active predators, equipped with specialized, sickle-shaped jaws to capture other invertebrates. After molting several times, the larva seeks a protected location to enter the pupal stage and spins a silk cocoon.
Unusually, this silk is produced by excretory organs called Malpighian tubules and spun from the anus. Inside the cocoon, the insect reorganizes its body into the adult form, which eventually emerges to focus on dispersal and reproduction.
Common Families and Their Habits
The green lacewings (Chrysopidae) are common in gardens and agricultural fields. Their larvae are known as “aphid lions” due to their appetite for aphids. These predators also consume mites, scale insects, and the eggs of other insects, making them a welcome presence for farmers and gardeners seeking natural pest control. The adults of many lacewing species feed on nectar, pollen, or honeydew.
The antlions, belonging to the family Myrmeleontidae, are known for the hunting strategy of their larvae. These larvae dig conical pits in loose, sandy soil, burying themselves at the bottom with only their jaws exposed. Unsuspecting ants and other small insects that slip over the edge of the pit slide down the sandy slope into the waiting mandibles of the predator.
The mantidflies (Mantispidae) exhibit convergent evolution with praying mantises. Adult mantidflies have enlarged forelegs adapted for grasping prey, much like a mantis, despite not being closely related. Their life cycle is specialized; the larvae of many species are parasites that seek out spider egg sacs to complete their development, feeding on the spider eggs within the silken case.
Ecological Significance
The primary ecological role of Neuroptera is that of predator, making them a significant force in regulating populations of other arthropods. Their larvae, in particular, are effective hunters in a variety of environments, from vegetation to the soil.
In agricultural and garden settings, the presence of lacewings can significantly reduce the numbers of common pests like aphids and whiteflies, decreasing the need for chemical pesticides. Antlions contribute to controlling ground-dwelling insect populations. By preying on a wide array of small, often herbivorous insects, neuropterans help maintain balance within food webs and contribute to the health of ecosystems.