Ants Sawflies Bees and Wasps: Hymenoptera

Only some ants, bees, and wasps sting. In these species only the females can sting. They use their egg-laying tubes, or ovipositors, to deliver a painful venomous sting that burns and itches. The burning is caused by an acid that is released into the wound with the venom or poison.

The larvae of parasitoid wasps spend their lives with their hosts, while the adults are free to move about the environment. Using special chemicals produced inside their bodies, some parasitoid larvae paralyze their larval hosts and stop them from growing. In other species they allow the host larva to continue to feed and grow so that it reaches maximum size, but it will die before reaching maturity. Depending on species, parasitoids either feed on the inside or outside of the bodies of their hosts. Some species feed alone, while others attack their hosts in groups. There are even some hymenopteran parasitoids that attack other hymenopteran parasitoids.

The larvae of many wasps live as parasitoids inside the bodies of insect larvae. The adults freely move about the environment and are often seen on flowers. For example, female scoliid wasps attack beetle grubs in their burrows or underground pupal cases. After laying her eggs, the females leave. The larvae will hatch, feed, and develop without any assistance. These and other wasps may or may not use their stings to paralyze their larvae's future hosts.

Other wasp females must first locate, capture, and paralyze food for their larvae, usually caterpillars, crickets and katydids, and spiders. They then drag their victims to a cavity or crevice (KREH-vuhs) in the ground or stuff them into previously built nests. Metallic blue or green cuckoo bees, which are actually thick-bodied wasps, do not construct nests and rely on the food stores of other hymenopterans to feed their young. Potter wasps build a potlike mud nest and lay their eggs inside. Then they provide the nest with all the paralyzed spiders necessary to feed their young through pupation and seal it with more mud. Hornets, paper wasps, and yellow jackets continue to feed their larvae as they develop. Many bees also continue to feed their young as they develop, but they give them pollen and nectar instead of insects and spiders.

All ants, but only some bees and wasps, are truly social insects. Social insects live in colonies with multiple overlapping generations that share the duties of rearing the young, gathering food, defending the colony, and expanding and repairing the nest. The labor is divided among different castes, or forms. The worker caste takes care of most of the nest chores. Some species have a soldier caste. Soldiers are larger, more powerfully built individuals that defend the nest. Workers and soldiers are always sterile females and are unable to mate or reproduce. Only members of the reproductive caste, queens and males, can mate and reproduce. The males are short-lived and die soon after mating. Queens mate one or more times before they start a new colony and never have to mate again. They will store enough sperm in a special sac in their abdomen to fertilize thousands to millions of eggs. Social hymenopterans use mud, leaves, and chewed-up bits of wood that are formed into paper or a paperlike material to build their nests.

Males of parasitic species usually look for emerging females in places where their hosts live. They will sometimes fight with other males to defend these sites. Others form mating swarms to attract females. In most hymenopterans, the females release pheromones (FEH-re-moans), chemicals that are very attractive to males of the same species. Courtship is common among ants, bees, and wasps and involves touching each other with antennae (an-TEH-nee), or sense organs, and vibrating legs and wings.

The life cycles of hymenopterans include four very distinct stages: egg, larva, pupa, and adult. In some parasitic species, a single egg will develop into several individuals. In many species females determine the sex of their offspring by controlling which eggs are fertilized. Fertilized eggs become females, while unfertilized eggs develop into males. They can also speed up or slow down the growth of their populations by producing females or males.

Sawflies and their relatives lay their eggs on or in leaves, stems, wood, and leaf litter. The females of some sawflies will stand guard over their egg masses until they hatch. Mature larvae pupate inside plant tissues or in the soil. Most species produce only one generation each year and overwinter, or last through the winter, as larvae.

Parasitic and parasitoid females search for and select the right host by using highly sensitive organs on their antennae and ovipositors. Some females will use only one host or a few closely related host species. Others will lay their eggs on a variety of similar hosts, such as caterpillars, in a specific habitat. Most parasitoids lay their eggs on or in the body of the host. The females often have long ovipositors to lay eggs in cocoons, burrows, and other protected places.

The larvae of sawflies and their relatives molt, or shed their exoskeletons, or hard outer coverings, up to eight times before becoming a pupa. Females sometimes molt one more time than the males of their species. In all other Hymenoptera the larvae molt up to five times before reaching the pupal stage.