A painless look at some of the state's most interesting insects.
Getting stung by an insect is a painful and usually memorable event. We learn from an early age to recognize and avoid insects that are brightly patterned with yellow or orange and black, or that are slender and have slender and sharply pointed rear ends, or that buzz about in a menacing way. The perception that stinging insects are instinctively aggressive at any time and place is wrong, however, and blinds us to the role they play in nature's balance. Stinging insects include species that are essential for the pollination of fruits, vegetables and flowers. Others are important predators of pest insects that eat both wild and cultivated plants. From this perspective, then, stinging insects are beneficial fellow creatures in this world. What is the real story about stinging insects?
Stinging insects are wasps, bees and ants of the Order Hymenoptera. As true insects, they have three body regions, six legs, antennae and compound eyes. Hymenoptera are further characterized by two pairs of membranous wings. Not all Hymenoptera can sting. The stinging Hymenoptera are in the Suborder Aculeata (from the Latin word aculeus, which means "sting"). Aculeata have tonguelike mouthparts for drinking and mandibles for chewing. All have a slender thread waist. The stinger is modified from the ovipositor, a structure that in most insects (including non-stinging hymenopterans) is a conduit for laying eggs. Aculeata lay eggs from an opening that bypasses the stinger. Since the stinger is modified from the ovipositor, you can be certain that if you have been stung by a wasp, bee, or ant, it was a female. Young Aculeata are grublike, soft-bodied, white and generally helpless. After feeding they undergo pupation, a tissue reorganization stage that transforms them into adults.
No Missouri ants inflict painful stings, but Missouri is home to hundreds of species of wasps and bees. Though most can sting (some are too small), only a few have stings that are painful and whose behavior is aggressive enough to make them pests. Most have only mildly painful stings and are rarely or never aggressive. Stinging insects with stings that hurt are usually large, or they live in social colonies.
The organ pipe mud dauber, Typragilum politum, illustrates the anatomy
of wasps and bees. The three body regions (head, thorax, abdomen),
six legs, antennae and compound eyes are common to most insects. The
two pairs of membranous wings characterize Hymenoptera; the thread
waist characterizes Aculeata. The sting of most female Aculeata is
concealed within a sting chamber. Illustration by Bernice B. DeMarco.
Adult bees and wasps feed on nectar from flowers and other liquid foods. Most young wasps are fed other insects, while young bees are fed pollen mixed with nectar. Nests of bees and wasps are often similar. Most Missouri stinging insects have nests built and provisioned by only a single female; that is, the species are solitary. Solitary species do not make hexagonal nest cells of wax like the honeybee. Nest cells of ground nesting bees are small cavities lined with waxlike secretions, excavated at the ends or along the sides of tunnels. They are sealed with a soilcap after being provisioned with a pollen/nectar mass and an egg. Ground nesting solitary wasps construct similar nests and cells, but the cells usually lack a waxlike lining. Insects or spiders that have been paralyzed by the wasp's sting are placed into the cell with the wasp's egg before the cell is sealed. Virtually all ground nesting solitary species use dirt to back-fill the tunnels they have excavated.
Many solitary species nest in hollow twigs or cavities such as beetles bore in logs. A few excavate their own cavities in twigs and wood. All of these usually construct a line of cells in the nest chamber separated by partitions of mud, pebbles, masticated vegetation, leaf and flower pieces, resin, wood chips, or compounds secreted by the bee. Completed nests are plugged at the entrance with similar materials. The nests of a few species of bees are simple small, exposed cells made largely of plant resin and attached to twigs, leaves or rocks. Mud daubers and potter wasps make nests of mud.
The young of most solitary species pass the winter dormant in nests and emerge as adults the following year. Adult males usually emerge from nests a day or two before females. They often live only a few days or weeks and have no function other that to fertilize the newly emerged females. Adult female solitary bees and wasps do all work associated with nest construction and provisioning, and usually live for only a month or two.
Only a few of Missouri's wasp and bee species are social. These include yellowjackets, hornets, paper wasps, bumblebee and honeybees. The honeybee lives in colonies year round, and its life history is not like native Missouri social species. A newly founded nest of a native social species may have only a single female in early spring, but by mid-to late-summer a colony can have from dozens of adults (paper wasps and bumblebees) to thousands (yellowjackets). The sting of social wasps is not used to paralyze prey as it is by solitary species; instead it is used to defend the nest and young. Since the sting of social species serves an exclusively defensive function, it is not surprising that it hurts!
Most adults of a social bee or wasp colony are worker females. Only a single egg-laying queen is typically present. Cooperative care of developing young by workers is characteristic of social species. Young social wasps and honeybees live in unsealed nest cells, and the workers give them food directly. Bumblebee young live in cells that may be open or closed and workers may feed the growing young directly or may place food in cells with young. Social sweat bees "mass provision" and close their cells in the same way as solitary bees.
In late summer, males and young queens of native social species are reared by successful colonies. Mating takes place in the fall. The egg-laying queen, all of the workers, and all of the males die by the end of the season. Only newly fertilized queens survive the winter to begin the cycle again the following spring.
