views updated May 21 2018

Hymenoptera (ants, bees, sawflies, wasps; class Insecta, subclass Pterygota) Very large, complex, and diverse order, whose members show a high degree of adaptive radiation. There are two suborders, the Symphyta (sawflies), which do not have a constricted waist, and the Apocrita (ants, bees, and wasps), of which there are about 105 000 species worldwide, in which the waist is constricted. Hymenoptera have two pairs of wings, the fore wings a little longer than the hind wings, and both pairs with relatively few veins. In flight, the wings can be linked together by means of hamuli. Adults can be found in a large variety of habitats. They have mouth-parts that are either adapted for chewing or with the maxillae and labium modified to form a proboscis for sucking nectar, etc. The antennae are usually fairly long, with 10 or more segments. The ovipositor may be modified for sawing, piercing, or stinging (for defence or the paralysis of prey and hosts). Members of the order have complete metamorphosis, the pupae being adecticous, and usually exarate. Pupation normally takes place in a cocoon, in a special cell, or in the body of the host (in the case of parasitic species). The larvae of many species are plant feeders; many others are parasitic, living in or upon the bodies of other insects; still others live in special nests, constructed by the adults, and feed on materials with which the nest is provisioned. Some Hymenoptera are social insects whose life histories and biology are well known. Many Hymenoptera are extremely useful in the biological control of pest species. Some are important pollinators. Others are pests of cultivated plants, in some cases causing serious defoliation. The taxonomic characters used in the classification of the order include wing venation, the legs, the antennae, the pronotum, the thoracic structures, and the ovipositor.


views updated May 23 2018

Hymenoptera An order of insects that includes the ants, bees, wasps, ichneumon flies, and sawflies. Hymenopterans generally have a narrow waist between thorax and abdomen. The smaller hindwings are interlocked with the larger forewings by a row of tiny hooks on the leading edges of the hindwings. Some species are wingless. The mouthparts are typically adapted for biting, although some advanced forms (e.g. bees) possess a tubelike proboscis for sucking liquid food, such as nectar. The long slender ovipositor can serve for sawing, piercing, or stinging. Metamorphosis occurs via a pupal stage to the adult form. Parthenogenesis is common in the group.

Ants and some bees and wasps live in colonies, often comprising numerous individuals divided into castes and organized into a coordinated and complex society. The colony of the honeybee (Apis mellifera), for example, consists of workers (sterile females), drones (fertile males), and usually a single fertile female – the queen. The sole concern of the queen is egg laying. She determines the gender of the egg by either withholding or releasing stored sperm. Unfertilized eggs become males; fertilized eggs become females. The workers fulfil a variety of tasks, including nursing the developing larvae, building the wax cells (combs) of the hive, guarding the colony, and foraging for nectar and pollen. The single function of the larger drones is to mate with the young queen on her nuptial flight.