Braconidae

The Braconidae are a family of parasitoid wasps. After the closely related Ichneumonidae, braconids make up the second-largest family in the order Hymenoptera, with about 17,000 recognized species and many thousands more undescribed. One analysis estimated a total between 30,000 and 50,000, and another provided a narrower estimate between 42,000 and 43,000 species. The Braconidae are currently divided into about 47 subfamilies and over 1000 genera, which include Aerophilus, Aleiodes, Apanteles, Asobara, Bracon, Cenocoelius, Chaenusa, Chorebus, Cotesia, Dacnusa, Diachasma, Microgaster, Opius, Parapanteles, Phaenocarpa, Spathius, and Syntretus. These fall to two major groups, informally called the cyclostomes and noncyclostomes. In cyclostome braconids, the labrum and the lower part of the clypeus are concave with respect to the upper clypeus and the dorsal margin of the mandibles. These groups may be clades that diverged early in the evolution of braconids. The morphological variation among braconids is notable. They are often black-brown (sometimes with reddish markings), though some species exhibit striking coloration and patterns, being parts of Müllerian mimicry complexes. They have one or no recurrent veins, unlike other members of the other famlily in Ichneumonoidea (Ichneumonidae), which usually have two. Wing venation patterns are also divergent to apparent randomness. The antennae have 16 segments or more; the hind trochanters have two segments. Females often have long ovipositors, an organ that largely varies interspecifically. This variation is closely related to the host species upon which the wasp deposits its egg. Species that parasitize microlepidopterans, for instance, have longer ovipositors, presumably to reach the caterpillar through layers of plant tissue. Some wasps also have long ovipositors to bypass caterpillar defense mechanisms such as spines or hairs, or to reach deeply-burrowed Coleoptera larvae in tree trunks. The larvae of most braconids are internal or external primary parasitoids of other insects, especially the larval stages of Coleoptera, Diptera, and Lepidoptera, but also some hemimetabolous insects such as aphids, Heteroptera, or Embiidina. Most species kill their hosts, though some cause the hosts to become sterile and less active. Parasitoidy on adult insects (particularly on Hemiptera and Coleoptera) also occurs. Members of Mesostoinae are known to form galls on plants. Braconids are often used as biological pest control agents, especially against aphids.