The Braconidae is a large family of parasitoid wasps. There are approximately 17,000 recognized species and many thousands more undescribed. One analysis estimated a total between about 30,000 and 50,000, and another provided a narrower estimate between 42,000 and 43,000 species. As of 2013, the species are grouped into 47 subfamilies and over 1,000 genera, which include Ademon, Aphanta, Asobara, Bracon, Cenocoelius, Chaenusa, Chorebidea, Chorebidella, Chorebus, Cotesia, Dacnusa, Kollasmosoma, Microgaster, Opius, Parapanteles, Phaenocarpa, and Psenobolus.
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 Ichneumonoidea, 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 intraspecifically. 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 because of caterpillar defense mechanisms such as spines or hairs.
The species Microplitis croceipes possesses an extremely accurate sense of smell and can be trained for use in narcotics and explosives detection.
At least some Braconidae appear to be very resistant to ionizing radiation. While a dose of 400 to 1000 rads can kill an average human, a dose of 180,000 rads was required to kill a braconid of genus Hadrobracon in an experiment.