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The Braconidae constitute one of the most species-rich families of insects. Although tropical faunas are still relatively poorly understood at the species level, most taxonomists in this group would agree that a rough, probably highly conservative, estimate of 40-50,000 species worldwide is reasonable as an extrapolation from the current described number of roughly 12,000 species. Among extant groups, the sister group of the Braconidae is the Ichneumonidae, an equally enormous group (Sharkey and Wahl, 1992; Quicke et al. 1999).
The family appears to date from early Cretaceous (assuming Eobracon is properly assigned to family - Rasnitsyn, 1983; Whitfield, 2002), diversifying extensively in the mid to late Cretaceous and early Tertiary, when flowering plants and their associated holometabolous herbivores, the main hosts for braconid parasitoids, radiated (Basibuyuk et al., 1999; Quicke et al., 1999; Belshaw et al., 2000; Whitfield, 2002). The species richness of the family is matched by a morphological diversity virtually unrivalled among the Hymenoptera. They range in size from approximately 1 mm in length to 3-4 cm (not counting the ovipositor, which in some species can be several times as long as the body).
Figure 1. Microgastrine braconid adult female (length approx. 2 mm). Image copyright © 2004 James B. Whitfield
Some of the groups are parts of extensive Müllerian mimicry complexes (Quicke, 1986), and exhibit striking color patterns (some of which are recurrent within regions), while others are among the most inconspicuous of Hymenoptera. The braconids display a bewildering array of wing venation patterns and body forms to stymie the beginning student. Female external genitalia (ovipositor mechanisms) vary considerably intraspecifically and are widely used for species discrimination;
Figure 2. Ovipositior mechanism of Andesipolis, for reaching into plant tissue. Image copyright © 2004 Won-Young Choi
Figure 3. Ovipositor mechanism of Cotesia, for inserting eggs into exposed caterpillars. Image copyright © 2004 Won-Young Choi
while the male genital capsules tend to be somewhat more conservative and have been underutilized relative to other insect groups.
Figure 5. Male genital capsule of Hypomicrogaster, from a relatively derived (microgastroid) lineage.
Image copyright © 2004 Josephine Rodriguez