J. HYM. RES. Vol. 13(2), 2004, pp. 295-301 The First Gregarious Species of the Agathidinae (Hymenoptera: Braconidae) C. E. Sarmiento, M. J. Sharkey, and D. H. Janzen (CES, MJS) S-225 Department of Entomology, Ag. Sci Cen.-North, University of Kentucky, Lexington, KY 40546-0091 USA; (DHJ) Department of Biology, University of Pennsylvania, Philadelphia, PA 19104 USA; email: djanzen@sas.upenn.edu Abstract. — Coccygidium gregarium Sarmiento & Sharkey, the first known gregarious species of the subfamily Agathidinae (Braconidae), is described. This species was reared from a larva of Euglyphis sp. (Lasiocampidae). The SEM images of its last antennal flagellomere reveal that the characteristic acuminate shape is due to the presence of elongated, presumably sensory, structures. This type of flagellomere, together with its carinate hind trochantellus, are traits present in the genera Coccygidium, Biroia, Dichelosus, Hemichoma and in the Afrotropical genus Hyrtanommatium, suggesting a close phylogenetic relationship. The apex of the ovipositor sheath bears a small pointed process present in other Coccygidium species and also in Biroia, Dichelosus, and Hemichoma but not in Hyrtanommatium; this trait may suggest a close relationship among these genera. SEM images of this structure show that it is covered by ampulliform papillae, here reported for the first time. The pores on the inner apex of the ovipositor sheaths and the ampulliform papillae are either secretory or sensory. The Agathidinae are comprised of ap- proximately 52 genera worldwide, with 20 occurring in the New World. Nearly 1000 species have been described, mostly from tropical areas. The subfamily has been re- vised at the tribal level by Sharkey (1992), and there have been several faunal treat- ments and generic revisions (Muesebeck 1927, Marsh 1961, Nixon 1986, Sharkey 1983, 1986, 1988, 1990, Simbolotti and van Achterberg 1999, van Achterberg 1990, and Briceno 2003). The genus Coccygidium de Saussure, 1892 (in this paper we follow the generic concept of Chou and Sharkey 1989; including Zelomorpha Ashmead) is probably the most species-rich genus of the tribe Disophrini. This genus includes about 35 described species distributed worldwide but more than 100 Neotropical species are awaiting description. Although Coccygidium has never been revised, cur- rent studies (by C.S. and M.J.S.) suggest that the Neotropical genera Biroia Szepli- geti, Hemichoma Enderlein and Dichelosus Szepligeti are derived clades within Coc- cygidium. All agathidines for which there are re- liable rearing records are reported as sol- itary koinobiont endoparasitoids of lepi- dopteran larvae. Members of Bassus and Agathis (Microdini and Agathidini respec- tively) oviposit in the host, placing the egg inside a ganglion of the ventral nervous system or attaching it to the lateral lobe of the protocerebrum; the larva remains as a first instar, floating in the haemocoel, dur- ing the feeding period of the host, and then quickly develops in the final larval and prepupal stage of the host; the final- instar parasitoid emerges after the host has spun its cocoon and completes its feeding externally (Shaw and Huddleston 1991, Sharkey 1997). Coccygidium species, as with all the members of the tribe Di- sophrini, possess short strong ovipositors and parasitize free-living caterpillars in