J. HYM. RES. Vol. 12(1), 2003, pp. 193-208 Food Plants and Life Histories of Sawflies of the Family Argidae (Hymenoptera) in Costa Rica, with Descriptions of Two New Species David R. Smith and Daniel H. Janzen (DRS) Systematic Entomology Laboratory, PSI, Agricultural Research Service, U. S. Department of Agriculture, % National Museum of Natural History, Smithsonian Institution, Washington DC 20560-0168, USA, email: [email protected]; (DJ) Department of Biology, University of Pennsylvania, Philadelphia, PA 19104, USA, email: [email protected] Abstract. — Food plants and biological information are given for 12 species of the family Argidae in Costa Rica: Atomacera raza Smith on Malvaviscus sp. (Malvaceae); Eriglenum crudum Konow on Machaerium acuminatum (Fabaceae); Sericoceros gibbus (Klug) on Coccoloba guanacastensis (Polygon-aceae); Sericoceros mexicanus (Kirby) on Coccoloba venosa and C. uvifera (Polygonaceae); Sericoceros vumirus Smith on Lonchocarpus minimiflorus (Fabaceae); Themos mayi Smith, n. sp., on Meliosma idiopoda (Sabiaceae); Ptilia versicolor (Klug) and Trochophora lobata (Erichson) on Rourea glabra (Con-naraceae); Didymia jonesi Smith, n. sp., on Connarus sp. (Connaraceae); Sphacophilus janzeni Smith on Hymenaea courbaril (Fabaceae); Sphacophilus edus Smith on Heteropterys laurifolia (Malpighiaceae); and Durgoa mattogrossensis Malaise on Bauhinia ungulata (Fabaceae). The male of Durgoa matto-grossensis is described for the first time. All species were reared in the Area de Conservacion Guanacaste, Guanacaste Province, Costa Rica. Little is known of the larval food plants and habits of most Neotropical sawflies. During the course of a Lepidoptera cater-pillar inventory, the second author reared and collected information on the larvae of a number of species of sawflies from the Area de Conservacion Guanacaste (ACG), which lies primarily in Guanacaste Prov-ince in northwestern Costa Rica. Details of the rearing records may be found on the website http://janzen.sas.upenn.edu and in Janzen (2000, 2001) and Burns and Jan-zen (2001). These rearings and notes are significant additions to our knowledge of Neotropical sawflies. Food plants of some species were recorded by Smith (1992, 1995), but life history notes were not in-cluded and several additional species have been reared since, including two new species described herein. We comment on 12 tropical species of the family Argidae. Argidae, Pergidae, and Tenthredinidae are the three dominant families of Sym-phyta in the Neotropics. The Neotropical argid fauna was treated by Smith (1992) who recorded 5 subfamilies, 32 genera, and 356 species. In Costa Rica, 5 subfam-ilies (including the addition of Dieloceri-nae in this paper), 16 genera, and 40 spe-cies are known (Smith 1995). Argidae are recognized by the three-segmented anten-na: scape, pedicel, and long, single-seg-mented flagellum. The flagellum is bifur-cate in some males. At least 22 species in 13 genera of Symphyta have been reared in the ACG. Two species of Argidae for which the food plants are known, Scobina consobrina (Norton) and S. guatemalensis (Dalla Tor-re), have been taken in Malaise traps in ACG but not reared. Both were reared previously from Sidn sp. (Malvaceae), the former in Nicaragua and the latter in Ve-racruz, Mexico (Smith 1992).