Parasitoid assemblage size and host ranges in a parasitoid (Hymenoptera)-Agromyzidae (Diptera) system from central Argentina A. Salvo* and G. Valladares Centro de Investigaciones Entomologicas de Cordoba, Universidad Nacional de Cordoba, Avda. Velez Sarsfield 299, CP 5000 Cordoba, Argentina Abstract A parasitoid community on Agromyzidae leafminers from Cordoba, Argentina was analyzed in terms of parasi- toid assemblage size and host ranges of parasitoid species. Samples were taken during 1991-1995 at natural, urban and agricultural habitats. The system consisted of 69 parasitoid species and 51 leafminer species on 109 plant species. On average, 12 species parasitized each host, when only numerically well represented leafminer species were considered for analysis. Each parasitoid species exploited on average seven species and three genera of Agromyzidae leafminers. Both parasitoid assemblage size and parasitoid host range were notably high when compared with similar Systems from other regions. ——————————————————————————————————————— Introduction Leafminers are insects whose larvae feed between the epidermises of leaves, consuming foliar mesophyllum (Askew & Shaw, 1974). In the galleries thus excavated the feeding larvae find shelter against harsh environmental conditions but little protection against parasitoids, which are the most frequent natural enemies of the group. In fact, this guild of phytophagous insects supports the richest parasitoid communi- ties, seemingly due to the physical characteristics of leaf mines (Hawkins, 1988). Parasitoid assemblages of phytophagous insects are usually studied in relation to a definite host spe- cies in a definite habitat. But knowledge of the entire community of parasitoids attacking all available host species within an ecological guild or a phylogenetically related group, on a regional scale over a variety of habitats, is essential to obtain reliable information about parasitoid host ranges, number of shared parasitoid species and host species, etc. (Askew & Shaw, 1986; Godfray, 1994). We aim to contribute to that knowl- edge by analyzing a parasitoid-leafminer-host plant system in Central Argentina. The fauna of leafminers in the study area is largely dominated by Agromyzidae (Diptera) (Valladares, 1982), a family which is well represented worldwide (Spencer, 1990). Knowledge about parasitoids associated with Agromyzidae in Ar- gentina is limited (Diaz & Valladares, 1979; Neder de Roman & Arce de Hamity, 1985; Valladares et al., 1982; Salvo, 1996; Salvo & Valladares, 1993, 1996, 1997) despite the hosts being relatively well known (e.g. Valladares, 1982, 1984, 1991, 1996). This paper provides a description of the system, analyzing the size of parasitoid assemblages on Agromyzidae species and parasitoid host ranges. Materials and methods Mined leaves were sampled from 1991 to 1995 at 30 localities in Cordoba province, central Argen- tina, including natural, urban and agricultural habitats. Some localities were sampled monthly whereas others were visited occasionally. Mined leaves of each available host plant were cut and placed in plastic bags, in which they were carried to the laboratory and kept until flies and parasitoids emerged. Special ——————————————————— * Fax: 5451 332097