LIFE-HISTORY AND DESCRIPTION OF IMMATURE STAGES OF EUARESTA-STIGMATICA (DIPTERA, TEPHRITIDAE) ON AMBROSIA SPP (ASTERACEAE) IN SOUTHERN CALIFORNIA

Euaresta stigmata Coquillett is bivoltine and nearly monophagous on fo ur native ragweeds, Ambrosia spp. (Asteraceae), in the southwestern Un ited States. In southern California, larvae of the spring (F-1) genera tion develop singly in and feed on one or both ovules of young fruitin g involucres of Anbrosia ilicifolia (Gray) Payne, with a small proport ion infesting the staminate involucres. Adults emerge after approximat e to 1 mo, with their reproductive organs immature. The F-2 generation develops in the involucres of fall-blooming Ambrosia acanthicarpa Hoo ker. The egg is described and illustrated for the first time for any s pecies of Euaresta. First, second, and third instars and the puparium are described and illustrated for the first time for E. stigmatica. Th e posterior spiracular plates of all three instars bear only three int erspiracular processes, whereas the larvae and puparia of all other no nfrugivorous tephritids described to date bear four such processes. Ad ult behaviors described from field and laboratory studies include cour tship, copulation, and territoriality. Male courtship displays include three behaviors previously undescribed for Tephritidae: a side-to-sid e dance, rapid side stepping, and a middle leg abduction. Hymenopterou s parasitoids of E. stigmatica include two solitary, primary larval-pu pal, endoparasitoids, Eurytoma sp. (Eurytomidae) and Pteromalus sp. (P teromalidae). Potential use of E. stigmatica as a biological control a gent for ragweeds in Eurasia is discussed.