PROC. ENTOMOL. SOC. WASH. 96(4), 1994, pp. 612-629 LIFE HISTORY AND DESCRIPTION OF IMMATURE STAGES OF PAROXYNA GENALIS (THOMSON) (DIPTERA: TEPHRITIDAE) ON NATIVE ASTERACEAE IN SOUTHERN CALIFORNIA Richard D. Goeden, David H. Headrick, and Jeffrey A. Teerink Department of Entomology, University of California, Riverside, California 92521. Abstract.— Pawxyna geualis (Thomson) is a multivoltine tephritid that develops in flower heads of a broad spectrum of Asteraceae in California. The egg, first through third-instar larvae, and puparium are described and figured for the first time. Distinctive mor-phological differences noted for these immature stages are in the sensilla comprising the lateral spiracular complexes of the meso-and metathorax and in the distribution and incidence of rugose pads on the anterior of the prothorax of the third instar larva. The larvae feed mainly on the ovules and soft achenes, but also may score the receptacle and imbibe sap at fresh wounds in these structures. Pupariation occurs in the larval feeding chamber among fragments of scored achenes. Premating and mating behaviors are de-scribed, including a characteristic, uplifted-wing movement newly designated as "lofting." Mate-guarding behavior by males following copulation is reported, apparently the first example among Holarctic Tephritidae. The principal natural enemies of immature P. genalis were the solitar>\ primary', larval-pupal, endoparasitic, chalcidoid Hymenoptera, Ewytoma sp. (Eurytomidae) and Pteromalus sp. (Pteromalidae). Key Words: Insecta, Paroxyna genalis, nonfrugivorous Tephritidae, mating behavior, immature stages, Asteraceae, flower-head feeding Twenty-one species of Paroxyna are lowed us to complete this study principally known from North America north of Mex-on Eriophyllum lanatum (Thomson) and ico (Novak 1974, Foote et al. 1993). but Senecio mohavensis Gray, two of its many only the life history and immature stages of recently reported host plants (Goeden 1994). P. albiceps (Loew). a common species in the Field observations primarily were made on northeastern United States, have been de-E. lanatum at a study site located in a gently scribed in detail (Novak and Foote 1968). sloping, dry clearing among conifers at This paper describes the life history and im-2030-m elevation in the National Chil-mature stages of a second Nearctic species, dren's Forest, San Bernardino National P. genalis (Thomson), the most commonly Forest (northern section). San Bernardino encountered Paroxyna in California (Goe-Co., during 1990-92. Flower heads con-den 1994) and an adopted natural enemy taining eggs, larvae, and puparia were sam-of the alien weed, tansy ragwort, Senecio pled at this and additional locations on this jacobaea L. (Frick 1964). and other host-plant species reported below and elsewhere (Goeden 1994). Senecio mo-Materiai^ and Methods havensis was sampled weekly during Feb-Locating field populations of P. genalis ruar\' and March, 1993. at 260-m elevation reasonably accessible from Riverside al-in Box Canyon. Riverside Co., in the Col-
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