PROC. ENTOMOL. SOC. WASH. 86(3), 1984, pp. 486^92 BIOLOGY OF TRIMERINA MADIZANS, A PREDATOR OF SPIDER EGGS (DIPTERA: EPHYDRIDAE) B. A. FooTE Department of Biological Sciences, Kent State University, Kent, Ohio 44242. Abstract. — iovrmX\on is presented on the natural history, life cycle, and larval feeding habits of Trimerina madizans (Fallen), an uncommon but widely distrib-uted species of Ephydridae. Females oviposit into the egg masses of the wetland spider Hypselistes Jlorens (Cambridge), a species of Micryphantidae. Larvae de-stroy the spider eggs and form puparia within the silken covering of the egg masses. The developmental period from egg deposition to emergence of adults averages 23 days. Apparently there is only one generation a year in the latitude of northern Ohio. Information is given on a species of Ichneumonidae (Hymenoptera) whose larvae also attack the eggs oi Hypselistes. The life cycle of T. madizans is contrasted and compared to that of Scatella picea (Walker), an algae-feeding, r-selected species of Ephydridae. The family Ephydridae is generally considered to be closely related to the family Drosophilidae within the superfamily Drosophiloidea (Hennig, 1958; Griffiths, 1972). Although the two families differ in number of species (Drosophilidae, 2500 species; Ephydridae, 1 400), both are widely distributed, have larvae that are largely microphagous, and have short generation times. Species of Drosophilidae are usually encountered in shaded woodland habits and have larvae that ingest mostly heterotrophic microorganisms such as yeasts and bacteria (Carson, 1971; Heed, 1968). In contrast, ephydrids are most commonly found in unshaded wetland habitats, and many species have larvae that feed primarily on autotrophic mi-croorganisms such as algae (Deonier, 1972; Foote 1979). Interestingly, both fam-ilies contain species that seemingly have abandoned the microphagous feeding habit and shifted to other nutrient sources. For example, predation on spider eggs occurs in both families. In Hawaii, larvae of species of the scaptomyzine genus Titanochaeta have been reported to attack the developing eggs of the spider family Thomisiidae (Wirth, 1952; Heed, 1968). Similarly, larvae of the ephydrid genus Trimerina prey on eggs of wetland spiders belonging to the family Micryphantidae in both Europe (Becker, 1926) and North America (Scheiring and Foote, 1973). The present paper outlines the life cycle, describes the larval feeding behavior, and presents natural history observations of Trimerina madizans (Fallen). Ad-ditionally, a contrast is drawn between T. madizans, a highly specialized and probably K-selected species, and Scatella picea (Walker), a very trophically gen-eralized and r-selected taxon within the family Ephydridae. Life History The genus Trimerina was established by Macquart (1885) for Notiphila mad-izans Fallen, a species originally described in 1813. The genus has remained
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