HOST RELATED DIFFERENCES IN THE DEVELOPMENT AND REPRODUCTION OF THE CEREAL RUST MITE, ABACARUS HYSTRIX (ACARI: ERIOPHYIDAE) IN POLAND Anna Skoracka 1 and Lechos³aw Kuczyñski 2 1. Department of Animal Taxonomy and Ecology, Institute of Environmental Biology, Adam Mickiewicz University, Umultowska 89, 61-614 Poznañ, Poland (e-mail: skoracka@amu.edu.pl, corresponding author); 2. Department of Avian Biology and Ecology, Institute of Environmental Biology, Adam Mickiewicz University, Umultowska 89, 61-614 Poznañ, Poland (e-mail:lechu@amu.edu.pl). ABSTRACT - Specific feeding and habitat conditions for phytophagous insects and mites are created by their host plants. Adaptations to the specific host plant may be reflected in differences in the life-history traits of phytophagous arthropods. Herein we tested whether host populations of the eriophyid mite Abacarus hystrix (Nalepa), adapted to feed on their natal host plants, differ in life history parameters. For this purpose the developmental time, survivorship, longevity and fecundity of A. hystrix living on two grass species, Lolium perenne L. and Elymus repens (L.) Gould, were compared. No significant differences in im- mature and male survival, sex ratio, median adult longevity and mean fecundity were recorded between host populations. Significant differences in the developmental time, female survival and oviposition rate be- tween populations studied were found. Immature development and the total developmental time from egg to adult were significantly longer on L. perenne compared to E. repens. Females from E. repens survived sig- nificantly longer than females from L. perenne. Females from E. repens oviposited at a slower rate, had two oviposition peaks, and throughout their life the oviposition increased and decreased gradually. Females from L. perenne oviposited at a faster rate, had only one oviposition peak, and the oviposition increased and decreased rapidly. It is concluded that A. hystrix populations from E. repens and L. perenne differ in alloca- tion of resources for development and reproduction. These differences may result from different degrees of adaptation of each population to various host plant characteristics. The effect of chemical composition and physical structure of the host on A. hystrix development and reproduction is discussed. The results obtained here support the hypothesis that the two populations of this mite from E. repens and L. perenne are highly specialized in their host use and may be regarded as host races or separate species. Key words - Acari, Eriophyidae, grasses, host plant, host races, life history traits, life strategies, phyto- phagous mites, survival, Poland. INTRODUCTION Feeding and habitat conditions created by a specific host plant have a great influence on the life history traits of phytophagous arthropods (Pande and Reddy, 1985; Bergh and Weiss, 1993; Tikkanen et al., 2000; Pang et al., 2004). Several intrinsic plant characteristics have been discussed as determinants of host plant suitability for herbivores to develop, e.g. chemical content, host quality, phenology, attractiveness and availability for predators (Jaenike, 1990; Wilson, 1994; Krips et al., 1998; Agrawal, 2000; Chapman, 2003). Chemical con- tents crucial for herbivore development and reproduction may include nutritional quality, especially nitrogen level (McNeil and Southwood, 1978; Strong et al., 1984; Wil- son, 1994; Hoffland et al., 2000), or primary and second- ary metabolites which function as toxins, deterrents and digestibility reducers (Rosenthal and Berenbaum, 1991; Stout et al., 1994). The differences in life history traits of phyto- phagous arthropods may be attributable to differences in the degrees of adaptation to the specific host plant. The adaptations can lead to species-wide polyphagy (when species easily acclimate to changeable conditions) or to narrow host specialization (when species are highly spe- cialized for host use) (Gould, 1979; Fry, 1999; Agrawal, 2000). Vol. 32, No. 4 Internat. J. Acarol. 397