Reproductive life histories of hematophagous tabanids (Diptera: Tabanidae) in Hokkaido with special reference to their autogeny

Developmental sequences of terminal follicles in laboratory-reared females and/or various reproductive characteristics, e.g. parity, follicular development and egg retention, in field-caught females of tabanids were observed to determine the modes of their reproduction. Out of 25 species from Hokkaido, Japan, (including 2 subspecies) studied, 12 proved to be autogenous in the first gonotrophic cycle (Chrysops nigripes, C. vanderwulpi kitaensis, Hybomitra borealis, H. olsoi, Atylotus sp., Hirosia sapporoensis, H. iyoensis, Tabanus kinoshitai, T. rufidens, T. fulvimedioides, Haematopota tamerlani, H. tristis) while 13 were anautogenous (C. japonicus, C. suavis, C. vanderwulpi yamatoensis, Hybomitra tarandina, H. distinguenda, A. horvathi, Tabanus chrysurus, T. sapporoenus, T. katoi, T. trigeminus, T. pallidiventris, T. nipponicus, T. trigonus). Most of the local populations of autogenous species (or subspecies) exhibited >90% parity, whereas average parous rates of anautogenous species were <50%. Criteria were proposed to distinguish between autogenous and anautogenous populations, based on the parity of field-caught females. Seasonal changes of parous rates are presented for several anautogenous species in different habitats representing different densities of probable host animals. Different host densities at the collection sites did not necessarily cause different patterns in seasonality of parous rates in host-seeking populations. Terminal follicles in ovaries among field-caught females ranged between G.G. Mer’s stages I-V, with most flies in stage II, I-II or I, but stages III-V follicles were rather frequently observed in a few autogenous species. The rates of appearance of parous females with retained eggs were higher in the species which had a larger number of ovarioles.