The predatory mite Hypoaspis miles: Biological and demographic characteristics on two prey species, the mushroom sciarid fly, Lycoriella solani, and the mould mite, Tyrophagus putrescentiae

The biology of Hypoaspis miles Berlese (Acarina: Hypoaspidae) fed on mushroom sciarid larvae (Lycoriella solani Winnertz) (Diptera: Lycoriidae) and mould mites (Tyrophagus putrescentiae Schrank) (Acari: Acaridae), was investigated by laboratory experiments at 20 degrees C, 75% rh. and LD16:Dg hours. H. miles had a significantly shorter development time and a significantly lower juvenile mortality when fed on sciarid larvae than on mould mites, the development time being 14.5 days and the mortality 3.5% on the former prey. The preoviposition and postoviposition periods of H. miles were not uninfluenced by the prey species and were 5-9 and 32-37 days, respectively. Oviposition periods of 53.2 and 68.5 days and female longevities of 82 and 109.6 days were observed on diets of sciarid larvae and mould mites, respectively. Male longevity (168-219 days) was uninfluenced by the prey species. The egg production of H. miles on sciarid larvae was estimated to be 44.4 +/- 4.33 eggs per female, as compared to 22.43 +/- 1.79 eggs per female on mould mites. The sex-ratio of the offspring was significantly influenced by the prey species, the ratios (female/(female + male)) being 0.66 on sciarid larvae and 0.54 on mould mites. The net reproductive rate (R(0)) for H. miles fed on sciarid larvae was approximately 27 which was three times higher than for mites feeding on mould mites. The innate capacity of increase (r(m)) was highest (0.0747 day(-1)) when sciarid larvae served as food, giving a doubling time of 9.3 days as compared to 12.8 days on mould mites. The ,generation times were 44.28 on sciarid larvae and 40.67 days on mould mites. The daily food consumption rate of juvenile and adult H. miles was 0.24 and 0.86 sciarid larvae and 10.8 and 21.7 mould mites, respectively. In terms of weight consumed, however, the consumption of sciarid larvae was 2-3.5 times the weight of mould mites. The ratio of females to males influenced the oviposition period and egg production of H. miles, with virgin females laying fewer eggs over a longer period of time as compared with females with access to males. The egg production in relation to the sex-ratio was described by models predicting a maximum number of eggs per female of 22.3 to be attained at a sex ratio of 0.69 (female/(female + male)) and a maximum daily number of eggs per female of 0.33 to be attained at a sex ratio of 0.37 (female/(female + male)).