SEX-RATIO IN FIELD POPULATIONS OF PHYTOSEIID MITES (ACARINA PHYTOSEIIDAE)

The sex ratio was determined for 15 spp. [Galendromus longipilus (Nesbitt), Amblydromella nodosus Deleon, Fundisetus morgani (Chant), Neoseiulus vagus, Typhlodromalus peregrimus (Muma), Phytoseius macropilis (Banks), Typhlodromus quadroporus Denmark and Knisley, Galendromus ruralis DeLeon, Neoseiulus umbraticus (Chant), Amblyseius andersoni Chant, Neoseiulus fallacis (Garman), Proprioseius meridionalis, Euseius finlandicus (Oudemans) Proprioseiopsis unicus and Galendromus pomi (Parrot)], of phytoseiid mites collected from 24 locations throughout New Jersey [USA] during the summers of 1973 and 1974. Each species had a characteristic sex ratio which ranged from .apprx. 52% female to .apprx. 97% female, although a sex ratio between 75 and 90% female was most common. The sex ratio of each species varied, but, except for 1 instance, did not show a significant trend in different populations or throughout the growing season. Sex ratio did not differ among different host vegetation species and was not related to species frequency or density. Regression analysis of 8 meteorological factors with sex ratio showed that variation in sex ratio is related to temperature, humidity and wind speed.