The Life History of a Mushroom Pest Mite, Pediculaster flechtmanni (Wicht) (Acari: Pygmephoroidea), with Studies of Alternate Morph Formation

Abstract

The cosmopolitan pest mite Pediculaster flechtmanni (Wicht) sometimes builds swarming populations in commercial mushroom houses, where it feeds on “weed” fungi. Females are dimorphic, one morph adapted for phoresy. Mites were cultured on Nigrospora oryzae grown on yeast extract agar at 21–28°C ambient and at 24°C constant. Preadult stages are egg, active larva, and quiescent larva, these stages lasting about 41, 7, and 43 h, respectively, at 21–27°C ambient. Female–female cycle is about 125 h at 21–27°C ambient. Females are physogastric, each producing about 200 eggs within one to six oviposition days. Net reproduction rate is approximately 65 females per female per generation. Sex ratios are initially female biased, often becoming male biased as mothers age. Unmated females, if they reproduce, are arrhenotokous. Pronounced sexual dimorphism in morphology and behavior is shown. Phoretic and nonphoretic females also differ from one another in behavior as well as in structure. Experiments suggest that the proportion of phoretomorphs increases as cultures age; this increase is not due to attenuated phoretomorph developmental time or increasing age of the mother; phoretomorph increase probably is related to environmental factors associated with habitat deterioration; and such factors could be pheromonal or nutritive, and they may act upon any stage in the life cycle.