234 Acarology 



an aedeagus is present, the larger female genital opening is lacking, 

 and the sensory organ on tarsus i of the male is greatly enlarged. In 

 Cheyletiella parasitivorax (Megnin) the male genital opening is dor- 

 sal. In other genera where the two sexes are known the males are more 

 or less similar to the females, varying in the characteristics mentioned 

 above. Ewing 1912 has studied the life cycle of a Cheyletus. Eggs are 

 laid near each other but not in clusters and the female remains near 

 them for some time after oviposition has ceased. One female laid 

 twenty-five eggs over a six-day period, another twenty-two eggs in 

 two days and another laid only a single egg. At laboratory tempera- 

 ture, on an average, the duration of the incubation period was 4.3 

 days, the larval stage 7.66 days, the first nymphal stage 4.5 days, the 

 second nymphal stage at least 5 days, and the adult stage 13 days. 

 The larva is similar to the aduh but has only six legs; the nymphs are 

 likewise similar to the adult but have four pairs of legs. Ewing found 

 that the young mites prefer eggs of other mites such as Acaridae with 

 which they are associated. In the milled wheat samples he found that 

 about 95 per cent of the acarids were killed in a short time by these 

 cheyletids. Rodionov and Furman 1940 in a study of Cheyletus 

 eniditus (Schrank) for control of granary mites {Acarus siro L., 

 Tyrophagus castellanii Hirst and Glycyphagus destructor (Schrank ) , in 

 Russia found that the cheyletids are not of great value in the control 

 of grain mites in granaries and that their presence only lowers the 

 purity of the grain. Their developmental period is longer than that of 

 the grain mites, and although they are more resistant to desiccation, 

 they are more susceptible to hydrocyanic gas. The strongly armored 

 hypopial stages of the grain mites were not attacked by the cheyletids. 

 The Cheyletidae, as a whole, are free-living predators, although 

 some are to be found in bird feathers, in squirrel, rabbit, or cat fur, 

 and sometimes appear to injure the host. The free-living forms are to 

 be found in association with infestations of other mites such as the 

 Acaridae and Tetranychidae, and with scale insects, but as yet they 

 do not appear to be of great importance in controlling mites or insects. 

 Because of their free-living habits many species are world-wide in 

 distribution. 



References: 



Baker, E. W. 1949. A review of the mites of the family Cheyletidae in the 

 United States National Museum. Proc. U. S. Natl. Mus. 99(3238): 

 267-320. 



