416 JOURNAL OF ECONOMIC ENTOMOLOGY [Vol. 5 



THE LIFE HISTORY AND HABITS OF CHEYLETUS 

 SEMINIVORUS PACKARD 



By H. E. EwiNG, Agricultural Experiment Station, Corvallis, Oregon 



Frequently found associated with some of our insect and mite pests 

 is a little predaceous acarid, pale in appearance and less than a milli- 

 meter in length. This species was first described by Professor A. S. 

 Packard in 1869. Since then it frequently has been observed by ento- 

 mologists, usually in stored grain or grain products. The scientific 

 name of this mite is Cheyletus seminivorus Packard. The specific 

 name, seminivorus, means seed devouring; and doubtless was given 

 to the species because it was believed that the acarid lived upon seeds. 

 At any rate, it was first found in stored cabbage seed. The species, 

 however, is not an enemy to seeds of any kind or to stored grains, for 

 it is entirely carnivorous. When it is found among seeds or in stored 

 grain it should be protected in every way, for it is there only to prey 

 upon some other species, which is the real pest, whose destruction is 

 to be desired. 



During the last winter the writer came into possession of a sample of 

 milled wheat which was infested with millions of Tyroglyphid mites. 

 Associated with these Tyroglyphids were found at first only a few 

 individuals of Cheyletus seminivorus Pack. Some of these were 

 selected to be used in a series of experiments upon the life history and 

 habits of this species. The following results were obtained. 



Life History 



Number of Eggs Laid and Rate of Deposition. Of the three females 

 which I succeeded in getting to deposit eggs, one laid a total of 25 

 in a period of 6 days; another 22 in a period of 2 days; while the third 

 laid only a single egg. The greatest number of eggs laid in one day 

 by a single female was 11. The average rate of deposition per day for 

 a single female was 5 1-3. All the females lived for several days after 

 egg deposition had ceased. The eggs were laid near each other, but 

 not in clusters; and the female remained by them for some time after 

 deposition had ceased. 



Length of hiciibation Period. Of the 48 eggs laid in captivity 32 

 hatched. The minimum incubation period found for any one egg 

 was 3 days, the maximum was 7 days. The average period of incuba- 

 tion for the 32 eggs was 4.31 days. These eggs were kept in cells at the 

 ordinary laboratory temperature. 



