124 Psyche [August 



live insects, while 282 were empty. That is, 43.6% of the scales 

 contained living insects; the remainder, more than half of the 

 scales counted, had been left over from the year before. 



In computing the percentages of scales given herein, 500 scales 

 were usually counted, rather more, than less. 



From these observations, as well as from others not mentioned 

 here, it is quite evident that the oyster-shell scale is in many places 

 kept in check by mites. At the time these notes were made the 

 m^tes were the only agents of natural control in evidence, and they 

 are therefore given the credit for keeping the scale in check. Of 

 these mites the most efficient was Hemisarcoptes malus. 



THE REAL MITE ENE]\IIES OF THE OYSTER-SHELL SCALE. 



Of the total of nine species of mites found in connection with the 

 oyster-shell scale, six were either parasitic or predaceous. These 

 six species will be taken up in order of their importance. 



Hemisarcoptes malus Shimer. 



Ideniiiy and Syywtiymy. This, the most important enemy of 

 the oyster-shell scale, was first described by Dr. Henry Shimer 

 (1868). Riley (1873) gave a drawing of a different species of mite 

 found with the oyster-shell scale, which he rather suspected was 

 not the same as Shimer's species. In regard to this figure, Riley 

 said: 



"I present, herewith, a side and ventral view of the species which so effectually 

 destroyed the contents of the Georgian scales, in order that the reader may get a 

 correct notion of the appearance of these mites. It may be a form of the Acarus 

 malus of Shimtr, but differs from his description in being almost four times, instead 

 of twice, as long as broad, as well as in other details." 



This drawing is of no other species than Monieziella entomo- 

 phaga (Lab.), a scavenger species found in association with the 

 oyster-shell scale both in this country and in Europe. It is by no 

 means a drawing of the (Acarus?) Hemisarcoptes malus described 

 by Shimer. Riley's description, however, refers both to Monie- 

 ziella, and to the species we are considering, Hemisarcoptes malus 

 (Shimer). This fact, with the misleading reference to Shimer's 

 species, has done much to confuse the identity of these two com- 

 mon mites found beneath the oyster-shell scales. 



Lignieres (1893) found both these species in Europe, and. 



