122 Psyche [August 



the scales as the first, did not feed on the sound eggs of the scale 

 insect, but acted only as a scavenger, feeding among shriveled 

 egg shells and following the first named mite in its work beneath 

 the scales. Besides these, several other mites were noticed in 

 connection with the oyster-shell scale, and observations thereon 

 are given in this paper. 



In order to understand the relations of these several mites to 

 the oyster-shell scale it will be necessary to give a brief outline of 

 the life history of that insect. Near Ames the eggs of the scale 

 insect begin to hatch from about the 10th of May to the 1st of 

 June, depending upon the season. The tiny crawling nymphs 

 soon settle down on the bark of the infested tree when a suitable 

 position has been found, and proceed to secrete their scale cover- 

 ing. This is completed in July, and late in that month the eggs 

 of the scale insect begin to appear under the scales. Thus, from 

 the first of August until about the middle of May, a period of nearly 

 ten months, the eggs may be found beneath the scales. It is no 

 wonder that the mites frequently have an almost unrestricted 

 swa}'^ during this period. 



IMPORTANCE OF MITE CONTROL. 



Walsh (1868) said that in examining six hundred scales about 

 the last of October in Illinois, he found "that at least two-thirds 

 of the whole number were either already gutted, or were under- 

 going the process of being gutted, by the minute larva of a mite." 

 From the description of the injury Hemisarcopfes mahis was prob- 

 ably the mite that was doing the work mentioned. 



On October 29, 1908, a lot of scales from apple twigs obtained 

 at Ames were examined, and many of them were found to be in- 

 fested with mites (probably Hemisarcopfes mains) which were 

 feeding on the eggs. Of 100 scales examined, 35 showed evi- 

 dences of mite injury, or revealed the presence of the mites. 



In the early spring of 1911 a lot of apple twigs infested with the 

 oyster-shell scale were taken from different orchards around Ames, 

 and at other localities in the state to the north of Ames. In prac- 

 tically all of these samples mite injury was evident beneath the 

 scales. In some cases the mites had done very effective work in 

 checking the scale, elsewhere they were not so effective. 



One sample taken from an orchard near Ames showed consid- 



