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1912] Etcing and Webster — Mites Associated with the Oyster-Shell Scale 121 



Agrilus ohlitus Wat. 

 One specimen. Madeira-Mamore R.R., Camp 39. 



Aqrilus molestus Wat. • 

 Independencia (Parahyba). One specimen taken by sweeping;. 



MITES ASSOCIATED WITH THE OYSTER-SHELL SCALE 

 (LEPIDOSAPHES ULMI LINNE). 



By H. E. Ewing and R. L. Webster. 



INTRODUCTION. 



The fact that mites frequently attack scale insects and so play 

 an important part in the natural control of those insects, is by no 

 means new, and most of the literature on tliis subject is not of 

 very recent date. The observations of Walsh (1868), Shimer 

 (1868), followed by other notes by Riley (1873), show us that the 

 importance of these mite enemies was even better appreciated in 

 a general way then, than at present. Some further careful obser- 

 vations by Lignieres (1893) in Europe threw much more light on 

 the exact relations of two of the most common mites which are 

 found imder the oyster-shell scales, many of which observations 

 the present writers have been able to verify in the work reported 

 on in this paper. 



The notes on which this paper is based were made by the writ- 

 ers in Iowa, largely in the vicinity of Ames, although by no means 

 restricted to that locality. The determinations of the mites are 

 on the authority of Mr. Ewing. This paper represents a part of 

 a larger article on the oyster-shell scale, to be published at some 

 future time as a bulletin from the Iowa Agricultural Experiment 

 Station, but it was thought best to present this portion of the work 

 in advance. 



NATURE OF MITE ATTACKS. 



The most eflScient mite found attacking the oyster-shell scale 

 in Iowa is one which feeds for the most part on the eggs of the 

 scale insect, although it feeds also on the insects themselves. This 

 mite is Hemisarcoptes malus (Shimer). Another mite, Monieziella 

 entomophaga (Laboulbene), which was about as common under 



