THE CITRUS MITE NAMED AND DESCRIBED FOR 

 THE FIRST TIME. 



By E. A. McGregor, 



Scientific Assistant, Bureau of Entomology, 



U. S. Dept. of Agriculture, Washington, D. C. 



The discovery which forms the text of this paper was the 

 outcome of a study of types in the red spider collection of the 

 Bureau of Entomology. Out of respect for previous workers in 

 the acarid group the author wishes to state here that the anatom- 

 ical studies, on which the present paper is based, were conducted 

 with the aid of an oil-immersion lens and a camera lucida 

 attachment. It has developed, through the studies of Mr. H. E. 

 Ewing and the present writer, that the microscopic structures 

 which constitute the taxonomic characters in the red spider 

 group must be examined more critically than has been the 

 practice with earlier workers if satisfactory specific demarcation 

 is to be secured. 



In 1885 Riley published* the original description of a mite 

 under the name Penthalodes mytilaspidis, stating that "it 

 possesses three claws, and that it is certainly predatory upon 

 scale insects" on citrus trees. In 1900 Banksf re-named the 

 species Tetranychus mytilaspidis stating that "This species 

 is a true Tetranychus and not a Penthalodes * * * On care- 

 ful observation I cannot discern any division to the lower 

 (tarsal) claw in the many specimens examined (including Riley's 

 types), ji; * * * probably feeds, like the other species of 

 the genus, on plant juices." In his figure Banks shows only 

 two divisions to the tarsal claw. 



The writer's studies of Banks' red spider types included the 

 slide which he says is probably the original type slide of Riley's- 

 Penthalodes mytilaspidis. In connection with this study the 

 author went carefully through all of Hubbard's and Riley's- 

 acarid material in the National Museum and in the Bureau col- 

 lection in an effort to locate material antedating that of the 

 slide which Banks considers to be the valid type of Penthalodes 

 mytilaspidis. Nothing was found that cast a shadow of a doubt 



*Hubbard, Orange Insects, p. 216. 



t'The Red Spiders of the United States, Div. of Ent., Tech. Ser. No. 8, p. 71. 



284 



