454 



Annals Entomological Society of America [Vol. VI, 



will be considered, as it is well chitinized, quite visible, and 

 offers great variations among different species, while only a few 

 exist among individuals of a single species taken from the same 

 host plant. 



GENERAL STRUCTURE OF THE PENIS AND EXPLANATION OF 

 TERMS USED IN REFERENCE TO ITS PARTS. (See Figure.) 



Inner lobe — The imbedded or attached part of the penis. It 

 is much less chitinized than the penis proper. 



Shaft — The free part of the penis. It is much more strongly 

 chitinized than the inner lobe. 



Basilar lobe — The enlarged proximal part of the shaft. It 

 is not always present. 



barb 



basilar labt 



inner lobe 



Fig. 1. Penis of male of Tetranychus telarius Linn., as seen from the 

 right side, X 1800; showing the various parts delineated and labeled. 



Hook — The dorsally curved distal part of the penis. It is 

 frequently absent. 



Barb — The flattened or knobbed or bent tip of the penis. 



Key to the Males thus far Examined. 



I. 1. Penis long, tapering, without hook. 



n. 1. Penis without basilar lobe; long, seta or spine-like. 



in. 1. Shaft less than 0.04 mm. in length, frequently 



doubly curved T. weldoni n. sp. 



in. 2. Shaft over 0.06 mm. in length, with but a single 



curve T. longipes Banks. 



II. 2. Penis with swollen part at the base of the shaft (basilar lobe). 



III. L Shaft strongly curved; without barb. .T. flavusn.sp. 



III. 2. Shaft less curved; with flattened barb 



T. borealis n. sp. 

 I. 2. Penis short, stouter, with hook. 



II. 1. 



II. 



Hook without, barb. 

 III. 1, Hook bent at an angle of from 30° to 50° to the axis 



of shaft T. mytilaspidis Riley 



III. 2. Hook bent at an angle equal to at least 90° to axis 



of shaft T. pratensis Banks 



Hook with prominent, flattened, recurved barb 



T. telarius Linn. 



