8r. 



Eighteenth Report State Entomologist of Minnesota — 1920 



the second of which is slightly removed at base and divergent apically (PI. IX). 

 Hind tarsus w^ith first segment shorter to slightly longer than the second, 

 sometimes slightly thicker than the second but never twice as thick. Claws 



distinctly cleft near 

 base, or more slender 

 and without a distinct 

 notch : arolia very 

 slender, bristle-like, 

 erect and parallel or 

 only slightly curved at 

 tips, in the smaller 

 species sometimes dif- 

 ficult to distinguish 

 from the hairs on tar- 

 sus. Structure of 

 the male genital clas- 

 pers giving specific 

 differences. 



Fig. 1. Deraeocoris olivaccuH Fabr., male genital claspers. 

 a, left clasper, lateral aspect : b, internal arm of left clasper ; 

 c, right clasper, lateral aspect. 



Methods of Study 



In this work exact measurements are given for structures of the 

 insect which are commonly compared, one part with another, or meas- 

 urements which in the writer's opinion are Hkely to be of value to 

 future workers in the group. By following this plan it is feasible for 

 a future student to make any comparison of strtictures he mav so de- 

 sire. Much has been said about the relative value of the various 

 methods of comparing one structure with another where width and 

 length are the factors involved, but it seems to the writer that the 

 surest plan for meeting all the comparisons that the future student 

 may require is to give all measurements in millimeters. This method 

 need not preclude calling attention to the fact that the second antenna! 

 segment may be twice the length of the third, but when in addition, 

 exact measurements are given for all the segments, the ftiture student 

 will also be in a position to compare the third or fourth segment with 

 the first member, or with other parts as the need arises. 



An explanation of the more important terms is as follows: 



Length of the insect is the measurement taken between the tip 

 of the tylus and the apex of the membrane ; ividth is taken at the 

 widest point on the hemelytra. 



Head : Width is measured from the dorsal aspect and taken across 

 the eyes at the widest point ; vertex is the space between the inner mar- 

 gins of the eyes at the top of the head; length is measured laterally, 

 taken at right angles to the base of the head, a point determined by 

 the base of the gula and the hind margin of the eye. 



