558 The University Science Bulletin. 



extend dorsad and ventrad, respectively. The spiracle of this 

 pleuron is difficult to locate, since it lies near the mesal margin of 

 the pleuron and is visible only from a ventral view of the abdomen. 



The sternum of the second segment is an elongate, narrow, chiti- 

 nous band which tapers laterad to a fine point. Superficially this is 

 taken as the first sternite, since the latter, because of its membran- 

 ous condition, usually is pulled off with the thorax when it is re- 

 moved. 



The third to eighth segments are practically all alike, being ring- 

 like, in form and differing only in size. The terga are heavily chiti- 

 nized and occupy the entire dorsal surface. The pleura are roughly 

 rectangular, somewhat inflated, and with both lateral and median 

 angles slightly rounding. The pleura are wider than either the 

 sterna or terga. The sterna are elongate, rectangular plates forming 

 the real ventral wall of the abdomen. 



The pygojer or gononiere is the modified ninth tergite, which is a 

 rounded, bulblike structure, bearing on its dorsal surface the anal 

 tube. The ninth sternite forms the plate beneath the genital ap- 

 paratus, and is called by Crampton (1922) the hypandrium (pi. 

 LIX, fig. 1). These make the ninth segment a very prominent seg- 

 ment of the abdomen. 



The anal tube (pi. LIX, fig. 2), as was stated above, is situated 

 on the dorsal surface of the abdomen, apparently fitting into a cir- 

 cular depression and connected to the pygofer by a membrane. It 

 is composed of two segments, which represent the tenth and 

 ele^'enth abdominal rings or uromeres. The tenth uromere is by far 

 the larger and is termed by Crampton the proctiger. The eleventh 

 segment bears the telson, which is triangular in shape and is divided 

 in the middle into two distinct halves by the anus. 



The female abdomen (pi. LIX, figs. 4, 5, and 6) is similar to that 

 of the male in most details. The first tergum is both membranous 

 and chitinous, but differs from the male in that there is only a 

 single, irregular band of chitin along its cephalic margin instead of 

 two. The first sternum and pleuron are much the same as in the 

 male. 



The second to seventh segments of the female show little difference 

 from those of the male. The eighth sternum, however, has been 

 slightly modified to admit the ovipositor. It is divided into two 

 distinct halves by the bases of the ovipositor valves, which extend 

 cephalad until they reach the caudal margin of the seventh sternum. 

 Each plate of this sternum is an inverted right-angled triangle, 



