487 



itself. The sternum of the second segment forms two heavily chi- 

 tinized hamules (Fig. 33, hm) which serve as covering plates. The 

 membranes immediately below these form a sheath for the penis (Fig. 

 33, ps). The latter is very heavily chitinized and is bent entad, extend- 

 ing to about the middle of the abdomen, and at the ental end are at- 

 tached heavy muscles which operate the organ. The tip of the penis 

 is largely membranous and flexible, and exhibits modifications which 

 appear to be of specific value in classification, at least in some genera. 

 The tip fits behind a heavy cephalic projection of the third sternum, 

 the seminal vesicle, when not in use (Fig. 33, sv). Small knob-like 

 projections may be seen extending ventrad from the lateral margins 

 of the second tergum and just caudad of the hamules. These are fre- 

 quently concealed in the Zygoptera but are large and conspicuous in 

 the Anisoptera where they are known as the genital lobes (Fig. 33, gb) . 

 The cephalic third or less of the third sternum is elevated, heavily 

 chitinized except at the tip, and extends some distance cephalad of the 

 cephalic margin of the segment. In a few Anisoptera this part is re- 

 ported as functioning as the penis, the parts already described for 

 Zygoptera being unimportant. 



The variations occurring in this organ throughout the suborder are 

 marked and are in all cases of generic rank as diagnostic characters. 

 In closely related specific groups, however, it can not be relied upon, 

 and recourse must be had to the anal appendages. 



Anal Appendages (Figs. 34, 38, 109; aas, aai). — At the caudal 

 extremity of the abdomen of the male there are always four appen- 

 dages; an upper dorsal pair, the superiors (aas), and a lower, the in- 

 feriors (aai). Of these, the upper is more often the longest, but it 

 may be reduced and shorter than the ventral pair. The anus opens 

 between and slightly dorsad of the bases of the mesal lobes of the 

 ventral pair. The dorsal pair of appendages is frequently forcipate, 

 and the tips are often contiguous and sometimes have between their 

 bases a knob-like projection. 



Ovipositor (Figs. 109-116). — The ovipositor of the female con- 

 sists of three pairs of valves or gonapophyses. The ventral, mesal 

 pair are slender and heavily chitinized, and are transversely ridged at 

 the tip and usually provided with a saw-tooth edge. The cephalic pair 

 of gonapophyses (oce) is derived from the eighth segment ; the median 

 fair (not shown in the figures) and the broad caudal pair (oca) from 

 the ninth segment. The caudal pair of gonapophyses differ much in 

 shape from the cephalic and median pairs. They are very broad at the 

 base, somewhat contracted at the apex, and bear short, chitinized, 

 curved subapical rods, the prostyles (prs). The ventral margins of 



