8o SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 89 



7. The ninth tergum is exposed, and usually large. Its anterior 

 ventral angles are produced forward as extensions to which are united 

 the inner rami of the first valvulae. 



8. The second valvifers have a pleural position on the sides of the 

 ninth segment beneath the lateral margins of the ninth tergum. Each 

 is movably articulated with the tergum at a point near the middle of 

 its dorsal margin, and is provided with antagonistic muscles from the 

 ninth tergum inserted before and behind the fulcrum. 



9. There are generally no intervalvular sclerites in the ninth venter, 

 and tergosternal muscles are absent in the ninth segment. 



10. The second valvulae are attached proximally, each by a single 

 arcuate ramus, to the anterior end of the second valvifer, and the 

 ramus slides on the concave margin of the inner ramus of the cor- 

 responding first valvula. 



11. The third valvulae are well differentiated from the second val- 

 vifers ; they form a pair of lobes ensheathing the distal end of the 

 shaft of the ovipositor ; rarely they are absent. 



12. The mechanism of the hemipterous ovipositor is very simple as 

 compared with that of the gryllid ovipositor ; its only muscles are 

 those of the first and second valvifers, and the pair of muscles from 

 the first valvifers to the inner rami of the first valvulae. 



13. An unusual condition bringing about the discharge of the eggs 

 directly into the channel of the ovipositor exists in some of the Cicadi- 

 dae, in which the genital chamber forms a large pouch opening above 

 the rudimentary eighth sternum, and has a second posterior exit be- 

 tween the bases of the second valvulae. The relation of this structure 

 to the usual structure in other Hemiptera is not understood, and it 

 appears that the morphology of the terminal parts of the female genital 

 ducts in the Hemiptera is a subject in need of further investigation. 



As between the Heteroptera and the Homoptera there is no essential 

 difference in the structure of the ovipositor. In each group, also, the 

 ovipositor is well developed in some forms, and reduced or absent 

 in others. According to the comparative studies of Ekblom (1926, 

 1930), an ovipositor is present among the Heteroptera in the families 

 Saldidae, Nabidae, Lygaeidae, Veliidae, Gerridae, Mesoveliidae, Cor- 

 izidae, and Corixidae, and is best developed in the Saldidae and 

 Nabidae; but the organ is well developed also in Notonectidae and 

 Coreidae. The structure of the hemipterous ovipositor will be shown 

 in this paper by examples taken from the Saldidae, Coreidae, Cicadel- 

 lidae, and Cicadidae. In connection with a study of the ovipositor it 

 is important to understand the segmentation of the abdomen, since 

 students of the Hemiptera are most frequently at fault concerning 



