IQOl] ENTOMOLOGICAL NEWS 73 



mould," seems to hold true for these three species, but his 

 statement* as to the specific value of minute differences of 

 coloration and its constancy must evidently be modified in 

 view of the variations above detailed. 



4. The shape of the hind margin of the occiput of the females, 

 far from being a constant differential, is verj' variable, although 

 the opposite view has usually been held for Gomphus ; on the 

 other hand the same margin in the males is nearly alike in all 

 three species. 



5. The po.ssibility of the modification of these results by the 

 study of material from other localities must not be forgotten ; 

 such studv is verv desirable. 



EXPLANATION OF PLATE IIL 



Fig. I. Vulvar lamina G. crassus 9 Columbus, Ohio, June i. 1896. 



Fig. 2. Id. G. externus 9 Havana, 111. 



Fig. 3. Id. G.fratermis $ Kankakee, 111., July 6, 1892. 



Fig. 4. Part of the left half of the vertex, dorsal view, G. externus 9 

 of fig. 2. 



Fig. 5. Id. G. crassus 9 of fig. i. 



Fig. 6. Occiput G.fraternus 9 Sandusky, Ohio, July 10, 1899. 



Fig. 7. " " " 9 " " " 9, " 



Fig. 8. " " " 9 " " " 10, " 



Fig. 9. " " " 9 Dixon, 111., July 12. 



Fig. 10. " G. externus 9 Havana, 111., July 10, 1897. 



Fig. II. " G. crassus S of fig. i. 



Fig. 12. Right superior appendage, viewed obliquely from above and 

 from the outer side, at 45° with the horizontal plane, G. externus ^, 

 Havana, 111,, July 9, 1897. 



Fig. 13. Id. G. crassus (J', Georgeville, Ohio, June 4, 1899. 



Fig. 14. Right superior appendage, profile view, outer side, G. externus 

 S" of fig. 12. 



Fig. 15. Id. G. crassus (J' of tig. 13. a, b, in figs. 12-15, tubercles. 



Fig. 16. Id. G.fraternus (J' Sandusky, Ohio, June 15, 1899. 



Fig. 17. Apex of abdomen, ventral view, G. extermis (^ of fig. 12. 

 s, s\ sternites of eleventh abdominal segment ; sp superior appendages ; 

 / inferior appendage (tergum of eleventh abdominal segment.) 



Fig. iS Id. crassus (J' of fig. 13. s, s\ t, as in fig. 17. The superior 



appendages of this male are indicated by the line The line 



shows the superior apF)endages of another male from the 



same locality, same date. 



"" L. c, p. 238. 



