6 Unk'ersity of Michigan 



very similar in the sexes. In Oxystigma (group 4}, 

 the frons is low and flattened. While in cyanofrons, 

 of this genus, the head pattern of the male suggests 

 group 3, the head pattern of the female is very similar to the 

 male, thus differing from the condition found in group 3. The 

 hind lobe of the prothorax offers a character which may he 

 valuable in certain cases in determining species, and used care- 

 fully, it may be useful in associating the sexes. In all the mate- 

 rial studied I have seen only one malformed prothorax. The 

 ■male abdomiiHil appendages, especially the superiors, are speci- 

 fically distinct, but are often very similar. I have detected no 

 variation within a species. The superior appendage by press- 

 ure or other causes is often rotated on its long axis ; so figures 

 may be more or less misleading, and. in the case of species hav- 

 ing similar appendages, such figures cannot be relied on for the 

 proper identification of specimens without reference to other 

 characters. The penes have been studied by Mr. Kennedy but 

 his results have not been published. He writes me that he 

 has found this organ showing no specific characters in this 

 genus. The genital valves are toothed along the ventral edge 

 in all species. In group 3 the valve is relatively thin or narrow 

 on the ventral edge, and the teeth are one-rowed. In all the 

 others the ventral edge is broader, the teeth are several-rowed 

 or paved, and the teeth are more flattened and scale-like than in 

 the single-rowed forms. In all species the style is tipped with 

 an acute translucent point which is formed by closely appress- 

 ed hairs or bristles. The toothed edge of the genital valve is 

 obviously the instrument by which an entrance is made for the 

 insertion of the ovipositor. Frequently the interstices of the 

 teeth are filled with minute debris, more or less concealing the 

 teeth. This seems especially true of those with paved teeth. 

 Among the females of group 3, where the teeth are single- 



