Occasional Papers of the Museum of Zoology 5 



known to me. In general the third joint is ahout 

 twice the second, but in some females of groups i and 2 

 {flavovittatuni, aurantiacum, triangulare) the third joint is 

 longer, but in no case is it three times as long as the second ; 

 in group 4 (Oxystigma), the two joints are more nearly equal 

 and are more robust than in the other three groups. Further 

 evidence for the indistinctness of structural differences be- 

 tween groups I and 2 is found in the fact that the female, 

 originally described as ovatimi, group i, (de Selys i) was later 

 (de Selys 2) referred to ochraccum, group 2. The species re- 

 ferred by de Selys to group i are, for convenience, discussed 

 with the species in group 2. The type of the genus Hetera- 

 grion is flavovittatuin; and of Oxystigma, petlolatuin. 



Characters of Groups and Species. — The proportions of 

 the second and third antennal joints have been mentioned 

 above. Face profiles and Jiead coloration: there are four 

 fairly distinct types of face profiles (figures 63 to 66). The 

 acute, up-turned frons is a male character confined to group 3. 

 It is associated with a brilliant yellow or orange face, a velvety 

 black posterior vertex (rarely the entire vertex) and a metallic 

 yellow or orange area on either side of the median ocellus, ad- 

 joining the frons (except in those species where the black of 

 the vertex reaches the frons). The females of these brilliant 

 males are very different. In some of them the face may 

 be largely black. The males of a few species of group 3 and 

 the females of all that group have the frons about right angled. 

 In groups I and 2 the frons is a little more rounded. It seems 

 to be the same in the sexes of all the species. In coloration 

 of head the male of flavovittatuni approaches group 3, but the 

 head patterns in both sexes of the species of group 2 are all 

 very different from group 3. With few exceptions they are 

 pale colored, variable, more or less indistinctly patterned, and 



