68 GEO. H. HORN, M. D. 



The last ventral segment by the character of its lateral margins 

 enables us to divide the genus into two primary series. In the first 

 the margins are distinctly serrulate, sometimes strongly so, occasion- 

 ally simply crenulate, many illustrations will be found on Plates ii 

 to V. In the second series the lateral margins are not serrulate, as 

 shown on Plates vi-vii, although in two species, cerea and Ubonoti 

 (figs. 175-176 and 195-196), the margin is interrupted beyond the 

 middle. 



The firm of the clypeus appears to have escaped observation, or 

 at least description by nearly every author, and no one seems to have 

 attached the importance to it which it deserves. The usual emar- 

 gination of the clypeus is triangular or oval, the broader the emar- 

 gination the more shallow it becomes. There are, however, several 

 curious forms as shown in figures 12, 81, 36, 46, which are, with the 

 exception of 36, restricted to a single species in each case. Other 

 modifications probably occur in exotic forms and will doubtless be 

 more accurately observed in the future. 



Modifications of structure dependant on sex are very numerous, 

 and occur in many parts of the body and its members. Descriptions 

 are given as fully as necessary under each species and many of them 

 illustrated on the plates, so that but little more than a few general 

 remarks will be here given. 



Form of body. — There is but little diflTerence in the sexes except 

 that the male is often more slender and the female more convex. 



Head. — This varies in form, color, sculpture and pubescence. 



Fortn. — The front of the male is usually nnich flatter, the female 

 more convex. 



Color. — Frequently the male head is green, while that of the 

 female is aeneous or cupreous. 



Sculpture. — In the majority of species the front is much more 

 densely and finely punctured and the callosities indistinct or want- 

 ing in the male, while in the female the punctures are coarser and 

 sparser and the callosities prominent. It is rare that the callosities 

 are more prominent in the male, while in a small number of species 

 the front is similarly (that is, coarsely and sparsely) punctured in 

 both sexes. 



Pubescence. — In those species with a very flat front that portion 

 is quite densely pubescent in the male and scarcely so in the female. 



