306 Annals Entomological Society of America [Viola 
plates of the segment. From this point backward there is no 
lateral portion to the plate it being entirely dorsal and with its 
margin rather oval in outline varying somewhat perhaps 
in some species. 
The base of the ventral segment at its sides is concealed by 
the lateral margins of the dorsal plate. Its lateral margins are 
nearly parallel almost to the end of the segment, the hinder 
margin being very broadly and bluntly acuminate. Along the 
median line of the plate extends a distinct ridge. 
Between these two plates projects the end of a third, only 
the outer portion of which is strongly chitinized. Its sides are 
approximately parallel and at the hinder end it bears three 
spines one in the center and one at each corner. The median 
spine is larger and stouter than the lateral ones and extends 
backward some little distance into the body of the plate forming 
a distinct central ridge on the under surface. The body of the 
plate as a whole is somewhat convex from side to side beneath. 
The homology of this three spined plate has not been worked 
out by the writer but as the reproductive organs are just above it, 
it would seem not impossible that it is the ventral plate of 
another segment partly drawn within the one described as 
terminal and of which the dorsal portion has either been lost or 
at least has not been observed in the course of this work. 
Last segment of the female. ‘The lateral margins of the last 
dorsal sclerite in the female are considerably prolonged ven- 
trally over the corresponding margin of the sternum of this 
segment thus concealing the latter. The edge of this portion 
extends backward and upward to the base of the spine near the 
margin on the’ventral plate (to be described later) above which 
it turns backward and gradually inward to form the hinder 
margin. The outline of this portion varies greatly in different 
species. On the side of the dorsal plate near its base and close 
to the edge of its dorsal surface a ridge arises extending back- 
ward and finally ending above the more or less spine-like 
structure of the ventral plate. This ridge varies in form in 
different species. 
The last ventral plate in the female is quite convex from side 
to side and its lateral margins turn inward almost horizontally, 
the two edges nearly meeting at the nearest point. This 
inflexed portion of each side is concealed by the dorsal plate 
only the hinder margin which varies in outline in different 
