10 CLASSIFICATION OF BUGS. 
divided into two orders of equal rank, but whether much is 
gained by this operation is doubtful. It seems best to divide it 
into three well marked groups or sub-orders. Prof. Comstock, 
who has given much thought to this group of insects, places the: 
Heteroptera first, because they resemble the ancient Hemiptera— 
the first to appear on the earth—more closely than the members 
of the two other sub-orders. He places the true lice next. These 
are very much lower in structure than the Heteroptera, but their 
simplicity of structure is the result of degradation due to para- 
sitic habits, hence represents a later development. They are 
probably descendants of some ancient form resembling some of 
the existing Heteroptera. We see in the bed-bug, an undoubted 
species of Heteroptera, a similar downward tendency due to its 
parasitic mode of life. The Homoptera, including no doubt also 
some very primitive forms, show the widest divergence from 
the hemipterous type. 
The three sub-orders can be separated by the following 
table: 
BUGS. 
(Hemiptera. ) 
A. Wingless Hemiptera, parasitic upon 
man and other mammals, with a 
fleshy, cmjpomtedeheak. <i... s96 PARASITA 
AA. Hemiptera with or without wings, but 
with a jointed beak 
B. First pair of wings thickened at 
the base, with thinner extrem- 
ities which overlap on the back; 
beak arising from the front 
part of the Head wc.c). <a sere BHETEROPTERAS 
BB. Wings of the same thickness 
throughout, and usually slop- 
ing at the sides of the body; 
beak arising from the hinder 
part of the lower side of the 
head So 5..26 «1a HOMOPTERA. 
