based on the principle of Cephalization.—Insects. 17 
general uniformity. ‘The integuments are less firm than in Hymen- 
opters. The mouth is simply suctorial, and self-feeding is the 
in 
only function. Individuals never live communities. The 
is attended with (1) an enlargement of the mesothorax (the seg- 
ment supporting the anterior pair) at the expense of the meta- 
thorax (or posterior segment of the thorax), and (2) an increased 
the gree of force thus concentrated is far less than that of the 
Size, in their many imitations of Hymenopters, in the semiaquatic 
life of some species, their less strength as compared with size, 
their habits, &c. It is stated on page 12 that the transition from 
1c. 
, The foot note on the preceding page states some of the rela- 
tions between Dipters and Hymenopters. On this point West- 
Wood says: “It seems to be admitted on all hands that the 
Insects which are the real analogues of the Hymenopters exist -in 
Ax. Jour. Sct.—Szconp Series, Vou. XXXVI, No. 109.—Jan., 1864 
3 
