416 MODERN CLASSIFICATION OF INSECTS. 
A remarkable peculiarity, exhibited by great numbers of these in- 
sects, is the secretion of a fine farinose matter, often in very great 
quantities ; and which occurs, not only in the typical tribes, but also 
among the Aphides, where a genus is even named, from this circum- 
stance, Eriosoma; and the Coccide, where, at least in some species, 
the secretion forms large scales, as in the female Dorthesiz, or greatly 
elongated anal filamentous fascicles, as in the males of that same 
genus. 
The characters of the wings, mouth, and transformations, upon 
which, as we have already seen (Vol.I. p. 18.), the three principal 
modes of distribution of the class have been built, separate this order 
from all the other suctorial insects ; the differences, however, existing 
between them and the Heteroptera are confined chiefly to the first of 
these characters, and hence the propriety of the separation of these 
two groups has been denied by many subsequent writers. De Geer, 
indeed, first separated these as an order, named Siphonata by Retzius. 
Latreille, however, in most of his works, and Fabricius considered them 
as forming together but one; the former dividing it, under the name 
of Hemiptera, into two suborders or sections, Heteroptera and Homo- 
ptera. It cannot be denied that the characters they have in common 
are so numerous and strong, that disagreement in the texture of the 
wings is not alone sufficient to warrant their separation. If, however, 
we adopt the separation of the Phryganez from the Neuroptera, and 
the Forficula from the Orthoptera, we are, as it seems to me, equally 
warranted in considering these two groups as quite as much entitled 
to the rank of separate orders. Another consideration has also much 
weight with me in retaining the order as distinct, namely, the analo- 
gical relations which exist between the mandibulated and suctorial 
tribes. Mr. MacLeay, we have seen (Vol.I. p. 27.), regards the 
Hemiptera (Heteroptera) as opposed to the Orthoptera, and the Ho- 
moptera as analogous to the Neuroptera; but neither of these rela- 
tions appears to me well founded. The Heteroptera, on the one hand, 
I consider as offering a far stronger series of analogies with the 
Coleoptera (such as the general shape of the depressed body, size of 
the scutellum and antenne, and, more definitely, the Buprestis-like 
form of some of the equally splendid Scutellere ; the Coleopterous 
form of others, as Odontoscelis scarabeoides, Thyreocoris melo- 
lonthoides Burm., Th. silphoides Fab., or Cephalocteus histeroides 
Duf.; or the Dyticus-like form of the equally aquatic Naucoris and 
