316 STATES OF INSECTS. (Jmago.) 
the genus, all of which are distinguished by long maxille; 
though in some they are as long as the body, and in 
others scarcely half that length. Gnathtwm is similarly 
characterized *. 
The mazillary palpi occasionally differ in the sexes. 
In Cerocoma those of the female are filiform, while the 
two intermediate joints of those of the other sex are much 
thicker than the first and the last >. In Hyleccetus and 
Lymexylon, those of the male are still more remarkable: 
they are pendent, the last joint very large, and laciniated 
so as to forma tuft®. The female ones grow gradually 
larger towards the end, but are not at all divided there*. 
The palpi of male spiders are of a very different struc- 
ture from those of the other sex, terminating in a very 
complex incrassated piece, which has been supposed to 
contain the organ of generation; but this, according 
to Treviranus, is a mistaken idea—that organ being, as 
usual, to be found in the abdomen’. In the common 
gnat the palpi of the male are as long as the proboscis, 
consist of five joints, and at the end are tufted with hairs; 
while those of the female are scarcely one-fourth of its 
length, have only three joints, and are not tufted. Whe- 
ther the Jabial palpi in any genus differ in the sexes, I 
cannot affirm with certainty: I have not, however, ob- 
served any such variation in them. 
I shall next mention some organs of the head, in which 
the difference between the sexes is often very striking 
and peculiar. You will readily conjecture that I am 
2 Linn. Trans. xii. 425—. t. xxii. f. 6. ° Prats XXVI. Fic. 2. 
© Ibid. Fie. 3. 4 Oliv. no. xxv. Lymexylon, t. 1. f. 1. 
© De Geer vii. 249 —. ¢. xiv. f. 20,21. Treviranus Arachnid. 36—~. 
tif. 16.a6c. t. iv. f. 35—37. 
