556 EXTERNAL ANATOMY OF INSECTS, 
often embraces posteriorly, as the collar does in front, 
by a suture; it varies occasionally in shape in the diffe- 
rent tribes, most commonly it is crescent-shaped, but in 
many Ichneumonide and others it is triangular? ; in the 
hive-bee, &c., it overhangs the succeeding piece of the 
alitrunk; in Melecta, Crocisa, &c., it is armed with a pair 
of sharp teeth®; in others (Oxybelus wnighumis, &c.) with 
one or more spines, and in some with a pair of long 
horns*. Before I describe this part in the Diptera, it 
will be proper to assign my reasons for considering a 
different piece as its representative, from what has usually 
been regarded as such, and which at first sight seems 
the analogue of what I admit to be the scutellum in the 
Hymenoptera. The dorsolum, and its concomitant the 
scutellum, belong to the first pair of the organs of flight, 
‘which are planted usually under the sides of the former, 
and in the case of wings, by their Anal Area, connected 
either mediately or immediately with the latter. Now, if 
you trace the sides of the piece that I have considered as 
the part in question in Hymenoptera, you will find that 
they lead you not to the base of the dower but to that of 
the upper wings’, and in the saw-flies you will see 
clearly that the Anal Area of these wings is attached to 
a process of it, a proof that it belongs to the mesothoraz, 
or region of that pair. Butin the Diptera, the part that 
has been usually called the scwtellum is not at all con- 
nected, either by situation or as a point of attachment, 
with the wing itself, but with the lower valve of the alula, 
2 PLATE LN. Fic. 11, 15. #. 
» Mon. Ap. Angl. i. t. vi. Apis**.a. f. 2. aa. 
* Stoll Cigales t. xxviii. f. 164. 
o PLaredee fic, 12,77, 
