EXTERNAL ANATOMY OF INSECTS. 699 
dinide and Siricide, the abdomen of which is united to 
the trunk by the whole diameter of its base; these may 
be further subdivided into those that have a very short 
pedicle and those that have a dong one; but as the mode 
of articulation in both these is the same, there will be no 
necessity to consider them separately. M. Cuvier has 
included the Diptera and Araneide in the same tribe 
with such Hymenoptera as have a petiolate abdomen ?; 
but as the manner in which the latter articulates with 
the trunk is widely different from that of the Diptera, &c., 
I thought it best to consider them as distinct; espe- 
cially as in the Diptera there is no tendency to a_pedi- 
cle, while only the above two tribes of Hymenoptera are 
wholly without it. ‘This learned author thus describes 
the articulation where the abdomen is connected by a 
pedicle. ‘ They have,” says he, “a real solid articula- 
tion, a kind of hinge in which the first segment is emar- 
ginate above, and receives a saliant portion of the trunk 
upon which it moves; this articulation is rendered solid 
by elastic and powerful ligaments ; muscles which have 
their attachment in the interior of the trunk are inserted 
in this first segment, and determine the extent of its 
movement.” But this passage by no means conveys an 
adequate idea of the singular mechanism by which the 
Divine Artificer has enabled these little creatures to im- 
part the necessary movements to an organ so bulky com- 
pared with its very diminutive point of attachment. As 
no author that has fallen in my way has examined the 
articulation of the abdomen with the trunk in these Hy- 
menoptera with the attention which it merits, I shall en- 
* Anatom, Compar.i. 451. + 
® De Geer notices something of the kind in Cimber femorata. ii. 947. 
