700 . EXTERNAL ANATOMY OF INSECTS. 



ihredinidce and Siricidte, 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 long 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 Araneidce in . 

 the same tribe with such Hymenoptera as have a petio- 

 late abdomen 3 ; 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; especially as in the Diptera there is no tendency 

 to a pedicle, while only the above two tribes of 'Hymeno- 

 ptera are wholly without it. This learned author thus de- 

 scribes the articulation where the abdomen is connected 

 by a pedicle. " They have," says he, " a real solid arti- 

 culation, a kind of hinge in which the first segment is 

 emarginate above, and receives a saliant portion of the 

 trunk upon which it moves ; this articulation is ren- 

 dered 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 ex- 

 tent of its movement 3 ." But this passage by no means 

 conveys an adequate idea of the singular mechanism by 

 which the Divine Artificer has enabled these little crea- 

 tures to impart the necessary movements to an organ so 

 bulky compared with its very diminutive point of attach- 

 ment. As no author that has fallen in my way has ex- 

 amined the articulation of the abdomen with the trunk in 

 these Hymenoptera with the attention which it merits b , 



1 Anatom. Compar.i. 4ol. 



b De Geer notices something ofthe kind in Chnbexfemorata. ii.947. 



