EXTERNAL ANATOMY OF INSECTS. 587 



prostemum ,■ the former being its base, and the latter its 

 vertex. The cavity of the manitrunk is divided longi- 

 tudinally by a double cartilaginous partition surmounted 

 by a bony frame, with an anterior condyle or tuberosity, 

 with which the inner part of the base of the clavicle of the 

 arm appears to ginglymate ; and the manitrunk is pre- 

 served from the injury the powerful action of the arm 

 might occasion, by the counteraction of this machine, to 

 describe which fully, would demand more space than I 

 can afford a . I men tioned under the mesostethium, the aper- 

 tures visible in the breast oiLocusta Leach and Acrida K. 

 Each of these apertures opens into an internal, tubular, 

 horny, process, which arching off is attached at the 

 other extremity to the sides of the trunk — a pair being- 

 appropriated to each segment; the first analogous to 

 the antefurca, the second to the medifurca, and the last 

 to the postfurca. In the medipectus and postpectus of 

 Acrida viridissima there is only a single aperture, termi- 

 nating in a single tube, which after rising vertically a 

 little way sends off a branch on either hand to the sides 

 of the trunk. Where there are three of these holes, as 

 in the antepectus and medipectus of Locusta Dux, there 

 are three of these processes, the intermediate one being 

 vertical. In the subsequent Orders the processes of the 

 endosternum are not sufficiently remarkable to require 

 particular notice: my further observations upon them 

 will therefore be confined to the Coleoptera Order. 



2. Medifurca h . This part, which belongs to the mid- 

 legs, is in many cases more conspicuous than the antefurca. 



a This machine is described by Dr. Eschscholtz, Beitrage zur 

 Nalurkunde, &c. Heft. i. 24—. t. i. ii. 

 b Plate XXII. Fig. 6. 



