THORAX : METATHORAX. 273 



is generally a horny covering, divisible, like the mesosternum, 

 into various pieces; of these, the central metasternum is 

 generally the most enlarged portion : sometimes being pro- 

 duced into a point extending beneath the abdomen, as in 

 Hydrous ; sometimes it is flat, and occupies nearly the entire 

 under surface of the metathorax ; at other times, as in 

 Dyticus, the posterior coxae or basal parts of the hind legs 

 (which are of a large size), are soldered to it, and hence the 

 points of these parts of the hind legs have been often termed 

 the bifid mucro of the metasternum (see fig. 123). The sides 

 of the metasternum in the Coleoptera are laterally margined 

 by a pair of longitudinal pieces, which are the episterna, or the 

 parapleura, of Kirby and Spence. The construction of the 

 various parts of which the metasternum is composed, would 

 require too much minute description to be available in a 

 work like the present : I shall, therefore, only further 

 notice, that in winged insects having a pedunculated abdo- 

 men, Messrs. Audouin and Latreille consider that the piece 

 which terminates the thorax behind is not a portion of the 

 metathorax, but, on the contrary, is the basal segment of 

 the abdomen. This opinion appears to me to have been suc- 

 cessfully refuted by MacLeay and Burmeister. 



The appendages of the metathorax are the posterior pair 

 of wings, or their analogous organs, the third pair of legs, 

 and the metathoracic spiracle. 



It still remains to notice a curious apparatus, consisting 

 of a ligament, which passes through a slit at the extremity 

 of the postscutellum in the pedunculated Hymenoptera, (see 

 fig. 124, 125, x x,) in the middle of which is an elevation of 

 a horse-shoe form, having two apparent and one real central 

 aperture. This ligament is termed by Kirby and Spence the 

 funiculus, and is serviceable in elevating or depressing the 

 abdomen. 



I now proceed to the description of the Organs of Lo- 



