EXTERNAL ANATOMY OF INSECTS, 381 
C. MetarHracma (the Metaphragm). A nearly verti- 
cal septum or partition, attached behind to the 
Postfrenum, and usually deeply cleft at its apex in 
Coleoptera, of a rather horny consistence, which 
forms the upper separation of the second cavity of 
the Alitrunk from that of the Abdomen?. It affords 
a point of attachment for many muscles of both 
alitrunk and abdomen. It includes the Septula. 
a. SEPTULA (the Septula). The lesser ridges and par- 
titions raised on the surfaces of the metaphragm, 
and on those of other parts of the cavities of the 
trunk, serving as points of attachment to various 
muscles °. . 
4. Posrprectrus (the Postpectus). The underside of the 
second segment of the alitrunk*. It includes the 
Mesostethium, Parapleure, Metasternum, Postfurca, 
Opercula, and Pedes Postici. 
A. MEsosTETHIUM (the Mesostethium). A central piece 
between the intermediate and posterior legs, and 
bounded laterally in Coleoptera by the Parapleure 
—along the middle of which, where it exists, the 
Metasternum runs 4. 
B. ParapLeurz (the Parapleure). Two pieces, one on 
each side of the Postpectus, included between the 
Scapularia, Mesostethium, and Pleure*. They in- 
clude the Spzracula Parapleuritica. 
a. Sprracuta ParapLeuritica (the Parapleuritic Spi- 
racles). Two spiracles, one in each of the Para- 
pleure of Scutellera ‘. 
4 Prate XXII. Fie. 10, 11, 2’. > [bid. Fic, 9—11. 2”. 
© Prates VIII. and IX. f. 4 Tbid. 7’. 
Abide 2 € Prare XXIX. Fic. 15, m’. 
