270 PTILOTA : IMAGO EXTERNAL ANATOMY. 



segment is typically composed, arc sufficiently distinct in the 

 mesonotum ; the first, or the praescutum (a 2) (prophragma, 

 Kirby and Spence) ; and the second, b 2, scutum (or the 

 dorsulmn, Kirby and Spence), are both distinct,but not conspi- 

 cuous parts in the Coleoptera, in which order the third piece, 



Ti 



126 



(c 2), is very conspicuous, being the triangular part which is 

 found at the base of the elytra, where they unite together, 

 and is ordinarily termed the scutellum ; but more properly 

 the scutellum of the mesothorax or mesoscutellum. Some 

 beetles, indeed, are said to be exscutellated, or destitute of 

 scutellum ; and so far as its occupying the ordinary exposed 

 situation is concerned, they are exscutellated ; but the same 

 part is to be found in a diminished form in all these beetles. 



In some few insects, as the Scutellerce ( Tetyrce), the scutel- 

 lum is so much enlarged, that it completely covers the abdo- 

 men. The postscutellum of the mesothorax, (d 2) or the 

 franum of Kirby and Spence, is also distinct, but not very 

 conspicuous, except by dissection. 



In insects having the upper wings transformed into horny 

 or leathery wing-covers, the mesoscutellum is very distinct 

 and elevated, being evidently serviceable in giving some kind 

 of support to these wing-covers. In insects with mem- 



