270 



PTILOTA : IMAGO — EXTERNAL ANATOMY. 



segment is typically composed, are sufficiently distinct in the 

 mesonotum ; the first, or the prsescutum (« 2) (prophragma, 

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

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

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



126 



Figs. 126, dorsal view of the thorax of a Tabanus ; ll!7, lateral view of ditto, lettered as 

 in fig-s. llS-123. 



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

 found at the base of the elytra, where they vmite 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 ScutellercB {TetyrcB), the scutel- 

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

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

 frcenum 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 mng-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- 



