EXTERNAL ANATOMY OF INSECTS. 559 



you will see clearly that the Anal Area of these wings is 

 attached to a process of it, a proof that it belongs to the 

 mesothorax, or region of that pair. But in the Diplera, 

 the part that has been usually called the scutellum is not 

 at all connected, either by situation or as a point of at- 

 tachment, with the wing itself, but with the lower valve of 

 the alula, which is with reason thought to be the repre- 

 sentative of the secondary wing of the tetrapterous Orders. 

 You may see this even in the common crane-fly ( Tipidd), 

 in which there is a real alula s connected by means of a la- 

 teral process, terminating in ligament, with this supposed 

 scutellum. If you examine further the same insect, you 

 will easily find what I regard as the true one in the bi- 

 lobed piece which receives the dorsohi?n, situated be- 

 tween the wings, and to the sides of which they are at- 

 tached. In Asilus, Tahanus, &c, this part is transverse, 

 and only distinguished on each side by an oblique im- 

 pressed line ; in the Muscidce it is square, and marked by 

 a straight transverse one. 



4. Frcenum a . This appendage to the scutellum and 

 dorsolum varies considerably in the different Orders, and 

 in many cases, as you will see, is a very important part, 

 being the process by which the former is mostly con- 

 nected with the elytra or upper wings. In the Coleo- 

 ptera, the elytra of which are nearly stationary in flight, 

 and therefore less require any counteraction to prevent 

 their dislocation, this part is commonly merely a process 

 or incrassation of the under margin of the scutellum, 

 which towards the base of the dorsolum is dilated to 

 form the socket for the elytra. Its use as a countercheck 



» Plates VIII. IX. XXVIII. f . 



