608 EXTERNAL ANATOMY OF INSECTS. 



tion of the wing that lies between the costal and post- 

 costal nervures ; and perhaps, in some cases, as in Mantis, 

 for there is the fold of the tegmen, the mediastinal may 

 be regarded as its limit ; the Intermediate Area is that 

 which lies between the postcostal or mediastinal nervure 

 and the anal fold of the wing ; and the Anal Area is the 

 remainder. These areas may perhaps best be made out 

 by tracing each to its axis. To study them carefully in 

 tegmina and hemelytra is of considerable importance ; 

 for in them we find the first outline of the general plan 

 upon which the wings of insects are constructed, and 

 which, as we shall see hereafter, more or less enters into 

 the composition of them all. 



4. Position, and folding in repose. With regard to 

 their position when not expanded, tegmina vary some- 

 what in the different tribes. In the Coleoptera we have 

 seen that, except in a few instances, the elytra unite at 

 their suture. Something like this takes place in Fulgora, 

 Cercopis and affinities, in the Homopterous Hemiptera ; 

 in these, though the union is not near so exact, yet the 

 tegmina do not lap over each other; they are usually 

 more or less deflexed, with scarcely any portion in a ho- 

 rizontal position : in Tettigonia F., Chermes, Aphis, &c, 

 the middle part only of these organs meets, from which 

 point they diverge both towards their base and apex a . 

 In the Orthoptera the position is quite different, for one 

 tegmen more or less lies over the other. In Blatta, in 

 which the tegmina are nearly horizontal, the left hand 

 one covers almost half the other b : in the other tribes of 

 the Order, with little variation, the Anal Area of the teg- 



a Stoll, Cigales, t. viii. /. 39. ,J Plate X. Fig. .2. 



