610 EXTERNAL ANATOMY OT INSECTS* 



gle ; and in others of the tribe they are nearly wedge- 

 shaped a . 



6. Neuration. The circumstance that most strikingly 

 distinguishes tegmina from elytra is their neuration or 

 veining : which adds much to their strength, without in- 

 creasing their weight so much as to render them unapt 

 for flight. To look at these organs in Blatta Petiveriana, 

 you would imagine them at first to be deprived of this 

 distinction ; but if you observe them attentively, particu- 

 larly their white spots, you will soon detect their ner- 

 vures ; and if you further examine their lower surface, 

 you will find them very visible. The gibbous Blatta 

 also, Blatta picta and affinities, the analogues of Erotylus 

 amongst the Coleoptera, have tegmina which, except at 

 their apex, exhibit but faint traces of the nervures of their 

 tribe, and approach to elytra besides by the innumerable 

 minute impressed points that cover them. In the OrtJio- 

 ptera and some Yiomo^texous Hemiptera the nervures may 

 be divided into longitudinal ones more or less ramified, 

 and traversing ones. In the Blatta the traversing ner- 

 vures cut the longitudinal ones nearly at right angles, but 

 not at regular intervals, so as to cover the tegmen with 

 quadrangular areolets; in Mantis precaria and affinities 

 the longitudinal nervures of the Anal Area diverge from 

 the base, and are traversed nearly as in Blatta, while 

 those of the Costal diverge from the mediastinal nervure, 

 but the traversing ones form innumerable irregular re- 

 ticulations; in Mantis sinuata K. b the whole tegmen has 

 such reticulations but less numerous ; in Locusta Leach 

 it is regularly reticulated at the base, but the areolets of 



a Stoll Cigales t. iii./. 12—15. and t.xvn.f. 92. 

 b Linn. Trans, xii. 449, no. 96. 



