THE ELYTRA. ll 



as an example of the difficulties to be met with in 

 forming a natural system, amongst the Coleoptera, it 

 sometimes happens, that the tarsal joints differ in the 

 two sexes, and some Tettigidae do not show their 

 trimerous characters in the fore legs. 



The Elytra. Oherflugel. 



On account of their semi-coriaceous texture, the 

 upper alse are called Elytra, and the lower organs alone 

 are styled Wings. 



A slightly modified nomenclature is used in this 

 treatise with reference to the wing-cells. It is chiefly 

 that adopted by Sahlberg, which appears to be more 

 simple than that constructed by Fieber and some 

 others. In the Cicadidae and the Membracid^, the 

 radial veins undergo many furcations, from which 

 arise a multiplicity of cells and reticulations ; but as 

 we pass to the Jassidae, and to still simpler genera, 

 the radial veins become restricted to three, or perhaps 

 only to two, main branchings, as exemplified in 

 Dicraneura, &c. 



The neuration of the elytra is often difficult to trace, 

 on account of the tendency of the membrane to 

 become horny ; the nerves or veins then fuse together, 

 and are lost in the substance of the wing. 



The elytra start from strong scale-like processes 

 articulated to the mesonotum (tegula3). They are 

 mainly supported by a robust costal vein, which, as a 

 rule, gives off no stout branches to other veins, but 

 anastomoses with them by short transverse veins. 

 The elytron is divided longitudinally by a straight 

 suture into the corium and tlic clavus, which last is 

 usually restricted to two unbranched veins. The 

 corium forms the largest part of the organ, and in 

 many species is bounded by a characteristic free 

 border, known as the hmbus, periphery, or appendix. 

 The clavus forms the efficient fold which overlaps the 

 margin of the flying apparatus, to the secure closure 

 of whicli the hmbus also conduces. 



6' 2 



