1 

 606 EXTERNAL ANATOMY OF INSECTS. 



some measure as sails, and help them in flying tra- 

 versely and before the wind a . 



ii. Tegmina b . By this name the learned Illiger has 

 distinguished the upper organs of flight of the 0?-tho- 

 ptera and Heteropterous Hemiptera c . They may be 

 considered under the same heads nearly as elytra. 



1. Substance. Tegmina differ very materially from 

 elytra in their substance, being generally more or less 

 diaphanous, though in Blatta Petiveriana the dark parts 

 are as opaque as elytra, and those of the Mantes that 

 resemble dry leaves are only semidiaphanous. These 

 organs are also of a less dense substance than elytra, 

 something between coriaceous and membranous, which I 

 shall express by the term pergameneous, as somewhat re- 

 sembling parchment or vellum. Another circumstance 

 relative to this head also distinguishes them, — they are not 

 lined with membrane. In some instances, as in B. Petive- 

 riana just named, they approach nearly to the substance 

 of elytra, and in B. viridis, some Mantes, and Tettigonia, 

 &c, they are little different from wings in their substance; 

 but this does not diminish their right to be considered 

 as tegmina, since their structure is altogether the same. 



2. Articulation with the trunk. I observed above that 

 the axis of elytra may be regarded as formed of three 

 parts, one appertaining to each of the areas or their re- 

 presentatives' 1 ; in tegmina, and indeed in wings in gene- 



a M. Chabrier says that the arc described by the tvivgs of Melo- 

 lontha vulgaris to that of the elytra, is as 200 to less than 50. Sur le 

 Vol des Ins. c. i. 440. 



b Plate X. Fig. 2. and XXVIII. Fig. 18—20. 



c Magas. 180G. Terminologie der InseM. 18. 1675. 



d Plate X. Fig. 2. is the tegmen of*. Blatta divided into areas. 



