98 BRITISH CICADA. 



they are more commonly torn through the efforts made 

 to spread them than they are successfully opened out 

 for correct drawing. 



It may be noted that wing-nervures act much 

 as distenders, somewhat similarly to the ribs of an 

 umbrella. They also partly determine the courses of 

 the folds. During the insect's lifetime the ribs have a 

 considerable spring, and the stout character and 

 strength of the furcated submarginal vein (Nahtrippe 

 of Fieber) principally causes the first and chief 

 plication. In the Deltocephali and the Typhlocybidfe 

 this submarginal wing-vein is markedly developed, 

 and the same is seen also in Faramesus, Thamnotettix, 

 Limotettix, &c. 



The elastic spring of the wing-nervures, under the 

 control of the living insect, is observable in the 

 familiar sight of a Coccinella or a Staphijlinus packing 

 up its voluminous wings under its small elytra, after 

 the end of a flight. Similar action occurs, but with 

 marvellous rapidity, after the leaps of the small 

 Typhlocybidas and other groups of the Tettigidge. 



A departure from the normal arrangement has not 

 yet been shown in any special neuration of the males 

 and the females ; but the fact that insects of other 

 families sometimes show examples of a male morph- 

 ology on one side and a female morphology on the 

 other, will make us wonder less at a few departures 

 from the strict type to be noted on my plates. I have 

 more attempted to draw what the microscope seemed 

 distinctly to show, than to make such drawings con- 

 form to what we might expect from details usually 

 furnished by the genus. To prepare for such drawings, 

 wings may be floated out on water, and deposited on 

 glass microscope slides. Unfortunately these dis- 

 sections are, when stored dry, liable to the growth of 

 mycelium and mould, even when mounted in glazed 

 dry cells. If, on the other hand, Canada balsam be 

 run in, the wings are made so transparent that their 

 venation becomes almost invisible. 



