PARASITES OF THE TETTIGIDiE. 47 



fresh blood is near seems to be trumpeted by these 

 msect plagues for miles around. 



Where there seems to be so little scope for action, 

 it is puzzling to argue how the correlations of taste, 

 necessary mouth-parts, and accommodating stomach, 

 should rise out of utterly different larval life-condi- 

 tions by mere natural selection ; and why these should 

 only appear in one sex. The probabilities of an un- 

 conscious haphazard selection exerted on two — to say 

 nothing of three — simultaneous modifications of 

 organs, perhaps of different physiological systems, yet 

 all in one direction, seem to be very remote. Again, 

 might we not argue, on the contrary, in favour of a loss 

 of parts in blood- sucking animals in the above in- 

 hospitable arctic regions, simply from the constrained 

 conditions of disuse ? Yet the mosquito is an adept 

 at its work, with no inherited education to help the 

 gratification of its sanguinary tastes. 



Previously to resuming the Diagnoses of the 

 Jassidae, it may be well to remark that of all the 

 Tettigidas probably the species comprised under the 

 sub-families Jassides and Typhlocybides are the most 

 difficult to identify. Species to the naked eye, and 

 even when assisted by a lens, often show such 

 similarity that they may be often mistaken. It is only 

 when morphological differences can be proved, such as 

 those to be noted in the details of the pygofer, that 

 definite characters can be found to justify separation, 

 one from the other. 



Undue multiplication of species, on trivial grounds, 

 must be regarded as an evil ; and perhaps this mistake 

 is on the increase. 



Mere staining of the membranes, or body tissues, 

 apart from the deposit of pigment, may be due to 

 climatal causes or to photographic action, and some- 



