46 BRITISH CICADiE. 



vegetable-feeding mite, on changing its food and 

 general habits, would find its eyes of little or no 

 practical value to itself, and might finally lose them 

 altogether. We see such to be the case in the 

 Trombidiidae, and also in the eyeless fleas of various 

 bats. 



Under somewhat different conditions we likewise 

 adduce the examples of certain eyeless Aphides which 

 live in subterranean ants' nests; and other cases of 

 similar nature will present themselves to ordinary 

 observers. 



Useful as this hypothesis may be, as to showing the 

 immediate cause of the degradation of organs by non- 

 use, the explanation nevertheless may prove to be only 

 partially true ; for Charles Darwin has told us that the 

 blind beetle, Bathyscia, is indifferently the inhabitant 

 of dark caves or of shady rocks quite away from such 

 caves (see 'Origin of Species,' p. 111). The same 

 observer adds that most probably such blind beetles 

 had originally seeing progenitors. 



Some surprise may be felt that organs specially fitted 

 for parasitic use are not passed from the larval to the 

 imago state. Should not these conditions, if not fur- 

 ther developed, at least show themselves rudimentarily 

 in the adults ? On the side of evolution Prof. Claparede 

 considers that the hair-claspers of parasitic mites 

 must have been independently developed, and formed 

 from special modifications of such parts as the legs, 

 the maxillae, or the palpi of previous species. 



After all, we must still speculate on the wherefore, 

 and how, and why, animals should take upon them- 

 selves such diverse tastes and diets, as those of vege- 

 table and subsequently of living juices of animals. 



Mosquitoes, born from larvae and bred within the 

 Arctic Circle, cannot, one in a million, have the 

 opportunity of tasting the blood of any mammal ; yet 

 explorers like Nordenskjold and J. Nansen describe 

 themselves as driven almost to distraction by the 

 thirsty attacks of these creatures. The notice that 



