242 GNATS OR MOSQUITOES — CHAPTER IX 



ticus, Noe, again, belongs doubtless, to a rather warmer 

 climatic band than C. cantans, its northern limit being 

 probably Italy ; but here again the species, though I have 

 received it from most parts of India, does not appear to be 

 really at home except in the hills, and such stray specimens 

 as have come to hand from the plains have been taken at 

 seasons when the climate has lost its tropical character; 

 whereas in the Nehilgerri Mountains, it appears to be one 

 of the commonest local gnats. 



Where, as in the case of C. annulatiis, Sclirank, and C. 

 spatJiipalpis, Rond., which I have taken in the Himalayas, 

 there is, at some season of the year, continuous temperate 

 land connection between the scattered habitat of any one 

 species, distributions of this sort are easily understood ; but 

 it is hard to see how C. cantans can have reached the moun- 

 tains of Southern India at any period more recent than the 

 glacial epoch, and the fact of certain species being common 

 to Africa and the island-continent of Australia is even more 

 difficult to explain, unless the}^ have been carried overseas 

 by human agency ; and in this connection it is interesting 

 to note that in at least one instance the species is one that 

 has an exceptional power of enduring captivity, Dr. Bancroft 

 having kept specimens for as long as five months in con- 

 finement. 



As a rule then, we must not expect to find species as 

 closely confined to certain localities as is the case with 

 many other insect families, but to this, as to all rules of 

 the sort, there are exceptions in which species have under- 

 gone differentiation to meet the exigencies of a peculiar 

 environment. A notable instance of this is afforded by a 

 late arrival at the British Museum, recently examined by 

 Mr. Theobald, of a most aberrant form, generically distinct 

 from any previously received, which has chosen as its home 

 the burrows of certain crabs that live on the shore of some 

 of the West Indian islands. This extraordinary gnat has, 

 he tells me, antennae twice as long as its body, and but for 

 the last two joints, clothed with scales from the scaphus to 

 the tip. It must be left to field naturalists on the spot to 

 ascertain how or why this queer Mosquito should require 



