6 GNATS OR MOSQUITOES — CHAPTER I 



supposed that all of them are Slvmlla, and some of the 

 most common and vicious of Indian species approach so 

 closely in general structure, and even in the general appear- 

 ance of the venation of the wing, to the anomalous gnats 

 of the genus Corethra, that they are difficult to distinguish 

 without close examination, as may he seen by comparing 

 the figure given on previous page, of a species (probably new) 

 of Phlebotomus, most pestilent in its attentions in Himalayan 

 hill stations during the rains, with that given of the wing 

 of Corethra in the systematic description of that genus, but 

 it will be seen that what looks like a gnat's hinder fork cell 

 is really not the fourth, but the fifth longitudinal vein, and 

 that the sixth, in place of being simple, is also forked : 

 distinctions that will be better appreciated after a perusal 

 of the following pages on the terminology of the group. 

 The insect, too, is clothed, not witli scales but with hairs. 

 A more darkly tinted species of the same genus is equally 

 troublesome in the plains. 



In almost all cases it is the female alone that attacks 

 man and animals, an exception being noted in the case of 

 C. salinus by Ficalbi in his description of that species ; but, 

 however bloodthirsty they may be, it is obvious that they 

 must mainly depend on other nourishment than blood, for 

 these insects are sometimes found in just the places where 

 air-breathing vertebrates are most uncommon. 



The males of some Indian species, notably of Stegomyiu 

 fasciatus (Fabr.), undoubtedly often settle on one, and 

 place themselves in position as if to bite, but I have never 

 seen one actually do so, although afforded every oppoi'- 

 t unity. 



In England, and probably in other parts of the world, 

 gnats may be seen feeding upon the nectar of flowers, and 

 here it is certainly their usual food, a fact I have often 

 verified by personal observation ; but Mr. Theobald has also 

 seen C. ciliaris sucking the juices of small Diptera. The 

 peculiarity of the females alone being addicted to blood- 

 sucking is shared with the Tahanidce, or gad-flies, whose 

 males, too, live entirely on the juices of flowers. 



Coming now to the question of terminology, it may first 



