118 GNATS OR MOSQUITOES — CHAPTER VII 



The necessity of sunlight is mentioned by Meinert, and 

 is also noted in a letter I had received from Dr. St. George 

 Gray, of St. Lucia, in the West Indies, and furnishes an 

 explanation of the failure of all our efforts to keep these 

 larva? in health in captivity. In speaking of the habits of 

 Culices, Mr. Aitken refers to the specially domestic species, 

 for those of many sylvan gnats are less tolerant of dirty 

 water than any Anopheles of my acquaintance, and those of 

 Mr. Theobald's new genus Stegoviyia, are the most dainty 

 larvae I know of in this respect, which probably accounts for 

 the fact that they are all essentially insects of the rains. 

 Species, such as G. fatigans, which live in really foul water, 

 subsist largely on the vibriones with which it swarms. 



Waterless tracts, or such as are desert owing to the 

 character of the soil, are necessarily free from Mosquitoes, 

 except through the indirect agency of man, but in by far the 

 majority of situations, food for both their stages of existence 

 is obtainable, and gnats of some sort are included in the 

 fauna ; though the species harboured will vary with the 

 sort of accommodation offered. 



In searching for larvae, it is little use attempting to do 

 so by a mere inspection, as owing to their universally pro- 

 tective colouring, it is easy to overlook them, even when 

 present in large numbers, if one merely stoop down and 

 peer into the puddle. The examination should be made 

 by dipping up some of the water from the surface of the 

 paddle in an ordinary tumbler, and examining it by trans- 

 mitted light. If care be taken not to disturb the mud at 

 the bottom, it will usually be easy to do this at once, but 

 should the water get stirred up, the specimen must be put 

 aside till it settles. 



The habits of the larvae, not only of the different genera, 

 but also of individual species of the same genus differ 

 greatly, and much misconception has arisen from hasty 

 attempts to generalise ; for, as a matter of fact, it is impos- 

 sible to say that you will find the larvae of Anopheles in 

 certain situations, or in water of a given degree of purity 

 or otherwise, as those of some species frequent only fairly 

 pure collections, while others are hardly less particular than 

 many, even domestic species of Culices. 



