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CHAPTER VII. 



On the Life History and Seasonal Prevalence of Mosquitoes. 



The life history of any species is necessarily mainly 

 determined by the nature of its food ; and in these insects 

 this differs entirely at different stages of their career ; for 

 while the larva is a purely aquatic animal, feeding on pond 

 organisms, vegetable and animal, the adult flying insect, 

 from the structure of its mouth, can subsist only on fluid, 

 or at most, emulsified forms of nourishment ; and as 

 naturalists are generally agreed that gnats cannot travel 

 to any considerable distance, it follows that food both for 

 adult and larva must be obtainable within a limited area, 

 for mosquitoes cannot and do not fly far. It is impossible 

 to fix any absolute limit to their powers in this respect, but 

 it may be safely asserted that few individuals ever stray 

 much more than a quarter of a mile from the pool in which 

 their larval youth was passed, and the great majority never 

 travel further than the nearest shady spot. Nor, in spite 

 of popular beliefs to the contrary, can they be carried far 

 by the wind. Mosquitoes, indeed, exhibit a well-founded, 

 instinctive dread of boisterous weather, and will not leave 

 shelter in a high wind. Those accidentally carried away 

 are, I am inclined to think, rapidly disabled. 



When serving as Naturalist to the Indian Marine Survey 

 I was necessarily at sea for months together, and though 

 butterflies, dragon flies, and other strong flying insects often 

 boarded us far out at sea, I found no evidence of small 

 and delicate species being transported in this way. 



A run up the Hooghly for coal would fill our cabins 

 with these unwelcome shipmates ; but, once fairly at sea, 

 their numbers rapidly diminished, though a certain number 



