﻿PLACES OF ANOPHELES IN SAINT LUCIA, BRITISH WEST INDIES. 255 



days, the last pupa appearing on the fifteenth day. The surroundings were very 

 favourable, and the experiment was made during the hot month of August. 



A favourable artificial breeding-ground can be formed by cutting down a large 

 tub to a depth of six inches. This is nearly filled with water, a little mud is 

 stirred in, and a few grasses and algae added. It should be placed in a protected 

 situation in the open, so that it gets the proper degree of shade and sunshine. 

 Into such a receptacle small larvae, a little more than a millimetre long, were 

 introduced, and in 85 cases the larval period exceeded 14 days only seven times. 

 I have hatched out many hundreds of larvae in these six-inch tubs : but here I 

 only include cases in which careful daily watching has shown that the food-supply 

 has been more than adequate, and no disease has crept in. Disease always 

 develops in artificial breeding-grounds, unless the water is properly changed, and 

 the grasses or algae are obtained from fresh healthy situations. In glass vessels 

 and in any adverse situations the larval period is greatly prolonged. I have 

 kept an infected larva 31 days before it became a pupa, but the imago appeared 

 in another two days. 



I have on seven occasions seen a larva change to the pupal condition, and the 

 same pupa hatch to an imago. The periods ranged from 47 hours 10 minutes to 

 54 hours 35 minutes. The statement is frequently made that the imago emerges 

 from the pupa during the late afternoon. This is not so with A. argyrotarsis or 

 A, albimanus, for as many emerge before noon as after this time. 



It is very important that the duration of the developmental stages of mosquitos 

 should be known, but obviously these cannot be stated to a day. 



The following table gives the probable durations in days for A. argyrotarsis 

 and albimanus : — 



— 



Under favourable 

 conditions. 



Maximum under 



unfavourable 



conditions. 



Egg stage 



Larval period 

 Pupal period 



l|-2 



11-14 

 2 



2% ? 



31 or more 



2i? 



14^-18 



36 or more 



The food of the larvae consists of small particles of decomposing vegetable 

 matter and minute water-plants ; they are also able to devour the larvae of other 

 Diptera, and will eat the decomposing bodies of all kinds of insects. 



The length of life of the imago is very difficult to determine ; but probably 

 there are very few individuals which exist for more than six weeks. A fortnight 

 is the a Average length of life in moderate-sized cages, with an abundant food- 

 supply. This does not include the males, which rarely live for a week. 



I once fitted up a room as a large cage. It was well cleared of spiders and 

 other insects. A continuous supply of fruit was kept in it for food, and every 

 second day I entered the room and allowed myself to be bitten. About 30 A. albi- 

 manus were hatched out and placed in the room. The last of them was alive on 

 the thirty-first day, but none could be found on the thirty-fourth, Between 

 these days I had been unable to enter the cao-e, 



