﻿254 L. NICHOLLS — SOME OBSERVATIONS ON THE BIONOMICS AND BREEDING- 



these marks grow indistinct, and may entirely disappear ; in diseased specimens 

 they are soon lost. At first this variability produced some chaos in my notes, in 

 which I had attempted to keep separate records of the breeding-grounds of the 

 two species ; but as I found that the places they frequented were so similar, I 

 have abandoned any attempt to discriminate between them. 



Pupae. — The pupae of these species (fig. 2) have a pair of palmate hairs on the 

 thorax which are similar to those situated on the dorsum of the segments of the 

 larvae. 



Fig. 2. — Pupa of Anopheles albimarvus^ Wied. ; 

 (a) lateral view, (b) dorsal view. 



The trumpets have wide openings on their inner sides. The markings of the 

 thorax^ vary greatly both in different specimens and at different stages of 

 development. 



Again, typical specimens of the pupae of A. albimanus can be distinguished by 

 two large white blotches situated on the posterior part of the thorax (fig. 2, b). 



Length of life-cycle. 



The egg hatches normally in 36 to 48 hours, but sometimes takes longer. It 

 is extremely difficult to obtain eggs from captive females, and even then, they 

 usually fail to hatch. I base the above length of time upon the following 

 experiment : — A favourite Anopheline breeding-ground was chosen, just as it was 

 drying up, and small pools were dug, and water added, which was taken from a 

 source Avhere no mosquitos could have had access to it. The pools were then 

 protected with muslin, which was removed as it became dark. The next day, 

 between 9 and 11 a.m., a thorough search was made for eggs, and in two of the 

 pools a few were found ; these pools were kept supplied with water to prevent 

 them drying up, and muslin tents were placed over them. In 36 hours the larvae 

 began to appear, and in less than 48 hours they were all hatched out. 



In other experiments in which newly formed pools were tented within 12 hours 

 of formation, I have had variable results. On one occasion it was indicated that 

 A. albimanus might hatch out in 24 hours. Unfavourable circumstances can 

 considerably prolong the egg-stage. , 



The length of the larval stage is very variable, and depends upon a number of 

 circumstances, such as the nature of the food supply, the health of the larva, the 

 protection from the elements, and the temperature of the water. Two of the 

 larvae in the above experiment changed to pupae in 11 and 1H days respectively 

 from the date of hatching ; but most of them pupated in between 12 and 14 



