207 



being a more active carrier of malaria than the other ; and this would 

 explain discrepancies in reports regarding the relative malaria-carrying 

 powers of certain species, their apparent harmlessness in one country 

 or part of it, and their importance in another. The methods used in 

 breeding are described. 



Experiments in reproductive capacity gave the average number of 

 eggs laid by a female oi A. hyrcanus, Pall., as 66, the maximum 

 obtained being 188, while for other species the relative figures were, 

 for A. hyrcanus var. paeditaeniatus, Leic, 53 and 147; for A. 

 barhirostris, Wulp, 69 and 293 ; for yl. maculatus, Theo., 63 and 300 ; 

 for A. karwari, James, 53 and 97 ; for ^. vagus, Don., 89 and 273 ; 

 for A. suhpidus var. malayensis, Hacker, 68 and 114; for^. ludloun, 

 Theo., 65 and 120 ; for ^. aconitus, Don., 38 and 117 ; for ^. kochi, 

 Don., 40 and 110 ; for A. fidiginosus, Giles, 58 and 95 ; and for A. 

 tessellatus, Theo., 29 and 49. The ova were generally laid in one batch. 

 Infection of Anophelines with the malaria parasite seemed to have 

 no adverse influence on oviposition. 



The results of desiccation on the ova in various stages and for 

 varying lengths of time showed that at a very early stage of incubation 

 the eggs of most species cannot withstand even short periods of 

 drought, an exception being noticed in A. barhirostris, which, even 

 in the preliminary stages, could withstand drying for 24-48 hours. 

 In the case of A . vagus some of the ova in which incubation must have 

 begun were able to retain their vitality up to 72 hours when dried, 

 and similar results were obtained with A. fuliginosus. Desiccation 

 always checked the development of the ova to some extent, in some 

 cases preventing it entirely, and in no instance did hatching take 

 place for a considerable number of hours after the restoration of the 

 eggs to water. In nature, the fact of the eggs having been laid in a 

 selected spot, even in the smallest pool, ensures their having the 

 requisite moist environment until they have attained a degree of 

 development that wiU enable them to retain their vitality in the event 

 of the drying up of the pool. When moisture becomes insufficient, 

 although the larvae may be ready to hatch, their actual emergence 

 may be delayed without injury for some little time, until conditions 

 have become more favourable to them. Irregularity in hatching 

 under normal conditions, in the case of eggs floating on water, has 

 been found to occur, at any rate in the laboratory. On the other hand, 

 hatching may be practically simultaneous in some batches although 

 the conditions may not be unifonn for ah the eggs of the batch. 



Oviposition was found to take place, in the case of all open-country 

 species, generally between 8 p.m. and 6 a.m. The length of the life- 

 cycle varied considerably, even in the case of larvae bred from ova 

 laid on the same day and kept under the same conditions ; these 

 variations undoubtedly depend, besides irregularity in hatching, upon 

 inequality in the rate of growth of the larvae. A number of instances 

 of such irregularities in the case of families of ^. maculatus are quoted, 

 as well as instances of A. fuliginosus and A. kochi. This inequality 

 in hatching and development must go far to ensure the continuance 

 of a particular strain. Larvae when removed from water rapidly 

 succumbed, even in a moist atmosphere, but pupae in the same 

 atmosphere were able to survive without water and complete their 

 metamorphosis within the usual time. The pupae of Aedes {Stegomyia) 

 albopictus, Skuse, a particularly hardy species, survived for hours, 

 even when thoroughly dry. Pupation generally took place durmg 

 the night, but in the case of A. albopictus, a diurnal species, it usually 



(8009) ^ - 



