MOSQUITO BREEDING IN SALINE WATERS. 31 



Hence it is of interest to note that in Somaliland Drake-Brockman recorded the 

 <:o-existence of Slegomyia larvae with those of Cidex sitiens, and stated that brackish 

 well-water was acceptable to the former. 



Macfie experimented with the larvae of Stegomyia fasciata at Lagos in the hope of 

 finding that common salt might be used as a larvicide in the case of this mosquito. 

 He showed that as regards domestic utensils the saline solution required to be of a 

 strength of 2 per cent, to ensure destruction of the larvae. Water containing 0-5 per 

 cent, of sodium chloride had no appreciable effect upon them. 



Fielding, working at Townsville, Queensland, found that the female Stegomyia 

 fasciata oviposited in 70 per cent, .sea- water. 



Darling demonstrated the fact that in Panam.a Stegomyia fasciata could breed in 

 brackish water of var\-ing chlorine content and that such water could also harbour 

 the aquatic stages of A . pseudopunctipennis, Theobald, A. malefactor, Dyar & Knab, 

 and Ciilex taeniorhynchus , V/iedemann. In swanips containing SO per cent, and more 

 of sea-water he found the larvae of A. albimanus, Wiedemann, and A. tarsimacidatus, 

 Goeldi, present in enormous numbers. Similar observations as regards A. albimanus 

 were also made by Jennings of the Isthmian Canal Commission. 



According to Peryassu the larvae of A . argyritarsis, Robineau-Desvoidy, in Brazil 

 are found in strongly brackish water as well as in fresh water. 



Howard, Dyar and Knab mention that certain Brazilian observers, experimenting 

 with the larvae of A. albimanus and A. argyritarsis, " found that in slightly brackish 

 water in»agos were produced in a normal nianner. In a mixture of 19 per cent, of 

 sea-water with fresh water only a very small proportion of larvae transformed to 

 images. Beyond this the larvae failed to pupate ; with 20 per cent, sea-water some 

 of the larvae survived three days ; with 30 per cent, all died after one day." 



Recent work by Taylor and Fielding in Queensland, Australia, shows that 

 A. anniilipes, Walker, is occasionally found breeding m salt waters. 



The latest research into the question of the occurrence of the larvae of Anophelines 

 in saline waters appears to be that by Sella, who had charge of the anti-malaria 

 campaign at Fiumicino, near Rome. His observations were carried out on the larvae 

 oi Anopheles maciilipennis or, as he calls it, A. claviger, and showed that a salinity up 

 to 6-7 per 1,000 of sodium chloride was without effect. Laboratory experiments 

 were also conducted, which indicated that the development of larvae is inhibited at 

 an early stage by concentrations of above 13-14 per 1,000, and that even those 

 exceeding 9 per 1,000 are no longer favourable to development. Pupae, however, 

 are able to tolerate a very strong concentration. From the point of view of the 

 employment of brackish waters in anti-malarial work it is interesting to note that the 

 investigations showed that solutions exceeding 20 per cent, must be employed in 

 order to ensure destruction within 10 hours, and exceeding 18 per cent, to obtain this 

 result within 24 hours. Further, it has been shown that larvae which have been 

 subjected to the action of the saline solution for several hours, if transported into 

 fresh water before they are dead, will survive. Apparently, to judge from cage 

 experiments, adult Anophelines are not influenced in laying by the mere salinity of 

 the water. 



So far as Stegomyia fasciata is concerned, its behaviour as regards brackish waters 

 and sea-water has also formed the study of French and Brazilian observers, as recorded 

 by Howard, Dyar and Knab in their important and comprehensive work on the 

 mosquitos of North America. 



Dr. Dalziel's note on the various species of Ciilex found breeding in the coastal salt 

 marshes of the United States of America doubtless refers to the observations of 

 Chidester, who made an exhaustive study of the subject. 



