260 



J. M. DALZIEL. 



The first five species in the list practically always occur in the same order in 

 samples taken from wells, provided that a fair number are examined. C. decens 

 favours nearly as great a variety of breeding places as S. fasciata. A. costalis 

 tends to be relatively more frequent in wells located on vacant premises. C. tigripes 

 was always in association with one or more of other species, viz., S. fasciata, 

 0. irritans, C. duttoni, C. grahami and C. fatigans, the larvae of the former preying 

 on those of the latter. The larvae of C. consimilis have not been found (in the 

 course of the work covered by these notes) except on the two occasions in wells, 

 where they were also associated with S. fasciata. The adults have been captured 

 in various houses of European ofiicials and in crab-holes on the same premises. 



Mosquitos breeding in Boats and Canoes. 



A weekly inspection of boats and canoes around the foreshore is made and gives 

 an opportunity for ascertaining the species which frequent them as breeding- 

 places as shown in the list below : — 



Species of Mosquito. 



Number of Occurrences. 



Anopheles costalis . . 

 Stegomyia fasciata 

 CuUciomyia nehulosa 

 Culex thalasshis . . 







9 



7 

 6 

 & 



„ sitiens 







3 



,, fatigans 

 Ochlerotatus irritans 







2 



1 



,, nigricephalus 

 Anopheles funestus 

 Culex duttoni 







1 

 1 



1 





36 



A. funestus was an unexpected find, and in spite of the existence of numerous 

 apparently suitable conditions on the island it does not appear in any of my lists 

 apart from this one, either as larva or adult. It is more abundant in fresh waters 

 far from the sea. 



In a majority of cases the water in these sources is brackish, being lagoon water 

 diluted by rain or vice versa. Under these conditions, although C. thalassius does 

 not head the list, it is probably the most abundant survivor; e.g., in a canoe contain- 

 ing distinctly brackish water, numerous larvae of C. thalassius and A. costalis 

 occurred, but of the sample obtained, only one imago of the latter hatched out, while 

 most of the former went on to full development. 



In the instances in which C. sitiens was found, the water was decidedly salt to 

 the taste, and the imagines hatched out readily in the samples obtained. Analysis 

 showed 1 '8 per cent, estimated as chlorine, an equivalent of 2 "99 per cent, sodium 

 chloride. The larvae of this species have not been found in other sources during 

 these observations. It has been recorded from Port Sudan in a pot sunk in salt 

 water (Theobald, Mon. Cul. v, p. 388). 



