248 J. M. DALZIEL. 



(Another edible crab, Callinectes sp. (probably C. marginatus), is an article of 

 food which is appreciated even by Europeans. It has a deeply serrated carapace 

 with a longer spine at each end. This is one of the swimming Crabs and is not 

 concerned in the matter of mosquito breeding). 



Attention was first drawn to the connection between mosquito prevalence in 

 certain houses and the propinquity of holes of the land-crab by observing the numbers 

 of mosquitos which issued when the holes were disturbed. Collections of adult 

 mosquitos made in the houses showed, in the second place, an almost exact cor- 

 respondence with similar collections of adults issuing from holes in the garden or 

 on neighbouring ground. Proof was then obtained by finding larvae and pupae in 

 the water 'of the crab-holes and hatching them out in the laboratory with ultimate 

 determination of the species. 



Crab-holes may be found in almost any part of the island, but they are most 

 abundant near the lagoon margins, where the sahnity of the water tends to prevent 

 their contributing to the mosquito pest. On the other hand, owing to the proximity 

 of the subsoil- water to the surface all over the island, it may be that every crab-hole, 

 except those daily washed by the tide, is at some time or other a potential source of 

 mosquitos, provided that the water it contains is fresh or only brackish to a moderate 

 degree and remains so for a sufficient number of days. 



On certain reclaimed areas in the town, which were originally creeks or inlets from 

 the lagoon, they are particularly numerous. Such areas are generally overgrown with 

 grass, and being at present without proper drainage they have acquired a spongy 

 character, riddled with crab-holes and half- swampy in the rains. In these circum- 

 stances Anophehne as well as other mosquitos breed freely, yet httle except palHative 

 measures can be taken until a more thorough reclamation with proper grading and 

 drainage can be applied to alter the whole character of the locality. Their eradication 

 is rendered the more important owing to the close proximity of native dwellings 

 with a congested population, along with the observed fact that Stegomyia fasciata 

 does not shun the crab-hole, and the regular inspection of premises by the mosquito 

 brigade doubtless tends to drive this domestic species to seek a less disturbed hatching 

 place in the neighbourhood of houses. 



Although a considerable amount of routine labour has been devoted to these places 

 in conjunction with general out-door work, most of the details recorded in these 

 notes are the result of efforts directed against crab-holes in the vicinity of European 

 Government Quarters near the lagoon and around the GoLf-course at the eastern end 

 of the inhabited town proper. In this area after attention was first drawn to their 

 presence and potentialities it was found that a reasonable amount of properly directed 

 effort was well repaid by results. 



A smaU gang of labourers with native overseers under supervision of a European 

 was detailed in May 1914 for out-door anti-mosquito work, and at first particular 

 attention was paid to crab-holes in or near occupied European compounds. The 

 part dealt wdth included Government House and various other residences of officials, 

 along with the adjoining grassy slope of the Marina Road towards the edge of the 

 lagoon, the Golf-course itself with the European compounds around it, and an 

 unreclaimed marshy portion of the same area (here referred to as the Golf-course 

 swamp). 



