42 



is so great that even if the species are not those at present known to 

 be concerned in conveying disease, an effort to ehminate tlie breeding 

 places is called for if it can be shown that the insects contribute 

 appreciably to man's discomfort, reasonable comfort being one of the 

 first conditions of health maintenance in the tropics. 



The holes in question are made by a land-crab, Caniisoma armatum. 

 Every crab-hole, except those daily washed by the tide, is a potential 

 source of mosquitos, if the water in it is not too brackish. The method 

 first employed in dealing with the holes was to pour into them a 

 disinfectant such as cyllin, with either cold or boiling water (about 1:9). 

 The latter was more effective in killing the crab, and had the further 

 advantage that cheap tar or crude creosote could be used. However, 

 a proportion of the crabs survived this treatment, and the hole 

 reappeared in a day or two ; and eventually the practice adopted 

 for general use was simply to dig out the crab. Mere obliteration of 

 the hole without destruction of the crab is a waste of time. 



The mosquito larvae found in crab-holes were, in order of frequency, 

 Ochlerotatus irritans, Ciilex decens {invidiosus) , Uranotaenia annidata, 

 Ochlcyotattis nigricephalus, Stegomyia fasciata (7-3 per cent, of the total 

 number). Anopheles costalis, Ctdex insignis, Cidiciomyia nebidosa, 

 Ctdex thalassiiis, C. rima, C. salishuriensis , Uranotaenia bilineata 

 var. fraseri, Stegomyia luteocephala, and Micraedes inconspicuosus. 

 All except the last two were also taken as adults in the crab-holes, as 

 were in addition Ochlerotatus punctothoracis, 0. caliginosus, Culex 

 fatigans, C. consimilis, and Mansonioides africaniis. The peculiar 

 habit of the larva of M. africanus, however, in relation to water lettuce 

 {Pistia stratiotes) suggests that it does not breed in crab-holes ; the 

 other four probably do so occasionally. 



References to crab-hole mosquitos in various parts of the world 

 are given [R.A.E., B, i, 64; etc.], and their relation to man is 

 considered. Crab-holes supply an almost domestic source of 

 5. fasciata ; their connection with A. costalis, however, seems 

 to be more or less accidental. Both these insects, which occurred, 

 in equal numbers, are carriers of Filaria bancrofti. 



An account is given of the collection of mosquito larvae in tree-holes, 

 with lists of the species of mosquitos and trees concerned ; and an account 

 and lists are also given of the mosquitos breeding in wells, boats and 

 canoes, roof-gutters, native pots, and various domestic sources, and 

 of the adult mosquitos collected. 



Lamborn (W. a.). The Habits of a Dipteron Predaceous on Mosquitos 

 in Nyasaland.— B////. Ent. Res., London, xi, pt. 3, December 1920, 

 pp. 279-281. 



An Anthomyiid fly of the genus Lispa was observed to be predaceous 

 on mosquitos." The latter were usually attacked just before they had 

 emerged from the pupa-case, or before their wings had expanded 

 properly. In one case the fly drew a mosquito pupa from the water, 

 impaled on its proboscis. Another Dipteron also occurred that was 

 probably predaceous on mosquito larvae. 



The pool where these observations were made was swarming with 

 Ctdex larvae, and there were a few predaceous larvae of a much larger 

 species of mosquito, probably either Toxorhynchites brevipalpis, Theo., 

 or Culex tigripes, Grp., which were seen attempting to secure the 

 ordinary Ctdex larvae, and successfully preying on Syrphids. 



