64 



are characteristic of the woods and forests inland, while others 

 are confined to the coast-line, being especially prevalent in man- 

 grove swamps. The latter forms are known locally as " maruim." 

 In some places they are such a pest that the inhabitants are 

 obliged to leave the neighbourhood at certain times. 



Dr. Lutz has for a long time been of opinion that the breeding- 

 ground of these midges would probably prove to be in the stink- 

 ing mud of the mangrove swamps. He accordingly examined 

 with great care this mud and the water standing above it, with- 

 out result. He also carefully examined the bark of the man- 

 grove trees, as well as their aerial roots, without success, and by a 

 process of exclusion, assisted by theoretical considerations, he 

 returned to the examination of the crab-holes which at first had 

 given no positive results. There are many species of crabs 

 inhabiting these swamps, only some of which make holes. These 

 holes are of two kmds ; one is dug out of the mud which for the 

 greater part of the day is under water to such an extent that its 

 upper opening is never quite dry, and the hole always contains 

 pure sea water. Another species makes holes in the sand at some 

 distance above the tide-mark, the water in these being generally 

 fresh, or at most brackish, and much cleaner than that in the 

 mud-holes, since it is filtered through sand. Experiments were 

 first made to ascertain whether these crab-holes really were the 

 breeding-places, and for this purpose a large area on the border 

 of a mangrove swamp was surrounded with a screen made of oiled 

 paper to which the insects would adhere. In the larger crab- 

 holes wide-mouthed bottles were placed which were afterwards 

 covered with a bell- jar smeared with a mixture of water, alcohol, 

 and glj^cerine in equal parts and a little carbolic acid, which 

 kills the insects and at the same time preserves them. The 

 bottles were frequently upset by the crabs and the observations 

 spoilt. He found that the small crab-holes in the mud area gave 

 practically no results. The larger ones on the dry shore yielded 

 a number of specimens of Ctilex reticulaUis, sp, n., as well as 

 Culex corniger, Theo., and C. (Culicelsa) taeniorliynclms, Wied. 

 Both these species are also to be found in fresh water, but the 

 author found them only on the coast line. On the other hand he 

 obtained no specimens of Deinocerites. He next pumped water 

 out of the large crab-holes, and when this was allowed to stand 

 a number of larvae of Ceeatopogoxinae appeared. He also 

 found that if these holes were dug out and the water allowed to 

 settle in them the larvae came to the surface. As a result of a 

 very large number of observations of this kind, he discovered that 

 only one of five species of Culicoides inhabited the more or less 

 fresh water in the crab-holes. This species showed little or no 

 periodicity and was but slightly affected by the tides. 



The author sought for the other species in the water which 

 circled freely between the mangrove trees, and was able on one 

 occasion to capture a number of free-swimming larvae which 

 yielded three further species. Dr. Lutz believes that the imago 

 only emerges when, with the fall of the tide, the pupa is 

 deposited upon the more or less dried mud. There is not time 

 for this between two spring tides, but it occurs at neap. 



