THE CAUDAL TUFTS OF MALAYAN" AXOPHELINE LARVAE. 95 



attached larvae then swaying backwards and forwards from the point of attachment. 

 Larvae are able readily to attach themselves to moving objects. 



In this way, then, the larva is able to avoid being swept away, and it can also employ 

 both sets of hooks together at one point, thenresting more or less parallel to the support- 

 ing object, its head down current, a measure of value doubtless when it has to sustain 

 itself against a greater pressure of water than it could withstand in any other position. 

 When the larva is floating unsupported against any object, the caudal fans are approxi- 

 mated and directed back, and in this position it was noted occasionally, especially in 

 A . macidatus, A . indefinitus and A . aitkeni, that the hooks from the bristles of opposite 

 sides may be interlocked. 



Were any confirmation as to the function of the dorsal tufts needed, it is afforded 

 by the study of these structures in A . aitkeni and A . asiaticus. In A . aitkeni, a regular 

 breeder in mountain streams, the number of hooks available for the support of the 

 larva is at least double, since both dorsal tufts bear them. In A. asiaticus, a breeder 

 in bamboos, the structures show a very definite tendency to atrophy, a fact suggesting 

 that the very special sort of habitat selected for the larvae is by no means a very recent 

 choice on the part of the female parent, an inference supported b3^ the size of the 

 primitive larval eye, which is very much smaller than in the larvae of any of the other 

 species of the group, and by the absence of the group of pigment spots arranged in 

 crescentic form, which in other species represent the developing compound eye. It 

 is interesting to note in the case of the bush-breeding Anophelines and in Stegomyia 

 (also a breeder by preference in dark places), an approximation to a similar condition.* 

 The presence of any hooks at all in the case of A . siibpicfiis var. vagus, and others which 

 breed by choice in the still water of muddy pools, is doubtless to be explained by recent 

 modification of breeding habits ; for until the advent of the white man to this country- 

 and the subsequent great economic development, there must have been comparatively 

 few such breeding-places available. 



Though these hooks must be the chief means of support to larvae, it is certain that 

 the young larvae of .4. maculatus, A . kanvari and A . aconitus are able to attach them- 

 selves to an object for a short period of time by their mouth-parts. It was necessary 

 in the course of some breeding experiments in connection with these species to transfer 

 young larvae from one porcelain bowl to another, and it was repeatedly found that 

 some with their heads applied to the surface of the bow4 could resist withdrawal into 

 a glass tube, and that if a current of water was then directed on them, they were not 

 readily dislodged, swaying to and fro at the point of attachment. The porcelain being 

 glazed, it would appear as if they had some power of attachment thereto by suction, 

 no booklets being present on the mouth-brushes. 



The supporting hooks found in the case of the larva would benefit the several 

 species but little, if there were not some sort of counterpart in the case of the pupa. 

 The usual text-book description of the way in which a pupa evades danger is that it 

 does so by diving and keeping itself submerged. Its specific gravity being less than 

 that of water, it remains below either by getting under some object, or by holding fast 

 by clasping it between its thorax and its flexed abdomen. This appears to be 

 true of certain of the Anophelines, but not of ah. It was recognised, for instance, by 

 the writer early in the course of a study of A . vagus in its muddy pools that the pupa 

 is able to sustain itself with its tail, apparently just simply applied to any portion of 



* In this connection it is noteworthy that, whereas in the fully-grown larvae of A. hyrcanus 

 and A. barbirostris (open-country breeders) the pigmented elements of both larval and imaginal 

 eyes reach a maximum development, in the case of A . iimbrosiis, the remaining Malayan repre- 

 sentative of the Myzorhyuchus group of Anophelines (a breeder by preference in jungle), they are 

 much reduced in size, especially in the crescentic eye, in which indeed they are so pale that the 

 determination of their presence is difficult. 



