92 W. A. LAMBORN. 



a drain after a two-inch shower. I have watched them at play in a clear pool at the 

 foot of a rock down which water was flowing with considerable force, since the rock 

 sloped to the pool at an angle of forty-five and its face was a foot long. The current 

 of water was still further increased in strength by the rock being funnel-shaped, and 

 all the water coming down the face was gathered into a solid stream as it entered the 

 pool. The larvae were playing not exactly like trout, head to stream, but were floating 

 round in the current, and every now and then one would swim right into the stream, 

 up it for a short distance, and then hang on the side of the apparently bare rock in the 

 full strength of the current." Further on (p. 116) he remarks that " the larvae have 

 the power of attaching themselves to objects." 



Anopheline larvae, at all events such as live in moving water, do not, as a rule, go 

 in search of food. They rest at one place, brushing constantly the minute particles 

 carried past into their mouths, consuming such as they wish, and ejecting the rest. It 

 is hardly to be expected that a larva undergoing extremely rapid growth and develop- 

 ment, on what would appear to be a precarious method of obtaining food material, 

 could afford to waste any of its energy through having to keep its position by strong 

 and constant muscular eft'ort. Some sort of mechanism involving a minimum 

 expenditure of energy, and not a means similar to the muscular effort that enables 

 a frsh to remain at one spot in a stream, was to be looked for. This is found in the 

 dorsal pair of tail fans, the true function of which is now pointed out for the first 

 time, so far as the writer has been able to ascertain. 



Patton and Cragg, in their " Text Book of Medical Entomology " (1913, p. 200), 

 describing the ninth segment of an Anopheline larva, state that " the dorsal border is 

 furnished with two pairs of long feathered hairs, which are directed backwards as a 

 tail. The ventral surface bears two rows of feathered hairs arising in the middle line 

 from an elongated and raised area of thick chitin. The two rows are set very close 

 together, so that when examined in side view they appear as one, and hang down at a 

 right angle to the long axis of the body as a sort of fin. Each hair is articulated into a 

 little round pit in the chitinised area." 



Giles in his work " Gnats or Mosquitos " (second edition, p. 46), describing the larva 

 of a Ciilex, states that on the last segment, " on either side, but originating in frcnt of 

 the anal tubercles, are a pair of large dense tufts of compound hairs, which are 

 employed in swimming in the same way as a fish's tail, and are so arranged as to form 

 an expansion of similar shape." In his description of an Anopheline larva (p. 60) 

 he states that " the last segment carries four anal tubercles, which, as well as the tail 

 fans, are rather less developed than in Culex." 



The American authors — Howard, Dyar and Knab — in their " Mosquitoes of North 

 and Central America and the West Indies," do not give any special description of 

 these tufts in Anopheline larvae. 



From the foregoing it is evident that no structural differentiation of the two sets 

 of brushes in larvae had been noted. In the larvae of Malayan Anophelines the 

 ventral tufts are as described. But with an objective even of such low power 

 as § in. marked differences are to be seen in the dorsal group. For the 

 purposes of description the larva of A. macnlahis at its last moult may be taken as 

 presenting appearances more or less typical of the majority (fig. 1). In this the dorsal 

 aspect of the ninth segment is furnished at its extremity with tw^o brush-like structures 

 on either side, each just to the outer side of the mid line. The upper and more internal 

 brush consists of a short plume of feathered hairs, which are straight, scanty, and on 

 one side almost double the length of those on the other. Most of the hairs taper 

 gradually and terminate in a .sharp point, but one or two of the longer ones may sho\\- 

 a terminal booklet so small as to require a \ in. objective for its detection. The second 

 structure, just to the lower and outer side of the former, consists of a leash of six 

 stout bristles, five of which are unbranched. They are considerably longer than any 

 in the other brush, there being a slight progressive increase in the length of each, to 



