1-1 W. WESCHE — THE LARVAL AND 



socketed on short tubercles ; these I call the sub-slplwnal plumes ; the 

 latenil plumes at the base of the siphon itself I call the siplwaal plumes 

 (PI. J, fig. 4). There is often a third plume (laterally) at the base of the 

 anal segment, and this is generally of simple hairs, it being exceptional to 

 find that condition in the other two. 



The Comb. 



This consists of a number of spines or scales on each side of the eighth 

 segment, which present remarkable specific characters * when they can be 

 seen; but the difference in their appearance, brought about by the angle 

 from which they are viewed, is so great that, in discriminating species, it 

 would be dangerous to rely upon this character alone. The combs are best 

 seen on the lighter-coloured larvse, and from a lateral view, with the siphon 

 lying as flat as possible in the trough ; if they cannot be made out then, as 

 sometimes happens, a dorsal view will partially show them. To secure this, 

 the siphon must be perpendicular, often out of tlie liquid : as I have already 

 explained, this is managed by placing the head in a corner of the trough. 



The combs on the Anopheline larvae are on the lateral supports of the 

 platform on wdiich the spiracles open. 



When mounted in balsam the combs are rendered so transparent that they 

 iire exceedingly difficult to see with the best of objectives and substage 

 illumination, and in this condition I find it almost impossible to count the 

 scales with any degree of accuracy. As I propose to describe only what I can 

 see with GO diameters, I shall not rely on the combs more than I can help for 

 specific characters. The difliculty of usibg these structures for such a purpose 

 is illustrated by my personal experience. I possess a beautiful preparation of 

 the larva of our British ^Edes cinereus, Mg., in formalin, made and given to 

 me by Mr. H. J. Waddington, F.L.S., of Bournemouth. Though I am able 

 to use a very good ^ on the comb, I cannot satisfactorily count the scales 

 or be sure of their real shape either with a high or a low power objective. 



I also drew some of the scales of the comb of Stegomyia fasciata, F., and of 

 S. afrkana^ Theo., from larvae lying in the trough of formalin, using a 

 I objective, and I could not separate these two species on what I saw, as my 

 drawings were practically the same. I suspect that with a little imagination 

 I could see on S. africana^ Theo., the elaborate structures that are figured, as 

 existing in S, fasciata, in Goeldi's * Os Mosquitos no Para ' (Brazil, 1906, 

 Plate F). Indeed at the present moment I am by no means sure that they 

 do not exist, nor can I be certain without making careful stained preparations, 

 capable of being examined with higher powers than those employed. 



The Siphon. 



This part varies so much and has so many subsidiary hairs and spines that 



* Since the above was written I have "been able to examine a greater number of 

 preparations ; I am now inclined to think that they are more of generic than specific 

 importance. — W. W. 



