rUPAL STAGES OF WEST AFRICAN CULICID.E. 15 



it is perhaps the most important character in the larva. The species con- 

 tained in the present collection exhibit a great variety in the form of this 

 oro-an, which is extraordinarily developed in some of them. In the Ano- 

 pheline larva3 it can scarcely be said to be present, but the homology of the 

 mii't^ is at once evident, if one of the stouter siphons^ such as that of Culea^ 

 twripes (PL III, fig. 11=)? is arranged so as to enable the observer to look 

 directly down on the spiracles (PL V, fig. 19), when a similar arrangement 

 to that which exists in the Anophelines will be seen. 



The siphon, be it long or short, contains the spiracles of the two trunks of 

 trachege that run down the dorsum of the larva : at the ends of these tracheae 

 are flaps or valves, which apparently may serve different purposes. In some 

 cases they appear to be pulled down by muscles so as to close, or rather 

 plug, the mouth of the siphon ; while in Cidex tigrrpes the presence of 

 certain sclerites, which have the appearance of apodemes, suggests that they 

 flap over the openings of the spiracles. I find in the larvse of Phorocera ' 

 seiriventris, Rondani ( = P. coneinnata, Mg.) such apodemes at the anal 

 spiracleSj and they are constantly present in the imagines of all Diptera, so 

 that when they are seen_, one may infer, with great probability of correctness, 

 that they are used to open and close the breathing apparatus. 



The siphon has a highly chitinised ring at its base, which is useful for 

 comparative measurements, and often_, on the ventral side^ a median ridge 

 on which are sometimes inserted plumes or hairs ; in other cases double rows 

 of plumes are found, one on each side of the median line. 



On either side, usually beginning at the base, and on the ventral side are 

 two rows of spines ; judging from a rather obscure description by Felt *, 

 these are his ''' pectensy I shall mention them as spines, or siphonal spines ; 

 they form a very important character in their various arrangements, and in 

 some cases their shapes. Besides these spines, there are often present stellate 

 and other hairs that aff'ord specific characters. 



The Anal Segment. 



This is the ninth segment of .the abdomen, and makes the thirteenth of 

 the whole larva, the number usually found in Nematocerous forms. The 

 part has four appendages at its end which are called the papillse^ and are 

 of various lengths, shapes and colours ; and in at least one species, two of 

 them are quite chitinous {Culiciomyia cinerea^ Theo.). On the dorsal edges 

 of the segment are long hairs and plumes, and on the ventral side a number of 

 . plumes, which may be quite at the end, or fringe the side ; this I call the 

 ventral beard. It is curious that however plumose the hairs may be on 

 the thorax and rest of the abdomen, the hairs on this segment, like the plume 

 at its base, are usually simple (PL I, fig. 4). In one species, Culex tigripes 

 var. fusca^ Theo., which presents a number of peculiarities in the mouth 

 and siphon, the surface of this segment is quite rough (PL III, fig. 12). 



* New York State Ed. Dep., 20th Report of the State Eutomologist— BulL 97: 

 Entom. 24, pp. 445-9. 



