124 Anopheles Maculipennis 
be very constant in certain genera. According to Christophers in 
Stegomyia the siphonic index varies between 1 - G and 2; in Desvoidea 
it is 17; in Culex, however, it varies very greatly being 43 in Culex 
fatigans Wied., while in C. mimeticus Noe, according to Theobald’s 
figure (1903, vol. iii. p. 157) it is at least 145 on account of its 
extremely narrow diameter; in Theobaldia it is 6, while in Taenio- 
rhynchus it is 13. In addition to the characters afforded by the siphon, 
numerous other structural variations occur, and some of which are 
proving of great utility in the specific determinations of the various 
larvae. The general form of the head, the characters of the antennae 
and the position of insertion of the antennal tuft, the form of the 
mouth-parts and especially of the labial plate are all of utility in the 
identification of species. Less useful characters are afforded by the 
variations in colour (very rarely) and in the form and arrangement of 
the cephalic and body setae. The anal gills present some degree of 
variation, being exceptionally long, according to Christophers, in 
a species of Stegomyia which mainly frequents the bottom of the water; 
in Desvoidea they are large and broad (Theobald, vol. iii. pi. XVI), 
and in most of the known larvae of this sub-family they are well 
developed, though in Gidex tigripes Grand, et Charm, and Acartomyia, 
according to Theobald’s figures, they appear to be wanting. A wide 
variation is exhibited in the pecten, or rows of teeth situated on the 
siphon and, similarly, much variability is seen in the group of scale¬ 
like structures which are collectively termed the comb, and situated on 
either side of the eighth abdominal segment. 
Perhaps, the most divergent larvae of the genus Gidex are those of 
C. mimeticus which, in addition to the features of the siphon already 
mentioned, are remarkable on account of the large curved pecten 
spines (Christophers, p. 10), and the cannibalistic species C. concolor 
Robin. Des. and G. tigripes. Both of the latter are highly modified, 
showing but little relationship with the Gidex larvae and whose 
affinities are with Megarhinus and Toxorkynchites. Christophers 
suggests provisionally the enlargement of the sub-family Megarhininae 
so as to include, in addition to Megarhinus , Toxorkynchites (thus doing 
away with the sub-family this genus represents), Mucidus, Psoropliora 
together with Gidex concolor and G. tigripes, and possibly Janthinosoma 
and Lutzia. All these forms are specially modified for cannibalistic and 
carnivorous habits in general. Their brushes are transformed into 
clasping organs for seizing their prey, the mouth-parts are also specially 
modified and the shape of the head and clypeus is very characteristic. 
