5 
appear to be of the nature of gills. In the case of a species of Stegomyza, in 
which these were of very great size, the larve habitually remained long periods 
without rising to the surface. Dorsally, immediately above the anus, four or six 
long hairs arise from one or two small chitinous plates. Ventrally, a double 
row of hairs forms a large fan-like expansion. ‘The variations in the hairs of the 
ninth segment are not great in the different genera and their arrangement is 
very similar in Anopheles, Stegomyza, and Culex. 
The Nymph.—The nymph consists of a large body formed by the conjoined 
head and thorax and of a tail composed of nine segments. The general shape 
and appearance of the nymph varies a little in the larger groups of mosquitoes, 
and it is possible by this means to distinguish the nymphs of Anopheles, Culex, 
and Mochlonyx. The most important structures showing variations are :— 
The breathing trumpets.——These rise from the dorsum of the thorax and 
show variations in the manner in which they project from the nymph, and in the 
details of their structures. No distinct differences were found by me in species 
of the same genera, but in different genera important variations were detected. 
The shape of the breathing trumpets of the nymph are of important generic 
significance. 
The tail fins and last segment are also subject to some variations. 
II, 
The larval features characteristic of many of the genera can in some degree 
be noted. 
Stegomyza.—The ova of S. fasctata were first described by Daniels and 
Ross.’ They are laid singly on the water, and form patterns as do those of 
Anopheles. Each ovum is surrounded by numerous small air chambers. 
The larve of Stegomyza are very characteristic and can be distinguished at 
once by the naked eye. They are found especially in water of a dark brown 
colour from decayed vegetable matter, but they are also found in ordinary rain or 
waste water or indeed in any small collection of water and even in nearly pure 
water in chatties or other receptacles. Their general appearance is more worm-like 
than that of other larve. The full-grown larve are generally loaded with fat and 
have a plump look. When disturbed they travel by means of a curious twisting 
and lashing motion seen in some small aquatic worms. When breathing at the 
sutface they adopt a nearly vertical attitude quite different from that of most 
Culex \arve which rest at a distinct angle to the vertical (PI. III, figs. 22 and 
20). Stegomyta larve spend much of their time at the bottom. They are vora- 
‘cious feeders and can be seen nibbling at solid substances such as dead insects. 
The body of the larva (PI. I, fig. 19) is cylindrical, The thorax and head 
