THE MOSQUITO AND GNAT. 207 
transferred to the upper part of the thorax and consists of two 
slender columns, one on each side, containing air tubes connected 
with the entire tracheal system. When air is wanted, the pupa 
rises to the surface with the tubes just protruded, and so gets a 
supply. For the final transformation the pupa extends itself on 
the surface of the water, the thorax opens widely, and by a series of 
extensions and contractions the perfect insect draws itself out, 
extends its legs and wings and soon flies away. On examining this 
insect we are at once struck with the lightness and grace charac- 
teristic of its class. ‘The six long slender legs, the delicate pair of 
wings, the small head and thorax, and the slender body, all unite 
in lending an appearance of elegance singularly unsuggestive of the 
bloodthirsty instincts of the little creature. The abdomen consists 
of eight segments, and tapers to a blunt point, presenting charac- 
teristic differences in the two sexes. The wings possess a very fine 
set of nervures, which, as well as the free edges, are thickly set 
with the well-known scales, about the markings of which there has 
been so much controversy. These scales, indeed, are present all 
over the body, and vary in shape with their position, but all exhibit 
a series of parallel longitudinal ridges, with the interspaces trans- 
versely striated. It is possible that the peculiar sound produced 
by the Gnat, and still more clearly by the Mosquito, is due to the 
number and position of these scales upon the wings. The legs, 
eight jointed and terminating in a strong double hook, are pro- 
fusely supplied with scales and hairs. Coming to the head, we 
find the upper surface and sides almost entirely occupied by a pair 
of compound eyes. No ocelli are visible. From two bulbous 
bases at the front spring the antenne, consisting in the female of 
thirteen joints nearly equal in length and sparsely set with hairs. 
In the male there are fourteen, short at the base, but gradually 
lengthening up to the twelfth, the remaining two being much longer, 
so that together they almost equal the rest in length. From the 
first twelve joints radiate sets of long curved hairs, which impart an 
extremely elegant plume-like appearance to the antenne. The 
fourteenth is somewhat thickened and studded with minute downy 
hairs quite different from the others. Can it be that the last seg- 
ment is the organ of smell? Just below the bases of the antenne 
are a pair of three jointed labial palpi, long and slender in the male 
and covered with hairs and scales; but in the female short and 
club-like. Between and below these are the oral organs, The 
most noticeable of these is the thick proboscis-like projection 
readily visible to the eye and almost half the length of the whole 
insect. This is the labium, the homologue of the under lip. On 
examination, it is found to be semitubular, with a divided bulbous 
extremity, and completely covered with closely-set scales and hairs. 
It is in fact the sheath for the piercing apparatus next to be described. 
