1901] MICROSCOPICAL JOURNAL. 253 
the nymph skin; after a little while it tries its wings and 
flies away. It will be noticed that the female gnat has 
no halteres.—T. G. Jefferys. 
The best account of the gnat known to me is that given 
by Proffessor Miall in his “Natural History of Aquatic 
Insects,’ from which the following are excerpts: ‘Small 
stagnant pools and ditches are the favorite haunts of the 
larve and pupa of the gnat. A ditch in a wood choked 
with fallen leaves is one of the best hunting-grounds, and 
in the summer months they may be found by the thous- 
and in such places. The larva, when at rest, floats at the 
surface of the water, Its head, which is provided with 
vibratile organs suitable for sweeping minute particles 
into the mouth, is directed downwards, and, when ex- 
amined by a lens in a good light, appears to be bordered 
below by a gleaming band. There are no thoracic limbs; 
the hind limbs, which are long and hooked in the chirono- 
mous larve, and reduced to a hook-bearing sucker in 
Simulium, now disappear altogether; a new and peculiar 
organ is developed from the eighth segment of the abdo- 
men. This is a cylindrical respiratory syphon, traversed 
by two large air-holes, which are continued along the en- 
tire length of the body to supply every part with air. 
The larva ordinarily rests in such a position that the tip 
of the respiratory syphon is flush with the surface of the 
water, and thus suspended it feeds incessantly, breathing 
uninterruptedly at the same time.’ Professor Miall’s 
explanation as to how it is possible for a larva heavier 
_than water to remain floating at the surface without ef- 
fort, as the larva of the gnat appears to do, is too long 
to give here. It deals with the surface film. “After 
three or four months the larve are ready for pupation. 
By this time the organs of the future fly are almost com- 
pletely formed, and the pupa assumes a strange shape, 
very unlike that of the larva. At the head end isa great 
rounded mass which encloses the wings and legs of the 
