252 THE AMERICAN MONTHLY [Sep 
Extracts from Postal Microscopical Society’s Note—books. 
Edited for Science Gossip. | 
DEVELOPMENT oF GNAT.—My object in these slides is 
to illustrate the transformation of an insect. I am not 
able to send a slide of the eggs of the gnat, but in “Science 
for All” Mr. Hammond says that they are laid in smal] 
boat-shaped masses which float on the surface of the 
water. The eggs themselves are of an oval form with a 
kind of knot at one end, and are arranged side by side 
and closely packed together. In Dunean’s “Transfor- 
mation of Insects” it is thus written: ‘The male gnats 
have pretty hairy antenna, like little feathers, and the 
females have antennsx which are almost plain. It is there- 
fore not difficult to distinguish one from the other, and it 
is rather important, for the females are the blood-suckers. 
When about to lay their eggs they seek the water, and 
with the assistance of their long hind legs collect and 
agglutinate them together and place the little boat-shaped 
mass upon the surface of the water, and then leave it to 
its fate.” The larve are soon hatched, and grow with 
great rapidity. They are almost always seen with their 
heads downwards and their tails towards the surface of 
the water. After the larve have grown toa certain size 
they undergo a change of skin and become nymphs or 
pups, and it may be noticed that when the nymphs come 
up to the surface of the water they do not present their 
tails like the larvz, so as to obtain air, but allow their 
backs to touch the surface, just where there are two res- 
piratory tubes. When the perfect insect is about to 
emerge from the nymph stage it floats on the surface of 
the water, perfectly at rest, and the skin of the back, 
which is exposed to the air, dries and splits open. Then 
the perfectly-formed insect begins to come out: first it 
protrudes its head, then a portion of its body, and after 
a short time one leg after the other is disengaged from 
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