The Gnat 
57 
the water it suspends itself head downwards 
and takes in its necessary supply of air 
through a spiracle or breathing vent in 
one of the tubes into which the end of the 
body of the insect is sub-divided. 
The pupal or chrysalis stage is hardly 
less interesting in its details, for even then 
the gnat as it approaches its last or perfect 
state is active. The pupae are provided 
at the tail with a kind of paddle, by means 
of which they are able to propel themselves 
along, and also to suspend themselves 
near the surface of the water for the 
purpose of respiration, but now the 
breathing apparatus has undergone a 
change and it is no longer from the tail-end, 
but through two little inlets in the thorax, 
i.e ., the part of the body between the head 
and the abdomen. When the pupa 
casts its skin it does not cast it away, 
as do some insects, but makes another 
use of it. The perfected gnat as it emerges, 
uses the old shell or skin as another raft 
until it has had time to take in its sur- 
roundings, make its plans, and get its 
wings ready for flight. If you notice when 
looking into your rain-water receptacle 
5— (2267) 
