83 
making headway by constantly inflating the frontal sac, at 
the same time pushing itself forward with the legs. When 
liberated, a great deal of time is devoted to combing out the 
hairs on the arista of the antennae, this being accomplished 
in the following way: the head is turned either to the right 
or left, as desired, and the frontal sac is then inflated on that 
side farthest from the thorax; this process lifts the antennae 
into a prominent position, and the long hairs of the arista 
are then rapidly and carefully combed out with the under 
surface of the anterior tibiae. The frontal sac also receive^ 
a share of attention, and so also does the abdomen, and 
occasionally the rudimentary wings. This stage is remark 
able, in that nature so provides that, under normal conditions, 
the insect may successfully escape from its larval habitat 
before the wings develop, and so impede its progress or 
render its escape impossible. 
2. In this stage the frontal sac is usually contracted, and the head 
presents a more normal condition; the fly also becomes 
quiescent, and remains as a rule in a fixed attitude, with the 
legs well displayed, and the head extended forwards, so that 
the narrow neck is stretched to its fullest extent. Air is then 
pumped into the body by repeated and alternate contractions 
and extensions of the abdomen. The body increases in size, 
and the integument becomes extremely pallid in colour. 
At this stage the wings are apparently filled with air, which 
passes rapidly along the costal region, then across to the hind 
margin, and finally the tip unfolds, sometimes aided by the 
use of the hind legs. The first portion of this stage some 
times occupies over twenty minutes ; but the wings develop 
as a rule in about three minutes. 
3. 1 he fly still remains more or less quiescent, but gives some 
attention to cleaning itself, and when the integument and the 
wings are sufficiently hardened the proboscis is raised from 
the ventral to its normal horizontal position ; when this is 
accomplished the insect takes flight. 
Defaecation lakes place shortly after the imago is perfected ; the 
faeces being milk-like both in substance and colour. 
