192 muscAa AUSTRALIS MACQ., M. VETUSTISSIMA WALKER, 
eggshell.* A few active movements of the larva, however, 
suffice to split the shell longitudinally, and the escaping 
larva burrows rapidly into the dung. 
In hot weather the larvae grow very rapidly and have 
usually finished feeding by the end of the second day and 
have pupated by the third day after deposition. Fully 
formed pupae have been found occasionally on the second 
day after deposition. In winter the larval stage is 
prolonged to about six days. During the beginning of 
October, when the larval stage was occupying four days., 
the following periods were noticed and measurements of 
the larvae made. The larvae were fixed in nearly boiling 
water and preserved in formalin. 
The larva at birth measures 3.5 mm. long by 1 mm. 
and is in the second instar. During the first 24 hours 
it grows enormously and at the end of that period measures 
7.5 to 9 mm. by 1.5 to 2 mm., by which time it is usually 
moulting. The anterior spiracles increase in size and 
each contains 13-17 processes ; the posterior spiracles also 
increase greatly in size and issue in three much convoluted 
slits (fig. 18). The chitin is thicker and blacker. These 
large black spiracles are rather characteristic of the larva. 
On the second day it measures 11 mm. by 2.5 mm. attaining 
on the third day its maximum size, now measuring 11.5- 
13 mm. in length by 2.5 to 3 mm. in breadth ; on the 
fourth day the larva is mature, ceases feeding and shrinks 
somewhat in size, measuring 10-11 by 2.5 mm.; the 
alimentary tract becomes emptied of food and the larva 
assumes a pale yellow colour with a deeper yellow patch 
on the anterior dorsal surface. At this stage the larva 
burrows up to the surface of the dung, then retreats a 
short distance—about half an inch—in its burrow and 
pupates, with the hed end pointing outward. Under 
laboratory conditions the larvae will leave the dung and 
pupate in damp sand. 
The puparium measures 7 to 7.5 mm. by 2.5 to 3 mm., 
and is at first yellowish grey in colour becoming dark grey 
*In one case an egg was laid in captivity. This, however, is quite 
exceptional. 
