G. S. Graham-Smith 
363 
XXX, figs. 13, 15 and 16). Three puparia were opened in December 1915 
(Graham-Smith, 1916, viii. p. 543) and kept together in a glass box in a warm 
room. The M. acasta larvae, which were white and glistening, remained almost 
motionless for five months. On May 22 excrement was deposited, and many of 
the larvae had changed into white glistening nymphs by May 30. The d nymphs 
became dark brown in colour and the $ nymphs black. This change in colour 
is gradual, and many of the $ nymphs may be white when others have become 
black. The first $ emerged on June 13, and two others in another puparium 
on June 26. The latter two ds fought and one of them killed the other. At 
this date the $ nymphs were still white. Another $ emerged on July 9 and 
was killed by the one which had emerged previously. The surviving ds each 
kept guard over the $ nymphs in his own opened puparium. By July 2 two 
of the $ nymphs had become black. The first $ emerged on July 17, and 
shortly afterwards mated with the d, which had previously emerged in her 
puparium. Two $s emerged on July 27 and several female nymphs had 
become black by the time. On July 31 several adult $s emerged, but many 
of the female nymphs were still white. 
It is evident from the observations recorded in the following paragraphs 
that in these opened puparia the events occurred in the same order as they 
do under natural conditions in intact puparia. The ds develop into imagines 
many days before the ?s, and fights between them are of frequent occurrence 
in which the weaker are mutilated, or killed. The survivor remains in the 
puparium and mates with the $s soon after they emerge. 
The emergence of M. acasta from, fly puparia. 
The $s of M . acasta emerge from an intact fly puparium through a small 
round hole, which one of them gnaws. The hole is usually situated near one 
end of the puparium, but is occasionally near the centre. Very rarely two 
such holes are produced in a puparium. (Graham-Smith, 1916, PL XXX, 
fig. 10.) The hole is only just large enough to allow a $ to pass out, but is 
not large enough to admit of the passage of a <J. Occasionally a $ has been 
seen to re-enter a puparium through such an opening, but usually after they 
have emerged the $s fly away. On one occasion, when the opening was 
blocked by the body of a $ which had died while attempting to emerge, 
another $ which wished to re-enter enlarged the opening from the outside. 
Since the ds are usually too large to emerge through the holes made by the 
? it is very rare to find one outside a puparium, and they seem to spend their 
lives within the puparia. This accounts for the large number of bodies of 
males found within puparia in previous observations (Graham-Smith, 1916, 
p. 532). The $s are fertilised before they emerge from the puparia. 
Judging from the behaviour of the parasites when kept in glass tubes only 
one $ is engaged at one time in the work of boring through the puparium, 
however many there may be within the puparium ready to emerge. This 
would account for the fact that multiple openings in puparia are very rare 
