BY T. H. JOHNSTON AND M. J. BANCROFT. 193 
as the development of the fly proceeds. When the imago 
emerges, it crawls out of the burrow, pushing any loose 
debris aside by inflating and deflating its ptilinal sac. 
In summer at Eidsvold, Burnett River, Queensland, the 
pupation period is from 9-15 days ; in winter 27-32 days 
These periods were observed under laboratory conditions 
without artificial heating and are probably longer than 
would obtain under natural conditions owing to the higher 
day temperatures outside. 
Of a given batch of larvae deposited by flies on the 
same day, females will, as a rule, be the first to emerge, 
then follows a period in which both males and females 
appear, and then a period in which only males emerge. 
‘There is usually a slight preponderance of males among 
bred flies, thus for over 300 flies bred out, the percentages 
were, males 57 % and females 43 %. When flies are 
-captured on stock the males are decidedly in the minority, 
since out of over 500 captured flies, only 7 %, were males. 
Froggatt’s (1916, p. 10) observations regarding blowtlies 
in New South Wales were somewhat similar, he having 
found that among captured flies only about 3 % were 
males. 
Often large numbers of flies may be bred from a single 
isolated: dropping of cowdung; thus one such deposit 
yielded 120 flies (70 males and 50 females). It must be 
remembered that a female fly deposits only one larva at 
a time, hence at least 120 females must have visited the 
mass for larviposition. Flies which have been bred and 
kept in captivity have never been observed to copulate 
or deposit larvae though both sexes were present. Perhaps 
copulation does not occur under such circumstances, as 
sperms have not been found in the spermathecae of such 
flies. In one insect which was kept in captivity for two 
months two equally developed ova were found in each 
ovary but there was no larva in the uterus. Attempts to 
discover the period between emergence and larviposition, 
and also between successive larvipositions have not been 
successful. Captured female flies will readily deposit one 
larva, but have not been observed to do so a second time. 
Particular notice of the number of follicles was not 
‘taken but in the specimen drawn (fig, 12) there was a larva 
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