194 wusca AUSTRALIS MACQ., M. VETUSTISSIMA WALKER. 
in the uterus, a developing egg and four follicles on each 
side. Thus the total was eleven, the twelfth must have 
been already born. We may then assume that the pean 
number of larvipositions is at least twelve. 
Patton and Cragg (1913, p. 130-139) discuss the 
pupiparous habit among flies. There are three distinct. 
degrees of this habit. Im many Tachinids which are not 
blood-suckers the larvae are delivered almost as soon as they 
hatch out of the egg. They undergo little or no develop- 
ment in the uterus and are laid in a large batch exactly as 
eggs are laid. The next degree is instanced by two cases 
M. corvina Fab. var. vivipara Portschinski and M. bezzi+ 
Patton and Cragg which are both blood feeders. Here the 
larva is retained and nourished for part of its life in the 
genital tract of the female but is deposited while still 
young and completes its growth under conditions similar 
to those of its allies. We may now add WM. australis to 
the category. In the third degree the larva is retained 
until it is ready to pupate, e.g., Glossina and Hippobosca. 
The authors then go on to discuss the reasons for the 
acceleration of the larval stages. In the Tachinids it is due 
to the fact that the food is usually the living larvae of 
other insects. The larval stage of the parasite must be 
complete before, or soon after, the host pupates lest the 
food supply be exhausted. In the other two cases there 
is no such obvious explanation, and it is probable that two 
factors enter into it. Firstly, the advantage of having 
the young larva protected within the body of the parent ; 
and, secondly, the rich food supply obtained by blood. 
sucking insects appear to have some relation to the 
pupiparous habit. The number of pupiparous forms is. 
high in comparison with the number of blood-sucking 
forms. The authors state that ‘“‘ the subject is a very 
obscure one, but the association of the blood-sucking habit. 
with the pupiparous habit is clear enough, and one should 
always be on the look out for larviparous forms among. 
those known to suck blood, whether they are biting flies. 
or not.” WM. australis is not dependent on blood for a 
living, but lives on any secretion; it will, however, 
greedily suck tke blood and juices from a sore or wound. 
