PUPIPARA. 
655 
often twenty or more on one animal). The life-history of these flies is 
of a curious and interesting type. We have seen that certain Calyptrate 
Muscoids ( Sarcophagidce and 
Tachinidce) often retain the 
eggs within the body until 
after they have developed 
into larvae, and that they 
are thus “ viviparous,” i.e ., 
produce their young alive. 
These larvae at once begin 
to feed, and when full- 
grown they pupate. The 
Hippohoscidce and probably 
all other Pupipara carry 
the process still further, their 
larva remaining inside the present fly’s body until ready to pupate, 
when they are deposited. The puparia, found lying generally on hard 
dry surfaces (floors, stone window-sills, shelves, etc.), are dark mahogany 
brown in colour, round and polished, with a black cap at one end, and 
look very much like round smooth seeds about half as big as a pea. 
When first laid they are nearly white (fig. 432). It is thus obvious that 
in Hippohoscidce the usual conditions found among Diptera regarding 
the taking of food are reversed. As a rule it is the larva which does 
most of the feeding required for the insect’s development, and this is 
true even in families such as Asilidce, in which the adults are predaceous, 
and in the blood-sucking Culicidce, Psychodidce , Simuliidce, and Tahanidce. 
The same rule applies to the Indian species of blood-sucking Muscidce , 
but the African Tsetse-fly retains the larvae until ready to pupate, in the 
same way as Hippohoscidce , and it is evident that this abbreviated life- 
history., is due to the fact that the adult fly is able by sucking blood to 
supply enough nutriment to carry on the life of the larva as well as its 
own. In accordance with this, since the fly can only absorb a limited 
quantity of blood, we find that reproduction in Hippohoscidce (and in the 
Tsetse-fly) is slow, only one larva being produced at a time, but the 
slowness of the process is to a great extent compensated by the protec¬ 
tion of the young from all the dangers of larval life ; that this protection 
is effective we see from the abundance of the flies. The shortening of 
Fig. 432— Puparia of Hippobosca. 
The one on the left is new laid, that in the middle is 
six hours old, and the one on the right a week 
old, and dark brown in colour, x 4. 
