106 HORSE AND CATTLE FLIES. 
Pupipara to which it belongs, the egg is hatched, and the maggot (or 
larva) feeds aud is nourished up to maturity within the abdomen of 
the parent fly. When fully developed this larva is deposited not as 
an ordinary maggot, but as a puparium, or pupa-case, within which 
the larva is then completing its immediate change to the pupal or 
chrysalis state, and from which puparium the perfect fly emerges, it 
may be in about a month, or it may be after a much longer period, 
according to weather and other circumstances. 
Thus the Forest Fly never exists actively on the infested animals 
excepting in imago (that is to say, in fly) state. It cannot be called 
oviparous, as assuredly it does not lay an egg, and as although it is 
considered that the fully developed larva, or maggot, has not turned 
to the pupal state within its case at the moment of deposit, yet this 
change takes place so almost immediately, and the change ewternally 
by which the ‘‘case’”’ hardens and otherwise assumes all ordinary 
characteristics of a puparium also occurs in such a few hours, that the 
name of Pupipara, or ‘ pupa-bearing,’’ was bestowed on this division 
of Diptera, or ‘‘ two-winged”’ flies, by Latreille, and continues to be 
still their distinctive appellation. 
In the course of the hundred and fifty-six years which have 
elapsed since the discovery was first made by Réaumur of the true 
nature of the egg-like body deposited by the Forest Fly, an enormous 
amount of attention has been given to the internal embryological 
development, but still the evternal conditions, although well known by 
technical observers, are by no means as generally known as they need 
to be for practical use; as, for instance, the egg-like puparium is still 
often believed (before it has coloured) to be an egg, and afterwards to 
be in some way connected with presence of Ticks. Therefore in the 
following pages some amount of detail, which may be of interest, as to 
the points in the life-history of the Forest Fly which practically 
concern ourselves are given, with references quoted to the original 
authorities, and also a list of works consulted is appended, where 
those who desire to enter on the early internal development (the 
‘‘embryology’’) of this and various other species of the Pupipara will 
find full microscopical details. 
The first discovery of the method of propagation of the H. equina, 
being by deposit of the egg-like body which proved to be really the 
puparium, was made by Réaumur in the middle of the month of 
October, 1739. But the season being then too late to continue 
investigations, it was not until September 18th in the following year, 
1740, that he was able to continue them (and to this day his observations 
on this part of the history leave nothing to be desired either for clearness or 
accuracy). 
Then he again found the egg-like body, of which the history was 
