400 TRANSFORMATIONS OF INSECTS. 
The bees are often attacked, according to A. S. Packard, 
by a fly which belongs to the genus Phora. “It is a small insect, 
about one line and a half long, which is found in Europe during 
the summer and autumn flying slowly about flowers and windows, 
and in the vicinity of bee-hives. Its white transparent larva is 
cylindrical, a little pointed before, but broader behind. The head 
is small and rounded, and at the posterior end of the body are 
several slender spines. The pupa case which encloses the deli- 
cate chrysalis is oval, consisting of eight segments, flattened above, 
and with two large spines near the head and four on the extremity 
of the body. When impelled by instinct to provide for the con- 
tinuance of its species, the Pora enters the bee-hive, and gains 
admission to a cell; then it bores with its ovipositor through the 
Nymph. Adult. 
METAMORPHOSES OF Volucella szonaria. 
skin of the bee larva, laying its long oval egg in a horizontal 
position just under the skin. The embryo of the P4ora is already 
well developed, so that three hours after the egg is inserted in the 
body of its unsuspecting and helpless host the egg is nearly ready 
to hatch. In about two hours more the larva actually breaks off 
the larger end of the egg shell, and at once begins to eat the 
fatty tissues of its victim, its posterior half remaining in the shell. 
In an hour more the larva leaves the egg entirely, and buries 
itself completely in the fatty portion of the young bee. The 
maggot moults three times. In twelve hours after the last moult 
it turns round with its head towards the posterior end of the body 
of its host, and in another twelve hours, having become full fed, 
it bores through the skin of the bee larva, eats its way through 
the brood covering of the cell, and falls to the bottom of the 
hive, where it changes to a pupa in the dust and dirt, or else it 
