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 PJiora enters the bee-hive, and gains 

 admission to a cell ; then it bores with its ovipositor through the 



Larva. Nymph. Adult. 



METAMORPHOSES OF Voliicella zoiiaria. 



skin of the bee larva, laying its long oval q^^ in a horizontal 

 position just under the skin. The embryo of the PJiora is already 

 well developed, so that three hours after the &^^ is inserted in the 

 body of its unsuspecting and helpless host the q%% is nearly ready 

 to hatch. In about two hours more the larva actually breaks ofl" 

 the larger end of the &^% 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 (t^^ 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 



