76 THE HUMBLE-BEE IV 
is not always the larve in the largest cocoons that 
are victimised. The maggots usually creep into the 
nest material to pupate: the puparium is at first 
yellowish-brown, afterwards it becomes dark red. 
The perfect flies emerge in two or three weeks ; 
they may be easily obtained by placing the pupe in 
a glass jar and covering it with muslin. 
A very interesting dependant on the humble-bee 
is the large fly, Volucella bombylans. This hand- 
some insect is about the size of a worker humble- 
bee and superficially resembles it closely, being of 
a stout build and covered with long hair which in 
some specimens is red at the tail and black over the 
rest of the body in imitation of B. dapzdarius and 
BL. derhamellus, and in others is white at the tail 
and marked with yellow on the thorax and base of 
the abdomen in imitation of the white-tailed, yellow- 
banded species, particularly B. jonellus and B. 
hortorum. Both forms occur plentifully in most 
districts and have, I believe, been bred from the 
same parent. But the mimicry of Vo/ucella does 
not end here. It is very fond of sunning itself upon 
flowers frequented by humble-bees, such as the heads 
of the greater knap-weed (Centaurea scabiosa), and 
if a specimen be grasped in the fingers it makes a 
buzzing noise so exactly like a humble-bee that the 
fear of getting stung makes one feel inclined to drop 
it instantly. Moreover, these flies hover about over 
grassy banks, etc., in the same manner as a Bomébus, 
searching for humble-bees’ nests in. which to lay 
their eggs, and at a distance I have often mistaken 
