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intelligible purpose. The flies of the genus Volucella enter the nests 
of bees to deposit their eggs, so that their larvae may feed upon the 
larvae of the bees, and these flies are each wonderfully like the bee on 
which it is parasitic. Kirby and Spence believed that this re 
semblance or mimicry was for the express purpose of protecting the 
flies from the attacks of the bees, and the connection is so evident 
that it was hardly possible to avoid this conclusion.”—(Contributions. 
PP- 75-6.) 
It is a very remarkable fact that this particular instance 
of aggressive mimicry, which was the first instance of 
mimicry which attracted the attention of scientific men, 
has recently been shown not to be quite so simple and 
convincing as it has hitherto been assumed to be. 
The hypothesis of aggressive mimicry implies that each 
variety of Volucellae preys upon the species of bee which it 
most resembles, the red-tailed variety on the red-tailed 
bee, and the yellow variety on the yellow-banded bee. But 
both varieties have been reared from the nests of each type 
of bee, both from the red-tailed and the yellow-banded. 
“It is still possible that both varieties are born of one mother ; 
and it is possible, too, that each female does her best to choose the 
nest of a bee like herself, but in support of this hypothesis, I know 
no evidence, and indeed Kiinckel, after considering this possibility, 
gives it as his opinion that probably the varieties of V. bombylans lay 
indifferently in the nests of all Bombi. ... In my rooms at this 
moment are several nests of B. muscorum, each containing many 
larvae of V bombyla?is. There is, then, evidence, that the two 
varieties, though they may breed together, yet remain substantially 
distinct ; and that though they respectively resemble different species 
of bees, they are both found together, not only in nests of bees which 
they resemble, but also, and in my own experience, more abundantly 
in the nests of another bee which they do not resemble. V. pellucens, 
though in no wise resembling the common wasp, yet lives in its nests, 
together with V inanis, which does resemble a wasp, and with 
V zonaria, which is like a hornet.”—(Mr. William Bateson. Nature, 
vol. xlvi., p. 586.) 
We have thus seen that the resemblance of one species 
to another is sometimes brought about apart from Natural