series), 1899, page 500]: "It was formerly assumed that the Volucella larvae lived on the larvae of the bees, and that the parent flies were providentially endowed with a bee-like appearance that they might obtain entrance into the bees' nests without being detected." Dr.Sharp goes on to say that what little is known on the subject supports the belief that the "presence of the Volucella in the nests is advantageous to both fly and bee.") I had no idea such a case occurred in nature; I must get and see specimens in British Museum.

I hope and suppose you will give a good deal of Natural History in your Travels; every one cares about ants--more notice has been taken about slave-ants in the "Origin" than of any other passage.
I fully expect to delight in your Travels.

Keep to simple style, as in your excellent letters,--but I beg pardon, I am again advising.
What a capital paper yours will be on mimetic resemblances! You will make quite a new subject of it.

I had thought of such cases as a difficulty; and once, when corresponding with Dr.Collingwood, I thought of your explanation; but I drove it from my mind, for I felt that I had not knowledge to judge one way or the other.

Dr C., I think, states that the mimetic forms inhabit the same country, but I did not know whether to believe him.