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of the larve of Volucella, a genus of parasitic flies. In this 
search I was not successful, but I noticed a number of very small 
beetles, which on examination, I found to be Cryptophagus 
pubescens, a species which, though widely distributed, is said to 
be rare in most localities. I sent some of them to Canon Fowler 
who informed me that this beetle had been recorded on the 
Continent as having been found in the nest of Vespa vulgaris, 
but that this was the first time he had heard of its having been 
so in this country. 
Some of these will be placed in the local insect cabinet in the 
Duncan Museum. 
I thought it might interest the members of the Bath Field 
Club if I made a few remarks on the association of insects of one 
species with those of another species ; insects as hosts, and insects 
as guests. 
The hosts are chiefly the various communities of social 
Hymenoptera, but among the guests we find both Insects and 
Arachnids of various orders. 
Of this association there are three kinds : 
lst. Where the strangers come as enemies, and are undoubtedly 
parasitic, and where their intrusion is resented ; 
2ndly. Where they come as friends, and are protected and 
sometimes fed by their hosts ; and 
3rdly. Where their intrusion seems to be a matter of in- 
difference, where they are simply tolerated. 
As an example of the first class we have flies of the Genus 
‘olucella, which enter the nests of various species of humble 
bees ; and I take this example as it illustrates one phase of that 
very curious fact known as Insect Mimicry. I have here dimorphic 
forms of Volucella bombylans, a male and female of each, which, 
though so different in appearance, are absolutely identical as a 
species, and differ only in their colour; and with them I have 
placed bees of the species whose nests they are said to invade, 
and you will notice how closely the one form with the red tail 
