nine British Species of the Genus Hylaus. 35 
Chancing to meet with a bank in which was a large colony of 
Colletes succincta, I pulled down a portion of it, and found large 
quantities of their cocoons, some empty, some containing the bee 
fully developed, others the stores of pollen and honey recently 
collected. I filled a few boxes with the cocoons containing in- 
sects, and on examining them at home, in two of them I found a 
specimen of Epeolus variegatus. This little bee has long been 
considered a parasite, but I believe this is the first instance of its 
being found in the nest of another bee. More than two-thirds of 
the cocoons were empty which I found in the bank, or I might 
probably have discovered more of Epeolus. ‘This is an instance 
of great disparity of resemblance between the bee and its parasite ; 
and I think it will be found, that close resemblance is only to be 
met with, and is only apparently necessary, among the social bees, 
for there can be no want of opportunity for a parasite to deposit 
unobserved her egg in the nest of a solitary bee; whereas in 
the social species they would be sure of detection; and, conse- 
quently, a very close resemblance is frequently met with, appa- 
rently to aid them in fulfilling the purposes assigned to them: as 
in the instance of the different species of Apathus parasitic upon 
Bombus, and also in the Diptera frequenting their nests. 
