264 
BRITISH BEES. 
their economy, but it may also be from crrrjXU, a little 
column, in application to their cylindrical form. In 
but few of the parasitical bees do we know the precise 
nature of tlieir transformations, I have therefore been 
obliged to be silent upon this point of their natural 
history, and I have nothing to state of its nature in 
these, although I expect there is much uniformity with 
but slight modifications in all. The species of this genus 
are parasitical upon the Osmice; thus th e S. phaoptera 
is found to infest the 0. fulviventris , and the S. octo- 
maculata intrudes itself into the nests of 0 . leucomelana, 
both of which occur tolerably abundantly near Bristol. 
I have no doubt that the south-west and west of England, 
if well searched, would yield many choice insects. 
It is singular that bee parasitism does not prevail 
throughout all the genera of bees, some being subject to 
it and others not. Thus the genera Colletes, Andrena, 
Halictus , Panurgus, Eucera, Anthophora, Saropoda , 
Megachile, Osmia, and Bombus have all parasites, 
whereas the genera Cilissa, Macropis , Dasypoda, Cera- 
tina, Anthidium , Chelostoma, Iieriades, Anthocopa, and 
Apis have none, as far as we yet know; and some of the 
genera of parasites frequent two or more genera indif¬ 
ferently, whilst others are restricted to a single one ; 
also some of the species of the parasitical genera infest 
indifferently several of the species of the genus to which 
their parasitism is mainly limited; other species have 
a more circumscribed range and do not visit the nests of 
more than a single species. What law may control all 
these seeming anomalies we cannot discover,—it may 
possibly be scent that guides them, and this may con¬ 
trol their parasitism by indicating the species they are 
taught by their instinct to be most suitable from the 
