he actual nests. Over and
over again, I bring wasp grubs and Volucella grubs together in small
test tubes, which are easy to observe. The first are well and strong; I
have just taken them from their cells. The others are in various stages,
from that of the snowflake born the same day to that of the sturdy
porcupine. There is nothing tragic about the encounter. The grubs of the
bumblebee fly roam about the test-tube without touching the live tidbit.
The most that they do is to put their mouths for a moment to the morsel;
then they take it away again, not caring for the dish.

They want something different: a wounded, a dying grub; a corpse
dissolving into sanies. Indeed, if I prick the wasp grub with a needle,
the scornful ones at once come and sup at the bleeding wound. If I give
them a dead grub, brown with putrefaction, the worms rip it open and
feast on its humors. Better still: I can feed them quite satisfactorily
with wasps that have turned putrid under their horny rings; I see them
greedily suck the juices of decomposing Rosechafer grubs; I can keep
them thriving with chopped up butcher's meat, which they know how to
liquefy by the method of the common maggot. And these unprejudiced ones,
who accept anything that comes their way, provided it be dead, refuse
it when it is alive. Like the true flies that they are, frank body
snatchers, they wait, before touching a morsel, for death to do its
work.

Inside the wasps' nest, robust grubs are the rule and weaklings the
rare exception, because of the assiduous supervision which eliminates
anything that is diseased and like to die. Here, nevertheless, Volucella
grubs are found, on the combs, among the busy wasps. They are not, it
is true, so numerous as in the charnel house below, but still pretty
frequent. Now what do they do in this abode where there are no corpses?
Do they attack the healthy? Their continual visits from cell to cell
would at first make one think so; but we shall soon be undeceived if
we observe their movements closely; and this is possible with my glass
roofed colonies.

I see them fussily crawling on the surface of the combs, curving their
necks from side to side and taking stock of the cells. This one does
not suit, nor that one either; the bristly creature passes on, still in
search, thrusting its pointed fore part now here, now there. This time,
the cell appears to fulfil the requisite conditions. A larva,
glowing with health, opens wide its mou