SOCIAL ECONOMY. 255 
however, work by moonlight. As a rule this species 
keeps less regular hours than the smaller wasps, and 
is not at all particular about bemg at home at night. 
So many of them are out of the nest at this time, 
that a night attack on hornets, however well con- 
ducted, is not usually as successful in exterminatng 
the swarm as a raid on wasps after dark. 
The usual end of wasps is by cold, wet, and old 
age. They seem, however, to ‘be liable, like bees, to 
epidemic diseases, though I am not aware that their 
- maladies have been studied as carefully as those of 
the more valuable insects. Honey-bees are known 
to suffer both from obstruction of the bowels and a 
kind of epidemic dysentery: they suffer also from at 
least two species of Entozoa—namely, Gordius and 
Spherularia.* The same Entozoa occur in wasps. 
It is strange that parasites of so large a size should 
be found in so small a space as that which the 
abdomen of a female wasp offers. The Gordius, 
which I have met with only once, a female, seemed 
to cause great distress to its “host.” The abdomen 
of the poor wasp was distended as if she was about 
to become the mother of a swarm, and she was con- 
stantly straining to rid herself of her burthen. She 
was only recently hatched, and could scarcely have 
ever left the nest, yet she had within her abdomen 
a parasitical worm more than thirty lines long. The 
presence of the Spherularie, which I have more fre- 
quently met with, and of both sexes, apparently 
gave rise to no symptoms, for it was quite by acci- 
* Lubbock on Spherularia Bombi. ‘Natural History Review,’ 
Vol. I, p. 44; Vol. IV, p. 265. 
