Hig PERFECT SOCIETIES OF INSECTS. 
rather plucked by its powerful jaws from posts, rails, and 
the like. This is carried in its mouth, and is thus ready 
for immediate use:—but upon this subject I have en- 
larged in a former letter*. The workers also clean the 
cells and prepare them to receive another egg, after the 
imago is disclosed and has left it. 
There is good reason for thinking, and the opinion has 
the sanction of Sir Joseph Banks, that wasps have senti- 
nels placed at the entrances of their nests, which if you can 
once seize and destroy, the remainder will not attack you. 
This is confirmed by an observation of Mr. Knight’s in 
the Philosophical Transactions», that if a nest of wasps 
be approached without alarming the inhabitants, and all 
communication be suddenly cut off between those out of 
the nest and those within it, no provocation will induce 
the former to defend it and themselves. But if one es- 
capes from within, it comes with a very different temper, 
and appears commissioned to avenge public wrongs, and 
prepared to sacrifice its life in the execution of its orders. 
He discovered this when quite a boy. 
It sometimes happens, that when a large number of fe- 
male wasps have been observed in the spring, and an 
abundance of workers has in consequence been expected 
to make their attack upon us in the summer and autumn, 
butfew have appeared. Mr. Knight observed this in 1806, 
and supposes it to be caused by a failure of males‘. I have 
since more than once made the same observation, and 
Major Moor, as well as myself, noticed it last year (1815). 
What took place here in the present year (1816) may in 
some degree account for it. Though the summer has 
@ Vol, I. 4th Ed. p. 607. > For 1807, 242— © Thid. 243. 
