104 ASSUCIATIONS AND MIGRATIONS 
variety of apartments, is always pitched over the 
plants on which they feed, and answers the double 
purpose of sheltering them from the heat of the sun, 
and from heavy showers of rain, neither of which is 
at all agreeable to their tender frames. After they 
have devoured all the leaves within the verge of their 
covering, they set to work, and construct a new one 
over some other roots of the same plant ; and it not 
unfrequently happens, that several of these encamp- 
ments are within a few feet of each other. On the 
approach of winter, they construct a stronger tent, 
consisting of one apartment. When the cold weather 
sets in, they retire within it, roll themselves up into 
a sort of ball, and lie huddled together until April, 
when they break up their community, become solitary, 
and continue so, till they assume the pupa condition. 
Where food is abundant, there have been many 
instances of papilionaceous insects performing won- 
derful migrations ; while others limit their excursions 
to a very narrow range. The Forester, (Ino Statices 
of Leach,) has been observed in vast numbers dis- 
porting on the north bank of the Serpentine, in 
Kensington Gardens, while not a single one was to 
be seen on the opposite bank, nor even in any other 
spot in the neighbourhood. Professor Rennie, on 
one occasion, observed many hundreds of the Burnet 
Moth, (Anthrocera filipendulee of Stephens,) on the 
north shore of the Great Cumbrya Island, at the 
mouth of the Clyde, but not on any other part of the 
