204 NORTH AMERICAN INSECTS. 
in the month of July, during which they pass through at 
least three transformations—from the egg to the caterpil- 
lar, and then to the pupa, which is brownish gray, with 
some golden spots. This butterfly is frequently found in 
Europe, where it is also a native; but there it is called 
“Mars, because some have discovered marks upon the wings © 
which are thought to possess some similarity to certain in- 
struments of war. 
The TuistLe Butrerrry (Vanessa cardui), Fig. 51, some- 
Figure 51. 

The Thistle Butterfly. 
times appears in such large numbers that their larvae devour 
not only the leaves, but also the blossoms of the thistle and 
burdock. As soon as one of these caterpillars issues from 
the ege it draws the points of two leaves together, fastens 
them with a silky thread, conceals itself therein, and eats 
the substance of it, until it attains its growth, which is one 
and a half inches long, when it is ready to metamorphose 
into a cocoon, from which the perfect insect proceeds in 
about two weeks. ‘The whole process of its three trans- 
formations occupies only four weeks—as it remains an egg 
one week, a caterpillar another week, and a cocoon two 
weeks. Thus three or four generations may appear in one 
summer. ‘The cocoon is generally of a golden-yellow color, 

