[Illustration: FIG. 14.]
Having reached its full growth, the caterpillar, Fig. 14, a, which is
about an inch in length, wanders off to some sheltered place, as under
a board, fence rail, or even under the edge of clapboards on the side
of a building, where it spins a button of silk, in which to secure its
hind legs, then the loop of silk to support the forward part of the
body.
It now casts its skin, changing to a chrysalis, Fig. 14, b, about
three-fourths of an inch in length, quite rough and uneven, with
projecting ridges and angular points on the back, and the head is
prolonged into a tapering horn. In color they are very variable, some
are pale green, others are flesh colored or pale ashy gray, and
sprinkled with numerous black dots. The winter is passed in the
chrysalis stage.
After the caterpillar changes to a chrysalis, their minute parasites
frequently bore through the outside and deposit their eggs within.
These hatch before the time for the butterflies to emerge, and feeding
on the contents, destroy the life of the chrysalis.
Birds and spiders are of great service in destroying these insects.
The pupae should be collected and burned if the abdomen is flexible;
but if the joints of the abdomen are stiff and cannot be easily moved,
they should be left, as they contain parasites.
Several applications of poisons have been used, the best results being
obtained from the use of pyrethrum as a powder blown on to the plants
by a hand bellows, during the hottest part of the day, in the
proportion of one part to four or five of flour.
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