The Life-History and Anatomy of Butterflies 
called the anal prolegs. These organs, which are necessary to 
the life of the caterpillar, do not reappear in the perfect insect, but 
are lost when the transformation from the caterpillar to the 
chrysalis takes place. There are various modifications of this 
scheme of foot-like appendages, only the larger and more highly 
developed forms of lepidoptera having as many pairs of prolegs 
as have been enumerated. 
The bodies of caterpillars are variously ornamented: many 
of them are quite smooth; many are provided with horny 
projections, spines, and eminences. The coloration of cater¬ 
pillars is as remarkable in the 
variety which it displays as is 
the ornamentation by means 
of the prominences of which 
we have just spoken. As 
caterpillars, forthe most part, 
feed upon growing vegeta¬ 
tion, multitudes of them are 
green in color, being thus 
adapted to their surroundings 
and securing a measure of 
Fig. 20.—Caterpillar of Basilarchia disippus 
the viceroy, natural size (Riley). 
protection. Many are brown, and exactly mimic the color of the 
twigs and branches upon which they rest when not engaged in 
feeding. Not a few are very gaily colored, but in almost every 
case this gay coloring is found to bear some relation to the color 
of the objects upon which they rest. 
Caterpillars vary in their social habits. Some species are 
gregarious, and are found in colonies. These frequently build 
for themselves defenses, weaving webs of silk among the 
branches, in which they are in part protected from their enemies 
and also from the inclemencies of the weather. Most caterpillars 
are, however, solitary, and no community life is maintained by 
the vast majority of species. Many species have the habit of 
drawing together the edges of a leaf, in which way they form 
a covering for themselves. The caterpillars of some butter¬ 
flies are wood-boring, and construct tunnels in the pith, or 
in the soft layers of growing plants. In these cases, being 
protected and concealed from view, the caterpillars are gener¬ 
ally white in their coloration, resembling in this respect the 
larvae of wood-boring beetles. A most curious phenomenon has 
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