DISEASES or THE COTTON PLANT. 199 
alternately stretching out and contracting the body in the 
form of an arch. They are thus enabled to advance nearly 
half their length every stride or step, and, from this ^cir- 
cumstance, derive their common name of " span-worm," or 
" looper." 
The favorite food of these insects appeared to consist 
of the petals. In some places they were very numerous, 
as many as four having been taken from one bloom alone. 
In color, they varied much from green to brown; but both 
were similarly banded with another color. The chrysalides 
were fixed by the tail to the leaves with a glutinous matter 
or silk, and measured about seven-twentieths of an inch in 
length ; were of a brownish-green color, and remarkable 
for having the upper part of the thorax somewhat square, 
flat, and furnished with two minute protuberances,, or 
spines, over the head and eyes. When disturbed, they 
instantly drop from the leaves, and suspend themselves in 
mid-air by means of a thread, which issues from the 
mouth; and although exceedingly abundant in one part 
of the field, yet they were scarcely to be found out of that 
particular spot. 
As these insects are very small, and eat holes in the 
petals of the flowers alone, they cannot injuriously aflFect 
the general crop. 
The Larger Span-Worm. 
Another span-worm, or caterpillar, appears in the Caro- 
linas, Georgia, and Florida early in October, and feeds 
upon the petals of the cotton flower. It measures, when 
ftdly grown, from an inch and a half to an inch and three- 
fourths in leng-th ; the color is reddish brown, marked with 
faint, longitudinal darker stripes ; the head is somewhat 
angular, and divided at the top ; there is a light spot on 
