No. 160.] 
347 
Its change to a “flax seed' 1 ' 1 or dormant larva . — When the worm, 
or active larva, has fully completed its growth, a slight diminution 
in the dimensions of the inner soft parts of its body commences, 
in which the outer and harder shin does not participate, this latter 
retaining its original full size. The result of this contraction is, 
that the worm gradually cleaves from its outer skin. It examined 
with a microscope when this change has recently commenced, a 
slight translucent space is observable at the head end, and a larger 
and more obvious one at the pointed or tail end, plainly indicating 
that the enclosed worm does not entirely fill its outer skin. This 
contraction continues, until the worm becomes entirely separated 
from its outer skin, and lies within it like the finger within a 
glove. The outer skin at the same time changes in color. 
From its original whiteness and transparency, it gradually becomes 
opake, brown, and finally of a dark bay or chestnut color. Though 
much less flat than a flax seed, its resemblance in color, size, and 
form, to that familiar object, is so striking as at once to be remark¬ 
ed by every one. 
Characters of the flax seed, or larva case . — Different specimens of 
these flax seed like larva cases (fig. h. i. j.) vary in length from 
0.13 to 0.19 and in breadth from 0.05 to 0.08. They are shining, 
cylindrical-oval, more obtusely rounded at the lower or head end 
than at the other, which is generally attenuated into an acuminated 
point or small projecting papilla. They are commonly composed 
of but nine obvious segments, and these are but slightly indicated 
by very faint acutely impressed transverse striae—a similar trans¬ 
verse stria, but still more faint, being sometimes perceptible 
(fig. h.) across the middle of some of the segments. Longitudinal 
impressed striae are sometimes present, (fig. j.) more conspicuous 
than the transverse and reaching a part or the whole length of the 
worm ; and between these the surface is minutely acuducted (i. e. 
appearing as if lightly scratched by the fine point of a needle) longi¬ 
tudinally — all these longitudinal impressions being perhaps caused 
by the pressure of the veins and fibres of the plant, against which 
the worm has been imbedded. On the under side, (fig. i.) towards 
the head end, the case is flattened, as if pinched together, so. much 
so that the anterior segment seems a mere empty fold of the mem¬ 
brane, without any inflation sufficient to make room for internal 
