38 DECIDUOUS FRUIT INSECTS AND INSECTICIDES. 
Spiracle oval, inconspicuous, brown; that of segment XI larger, somewhat 
obliqued, and farther dorsad. The crotchets of the legs are variable in number, 
often unsymmetrical, and generally arranged as follows: 
rroleg. Anterior row. Posterior row. 
il 14-18 12-14 
ye 14-17 12-15 
ay 14 a 
4, 12 all 
Anal. 8 0 
For the first four prolegs, the crotchets vary from 11 to 18 in number; for the 
anal proleg they vary from 8 to 9. There are generally more present than in 
Sanninoidea exritiosa (see fig. 10, ¢). 
As compared technically with the full-grown larva of the peach borer, the 
latter is 34 mm. long, 6 mm. in greatest width, with the width of the head 
at least 83 mm. The head of NS. exitiosa is slightky darker in color, with a dis- 
tinct, though variable, subtriangular pale area on each epicranial lobe, where 
they join below the vertical triangle; the mandible is relatively more robust, 
darker at the teeth, four of the latter distinct, the second tooth longest and more 
slender, the outer next in length, the third one-third shorter than the second, 
and obtusely rounded, the fourth a distinct tooth, but abruptly shorter, approach- 
ing the fifth, which is a mere serration; the two mandibular sete are larger. 
The lateral margins of the clypeus are straight, each one changing angle at its 
basal third, making the clypeus shaped like (4, instead of triangular; the basal 
corners of it are truncate. The parclypeal pieces are generally straight, but 
curving basally to follow the margins of the clypeus; they are uniform in width. 
The first two ocelli and the sixth are practically pigmentiess. The shields are 
darker yellowish. The arrangement of the tubercles is the same, but they are 
relatively larger, as are also the accessory warts and the setz. There is a less 
number of crotchets in the prolegs, ranging from 8 to 16, and in the anal proleg 
from 5 to 8. 
Though these technical differences exist, they can not be recognized 
in all points without considerable study, and an examination of a 
series of larvee. The most conspicuous difference is the greater size 
of the larva of Sanninoidea exitiosa and its different aspect. 
During the course of its growth the larva molts several times, each 
casting of the skin marking the end of a separate period of larval 
development called an instar. There is no direct evidence by rearing 
to show how many of these instars there are, but it has been shown 
that the heads of lepidopterous larve are of certain limited sizes in 
each instar, and therefore by measurements of a large series of the 
heads of these larve, the conclusion is reached that there are six, as 
shown in Table I. The larva molts five times. The length of the 
separate instars has not been determined, but Mr. Quaintance records 
a little over seven months as the length of the larval stage for an 
individual reared on peach out of doors, from September to the fol- 
lowing April, in the latitude of Washington, D. C. 
