40 BULLETIX 885, U. S. DEPARTMENT OF AGRICULTURE. 
mm. and the inner pair 0.048 mm. Spines at the vasiform orifice rather short and 
thick, scarcely 0.032 mm. long. Thorax with a pair of stout, curved spines 0.020 
mm. long, arising close to the median line just cephalad of the first abdominal segment. 
A second pair of spines 0.24 mm. long arising from the cephalic portion of the case 
near the median line. These are curved evenly backward. While minute teeth 
are present on the caudal margin, there is no indication of a caudal comb. 
Color rather dark brown under the microscope, almost black on the leaf. 
SECOND LARVAL INSTAR. 
Plate X, B. 
Size averaging 0.4 by 0.288 mm. Shape rather broadly elliptical, broadest across 
the caudal portion of the thorax. Margin minutely crenulate, caudal comb slightly 
differentiated. Abdominal segments not very distinctly separated. Vasiform orifice 
oval, slightly tending to triangular on caudal portion, operculum almost completely 
filling orifice. Inner pair of caudal spines hair-like, 0.096 mm. long, outer pair minute, 
spines at vasiform orifice about two-thirds the length of caudal pair. Dorsum with a 
number of stout, heavily chitinized spines situated as follows: A pair situated near 
vasiform orifice, each spine about 0.112 mm. long; two pairs somewhat cephalad of 
these and about equal in length, each spine about 0.144 mm. long; one pair near 
median line, each spine about 0.064 mm. long; and a pair just cephalad close to medial 
line, each spine fully 0.192 mm. long. Near the outer margin, slightly more cephalad, 
is a pair of spines 0.128 mm. long; close to the median line is a pair 0.192 nun. long, 
and cephalad of this two pairs, the spines about equal in length and measuring about 
0.096 mm. Dorsum slightly arched but not prominently so. Color dark brown. 
The color changes of this and other instars have been treated elsewhere in this bulletin 
(p. 31 to 36). 
THIRD LARVAL INSTAR. 
» 
Plate X, C. 
Size averaging 0.736 by 0.464 mm.; shape elliptical, broadest just cephalad of 
middle pair of spines. Margin crenulate; teeth 0.01 mm. in length, 0.007 mm. in 
width, caudal comb consisting of four marginal teeth slightly larger than the rest. 
Abdominal segments indistinct, a row of small, closed pores marking terminations of 
abdominal sutures. Vasiform orifice small, oval, situated on a slight tubercle, oper- 
culum cordate, filling three-fourths of the orifice. Lingula not visible. Dorsum with a 
number of stout spines of varying lengths situated as follows: A pair laterad and 
cephalad of vasiform orifice, each spine about 0.19 mm. in length; a pair of spines at 
termination of each abdominal suture, those on segments three and four being the 
longest. Seven pairs of spines on thoracic portion of dorsum, two short pairs near 
meson, a longer pair near cephalic margin of case, and four pairs outlining boundaries 
of thoracic segments of pupa case, the pair nearest to eye spots being 0.24 mm. in 
length, the pair at dorsal portion of thorax 0.30 mm. in length, the other two short 
and stout. A pair of long, slender setae situated cephalad and caudad of the vasiform 
orifice, and a short, stout pair on the metathorax near the meson. Dorsum slightly 
arched. Color dark brown. 
FOURTH LARVAL INSTAR OR PUPA. 
Plate X, D. 
Size variable, averaging 1.5 mm. to 0.89 mm.; shape regularly elliptical with dorsum 
arched; median ridge high, but not markedly distinct from dorsal area, excepting 
near the caudal portion of abdomen and at vasiform orifice, which is elevated into a 
more or less prominent tubercle. Color dense black, so much so that even prolonged 
boiling in potassium hydroxid does not remove the color. When the denser dorsal 
