BIRCH CATERPILLARS. 493 
26. Prionia bilineata (Pack). 
Order Lepidoptera; family Platyptericid^e. 
Dr. Dimmock has worked out the history of this interesting moth, as 
will be seen by the following account by Mrs. Dimmock in Psyche, iv, 
p. 278 : 
Platypteryx bilineata Packard (Proc. Entom. Soc. Phil., Nov.. 1864, v. 3, p. 359). 
Packard {I. c.) writes: "Dr. Harris lias reared this from the larva, which pupated 
July 25; imago August 15." Harris (Entom. Corresp., 1869, p. 142) gives a crude 
figure of the larva of some American species of Platypteryx f, and Packard (Guide 
Study Ins., 1869, p. 293) repeats this figure as that of a species of Dryopteris; no food- 
plant is mentioned by either author. The European species, Platypteryx lacertula, feeds 
on birch. The larva of P. bilineata is found upon Betula alba, in eastern Massachusetts, 
about the first of July and again early in September ; hibernation takes place as 
pupa in the September brood. Dr. G. Dimmock will later describe the egg, larva, 
and pupa of this insect in detail, but the following notes will suffice for the recogni- 
tion of the larva and pupa. The full-grown larva is about 12 mm long, tapering 
from the anterior to the posterior end, which latter terminates in a single point, 
turned upward, in place of the anal legs. The dorsal surface of each segment 
bears four tubercles, each supporting a single short hair. The arrangements of these 
tubercles is peculiar : segment 1 has small tubercles arranged thus . . . . ; segments 2 
and 3 each have large tubercles arranged • • • (the head in each case supposed to be 
upward) ; segments 4-10 each have small tubercles arranged .-•. ; segments 11 and 12 
each have two large and two small tubercles arranged • . . • . The slight cocoon is 
made between leaves of the birch which the larva has drawn together for the pur- 
pose, and the pupa within it is densely covered with a white bloom. 
Moth. — Female : A delicate thinly-scaled species of an ocherous-silvery color ; the 
ocherous scales appearing along the outer border, and lining the transverse lines. 
These two lines are in the middle of the wing, the outer being a little flexuous ; both 
are dark, the inner one lined within and the outer one lined externally with ocherous. 
A distinct black discal spot. The fore wing is thickly covered with long transverse 
brown strigse or short lines, which become near the outer edge oblique and sinuate, 
forming an obscure submarginal line. Secondaries paler and dusky perlaceous. Discal 
dot distinct, and beyond is a transverse dark line, once angulated opposite this spot. 
Beyond this line the wing is obscurely strigated. Beneath, the forewings are more 
yellowish towards the outer edge, and on the secondaries, especially so beyond the 
outer line, which, with the discal dot, is much plainer than on the upper surface. 
Head and body thoughout concolorous with the forewings. Expanse of wings, 1.30 
inch. 
27. Drepana arcuata Grote. 
Mr. S. L. Elliot has bred this moth from the birch in Central Park, 
New York. It is closely like the European larva, being green, the head 
Inroad, the body tapering behind, ending in a sharp point with red 
spots on the thoracic segments. Mr. Elliot tells me that it rolls up a 
leaf, and eats a little off, then goes to another leaf, cuts it, and bends it 
over, and in this way becomes quite destructive.* 
* For a detailed account of the metamorphosis of this moth see my article, The 
Life-history of Drepana arcuata, etc., in Proc. Brit. Soc. Nat. Hist., xxiv, 1890. 
