1890 .] 
491 
[Packard. 
segment is not so large as the eighth, but it is well developed. The 
tenth is conical, merging insensibly into the remarkably developed 
suranal plate, which is drawn out into a long, thick appendage, 
blunt at the end and with two constrictions dividing it into three 
segments; it is about one-fourth as long as the body and covered 
with coarse spinules which are larger on the filamental portion than 
on the base of the plate, while those on the outer half of the appen- 
dage are as large beneath as above and beneath are arranged in 
three rows. These spinules are slender, papilliform and give rise 
at the end to a stiff, sharp seta, resembling those on the body of 
Empretia, Euclea and other Cochlidise. The anal legs are more 
distinctly developed than in Drepana, but still are only represented 
by two rounded tubercles scarcely projecting beyond the body and 
bear at the end four or five elongated piliferous warts, but no pad- 
dle-shaped, tenant hair like that in Drepana. The thoracic legs 
are rather small and short, as are those of Drepana. 
The abdominal legs, though distorted and dried in the blown 
specimen, are seen to have the same arrangement of crochets as 
previously described in the case of Drepana arcuata. 
The head is dark, rust-red, with the surface between the warts 
highly polished. 
The colors of the dried blown larva are, in general, as described 
from life by Mr. Grote. 
It will be seen that the larva of Dryopteris differs in some re- 
markable respects from that of Drepana, viz. : (1) the head is 
much smaller and ends above in two knobbed cones, while (2) the 
clypeus is of a peculiar shape ; (3) there are no piliferous warts vis- 
ible on the body ; (4) the large, fleshy median dorsal tubercle is an 
unique feature, while (5) the suranal plate is greatly developed over 
that of Drepana. And yet, with all these striking differences, the 
larva of Dryopteris is as well fitted as that of Drepana by its pro- 
tective mimicry to avoid the gaze of birds and insect enemies, 
while its longer, bizarre “ tail” renders it still more forbidding to 
any insect assailants. 
SEASONAL DIMORPHISM IN DREPANA ARCUATA AND IN DRYOPTERIS 
ROSEA. 
As is well known, Mr. Alfred R. Wallace applied the expres- 
sion “ seasonal dimorphism” to cases like that of the European 
butterfly, Araschnia, which has two forms, previously regarded as 
