150 STATES OF INSECTS. (Larva.) 
horn-like style, which issues from the lower side of the 
first segment, between the head and the legs of the case- 
worms (Trichoptera): he does not describe it as retrac- 
tile, or it might be regarded as analogous to those of 
Lepidoptera similarly situated, that I have just noticed*. 
In that of the emperor-moth (Saturnia Spini), there are 
perforated tubercles, which when the animal is molested 
spirt forth a transparent fluid®. 
The horn-like appendage of the puss-moth (Cerura 
Vinula) is situated at the tail of the insect, and is com- 
posed of two distinct cylindrical diverging branches, each 
about four lines long, not united at the base. Each of 
these is hollow, and includes a smaller cylindrical piece, 
which can be protruded at pleasure, and withdrawn again 
as a pencil within its case; or, rather, as the horns of a 
snail. The two outer horns are tolerably firm, move- 
able at their base, and beset with black spines; the in- 
terior tentacula are fleshy, moveable in every direction, 
and in full-grown larvee of a rose colour. The animal 
seldom protrudes them, unless in some way disturbed ; 
and frequently it approximates the two outer cases so 
closely that they resemble a single horn. It appears to 
use these inner horns, when protruded, as a kind of whip 
to drive away the flies, especially the Ichneumons, that 
alight upon its body. When touched in any place, it 
will unsheath one of them, and sometimes both, and with 
them strike the place where it is incommoded*. A si- 
milar organ is found in some other Bombycide, as Aglia 
Tau and Cerura Furcula. Reaumur mentions a cater- 
pillar that to this kind of tail added the resemblance of 
* De Geer ii. 507. ¢. xi. f. 16. c. > Ros. iv. 162. 
© De Geer i. 322—. See Pirate XIX. Fic. 2. a a. 
