1890.] 
99 
[Packard. 
The above facts would seem to indicate that when there is a well 
developed cervical shield in Lepidopterous larvae it is due to a local 
dorsal hypertrophy of the cuticular layer originating from the fric- 
tion caused by the movements of the larvae in its mine or burrow 
in rubbing against the solid walls of its habitation. The soft base 
of the head, which is generally retracted under the shield, is thus 
protected from injury. 
VI. SUGGESTIONS AS TO THE ORIGIN OF THE “CAUDAL SPINE” 
IN THE ATTACIDiE (OR SATURNIAD^e) . 
Much has been said by Mr. Poulton in his valuable paper read 
before the Entomological Society of London 1 as to the nature and 
use of the so-called “caudal horn ”of sphinx larvae. Attention was 
first called to the subject by Professor R. Meldola in the appen- 
dix to Weismann’s essay “On the markings of caterpillars ” 2 wherein 
he thus refers to the young caterpillars of Choerocampa lycetus , 
Cramer. “A most suggestive feature is presented by the caudal 
horn, which in the young caterpillar is stated to be freely movable. 
It is possible that this horn, which was formerly possessed by the 
ancestors of the Sphingidce , and which is now retained in many 
genera, is a remnant of a flagellate organ having a similar function 
to the head-tentacles of the Papilio-larvae, or to the caudal appen- 
dages of Dicranura.” 
It is to be observed that while the adjective “caudal” is a little 
unfortunate and misleading since the horn is developed on the 
eighth abdominal, or two segments from the end of the abdomen, 
yet its use is undoubtedly to repel attacks of insects and reptiles 
as well as birds. It may also perhaps be said to have been de- 
rived rather from a nodding or slightly movable tubercle armed 
with a terminal spine, than from a “flagellate organ,” but the gen- 
eral use of the appendage is evidently as suggested by Meldola. 
We have been led by an examination of the movable fleshy tu- 
bercles tipped with spines, not uncommon on various parts of the 
body of Notodontian larvae, to believe that the caudal spine of 
Ceratocampidae and of Sphinges, etc., was derived from either a sin- 
gle or double piliferous tubercle, and this view was, we think, sug- 
gested to us before meeting with Muller’s opinion quoted by Poul- 
ton. 
1 Trans. Ent. Soc. London, 1885, 302, and in later volumes. 
2 Vol. ii, p. 527. 
