148 STATES OF INSECTS. (Larva.) 
ordinary extent, or retract them within the stalk, so as 
wholly to conceal them. Sometimes it protrudes one 
fork, keeping the other retracted; and often withdraws 
the whole apparatus for hours together under the skin, 
and its place is only marked by two tawny-coloured dots, 
so that an ordinary spectator would not suspect the ex- 
istence of such an instrument?. Unfortunately this larva 
is rare in this country, so that I can scarcely flatter you 
with the hope of seeing this curious organ in a living 
specimen, unless you choose to import a parcel of its 
eggs from the south of Europe, where it is common. This 
you will think rather a wild proposition; but why 
should not Entomologists import the eggs of rare insects, 
as well as botanists the seeds of rare plants? But if you 
will be satisfied with the dissection of a dead specimen, 
I have several, done by the ingenious Mr. Abbott of 
Georgia, in which this part is well exhibited. 
Another small caterpillar, as it should seem, of a geo- 
meter, prepared by the same gentleman, exhibits a pair 
of similar horns on the fifth and sixth segments: in these 
the common base from which the fork proceeds is very 
short and wide, and each branch grows gradually more 
slender from the base to the apex, where it is involute. 
Whether these are retractile, or whether they correspond 
with those of P. Machaon in their nature and use, cannot 
be ascertained from a dead specimen: as they belong to 
a larva of a quite different tribe of Lepidoptera, the pro- 
a Reaum. i. t. xxx. f. 2. N. Dict. d? Hist. Nat. xxiv.490, 497—. 
> Ray says he found it feeding on common fennel, about Middle. 
ton in Yorkshire: Lett. 69. The indefatigable Mr. Dale recently 
found many in the neighbourhood of Whittlesea-mere, feeding on 
Selinum palustre. It will also eat the wild carrct. 
* This gentleman was remarkable for the admirable manner in 
which he prepared caterpillars, so as scarcely to differ from life. 
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