256 SENSES OK INSECTS. 
of a boot or shoe, so insects feel sufficiently through the 
crust of their legs for all purposes of motion. Besides, 
the points that are covered by a thinner cuticle are often 
numerous; so that touch, at least in a passive sense, may 
be pretty generally dispersed over their bodies ; but ac- 
tive or exploring touch is confined to a few organs, as 
the antennce, the palpi, and the arms. The two last I 
shall now discuss. 
Various opinions have been started concerning the use 
of the palpi. Bonsdorf thought that they were organs 
of smell ; Knoch, that this sense was confined to the 
maxillary ones, and that the labial ones were appro- 
priated to taste 3 -: but the most early idea, and that from 
which they derive their present name of palpi [feelers), is, 
that they are organs of active touch ,- and this seems to me 
the most correct and likely opinion. Cuvier, himself a 
host, has embraced this side of the question b , and Leh- 
mann also admits it c . The following observations tend 
to confirm this opinion. The palpi of numerous insects 
when they walk, are frequently, or rather without inter- 
mission, applied to the surface on which they are moving 
— this you may easily see by placing one upon your 
hand; which seems to indicate that they are feelers. In 
the Araneidce they are used as legs ; and by the males 
at least, as exciting if they be not really genital organs' 1 . 
In the Scorpionidce they answer the purpose of hands : 
besides being usually much shorter than antenna?, they 
a Lehmann De Sens. Extern. Anim. Exsang. De Olfactu. 
b Cuv. Anat. Comp. ii. 675. c Ubi sujir. 
d Marcel de Serres says they are connected with testes seated in 
the trunk {Mem. du Mus. 1819. 95); but Treviranus denies this 
(Arachnid. 3«— . t. iv./. 33). 
