EXTERNAL ANATOMY OF INSECTS. 695 
in the Neuropterous genus Nymphes there is a minute 
one under each claw. It is discoverable between the claws 
‘in many Hymenoptera, as Apis+, Vespa, &c. But the 
genus that exhibits to the curious Entomologist the most 
singular and elaborate apparatus of this kind is Dytiscus ; 
and the examination of the under side of the hand of 
any male of this genus will almost compel the most in- 
attentive observer to glorify the wisdom and skill of the 
ALLFATHER so conspicuously manifested in the structure 
of these complex organs. For this part in these, instead 
of two or three pedunculate cups as in the insects just 
mentioned, is composed of a vast number, some large 
and some small. If you take a male specimen of the 
common D. marginalis, you will find that the three first 
joints of the hand are very much dilated, so as to form a 
plate or shield nearly circular, fringed all round with 
stiffish hairs ; if you next examine the under side of this 
plate with a good magnifier, you will discover at the 
base, where it is united to the cubit, two circular cups, 
the external one more than three times the size of the 
other, with an umbilicated centre’; besides these two 
larger cups the rest of the shield is covered by a vast 
number of minute ones of a similar construction ©: the 
larger cups are nearly sessile, but the smaller are 
elevated upon a tubular footstalk ¢; the three first joints 
of the intermediate farsz are also dilated, but not into 
an orbicular shield, and thickly set with minute pedun- 
culated suckers *. ‘The structure varies however in dif- 
ferent species. ‘Thus in D. limbatus the shield is trian- 
* Prats XXVII. Fic, 55. é. > Prats XV. Fie. 9. a. 
© Tbid, b. * Philos. Trans. 1816. t, xx. f. 9, 12—15, 
© Tgit. £x. fe 4, UE. 
