TO TtlE FEET OE INSECTS. 



27 



Those presented by Pterostichus were then somewhat minutely 

 described, as the largest the author had had the opportunity of 

 observing whilst living and in action. They may be considered 

 as composed of two portions : the first is an elastic membrane, 

 perfectly smooth on the lower surface to admit of its exact adapta- 

 tion ; the second, on which the former is borne, is a long stem or 

 pedicle arising at an oblique angle from the tarsal joint, and bent 

 suddenly downwards near its insertion into the membranous 

 portion, by which the latter is rendered capable of being brought 

 into contact through its whole extent with the surfaces to which 

 it is applied. In the beetle in question the membrane is reniform, 

 with its long axis directed transversely. Amara was then noticed 

 as possessing similar organs, with some of the Carabi ; it appeared 

 that, as a general rule, their number was increased as their size 

 diminished. The presence of scale-like hairs on the back of these 

 membranous expansions in some cases was mentioned as affording 

 a clue to the condition in Caralus, where irregular elevated 

 wrinkles simulate such corrugations as would be produced by the 

 contraction of a membranous tube. 



The structure of these expanded membranous organs was shown 

 to agree in every respect with that of true hairs — as being hollow 

 for some distance, seated in a depression of the integument on a 

 slight papilla, and shut off from the cavity of the joint by a delicate 

 membrane, to which some fibres (including probably a nerve) could 

 be traced. These statements were borne out by examinations of 

 the parts in Carabus and Dyticus, whence the scarcely expected 

 result was obtained that the " suckers " of the latter are themselves 

 onlv hairs still more modified. 



mf 



Various forms of these spathulate hairs, and plans of their 

 arrangement on the tarsi, were mentioned, with the different insects 

 on which the author had met with them. 



The strong resemblance in the structure of the bilobed Dipte- 

 rous pulvillus to the almost equally cleft third joint in Curculio 

 and Chrysomela, which are both furnished with these spathulate ap- 

 pendages, led the author to throw out the suggestion that the former 

 was, in a homological sense, a modified joint. The principal diffi- 

 culty in accepting such a view (namely, the position of the claws) was 

 combated by showing that the latter are themselves only modified 

 hairs, usually converted into hooks to serve a special purpose*. In 



* Since tho above was written, the author has had the opportunity of examin- 

 ing the feet of the Ephemera in the living fly, and has ascertained the curious 

 fact, that whdst one of the ungues remains in its normal condition as a strongly 

 curved, horny hook, the other is converted into a soft fleshy sucker. 



