MR. TUFFEN WEST ON THE FOOT OF THE FLY. 413 



der of the membranous expansion. In the function they perform, these rays may be aptly 

 compared to the ribs of an umbrella. In the large suckers they are very strongly 

 marked ; in the smaller, which are only 2^ inch in diameter, they are but faintly to be 

 traced. An interesting indication of bilateral symmetry may be observed in both the 

 great suckers. These are freely and to a great extent moveable on their very short 

 membranous pedicles. The mode of attachment of the small suckers to their pedicles, 

 by means of a very narrow tendinous cord, is also such as to admit of free motion (fig. 36). 

 It will be seen, on reflection, that much power of adaptation to varying surfaces Avill thus 

 be gained*. The pedicles of the smaller are strong, horny columns, '005 inch in length ; 

 •0007 inch in thickness at the centre ; they expand a little towards either end, the lower 

 or outer being the larger. 



The pedicles of the small suckers were found so closely to agree with the description 

 already quoted of the structure of true insect hairs, that it is unnecessary to describe it 

 or do more than refer to the figures given of it and of the base of one of the fringing 

 " guard-hairs " (figs. 37, 38). 



There was hence no resisting the remarkable and unlooked-for conclusion, that the 

 suckers of the male Dyticus are extreme modifications, in one direction, of true hairs for 

 holding piu-poses — that therefore they must be classed with all modifications of hairs, 

 however different in external appearance, for similar purposes. 



It is curious to observe how a truth, when once obtained, receives support from all other 

 truths with which it maybe connected. It occurred to me to examine, in connexion with 

 this part of my subject, the singular hand of the male HyclropMlus (fig. 40, PI. XLIII.), 

 which is entirely for sexual purposes — so mtich so that the insect walks on the end of the 

 tibia alone, and drags the tarsus after it. This portion of the limb has the usual number 

 of five joints, the last of which is alone enlarged into the form of an irregular hollow 

 shield. On the under surface of this shield are a few true hairs, not spines, as the papillee 

 on which they are seated and the articulation at their points of attachment to these 

 papillse distinctly show. The longest of these hairs are proximal ; they are all pointed, 

 and appear loose, ill-formed, and, as it were, dragged backwards. Yet this unquestion- 

 ably represents the hand of Dyticus, — the last the most completely suctorial .organ of its 

 kind we are acquainted with. 



I now come to mention briefly the subject of tenent hairs specially subservient to 

 climbing or holding, as distinct from sexual purposes. None of these are so large as 

 most of the appendages which have been hitherto mentioned. They are also more slender 

 in the shafts, generally very numerous, and horny almost to the very tip, where the small 

 membranous expansion suddenly commences. The remarkable bending downwards near 

 the tips attains its maximum amongst the tenent hairs of this section. 



Clytus elongaUis, one of the Cerambycidse (fig. 41, PI. XLIII. ), furnishes a characteristic 

 example!. After the minute descriptions which have been already given of several forms 



* I have seen a male Byticus swimming about with the shell of a Paludina vivipara attached to the suckers of one 

 of its hands. 



•|- " The tarsi " of the Longicornes " have the three basal joints cushioned beneath, the first and second being dilatetl, 

 the third deeply bilobed, the fourth small and nodose and inserted between the lobes of the third, and the fifth long 

 and slender." — Westwood, Introd.vol. i. p. 356. 



3 £2 



