MR. TUFFEN WEST ON THE FOOT OF THE FLY. 409 



here, taking all on each fore tarsus together, is IM ; they are arranged as follows : on each 

 side of the first joint 20 ; of the second joint 16 ; and of the third joint 12. They are the 

 ** vesicles" of authors. Those of each series appear to nie generally to differ a little in 

 size, the larger being generally proximal. The points of attachment form elegant, very 

 slightly curved lines, as follows : on starting from the odontoid jDrocess at the proximal 

 end of a joint, they are near together, but rapidly diverge; so that those which arise just 

 within the truncated or incised anterior margia of the joint are mdely separated. 



When viewed from the side, these large tenent hairs are seen to leave the joint from 

 which they arise, at a very oblique angle (fig. 22 b) : they proceed with a gentle curve 

 forwards, until, on approaching their fore end, their direction becomes changed from 

 nearly horizontal to almost vertical ; near the end of this bend downwards, the texture, 

 which was previously horny, begins to alter, becoming like a very firm membrane, or 

 even tendon, at the same time increasing rapidly in width, so as from a rounded form 

 to assume a broad fan-shape, becomiag continually thinner from above downwards. 



It can be distinctly seen, with due care, that the shaft of each of these modified hairs 

 is tubular ; but at the bend, the central hoUow is imperceptibly lost to the eye, and a 

 granular structure becomes visible, the granules having a tendency to assume a linear 

 arrangement. At the extreme end both the texture and the direction again change sud- 

 denly : the part is flattened out into an extremely translucent, soft, and elastic structiu'e, 

 of a membranous texture, and narrowly reniform in its shape when seen pressed against 

 the glass of the live-box : faint radiating lines are visible in it, and its direction becomes, 

 when in use by the insect, once more horizontal. In P. ni[/er, the diameter of one of 

 the largest of the membranous expansions is, in its major axis, "0032 inch, in its minor 

 axis -0012 inch ; entire length of the tenent hair, "0145 inch. 



The soft membranous expansions, when not in use by the insect, point downwards; 

 when applied to a surface of which it is desired to take hold, their direction is at once 

 changed, and their form becomes altered through the flattening effect of the pressure. 



The colour of these tenent hairs is at their origin of a clear chestnut-brown, which 

 gradually passes into straw, and at the broadest part is so faint as to be scarcely percep- 

 tible. This is worth remarking, because it serves as an index to the relative amount 

 of chitinous impregnation of the different parts. It is best seen when the tarsus has been 

 made partially transparent, and will prove of importance when the action of the different 

 parts of the tenent hair comes to be considered. 



It will be well now to pause a little, and see what has, up to the present stage of the 

 inquiry, been ascertained respecting the composition of each tenent hair on the hand of 

 a large Geodephagous Beetle. Putting all the observations together, it becomes clear that 

 there are : — 



1. A tubular shaft, of a rounded form, which cm'ves do\^iiwards very gently imtU 



each joint is provided with a double hairy cushion, extending beyond the extremity of the joint ; but 



in Broscits cephalotes the cushion of each joint is entire and nearly circular. And Burmeister figures a tarsal joint of 

 Zahrus, with cushions transversely striated, as in Harpalus. — Westwood, Introd. vol. i. p. 84. 



"Two anterior tarsi of the male alone dilated" (" Harpalides ") ; "first division, Feronidea." " Four anterior tarsi 

 dilated in the males ;" second division (Harpalidea). — Ibid. p. 85. 



