MR. TUFFEN WEST ON THE FOOT OF THE FLY. 109 
here, taking all on each fore tarsns together, is 111 ; they arc arranged as follows : on each 
side of the first joint 20 ; of the second joint 10 ; and of the tliird joint 12. They are the 
"vesicles" of authors. Those of each series appear to me generally to differ a little in 
size, the larger heing generally proximal. The points of attachment form elegant, very 
slightly curved lines, as follows: on starting from the odontoid process 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 margin of the joint are widely separated. 
When viewed from the side, these large tenent hairs arc seen to leave the joint from 
which they arise, at a very oblique angle (fig. 22 #) : 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, becoming continually thinner from above downwards. 
It can be distinctly seen, with due care, that the shaft of each of these modiiied hairs 
is tubular; but at the bend, the central hollow 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- 
o 
© ~ a 
denly : the part is flattened out into an extremely translucent, soft, and clastic structure, 
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. niger s 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, -0115 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, then 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 lias 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 curves downwards very gently until 
each joint is provided with a double hairy cushion, extending beyond the extremity of the joint . i but 
in Broscus 
circular 
figu 
Zabrus, with cushions transversely striated, as in Harpalus. — Westwood 
« 
dilated 
) ; u first division, Feronidea." * Four anterior 
dilated in the males ;" second division (Harpalidea).— Hid, 
