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



surface are the organs which have been so frequently mentioned as "hairs," "hair-like 

 appendages," "trumpet-shaped hairs," &c. That these are the immediate agents in 

 holding is now admitted by almost all ; it will be convenient to term them ' " tenent " 

 hau'S,' in allusion to their office. The delicacy of their structure in the fly ; the bend 

 near their estremity, after which on each supervenes an elastic membranous expansion, 

 capable of close contact with a highly polished surface, from which a very minute quantity 

 of a clear, transparent fluid is emitted when the fly is actively moving ; all this is now 

 admitted by the best observers. It simply remains to add that the tubular nature of 

 the shaft of the tenent hairs on the foot of this insect has been surmised, although its 

 minute size and homogeneity liardly permits of the surmise being actually confirmed by 

 visual inspection. At the root of the pulvillus, on its under-surface, is a process, which 

 in some instances is short and stout, in others long, greatly curved, and tapering to its 

 extremity {Scatophaga), setose {Empis), plumose {HippoboscidcB), or, in one remarkable 

 example {Epliydra), so closely resembling in its appearance the very rudimentary pulviUus 

 mth which it is associated, that I was for some time unable to decide whether it was a 

 third lobe of this organ, or, with the other examples named and to be more fully 

 described hereafter, a peculiar tactile hair, which is present, in some modification or 

 other, in all insects, so far as my present experience goes. This tactile hair has been 

 considered by two excellent observers* to be a spring, by the help of which the Fly is 

 enabled to detach its cushions from any surface to which tliey have been apphed ; but I 

 shall in due course proceed to show that this opinion is erroneous. 



Just at the base of the fifth tarsal joint, on its under surface, there is present, in Eri- 

 stciUs, a pair of short, very slightly ciu'ved hairs, which point almost directly downwards. 

 These were first shown to me by E,ichard Beck ; but the discovery of their existence is so 

 recent that time has not yet permitted of further search for analogous structures. In the 

 instance named, they appear as if they might be little props. 



It will be best now to take into consideration the large appendages to the hands 

 (fore tarsi) of the Harpalide Beetles. These are also tenent hairs, on a comparatively 

 gigantic scale : from this very fact of their size, and our consequent ability to dissect them, 

 and to submit their parts to varying treatment, we shall be enabled to feel confidence 

 in the deductions which may be drawn from them, when applied to tenent hairs even 

 of the'minutest size or the most rudimentary character. 



The largest of these appendages which I have been able to study on the living insect 

 were found on the hands of a species of Fterosticlmsf (fig. 20«, PI. XLII.). Their number 



* Lister; Black wall. 



f "Latreille and Dejean have dlTided tliis subfamily Harpai,ides into tliree groups, -uiiich, from the structure of 

 the anterior tarsi of the males (upon which they are chiefly founded), they term Quadrumani, Simplicimani, or -pedes, 

 and Patellimani." " Audouin and Brulle have noticed (without acknowledging the observation as that of Leon Dufour," 

 " a peculiarity in the construction of the Patellimani (Chlseniens), the males of which have the cushion-like clothing 



of hairs on the under surface of the foot generally distributed over the sole of the tarsus In the 



Quadrumani (Harpaliens), the dilated joints of the anterior male tarsi are furnished beneath with a double series of 

 narrow cushions, which, in H. rufipes, appear to be fleshy and transversely striated, and to be destitute of pilosity. 



This character, although it may be sufficient to separate the Chlajniens from the Harpaliens," , 



does not, however, appear to be a fixed character, being liable to much variation in the Feroniens : thus, in Ahax striola, 



