insects' hairs. 589 



bend near their extremity, in each of which supervenes an 

 elastic membranous expansion, and from which a very 

 minute quantity of a clear, transparent fluid is emitted 

 when the fly is actively moving, explains its capacity for 

 clinging to polished surfaces. 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 hardly admits of actual con- 

 firmation. At the root of the pulvillus, or its under sur- 

 face, is a process, which in some instances is short and 

 thick, in others long and curved, and tapering to its ex- 

 tremity (Scatophaga), setose (Empis), plumose (Hippobos- 

 cidw), or, in one remarkable example (Ephydra), so closely 

 resembling in its appearance the very rudimentary pul- 

 villus with which it is associated. Just at the base of the 

 fifth tarsal joint, on its under surface, there is present, in 

 Eristalis, a pair of short, very slightly curved hairs, which 

 point almost directly downwards. It became desirable to 

 endeavour to ascertain how far the structure of these 

 tenent-hairs agrees with that of true hairs, on which some 

 valuable critical observations were made last year by Dr. 

 Hicks. 1 



"Tenent-hairs are usually present in some modification 

 or other, that it is really difficult to name a beetle which 

 has not some form of them ; the only one I yet know that 

 seems to me really to possess nothing of the kind is a 

 species of Helops, which lives on sandy heaths ; I suppose 

 the dense cushion of hairs on the tarsi here to be for the 

 protection, simply, of the joints to which they are attached. 

 I have detected them on the tarsal joints of species of 

 Ephydra, and on the first basal tarsal joint of the Drone 

 of the Hive-bee. A very rudimentary form of tenent-hairs 

 is present on the under surface of some of the Tree-bugs 

 {P zntatomidoe), which have in addition a large, deeply-cleft 

 organ at the extremity of the tarsus, which appears to be 

 a true sucker. 



" When walking on a rough surface, the foot represents 

 i<hat of a Coleopterous insect without any tenent appen- 

 dages. The ungues are always attached to the last joint of 



(1) See Trans. Linn. Soc. vol. xxiii. p. 143. 



