UG 



Note on Some Recent Observations op the Foot of the 



Hodse-Fly. 



By A. C. E. Merlin. 



(Read April 19^, 1895.) 



Since finding that the hairs of the Pulvillus of the house-fly's 

 foot are terminated by a delicate scythe or sickle-shaped filament, 

 and not by a knob or sucker as hitherto supposed, it occurred to 

 me that it would be interesting to endeavour to confirm the exist- 

 ing theory that the hairs in question are the real agents by which 

 flies attach themselves to and walk upon smooth glass surfaces. 



For this purpose I imprisoned a fly in a Rousselet live box, 

 leaving the insect plenty of room to walk over the large cover glass 

 of the apparatus, intending merely to study its movements with a 

 powerful aplanatic hand lens. While doing so I noticed that it 

 suddenly appeared to have difficulty in removing one of its feet 

 from the clean surface of the glass, ani the next instant the leg 

 gave a violent jerk and the foot was torn off at the fourth tarsal 

 joint, and was left adhering to the under surface of the cover, 

 while its owner walked off, apparently undisturbed by the accident. 

 On releasing the fly and replacing the cover I was able to view the 

 expanded pulvillus under the microscope exactly as left by the fly. 



On examination with Zeiss's 16*0 mm. and 4*0 mm. objectives 

 with 12 and 18 eye-pieces, using a f cone from an Abbe achromatic 

 condenser, it was clearly seen that the end of each tenent hair was 

 attached to the glass by a comparatively large globule of some 

 transparent fluid which enveloped the sickle filament. 



I secured a photograph of this object with the 4*0 mm. apochro- 

 matic objective, using a 12 compensating eye-piece for projection, 

 and a J axial cone. The illumination was from the edge of the 

 flame of a small paraffin lamp. Annexed hereto is a platinum 

 print taken from the untouched negative thus obtained, showing 

 some of the hairs adhering to the under surface of the cover. 

 Near the edge of the print two hairs can be seen joined to each 

 other at their extremities by a mass of the gummy fluid. 



