348 



Further Note on Some Recent Observations on the Foot 

 of the House Fly. 



By A. A. C. Eliot Merlin. 



(Bead January loth, 1897.) 



Witii reference to my note read April 19th, 1895, I have now 

 succeeded in mounting specimens of the fly's foot with the 

 pulvilli and tennent hairs stained, and showing, adhering to the 

 ends of the hairs, the viscid globules by means of which the 

 insect is enabled to attach itself to smooth surfaces. 



I forward with this note a specimen of a fly's foot so mounted 

 and stained with fuchsin, which may be fairly well shown under 

 a good dry lens. The details, however, are seen better with an 

 oil immersion. Some of the hairs on this slide show the sickle 

 filaments deeply stained and devoid of any adhering substance, 

 others have a small quantity of the gummy fluid held within 

 the hollow of the sickle, while the majority of the hairs are 

 tipped with large globules that could easily be mistaken for 

 permanent knobs or suckers. 



The specimen also distinctly shows that the shafts of the hairs 

 fringing the palvilliis do not spring separately from it, but each 

 root or stem forks off near the base, forming two hairs. I 

 believe Mr. Nelson first drew attention to this fact in his letter 

 to the " English Mechanic " of March 22nd, 1895. 



I had hoped that the staining would have rendered visible 

 the orifice from which the adhering substance exudes, as the 

 opening should be large, considering the size of the attached 

 globules, but no such orifice has been detected. Judging, how- 

 ever, from the way the viscid substance seems in most cases to 

 be held within the hollow of the sickle, it appears possible that 

 a slit may exist along the filament capable of expanding and 

 allowing the substance to exude freely. 



The foot in question has been subjected to no cleaning pro- 

 cess. Any attempt at such would inevitably clear away the 

 globules adhering to the hairs, as is the case in ordinary 

 preparations. 



