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e,e3iarks on the e3iissi0n of musical notes and on the 

 Hovering Habit of Eristalis tenax. 



By W. H. Harris. 



{Read April ITtli, 1903 ) 



Among the Diptera common to Great Britain there is one family, 

 the Syrphidae, some species of which offer to even the most 

 superficial observer two very distinct and remarkable peculiarities 

 — namely, their ability to emit musical notes, and their hawk-like 

 or hovering propensity. 



In the " Introduction to Entomology" by Kirby and Spence there 

 are some remarks as to the manner in which the former of these 

 actions is performed by certain species of flies, but with regard 

 to the latter, no attempt is made to explain by what means they 

 accomplish this feat, nor have I ever been successful in my 

 endeavours to discover any literature on the subject. 



Thrown back on my own resources, I have attempted to 

 investigate for myself, and the following remarks are the outcome 

 of adopting this course. 



Emission of Musical Notes. 



With regard to the emission of sound, I must be permitted to 

 make an extract from the work quoted, showing the nature of 

 the investigations made by several old observers whose names 

 are deservedly held in great respect, some of which are exceedingly 

 curious and others scarcely worth repeating. 



De Geer, whose observations seem to have been made upon 

 aphidivorous flies, appears to have proved that " the sounds were 

 produced by the friction of the root or base of the wings against 

 the sides of the cavity in which they are inserted. To be con- 

 fi.rmed of this, he aflS.rms, the observer has nothing to do but 

 to hold each wing with the finger and thumb, and stretching 

 them out, taking care not to hurt the animal, in opposite 

 directions, thus to prevent their motion — and immediately all 



JouRN. Q. M. C, Series II. — No. 53. 35 



