I 9 6 THE YOUNG NATURALIST. [September 



bined with the rapid vibration of the wings, are undoubtedly the 

 prime agents in the production of this familiar sound, for it has been 

 found that the intensity is lowered by removing one organ and allow- 

 ing others to remain. 



The actual function of the halteres is very obscure, and numberless 

 uses have been assigned to them. My own experiments tend to show 

 that they have some mysterious affinity with the anterior wings, for 

 if they suffer mutilation, the flight of the insect is sensibly affected. 

 I cut off the left haltera from a specimen of Musca vomitoria, but the 

 fly, when released, was then unable to sustain itself on the wing for 

 any length of time ; moreover, it flew in a jerky and uncertain manner. 

 When the right haltera was removed in addition, the insect was quite 

 unable to leave the ground beyond a sort of a jump about an inch 

 high, and when dropped from the hand, fell helplessly. They cannot 

 constitute a very vital part, notwithstanding their intimate influence 

 over the organs of flight, as the specimens operated upon lived a week 

 afterwards, partaking of nourishment, but totally unable to fly. 



The exact reverse of the Diptera is found in the Strepsiptera, a 

 group of parasitic insects infesting bees. In these curious creatures, 

 the fore-wings of the male appear as a pair of mesothoracic, twisted 

 appendages, somewhat resembling the halteres of our two-winged 

 friends, and therefore fitly termed pseudo- halteres ; the posterior organs 

 are large and amply developed. The females are entirely apterous. 



In bringing to a close the preceding notes upon the structural 

 variation of such important organs as those to which I have attempted 

 to draw deserving attention, I would wish to express my sincere and 

 grateful thanks to many kind friends who have assisted me with speci- 

 mens from time to time, and thus materially helped me in the work of 

 figuring some interesting forms. To G. C. Bignell, Esq., of Plymouth, 

 such thanks are more particularly due, for the characteristic and 

 generous manner in which he placed many rare species at my 

 disposal. 



Finally, I add the hope that opportunities may not be wanting, to 

 afford me, in the future, material for additional observations upon a 

 subject that I have found to possess the highest possible interest. 



Mossy Bank, 



Egremont, 



Cheshire. 



