74 THE MICROSCOPE. 



three or four longitudinal ridges ; the inner margin 

 of this nervure spreads out into a thin, narrow mem- 

 brane ; other nervures, much smaller than the dark 

 one, border the space which forms a drum, or tym- 

 panum. In front of the drum is clearly to be seen a 

 transverse side with numerous file-like teeth, from the 

 middle portion of which side there proceed three 

 nervures ; two are simple ; the other, which is con- 

 nected at the base to the file by three short and 

 strong processes, branches into two parts. All these 

 three nervures are strong at the base, and then become 

 attenuated ; they stretch across the tympanum till they 

 touch and become part of the narrow membrane of 

 the large dark nervure spoken of above. The insect 

 then produces the sound by rubbing the wings to- 

 gether; the files are rapidly drawn one across the 

 other, and the sound greatly intensified by the action 

 of the drum, or tympanum, I have endeavoured to 

 describe. I ought, however, to say that some ob- 

 servers believe the sound is produced by the rubbing 

 of the file across the large longitudinally -ridged 

 nervure. It would be difficult to decide the point, 

 but I can readily conceive either mode would produce 

 the well-known sound. 



You will be struck with the beautiful iridescent 

 hues observable in the wings of some insects. The 

 aphides, or plant-lice those noxious pests known to 

 farmers as " smother fly/' and to the popular mind as 

 "blight" exhibit this iridescence in a remarkable 

 degree. By turning the wing you may be examining 

 to various directions, you will ascertain the angle at 

 which the iridescent hues are best seen. 



The feet of insects will be sure to occupy your 

 attention, and their study to afford you delight. The 

 foot of the house-fly is a very common microscopic 

 object, and one especially interesting. It has long 



