INSECTS: THEIR EARS AND EYES 195- 



In the tribe of two-winged insects, which we term, par 

 excellence, Flies (Muscadce), the antennae are of peculiar 

 structure. The common House-fly shall give us a good 

 example. Here, in front of the head, is a shell-like con- 

 cavity, divided into two by a central ridge. Just at the 

 summit of this project are the two antennae, originating 

 close together, and diverging as they proceed. Each an- 

 tenna consists of three joints, of which the first is very 

 minute, the second is a reversed cone, and the third, which 

 is large, thick, and ovate, is bent abruptly downward 

 immediately in front of the concavity. From the upper 

 part of this third joint projects obliquely a stiff bristle or 

 style, which tapers to a fine point. It is densely hairy 

 throughout; and is. more beset with longer hairs on two 

 opposite sides, which decrease regularly in length from the 

 base, making a wide and pointed plume. 



Such are a few examples of what are presumed to be 

 the ears of Insects; let us now turn our attention to their 

 eyes. And we can scarcely select a more brilliant, or a 

 larger example, than is presented by this fine Dragon-fly 

 (sEshna), which I just now caught as it was hawking to 

 and fro in my garden. How gorgeously beautiful are these 

 two great hemispheres that almost compose the head, each 

 shining with a soft satiny lustre of azure hue, surrounded 

 by olive-green, and marked with undefined black spots, 

 which change their place as you move the insect round I 



Each of these hemispheres is a compound eye. I put 

 the insect in the stage -forceps, and bring a low power to 

 bear upon it with reflected light. You see an infinite 

 number of hexagons, of the most accurate symmetry and 

 regularity of arrangement. Into those which are in the 

 centre of the field of view, the eye can penetrate far down, 



