4 THE MICROSCOPE. Jan., 



B, then the tibia or shank, C, then the tarsi, D, (these 

 are small joints just above the foot,) and the foot, F, 

 which shows two little hooks. In securing the fly 

 some of the parts may have been destroyed or they 

 may be in such a position as to be hidden by some 

 other part, so it is well to look at several until you 

 can tell each part readily. In this position the tongue or 

 proboscis is not visible. In order to see this, place the 

 fly upon its side. At the front of the head just below the 

 antenna? will be seen the tongue, if it is extended. Fig. 

 2 is a sketch of the head of a fly with the tongue, T, 

 very much extended. It does not often show as much as 

 this. The figure also shows the palpi. 



Take all three of the lenses together using the little 

 diaphragm and place the fly on its side with the head on 

 the center of the stage and the tongue towards the light, 

 move the stage up very slowly and when there is a good 

 focus, fasten it. The object seems now much nearer to 

 the lens than before, this is due to the higher magnify- 

 ing power which is now about thirty diameters. 



The diaphragm is used to shut off a part of the light 

 so as to show the object more distinctly, and it makes 

 the field smaller. IS'ow look at the redish brown oval 

 spot, (Fig. 2 Ej and you will see the little hexagonal 

 lenses of which there are 2000 in each eye, arranged very 

 much like the cells of the honey-comb, (Fig. 5.) These 

 are the parts of the compound eye and are each con- 

 nected with the nerve of sight. Each part of this com- 

 pound eye is so arranged as to form a perfect picture. 

 Carpenter in his work on the microscope (page 908), 

 gives a picture taken through one of these compound 

 eyes. At A is one of the antennae or feelers. This is 

 composed of joints and by their number, shape and po- 

 sition, the genera and species of different insects are dis- 

 tinguished. The antenna of this fly has three joints, 

 Fig. 4, but the first two are so small and near the body 



