1895 THE MICROSCOPE. 5 



that we cannot see them. The last joint is covered with 

 long hairs. An organ has recently been discovered in 

 the antennae of some insects which is thought to be the 

 organ of hearing. 



The tongue, (Fig. 2 T), is a broad fleshy lobe which is 

 crossed with spiral fibers by which the fly is able to suck 

 the juices it feeds on. There are little short stiff hairs 

 set around the base of the tongue. It is these by which 

 we are so much annoyed. M indicates the palpi. These 

 correspond to the instrument that the mosquito uses to 

 pierce the flesh of his victim when he seeks blood. 



Move the fly so as to show his wings. If these are at 

 the right angle they will show beautiful iridescent 

 colors. Notice the veins in the wings, as their arrange- 

 ment is important. Compare these with the wings of 

 other insects. See along the outer edge of the wing the 

 little row of hairs, then the beautiful net work of veins 

 and in examining the wings of different flies, notice that 

 the larger the fly the stronger and more numerous the 

 veins. The wings of the Miisca dornestica make 600 

 strokes in a second, which carries it five yards and if 

 alarmed it can fly thirty feet in a second. The veins in 

 the wings we are told are hollow air vessels which com- 

 municate with the lungs, for even the little fly has lungs 

 and an organ which acts as a heart to send the blood 

 throughout his body and into his wings. He has also 

 an alimentary canal, salivary vessels, biliary tubes, and 

 a chylific stomach which seems to supply the whole ali- 

 mentary canal with the power of digesting food. Flies 

 have a crop or gizzard which is used chiefly as a reser- 

 voir for food when the insect takes more than it needs 

 for its immediate wants. 



The legs. — Take one from the body and arrange so as 

 to see the foot. If you are to handle such snail objects 

 you will find a pair of pointed forceps necessary. These 

 you can buy or make. Take two pieces of good elastic 



