22 Practical Zoology. 



2. Cut off the head, lay it on a glass slide, and with a one-inch 

 objective examine the short antennae in front of the head. 



3. Look on the top of the head for simple eyes. 



4. With a lens examine the under part of the head to see the 

 tongue. How does it move? Remove it and look at it with a 

 one-inch objective. How is the tongue used? 



THE THORAX. 



1. How many legs are there? To what are they attached? 

 How many segments has each leg? 



2. The wings ; how many are there? Back of each wing find 

 a short membrane, the winglet. Note the folded portion connect- 

 ing the wing and the winglet. 



3. A little farther back are two slender stalks ending in rounded 

 knobs ; these are the balancers, and are considered as representing 

 the hinder wings found in most insects. Note the effect of re- 

 moving the balancers. 



4. The wings describe a figure 8 in flying, and make over 300 

 vibrations (i.e. go up 300 times and down 300 times) in a second. 



5. On each side of the thorax, just back of the head, find a 

 narrow opening with a yellow, liplike border; examine closely 

 with the aid of lens and microscope. It is a breathing pore, or 

 spiracle. 



THE ABDOMEN. 



Are there spiracles on the abdomen ? How many rings has the 

 abdomen? Draw the fly as seen from above (dorsal view). 



The house fly lays its eggs about stables ; after a day or two 

 the egg hatches out as a maggot, which eats voraciously and 

 grows rapidly ; in about a week it ceases eating, becomes dry 

 and brown, resembles a seed, and does not move ; from this pupa- 

 rium the fly emerges. The adult fly is short-lived, tho some live 

 over winter. Watch the development of the egg which the flesh 

 fly lays on meat and dead animals. How many kinds of flies do 

 you know? How do they differ? How does the fly walk on the 



