244 ZOOLOGY 



lower lip covers the large biting Jaws which can be extended so as to 

 grasp and hold its prey. The nymphs of the dragon fly take oxygen out 

 of the water by means of gill-like structures placed in the posterior part of 

 the food tube. They may live as larvae from one summer to as long as two 

 years in the water. Thej' then crawl out on a stick, molt by splitting the 

 skin down the back, and come out as adults. 



A nearly related form is the damsel fly. This may be distinguished from 

 the dragon fly by the fact that when at rest the wings are carried close to 

 the abdomen, while in the dragon fly they are held in a horizontal position.^ 



May Flies. — Another near relative of the dragon fly is the May fly. 

 These insects in the adult stage have lost the power to take food. Most 

 of their life is passed in the larval stage in the water. The adults some- 

 times live only a few hours, just long enough to deposit their eggs. 



The Order Coleoptera 



Beetles. — Beetles are the most widely distributed of all insects 

 and by far the most numerous. There are over one hundred thou- 

 sand living species; more than all other animals in the world 

 exclusive of the insects. 



Any beetle will show the following characteristics:^ (1) The 

 body is usually heavy and broad. Its exoskeleton is hard and 

 tough. The lower side of the abdomen is also hard. The chitinous 

 covering is better developed in the beetles than in any other of the 

 insects. (2) The three pairs of legs are stout and rather short. 

 (3) The outer wings are hard and fit over the under wings like a 

 shield. These sheathlike wings are called elytra. (4) The mouth 

 parts are fitted for biting. They consist of very heavy curv^ed 

 pincher-shaped mandibles, which are provided with palps. There 

 is an upper and lower lip. 



The Living Beetle. — Use any large beetle to answer the following questions. 

 Identify the above-named parts in 3'^our specimen. Test the ability of 

 any large beetle to bite. Are the jaws strong? Give proofs. Do the jaws 

 move in the same plane with your own? Does the beetle have antennae 

 (feelers) ? How does the beetle use its legs in walking ? Is there any 

 regular order? If the animal is allowed to walk over an ink pad or through 

 a drop of ink, its track may easily be traced on paper and then transferred 

 to your notebook. In what respects is the beetle protected from its 

 enemies ? How is it adapted to the life it leads ? 



^ The old seven-order system of classification is useful for pupils of first year in 

 the high school. Tliis allows a place for many forms otherwise not easily classified 

 under the order Neuro-ptera. 



2 For laboratory directions on beetles, see Hunter and Valentine, Maniuil, page 



