INSECTS AND THEIR CONTROL 225 



clubbed at the end, and the members fly in the daytime only. 

 Moths, on the other hand, have unclubbed antennae, fly at 

 night, and fold the wings over the body when at rest. Hyme- 

 noptera include bees and wasps. Coleoptera, which com- 

 prise beetles, are very numerous in the animal kingdom, 

 containing more individuals and species than any other 

 known division of animals. Coleoptera are distinguished 

 by the existence of two unlike pairs of wings, the under 

 pair being used for flight, while the upper pair is differ- 

 entiated into a hard shell-like protective covering. The 

 Orthoptera constitute one of the best known of all the insect 

 divisions, including such well-known types as the grass- 

 hopper, katydid, and locust. Historically, this group was 

 one of the first to come under general observation, and it 

 has been one of the most baffling as regards control. Homop- 

 tera include plant-lice, technically known as aphids, and 

 scale insects. Every orchardist has come into contact very 

 intimately with this last group for they are among the 

 most injurious known and the most difficult to control. 



335. Metamorphosis. During its life process, the normal 

 insect undergoes a number of changes. As a rule, it starts 

 as an egg, hatches out into the larval or worm form, then 

 enters what is known as the pupal stage, in which it is dor- 

 mant for a time, and from which it finally emerges a full 

 grown or adult insect. This process is known as metamor- 

 phosis. It is made clear most easily by a study of one or two 

 specific examples. 



336. Some examples of metamorphosis. The butterfly 

 lays its eggs and these hatch into caterpillars. The cater- 

 pillar feeds on vegetation of various sorts, growing rapidly 

 the while. Finally it spins about itself a cocoon and becomes 

 what is generally known as a chrysalis. It may remain in 

 this form a few days or several months, depending on cir- 

 cumstances; but finally it assumes the adult shape and 

 emerges as a full grown butterfly. The cycle is then repeated. 



