XXVIII. FRIENDS AND ENEMIES OF PLANTS Continued 



2. ANIMAL FORMS 



Insects. If you were called upon to name some animals that 

 are classed as insects, you might mention ants, flies, bugs, beetles, 

 butterflies, and moths ; but at the same time you might wonder 

 why they are all grouped together when some of them differ so much 

 from one another. A little study will show us, however, that 

 they have this much in common. They have six legs, and their 

 bodies are divided into three parts the head, the thorax, and 

 the abdomen. They breathe through tiny holes, called spiracles, 

 arranged in a row along each side of the abdomen. On the head 

 are found the mouth, eyes, and the antennae. 



Such insects as the butterflies, bees, houseflies, and beetles, pass 

 through four stages before they reach maturity : the first is the egg; 

 the second, the larva; the third, the pupa; and the fourth is the 

 adult, or imago. 



The tiny egg is deposited in some safe place where, after a certain 

 time it hatches out into the larva state, in which it becomes a worm- 

 like creature so different from the original insect that we should 

 hardly suspect that there was any relationship between them. 

 This is also frequently called the grub or caterpillar stage. While 

 in this state they eat almost continually and do a great deal of 

 damage. Finally it enters the pupa stage and eats nothing. It 

 goes into a kind of sleep, and while in this condition it gradually 

 changes into a fully developed insect. This last stage we call the 

 imago. Some insects do not pass through all these stages, as in 

 the case of the locusts and grasshoppers. 



Insects do a great deal of injury, but we must not regard all of 

 them as troublesome pests. The honeybees furnish us with food 

 in the form of honey, the silkworm supplies us with silk and mate- 

 rials for clothing, while some insects do us valuable service by 

 carrying pollen from one flower to another and causing flowers to 

 b'j fertile which might otherwise remain sterile. 



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