6 FRUIT INSECTS 



the larva. The pupa is a resting stage in which the organs of 

 the larva are broken down and made over into those of the adult. 

 In the pupa the antennae, legs and wings of the adult are usually 

 evident, closely applied to the body and covered by the pupal 

 skin. When the remarkable internal structural changes in the 

 pupa are complete the adult winged insect emerges. In this 

 type of development there are four stages, viz. egg, larva (5-6 

 instars), pupa, adult. Butterflies, moths (caterpillars) and 

 beetles have complete metamorphosis. 



The control of insects. 



In spite of the many natural checks to which insects are sub- 

 ject, such as extremes of temperature, drought and wet, the 

 depredation of parasitic and predacious enemies, and the results 

 of fungous and bacterial diseases, it is usually necessary to pro- 

 tect the fruit crop by artificial means. The control of each 

 insect is a special problem, and its solution requires a thorough 

 knowledge of the life history and habits of the insect as well as 

 an understanding of the nature of the crop and the conditions 

 under which it is grown. 



Substances used for killing insects are known as insecticides, 

 and are discussed in the last chapter of this book, page 474. 



Spraying. 



Insecticides are most commonly applied in the form of a 

 liquid by means of a spray pump. In the case of poisons 

 the object is to cover the foliage evenly with the spray so that 

 the insect will be sure to get it in feeding ; in the case of con- 

 tact insecticides it is necessary to hit each insect. Spraying 

 is an art, and the finer points can only be learned bj^ practice. 

 Success will depend on the timeliness of the application and the 

 thoroughness with which the work is done. Young insects are 

 killed more easily than old ones, and it is easier to kill a few 

 early in the season than to wait until they have become abundant 

 before spraying. In spraying the grower should always have 

 a definite object in view. He should study his trees, find out 



