398 ECONOMIC INSECTS 



is lapped and sucked. The larvae of true flies are called maggots. 

 The metamorphosis is complete. 



Hymenoptera (membrane winged), bees, wasps, ants and saw- 

 flies. The most beneficial representatives are true honey-bees, 

 bumble-bees and ichneumon. The latter is parasitic upon injurious 

 insects. Among the harmful group may be mentioned currant 

 worm, pear-slug, grape-slug, saw-fly, several forms of ants and 

 some species of wasps. The metamorphosis is complete. True 

 bees have mouth parts adapted to both biting and lapping or suck- 

 ing during their adult stage. Wasps and ants have strong jaws 

 for biting. In the larval stage the mouth parts of many of the 

 families are very rudimentary, while in others they are highly 

 developed and adapted to biting and chewing. 



Life History of Insects. After determining the order to which 

 any injurious insect may belong much may be known about its 

 life history, but certain definite information is necessary about 

 each species to know how best to combat the enemy. Its most 

 vulnerable points may be determined only by knowing the places 

 where the eggs are laid, the kind of food preferred by the larvae, 

 in what stage the winter is usually passed, and other important 

 points. After such information is once obtained and'published, it is 

 usually easy for the farmer or gardener to apply suitable remedies. 



Remedies. There are a number of suitable remedies to use 

 in fighting insects: Rotation of crops will often rob the enemy 

 of the food which it must have. Fall plowing will often destroy 

 those which live through the winter under the surface of the ground. 

 Insects are then more likely to be destroyed by winter weather 

 or by birds and parasitic insects. Trap crops are useful in many 

 cases; they provide plants on which the injurious insects will 

 accumulate and where they may be destroyed more easily and 

 without danger to the main crop. 



Spraying and dusting are often thought of as the chief remedies 

 against injurious insects. In many cases spraying is much more 

 effective than dusting, but the latter is much less expensive, where 

 it can be used at all. More chemical may be used in the dusting 

 of potatoes than in spraying them, but the labor is much less. 



Natural Enemies. Insects are often kept in control by their 

 natural enemies. Serious scourges of the Rocky Mountain 

 locust, for example, are seldom known. It is believed that a 

 fungous disease, and perhaps other enemies, hold them in check. 

 So it is with many species of insects. 



