162 Principles of Plant Culture. 



b — By insects, worms, slugs and snails. Since worms, 

 slugs and snails work the same kind of injuries as 

 some incests and are controllable by the same meth- 

 ods, we do not distinguish between them in the follow- 

 ing paragraphs. 



276. Many Insects are Beneficial by destroying harm- 

 ful insects or by promoting pollination (150). We 

 should not, therefore, wage indiscriminate warfare upon 

 all insects. 



277. Methods of Preventing Insect Ravages to 

 plants are various, as inclosing the plants, trapping, 

 repelling or removing the insects, destroying them by 

 means of insecticides, or preventing reproduction by 

 destroying the eggs. The important question in the 

 case of any injurious insect is by which one of these 

 methods it may be most eifectually and cheaply con- 

 trolled. 



278. Inclosing the Plants is practicable in a few 

 eases, as with the striped cucumber beetle.* The hills 

 in which cucumbers, 

 melons, squashes, etc., 

 are planted, may be 



covered with a frame F'G. 67. Screen-covered frame, for 

 . protecting hills of the melon and cu- 



havmg nne-meshed wire cumber. 



or cotton netting tacked over the top, which prevents 



the beetles from gaining access to the plants (Fig. 67). 



279. Trapping the Insects is practicable in a few 

 cases, as with cutworms, which often conceal themselves 

 during the day beneath objects on the ground. They 

 will frequently be found in numbers beneath handfuls 



• Diabrotica vittaia. 



