38 INSECT PESTS OF FARM, GARDEN AND ORCHARD 



market. Unfortunately, many of the most destructive insects 

 are not attracted to lights. The codling moth and corn earworm, 

 for instance, are rarely seen at the lights. In some cases where 

 injurious forms are flying to the lights freely, for instance, when 

 June-beetles are particularly abundant, they may be trapped by 

 this method with some resulting benefit. As a rule, however, 

 not enough individuals will be killed to make any noticeable 

 difference in the injury to the crops attacked and while some in- 

 jurious forms are being killed many beneficial ones will also be 

 destroyed. The method is not, therefore, commonly recom- 

 mended as a practical means for insect control. 



Mechanical Means for the Collection of Insects. Some benefit 

 is realized from the collection of insects by mechanical means. 

 Of these the most simple is hand-picking. This is practical on a 

 small scale and is used for the control of tomato and tobacco 

 horn-worms and many other insects, being used even for the con- 

 trol of the Colorado potato beetle in small fields. Grasshoppers 

 are collected by the use of hopperdozers as described in the dis- 

 cussion of those insects. Leaf hoppers are collected sometimes 

 with machines of similar construction but adapted for use with 

 row crops. Leafhoppers and flea-beetles are collected with some 

 success by the use of shields covered with sticky material and 

 carried along the rows of plants attached in such position that 

 insects disturbed will be caught on the sticky material when they 

 hop or fly from the plants. Flies are trapped in large numbers 

 and trapping is one of the best means of control for these insects. 

 Mechanical means of collecting and killing insects are generally 

 less satisfactory than the use of spra}^s when the latter are avail- 

 able for the control of the insects but serve a useful purpose for 

 some forms which can not readily be controlled by spraying. 



