GENERAL CROP TESTS 



85 



Other insects — ants, wasps, bees and flies — and in the fond- 

 ness of ants for this substance there is developed a curious 

 inter-relationship. 



The various phases of development, the varieties of forms 

 produced by some genera, in fact, the life economies of these 



Fig. 47.— Melon aphis, a. Winged female; 

 aa. enlarged antenna of same; ab. dark 

 female, sida view: b, young nymph or 

 larva c. last stage of nymph; d, wingless 

 female — all greatly enlarged. (Author s 

 Illustration, U. S. Dept. Agr.) 



Fig. 48.— Flavescent leaf- 

 hopper (Empoasca flaves- 

 cens). Highly magnified. 

 (Author's Illustration, U. S. 

 Dept. Agr.) 



insects would fill several volumes, and there is such great 

 diversity of habit that it is difficult to generalize. 



The species which feed upon vegetable crops live for the most 

 part on the under surface of leaves; but some are root-feeders, 

 and the destructive grape phylloxera is an example of one of 

 these subterranean forms which produce galls. 



The melon aphis (fig. 47) is one of our commonest and best 

 known vegetable-feeding forms of this class. 



The best remedies for aphides are kerosene emulsion, fumiga- 

 tion with bisulphid of carbon and with tobacco extracts, clean 

 cultural methods of farming and the encouragement of natural 

 enemies. These remedies are considered on pages 165 to 168. 



The Leafhoppers. — Leafhoppers are familiar to nearly 

 everyone, although not everybody knows them by this name. 



