LEAF HOPPEES INJURIOUS TO CEREAL AND FORAGE CROPS O 



to other kinds of plants during the last nymphal stage. It has been 

 noticed that many species which seem to be very closely restricted to 

 particular plants in the earlier nymphal stages scatter freely during 

 the last nymphal stage to different kinds of plants, showing a dis- 

 tinct disposition to vary their diet. 



General migrations of the insects are not common, but there must 

 be local migrations from field to field, especially at times when the 

 food supply becomes scarce or unsuitable on account of the ripening 

 of the plant. At such times there may be a general dispersal of the 

 insects; for instance, from wheat fields to adjacent grasslands or in 

 the fall from grasslands to near-by fields of fall wheat, oats, rye, etc., 

 which furnish a much more attractive food for that season. Migra- 

 tions by flight for long distances are unknown for any of the species, 

 but some recent observations indicate the possibility of their carriage 

 in wind currents of the upper air. There has been observed in many 

 cases a distinct tendency for the leaf hoppers to gather at night 

 around conspicuous lights, and although it is not known whether all 

 of the species are thus attracted, so many different ones have been 

 noted as being attracted by artificial lights that it may fairly be 

 presumed that the habit is quite general. Many instances are on 

 record where immense numbers have been observed assembling 

 around lamps or street lights, and often this must result in the 

 destruction of great numbers of individuals. 



HIBERNATION 



The different species of leaf hoppers do not all hibernate in the 

 same stage. Those species which pass the colder months as adults 

 lay their eggs in the spring. Some species hibernate as partly grown 

 nymphs, and in other species, particularly the grass-infesting forms, 

 hibernation is apparently common in the egg stage. The stage in 

 which hibernation takes place is of the greatest importance, especially 

 in connection with methods of control based on the treatment that is 

 possible in late fall and in early spring. It is also important in the 

 case of those forms which become active in mild weather during the 

 winter and are thus exposed to conditions which may affect their 

 survival. 



LIFE HISTORY IN GENERAL 



So far as has been determined, the eggs of the species affecting 

 grains and grasses are deposited in the leaves or stems of the food 

 plants of the nymphs. The method of deposition has not been accu- 

 rately noted in very many instances, but, for such as have been 

 observed, it consists in the pushing of the eggs by means of the strong 

 ovipositor into the margin of the leaf or into the spaces betAveen the 

 leaf and the stem. The number of eggs deposited probably varies 

 with the species. The number has been recorded in the case of a 

 few individuals, and in some cases it must be considerable, as the 

 insects multiply at a rapid rate. Hatching takes place either in a 

 few days after oviposition or, in the case of hibernating eggs, early 

 in the following spring, and consists simply in the emergence of the 

 nymph from the broken end nearest the outside of the opening into 

 which the egg has been forced. 



