4 CIRCULAR 2 41, U. S. DEPARTMENT OE AGRICULTURE 



catching them the writer secured in some instances more than a 

 million per acre, and obviously this number must fall short of the 

 number actually present. Some careful estimates based on actual 

 captures over plats 5 yards square were made at the writer's sug- 

 gestion in the fall of 1908 by V. L. Wildermuth. These captures 

 were in timothy and bluegrass-timothy pastures, and although it 

 can not be assumed that all the leaf hoppers in the given area were 

 caught, the average for all these captures gives a result of about 

 1,000,000 per acre, in some cases as many as 2,000,000 per acre 

 being recorded. 



CROPS AFFECTED 



While the present survey is intended to cover the various cereal 

 and forage crops, it must, for a number of reasons, be more complete 

 for those that are of most general culture. In general, it may be 

 stated that all of the crops belonging to the grass family and most 

 of those in common cultivation belonging to the legumes are infested 

 by one or another, often by many, species of leaf hoppers. The 

 abundance and corresponding injury vary greatly with these crops 

 for different parts of the country and under different cultural con- 

 ditions, as also with different seasons, so much so that general state- 

 ments for annual crops are hardly applicable here. One of the most 

 obvious conclusions, however, is that the greatest drain occurs where, 

 owing to continuity of crops or by close association of common 

 food plants, there is offered an exceptional opportunity for the 

 survival and increase of the insects from generation to generation 

 through a season or during a series of years. 



GENERAL HABITS OF LEAF HOPPERS 



There are several features in the general habits of these insects 

 which may be discussed for the group, although there are certain 

 ones in which each particular species must be considered by itself. 

 In their food habits, as has been mentioned, there is a wide diversity, 

 some species affecting a great variety of plants, others a very few. 

 The various species, however, agree pretty generally in attacking the 

 leaves or the freshly grown portions of the stem of the plant, making 

 their punctures where they can secure the sap with the greatest ease, 

 thus affecting the growth of the more succulent portions. 



In many instances the insects show a distinct adaptation to certain 

 parts of the plant, to the extent that the shape and color of the body 

 blend with the part upon which they are feeding, notably in cases 

 where the coloration coincides with the markings at the joints of the 

 stems, causing the most perfect resemblance of the insect to the joint. 

 Some of the insects affect the seeds or blossoms, others cluster near 

 the ground, and some have even been reported as affecting the roots, 

 but only a very few species have been noted attacking the plant in 

 this manner. 



There is no distinct adherence to a particular plant except during 

 the earlier nymphal stages or for certain species which have aborted 

 wings and are, therefore, unable to fly. Practically all of the species, 

 however, jump with great facility and if disturbed will jump and 

 may come to rest on the ground or some adjacent plant. A general 

 habit which is of importance is a tendency of the insects to disperse 



