LEAF HOPPEES INJURIOUS TO CEEEAL AND EOEAGE CEOPS 9 



INSECTS 



The insect enemies of the leaf hoppers are not so numerous as they 

 are for some other groups of insects, but there are a number which 

 may be considered as of sufficient importance to notice. 



PREDATORS 



Among the predacious forms perhaps the most abundant and 

 efficient are the little bugs of the family Xabidae. some of which are 

 found in great abundance in the meadows and pastures where the 

 leaf hoppers occur. The most abundant of the species is Reduviolus 

 feigns L., which occurs throughout the United States and may be 

 found in almost every kind of grassy land. That it is a frequent 

 predator upon the leaf hoppers is indicated hj its attack upon them 

 when they are taken together in the net. although seldom found 

 with the insects actually impaled upon their beaks in the field. It is 

 probable that they puncture and suck the blood of the insect very 

 quickly and discard the dead body so promptly that they are 

 not found with them actually impaled. There is no question but 

 that they draw upon the leaf hoppers as one source of their food 

 supply, and they may be one of the principal agencies in keeping the 

 leaf hoppers in check. 



Another group which is less notable is the genus Geocoris, in the 

 family Lygaeidae. These are minute flattish bugs, with prominent 

 eyes, which occur as widely distributed common insects on the ground 

 among the grasses and other low-growing vegetation. Their attack 

 upon leaf hoppers has been reported by various observers, and dur- 

 ing the season of 1910 a definite instance of the species Geocoris 

 decoratus Uhl. was noted by Herbert T. Osborn, of the Bureau of 

 Entomology. This species was found at Wellington, Kans., in a 

 number of instances with small leaf hoppers impaled on its beak, 

 and numbers of dead leaf hoppers were found in the vicinity. 



PARASITES 



In the parasitic insects affecting the members of this group is found 

 another constant factor of control, and one which is perhaps far more 

 important than is readily appreciated. Among these forms are num- 

 bers of Hymenoptera, Diptera, and Stre23siptera. Of the Hymenop- 

 tera the most abundant parasites are included in the families Proc- 

 totrypidae and Dryinidae and in the genera Gonatopus and Dryinus. 

 These parasites attack the nymphs more particularly, but are often 

 found upon the adults and are conspicuous, inasmuch as for many 

 of the species the parasitism takes the form of an external sack- 

 like structure in which the larva develops on material sucked from 

 the body of the host. In some of our native species of leaf hoppers 

 these parasites have been found in something like 20 per cent of 

 the individuals, so that it is evident that they must constitute a 

 quite distinct check. 



An extensive series of records showing the parasitism of these 

 forms is found in the reports of the Hawaiian Experiment Station, 

 in the papers of Perkins (23) and others in connection with investi- 

 gation of leaf hoppers affecting sugarcane. Many species were col- 

 lected and reared from leaf hoppers occurring in the United States 



129811—32 2 



