Natural Enemies. 



In one of his bulletins Professor Osborn has given quite an 

 extended account of the natural enemies of the leaf hoppers. 

 We will do little more than to give the substance of this and 

 of one or tv^o other papers, for comparatively little work has 

 been done on this line. 



The natural enemies of the leaf hoppers may be divided 

 into four groups, as follows : 



1. Predaceous enemies. 



2. Parasitic enemies. 



3. Fungus diseases. 



4. Climatic conditions. 



The predaceous enemies of leaf hoppers do not seem to be 

 an important means of control. Among such enemies are the 

 birds, but even such active foes do not seem to be very efficient 

 in controlling them. It has been found that while a goodly 

 number of birds feed upon Cicadellids, yet in the aggregate 

 such food forms but a small part of their dietary. Professor 

 Osborn sums up the relation of birds to leaf hoppers as follows : 



1. 119 species of birds are known to feed upon leaf hoppers. 



2. Only 700 out of 47,000 bird stomachs examined contained leaf 

 hoppers, or less than one out of every fifty. 



3. The leaf-hopper content of a majority of these stomachs was only 

 from 1 to 10 per cent, so that not more than one-thousandth part of the 

 food of birds can be composed of leaf hoppers. 



Domestic birds such as turkeys and chickens are said to 

 feed on leaf hoppers, but their inroads on such insects could 

 not be considered as serious. 



Toads and frogs, being insectivorous, should use a small 

 proportion of leaf hoppers in their dietary, Gibson states 

 that the former has been observed feeding on them in alfalfa 

 fields. 



Among the Arthropoda themselves we find perhaps the most 

 efficient predaceous foes of the leaf hoppers, though all com- 

 bined do not seem to do anything appreciable in holding them 

 in check. Various spiders and mites are said to be among 

 such enemies. Slingerland and Johnson give the names of 

 mites predaceous on the grape-leaf hopper in their bulletins 



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