130 Recent Literature. [.Jan. 



3.03 (152), Vireo huttotri, 4.7 (58), and Wilsonia pusilla, 5.6 (67). In addi- 

 tion several other species of birds, whose food habits are known from exam- 

 ination of a large number of stomachs., eat leafhoppers to an extent of from 

 1.28 to 3 per cent, of their annual diet. This group includes such common 

 species as Chordeiles virginianus, Sayornis phcebe, Archilochus colubris, 

 Empidonax difficilis, Geothlypis trichas, Iridoprocne bicolor, Penthestes 

 rufescens, Petrochelidon lunifrons, and Riparia riparia. 



These 24 species certainly feed as extensively as could reasonably be 

 expected upon this single rather restricted group of insects. In the writer's 

 opinion this is true also of other species among those whose Jassid feeding 

 records are tabulated But Professor Osborn draws a different conclusion 

 part of which is as follows: " While at first thought we might consider birds 

 as a most important element in control of these insects, a closer study re- 

 veals many reasons why they must depend upon them but little as a food 

 supply. Even with this more conservative view in mind, however, the 

 actual conditions as represented by the records of the Biological Survey are 

 rather disappointing since they show that for practically all of our birds 

 the leafhoppers constitute so small a portion of their food supply that birds 

 very properly may be considered as almost negligible in any consideration 

 of the natural agencies of control." (p. 23.) 



Let us see what is said regarding some of the other natural checks. Again 

 quoting : " Among the predaceous forms we have as the most abundant and 

 efficient perhaps the little bugs of the family Nabidae, some of which occur 

 in great abundance in the meadows and pastures where the leafhoppers 

 occur. The most abundant of the species is Reduviolus ferus L., which 

 occurs throughout the entire range of the United States and may be found 

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

 the leafhoppers is indicated by its attack upon them when they are taken 

 in the net, although it must be said that they are very seldom found with 

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

 that this comes from their puncturing and sucking the blood of the insect 

 very quickly and discarding the dead bodies so promptly as not to be found 

 with them actually impaled. I have no question that they feed upon the 

 leafhoppers as one source of their food supply, and believe them to be one 

 of the principal agencies in keeping the leafhoppers in check." (p. 32.) 



Thus probabilities and beliefs as to efficiency give tins natural enemy a 

 high rank while nearly five pages of finely printed tabulation showing the 

 extent to which more than 120 species of birds are known to feed upon these 

 insects, show in this author's opinion that " birds very properly may be 

 considered as almost negligible in any consideration of the natural agencies 

 of control." 



Another case concerns the genus Geocoris in the family Lygaeidae. 

 Several reports that they attack leafhoppers and one definite record elicit 

 the remark that they "certainly must contribute largely toward the reduc- 

 tion of the leafhopper pest." (p. 33.) A page of generalities upon the 

 probable leafhopper enemies among spiders, with no definite instances what- 





