1913 ~ J Recent Literature. 131 



ever of spiders preying upon these insects preface the following remark: 

 "When we consider the carnivorous habit and observe the immense num- 

 bers of spiders in the fields, and realize that in many cases leafhoppers are 

 the most abundant and accessible food supply for them, it is easy to credit 

 the spiders with immense service in this direction." (p. 35.) 



In view of the nearly complete lack of evidence these strong claims for 

 the value of spiders and heteroptera, as enemies of leafhoppers, are entirely 

 unjustified. The tone of this section of the discussion of natural enemies, 

 bears no relation to that of the section treating birds; the treatment is 

 illogical and unjust. 



Probably on account of long concentration upon the group of leafhoppers, 

 the author has let this really inconsiderable portion of our insect fauna, 

 obscure his sense of proportion. An oak leaf held close to the eyes will 

 hide the world. As a matter of fact leafhoppers are only a small section 1 

 of one order of insects, and not only are some other groups of this order 

 just as abundant in individuals, but the same is true of many groups in 

 other orders. Birds draw their food from all these sources and there is no 

 evidence that leafhoppers contribute less than their appropriate propor- 

 tion to the total food of birds. 



The author therefore has no right to be disappointed that leafhoppers 

 constitute a small portion of the food of practically all our common birds. 

 So also do the Coccidse or scale insects, the Tettigidse among Orthoptera, 

 the Carabidse, among beetles, etc., but this is no proof that these insects 

 are not preyed upon in the proportion of their abundance to that of insects 

 as a whole. It must be remembered also that animal food as a whole 

 including Crustacea, mollusca, arachnida, other invertebrates and verte- 

 brates, forms probably not more than half of the total food of birds, this 

 circumstance reducing by half the percentage required to give any group 

 of animals proportional representation in the subsistence of birds. Further- 

 more it must be recognized that many common birds have arboreal or other 

 specialized habits that keep them out of grass lands, the metropolis of leaf- 

 hoppers. 



It would be just as reasonable to say that hymenoptera may be consid- 

 ered as negligible in the control of leafhoppers,, because only a few species 

 are recorded as parasites of leafhoppers, and the majority of the species 

 leave them alone, yet the author says that this order as a means of control 

 is perhaps far more important than we readily appreciate. It probably 

 cannot be proven that any class of predaceous or parasitic enemies of in- 

 sects takes more than a small proportion of the total number of any re- 

 stricted group of the prey (averaging the results for a long series of years). 



In brief the arguments made by the author in the case of bird ememies 



* For instance the number of species of leaf-hoppers forms only 1.34 per cent of 

 the total number of species in Smith's "Insects of New Jersey" and only 1.22 

 per cent of the insects of the woild as tabulated by Handlirsch (Die Fossilen 

 Insekten, Part VI). 



