136 RWttnl I. iU ratine. [']$$. 



compared with one taken in a non-infested district, showed birds to be 

 about three times as abundant in the infested Areas daring hours of feeding." 

 (p. L7.) 



•• The failure of birds to cheek an insert outbreak is evident to all. Their 



success in preventing insects from beooming abnormally abundant is not so 

 apparent but is no less real. All obtainable evidence, however, points to 

 the fact that the regulative influence exerted by birds when insects : 

 be found in normal numbers, although less: apparent, is none the less impor- 

 tant, for at such times artificial control measures are seldom used." (p. 19.) 



It is upon the comparative value of artificial control and the activities 

 of natural enemies that the reviewer would make a few remarks. There 

 deep-seated, and persistent (because founded on love of ease' idea that 

 if natural enemies are only sufficiently encouraged and protected, crop pro- 

 duction free from the annoyanoe ol insect pests will be assured. That this 

 is a dream impossible of fulfillment, is evident from the fundamental inter- 

 relations of living things. Natural enemies have developed because I 

 was ..'' excess of individuals of certain species that could be destroyed with- 

 out any permanent decrease in the numbers of the species as a whole. In 

 creatures with annual or shorter generations as is the case with mos 

 all but an exceedingly small proportion of the offspring must die without 

 participating in reproduction; the way of their taking off is unimportant, 

 they may as well be eaten, as to starve, dry up or freeze Whatever hap- 

 pens to the supernumeraries, a small but fecund minority remains, and the 

 average number of the species is about the same from year to year. If 

 there is an excess o\ individuals, under natural conditions, that sa 

 lemands of enemies, without endangering the existence of the sp< 

 what an overwhelming excess of a species there must be where we gh e over 

 acres or hundreds of acres to pure cultures of its favorite UhhI plants \ 



er there are constantly recurring outbreaks with which natural ene- 

 mies are unable to keep pace even in a relative Wl 



As the writer has pointed out elsewhere- when we consider tl 

 of insect control net die commercial success ps, it is evident 



that man must almost invariably depend upon his own efforts. \\ <. 

 know about natural enemies, give them all due credit, and protect them, 

 but we must b ■- - "g their services People are onhj 



easily misled in this direction but the final result of too great faith in na< 

 enemies is disappointment. Let the student of natural economies see 

 therefore that blame for such disappointment cannot justly be laid 

 him. n\ l M 



Some Bird Enemies of Amphipods In an interesting paper : covering 

 d life histories of -I species of amphipods found about It': 



x - 1911. p. MS 



tbdruck aus Inti - ottw Hjrdrobiolagte u Hydro* 



^.:iu<l III 1911 11913). .: ! pp. 



