134 Recent Literature. lAvk 



greatest, alfalfa Gelds averaged about twenty-five to the square yard. In 

 Bome pasture land along the canals, the cumbers wore estimated at thirty 



per square yard." 



" Los Banos, largely OB aCCOUnl Of its great irrigation system and the 

 large amount of land which lias been swamped, supports a very Large bird 

 population. Water-birds and shore-birds are very abundant along the 



canals and in the marshes, whereas the pasture lands, alfalfa and the trees, 

 furnish food and cover for many land birds. During the week's stay. 

 July 10 to 17, 1912, twenty-two species of water- and shore-birds were 

 recorded, and forty species of land birds." fjK 4.) 



" blackbirds, kingbirds, shrikes, and meadowlarks appeared to be 

 feeding almost wholly upon grasshoppers, and so must be considered among 

 the most efficienl destroyers of these insects Kingbirds and shrikes, better 

 known as butcherbirds, were constantly seen to catch a grasshopper, carry 

 it to the telephone wires, beat it to pieces, and eat it. The work oi these 

 birds and also oi blackbirds and orioles was so evident that several ranchers 

 reported these birds as being beneficial in the destruction oi grasshoppers." 

 (p. 7.) 



" Only a few birds of each species were examined, but even these small 

 numbers should give a fairly accurate idea of the extent to which birds in 

 the infested areas were feeding on grasshoppers.". ... " The burrowing 

 owl must be considered the most efficient destroyer, since parts of twenty- 

 eight grasshoppers were found in the one stomach examined. Blackbirds 

 and meadowlarks, however, because of the large numbers oi individuals, 

 were doing the most effect ive work." (pp. 7 8 



The total number of grasshoppers daily destroyed by the entire bird 

 population per square mile in the infested area, is estimated at 120, 1 15, and 

 Mr. Bryant adds: " Emphasis can well be placed on the fact that a diminu- 

 tion of the numbers of an injurious insect must cause a corresponding dimin- 

 ution of the damage done. If twenty grasshoppers are causing damage 

 on a square yard of alfalfa the loss of even two must cause some diminution 

 in the amount oi damage done, however slight it may be. Consequently 

 the large numbers of grasshoppers taken by birds during the outbreak must 

 have meant a decrease in the possible damage in spite of the fact that such 



a decrease could not be noted." (pp. 10 17.) 



Possibly this conclusion is accurate with regard to injury by grasshoppers, 

 but it is obvious that it is not widely applicable to the reduction oi damage 

 by the destruction of insect pests by their natural enemies. For instance 

 after even a high percentage oi such pests as the plum curculio, codling 

 moth, nut-weevils and the like, are destroyed, if the survivors thoroughly 

 distribute their eggs, the damage to the crop will be as gieat as before, 

 since one larva in a fruit as effectually ruins it for marketing as would 

 several. It may further be remarked with reference to Mr Bryant's state- 

 ment that a decrease in damage which cannot be noted is not commercially 

 significant . 



The author's conclusions, in the main are very conservative: " Since 



