XXII 

 THE ECONOMIC RELATION OF MAMMALS TO INSECTS 



Some groups of mammals almost deserve to rank with insectivorous 

 birds as insect destroyers, helping to keep the insect hordes within 

 reasonable bounds. This is particularly true of the Insectivora (moles 

 and shrews) and Edentata (anteaters and armadillos), which destroy 

 insects that live on and beneath the ground, and the Chiroptera (bats), 

 which feed upon the flying insects, though many other mammals are 

 also highly insectivorous and others take some insects. 



The food of the bats of the United States and Great Britain consists 

 almost exclusively of nocturnal flying insects of many kinds, thus 

 supplementing the work of insectivorous birds, which live chiefly upon 

 diurnal insects. The total amount of insect life annually destroyed by 

 these flying mammals is enormous. Stomachs of bats shot in the early 

 evening, after only twenty minutes of flight, have been found packed 

 with insects, and they probably take several such meals each twenty- 

 four hours. Great deposits of bat guano in caverns are composed of 

 insect remains. 1 "Bat towers" have been erected in Texas for the pur- 

 pose of controlling mosquitoes and accumulating commercial deposits 

 of guano, but though the bats doubtless take some mosquitoes, they 

 by no means take as many of these pests as some people suppose. 

 Mosquito remains are not conspicuous in the guano from either the 

 towers or caves, and in most regions bat towers would not produce 

 enough guano to pay for their erection. 2 Nevertheless, it is significant 

 that, according to Fargo, on Bird Key, Florida, there are bats and 

 no mosquitoes, while on neighboring keys there are mosquitoes and 

 no bats, 3 unless the presence and absence of mosquito-eating birds may 



1 Bailey, Farmers' Bull., No. 335, p. 31, 1908 ; Bats of Carlsbad Cavern, Natl. Geog. 

 Mag., XLVIII, 321-330, 1925; Animal life of Carlsbad Cavern, pp. 108-129, 1928. Nelson, 

 U. S. Dept. Agric. Bull. No. 1395, 1926. Huey, Journ. Mammalogy, vi, 196-197, 1925. 

 Hatt, ibid., rv, 260-261, 1923. Seton, ibid., in, 52, 1922. Pittman, ibid., v, 231-233, 



1924. Goodwin, ibid., ix, 104-112, 1928. Grinnell, California Fish and Game Comm. 

 Teachers' Bull., No. 6, 1916. Poulton, British insectivorous bats and their prey, Proc. 

 Zool. Soc. London for 1929, pp. 277-303. 



2 Campbell, Bats, mosquitoes and dollars, 1925. Storer, Journ. Mammalogy, vii, 

 85-90, 1926 ; Science, LXIII, 337-338, 1928. McAtee, Ann. Kept. Smithsonian Inst. for 



1925, P- 416. Goldman, Journ. Mammalogy, vii, 136-138, 1926. Hall, California Fish 

 and Game, xn, 136-137, 1926. 



* Fargo, Journ. Mammalogy, x, 203-205, 1929. 



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