15 



hours two hundred times its original weight. 1 The food taken 

 during fifty-six days by a caterpillar of Telea polyphemus equals 

 in weight eighty-six thousand times the original weight of the 

 caterpillar when first hatched from the egg. This enormous 

 voracity accounts for the excessive destructiveness of insects 

 when in abnormal numbers. It explains in part why the yearly 

 injury caused by insects to agricultural and forest products in 

 the United States exceeds $1,000,000,000. 



Fortunately the appetites of birds closely match those of in- 

 sects. A single polyphemus caterpillar may eat 120 oak leaves 

 during its lifetime. But the birds destroy nearly all these cater- 

 pillars and so the species rarely becomes numerous enough to 

 be injurious. 2 Samuels says that Trouvelot, to test the effective- 

 ness of birds, placed 2,000 of the polyphemus caterpillars on a 

 tree near his door, and in a few days the birds had eaten them 

 all. 3 



In 1861 Trouvelot began his attempt to produce silk from 

 American silkworms. He experimented at Medford, Massa- 

 chusetts, for several years, and from 1864 to 1870 he raised the 

 larvae of Telea polyphemus in large numbers. It was about 1869 

 that, in the course of his importations of European insects for 

 experimentation, he introduced and accidentally liberated the 

 gypsy moth which has proven a very destructive and expensive 

 pest. For six years or more he reared polyphemus caterpillars 

 in astonishing numbers, having over five acres of shrub oak and 

 other bushes fenced in and covered with netting for this pur- 

 pose. He found birds by far "the most formidable enemies of 

 the caterpillars," and he tells us that birds came from far and 

 near to destroy them. The smaller birds forced themselves 

 through the meshes of the net, and the larger ones found holes 

 through which they were able to enter, and he was " obliged to 

 chase them all the day long, as when pursuing them on one side 

 they would fly to the other," and feed until he reappeared. 4 



Samuels tells us that Trouvelot was obliged to shoot many 

 birds, especially robins; that he never found any fruit in the 



* Lintner, J. A.: Sixteenth Annual Report, New Jersey State Board of Agriculture, 1888-89, 

 p. 295. 



1 Trouvelot, Leopold: The American Silk Worm, American Naturalist, Vol. 1, 1867, pp. 85, 

 89, 145. 



Samuels, E. A.: Birds of New England, 1870. p. 156. 



Trouvelot, Leopold: American Naturalist, Vol. 1, 1867, pp. 89 and 145. 



