184 HALF HOURS WITH IXSECTS. [Pacicaed. 



apple years. Seasons when through favoring causes certain 

 species appear in extraordinar}^ numbers. The causes would 

 not seem to be wholly climatic, for during seasons that may 

 seem to be peculiarly favorable to insect life, every species 

 does not abound in equal numbers. It seems more probable 

 that the increase in a species is owing to a decrease in the 

 numbers of the ichneumons attacking it, though the causes 

 leading to the partial extinction of the ichneumon may be 

 unknown. How full of interest would be a study of such 

 phenomena as the periodical or unusual abundance of certain 

 animals ! No subject could be more attractive to the biolo- 

 gist, while none is of more practical importance to the gar- 

 dener or farmer ; and it is just such studies as these that 

 our young students should take up. 



"In the year 1791," says Fitch, "the orchards and forests 

 of New England were overrun by this worm, and the leaves 

 of the apple, oak and other trees were devoured by it. It 

 was at this time that it received the name ' Palmer worm,' 

 by which it has since been currently designated. This name 

 was evidently derived from our English translation of the 

 sacred scriptures. Another insect, which a month or two 

 before had devastated the fruit trees to an extent never pre- 

 viously known, appears simultaneously to have received the 

 name which it still retains, the canker worm ; for previously 

 to this date we find this name given to what is now called 

 the army worm." (Leucania unipunctata.) "Another re- 

 markable visitation of these insects occurred in the 3'ear 

 1853, unparalleled by any event of this kind within tlie mem- 

 ory of the present generation." It appeared " suddenly in 

 excessive numbers" from Maine to eastern New York. The 

 Palmer worm appears about the middle of June, about the 

 time the canker worm is entering the earth, and continues 

 till the close of the month. It strips off the foliage, thus 

 emulating the gastronomical feats of the canker worm. Dr. 

 Fitch says that should, " after a A'isitation from these worms, 



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