APPLE INSECTS — BUDS ANT) FOLIAGE 11 



The Spring Canker-worm 



Paleacrita vernata Peck 



Canker-worms are among the oklest and most destructive of 

 American orchard j^ests. The term " cancker-worme " appar- 

 ently originated in England in 1530, and was used for several 

 different insects in the first authorized English version of the 

 Bible in 1611. As early as 1661, John Hull quaintly related 

 that " the canker-worm hath for four years devoured most of 

 the apples in Boston, that the apple trees look in June as if it 

 was the 9th month" (meaning November). Several other seri- 

 ous outbreaks of canker-worms were recorded in New England 

 during the next century. Although the scientific name of 

 vernata was applied to these canker-worms in 1795, and another 

 name, pometaria, was proposed for some of the moths in 1841, 

 it was not demonstrated until 1873 that two quite different 

 species of insects had been masquerading as the canker-worm 

 in America for more than 200 years. 



Canker-worms belong to the Geometrid group of moths whose 

 caterpillars are called measuring-worms, span-worms or loopers 

 from their peculiar manner of walking. Although several 

 kinds of these measuring-worms are destructive to fruits, often 

 working in the same orchards, the term canker-worm is restricted 

 to the two distinct species recognized in 1873 and then given 

 the common names of the spring canker-worm and the fall 

 canker-worm. 



Both of these native species often occur together in injurious 

 numbers in the same locality. The apple and elm are favorite 

 food-plants, although several other fruit and shade trees are 

 often attacked. The caterpillars appear on the trees in early 

 spring and work mostly during May, skeletonizing the leaves, 

 which soon turn brown. In June badly infested trees or or- 

 chards often appear from a distance as though a fire had swept 



