?22 OHIO EXPERIMENT STATION: BULLETIN 332 



outbreaks, that the planting of English and Camperdown elms be 

 discontinued because of their high susceptibility to attack. 



CANKERWOEMS 



(Alsophila pometaria Harris ) 



(Ptdeacrita vernata Peck) 



Two distinct species of cankerworm exist in Ohio, commonly 

 known as the fall and the spring species. They are similar in both 

 appearance and habits, and since control methods are practically 

 identical the two insects will be considered together. For a good 

 description of the technical differences of the two species the reader 

 is referred to the "Manual of Fruit Insects" by Slingerland and 

 Crosby (10). 



Description. — Cankerworm larvae are slender, looping cater- 

 pillars, belonging to that group commonly called measuring worms. 

 When full grown they measure about an inch in length and are very 

 slender. (See Plate XXVII, Fig. 4.) They vary in color from a 

 light variable brown to almost black, though most of them bear some 

 form of striping which runs lengthwise of the body, more frequently 

 the stripes being narrow, faint yellow on a dark background than 

 any other form and color. The male moths have a wing expanse 

 slightly over an inch, the hind wings being light gray and the fore 

 wings somewhat darker in color. (See Plate XXVII, Fig. 1.) The 

 female moths are wingless, medium gray in color, and about one- 

 half of an inch long. (See Plate XXVII, Fig. 2.) The fall species 

 has in most cases a dark broad line extending lengthwise of the 

 back. 



The pupae of both species are found slightly beneath the sur- 

 face of the ground, that of the fall species being inclosed in a thin, 

 tough, silken cocoon, while the spring species has little more than 

 its earthen cell for protection. 



The eggs of the spring species are oval, iridescent-metallic and 

 are not deposited in regular formation, while those of the fall species 

 are dark grayish-brown, resembling in shape tiny flower pots and 

 bearing a dot and ring on the top. They are deposited in regular 

 formation, sitting on the small end and most frequently are found 

 as bands surrounding the smaller twigs. They average in the 

 neighborhood of 200 in a band, though bands of twice this number 

 have been observed. (See Plate XXVII, Fig. 3.) Sometimes they 

 are deposited in patches on the trunk and larger limbs of the tree. 



Life history. — The eggs hatch in the spring with the develop- 

 ment of the foliage and at once the tiny caterpillars begin feeding. 

 From the very outset, tiie insects possess the power of spinning 



