THE CAKKERWORMS 5 



it has been used to a limited extent for other species belonging to 

 the same group. In recent years the two common species have been 

 known respectively as the fall cankerworm (Alsophila pometaria) 

 and the spring cankerworm (Paleacrita vernata) , referring to their 

 respective seasons of usual emergence. 



DIFFERENCES BETWEEN THE SPECIES. 



Table 1 gives briefly the most conspicuous differences by which 

 the two species may be distinguished in all stages. 



Table 1. — Distinguishing characteristics of the fall and spring canlcerworms. 



Stage. 



Fall cankerworm. 



Spring cankerworm. 



Egg 



Brownish gray, in the form of a 



Dull pearl, oval in shape, laid in 





flowerpot, laid in a compact, 



loose clusters in protected 





single-layered mass in exposed 



places, almost exclusively in 





locations, chiefly in the fall. 



the spring. 



Larva 



A pair of rudimentary prolegs on 



No prolegs on the 5th abdominal 





the 5th abdominal segment. 



segment. 



Pupa 



Enclosed in a tough cocoon, with 

 particles of earth woven in 

 with the silk. 



No cocoon formed. 



Adult 



Abdomen without spines 



Abdominal segments bearing 

 double transverse rows of red- 







dish spines. 



FOOD PLANTS. 



Both species of cankerworm seem to have a preference for apple 

 and elm, but also feed on a wide range of food plants, including 

 many of the common deciduous fruit and forest trees, particularly 

 those included among the Rosaceae. The following list has been 

 brought together from a number of sources ; there has been no oppor- 

 tunity for verification of many of the records, but they are probably 

 accurate for the most part. 



Both species have been recorded as feeding on the following hosts : 



Acer spp Maple. 



Acer negundo L Boxelder. 



Acer saccharinum L Silver maple. 



Betula spp Birch. 



Carya spp Hickory. 



Castanea dentata (Marsh.) Borkh American chestnut. 



Celtis occidentalis L Hackberry. 



Crataegus spp Haw. 



Cydonia oblonga Mill Quince. 



Fraxinus sp Ash. 



Juglans nigra L Black walnut. 



Prunus armeniaca L Apricot. 



Amygdalus persica L Peach. 



Prunus domestica galatensis Hort Prune. 



Pyrus communis L Pear. 



Malus sylvestris Mill Apple. 



Quercus spp Oak. 



Salix spp Willow. 



Tilia americana L American linden. 



Ulmus americana L American elm. 



