118 



FRUIT INSECTS 



The Western Tent-caterpillar 



Malacosoma fragilis Stretch 



From the Rocky Mountains westward the apple-tree tent- 

 caterpillar is replaced by a number of forms all very much alike 

 in habits and in the form and coloration of the moths. The 

 caterpillars, however, are different. From the Rockies to the 

 Sierras and from Mexico to Canada the dominant form is 



M. fragilis. It forms a 

 web like its eastern rela- 

 tive and has a similar life 

 history. 



In Colorado the larvae 

 become full-grown by July 

 1, and the moths emerge 

 and lay their eggs during 

 the latter part of the 

 month. The full-grown 

 larva is similar to the 



Western tent-caterpillars. . /• u x • i 



eastern lorm but is pale 

 blue or blue-gray on the sides, and the median line has a 

 row of bluish spots instead of the whitish line (Fig. 128). 

 The species is single })rooded. The larvae feed on apple, wil- 

 low, poplar, wild cherrj^, wild rose and wild gooseberry. 



Control. 



The same remedial measures are suggested for this species 

 as for the apple-tree tent-caterpillar. 



Another species, Malacosoma pluvialis Dyar occurs in the 

 Pacific Northwest. Very little is known concerning it except 

 that in habits and life history it does not differ greatly from the 

 other species. 



Reference 

 Ore. Agr. Exp. Sta. Bull. 313. 1894. 



