REVISION MALACOSOMA HUBNER IN NORTH AMERICA 89 



EGG MASS.— Typically it is laid as a helical ring (figs. 108 and 113) 

 which completely encircles a small twig. The eggs are covered with 

 dark brown spumaline containing many bubbles of various sizes. 

 M. tigris and M. constridum are the only other North American species 

 which lay their egg masses as a helical ring completely encircling the 

 twig. No spumaline covers the egg masses of tigris (fig. 106), and the 

 Qgg mass of constrictum is covered with a light yellow spumaline con- 

 taining approximately one large bubble per egg (fig. 107). 



TENTS. — M. disstria is the only North American species which does 

 not build some kind of a tent. Small larvae cluster together on leaves 

 or twigs, and larger larvae cluster on branches or trunks of trees when 

 not feeding (fig. 332). Before molting they spin a rather inconspicuous 

 matting of silk on a branch or trunk which they use for attachment 

 when molting. The skins left attached to the molting site often have 

 been interpreted by casual observers as dead caterpillars. 



COCOONS. — ^The cocoons are suffused with a lemon-yellow powder 

 similar to that of some other species, but the cocoon-building habits 

 of disstria differ in some respects from those of the other species. The 

 cocoon itself (fig. 309) has a more conspicuous outer envelope of silk 

 than do the cocoons of most other species, but the most striking dif- 

 ference lies in the normal habit of disstria larvae to spin their cocoons 

 in one or more leaves which have been webbed together with the outer 

 envelope of silk. At times of high populations the only leaves remaining 

 on the trees may be those which have been used in spinning cocoons 

 (fig. 331). Other species usually select cocooning sites in the litter or 

 in more protected situations. 



FOOD PLANTS. — M. disstria has the widest host range of any North 

 American species, and will oviposit on a large number of different 

 species of deciduous trees. It will feed on even more, possibly helping 

 to account for its being the most widely distributed species in North 

 America. In the North and West its preferred host is aspen, Populus 

 tremuloides; in the South it has heavily defoliated tupelo gum, Nyssa 

 aquatica, blackgum, Nyssa sylvatica, sweetgum, Liquidambar styraciflua, 

 various species of oaks, and many other deciduous trees. In short, it 

 oviposits and feeds on practically all species of deciduous trees, and 

 has been reported to cause serious defoliation in most parts of its range. 

 During outbreaks larvae will defoliate the underbrush after stripping 

 their normal hosts, and even will eat herbs when no other food is 

 available. 



One species which disstria avoids is red maple, Acer rubrum, which 

 will remain completely untouched in an area that has been completely 

 stripped of all other leaves. The red maple, however, does not escape 

 entirely, since the caterpillars use its leaves to wrap their cocoons. 



