21 
tremendous and unexampled work being done by the United States 
Department of Agriculture and the state of Massachusetts in bring- 
ing from Europe the native parasites of these insects. This work 
is making successful progress, and it is all the more hopeful because 
the parasites of both these species seem to keep them substantially 
in check in the Old World, where they rarely become seriously 
destructive. 
The Forest Tent Caterpillar 
{Malacosonia disstria Hbn.) 
There occasionally appears in the forest region of southern 
Illinois an overwhelming eruption of caterpillars which denude 
large areas of woodlands, especially the oaks and the maples, and 
the black and sweet gum trees, and thence invade orchards, parks, 
and town premises, carrying the same destruction to fruit and shade 
trees generally. This is one of the species which moves in masses 
such as actually to delay the passage of railroad trains, piling up 
Fig. 18. Baltimore Oriole attacking nest of Forest Tent Cater- 
pillar, Malaconoma disstria. (New Hampshire Experiment Station.) 
