INSECT PESTS OF OHIO SHADE AND FOREST TREES 215 



attack occurs in parks and on city streets. A half-dozen unsightly 

 webs actually are sufficient to ruin the esthetic value of even a 

 very large tree. 



Food plants. The fall webworm is a general feeder. One 

 hundred and twenty food plants have been listed by the U. S. De- 

 partment of Agriculture, according to Doctor Felt (8). In Ohio, wild 

 cherry seems to be the preferred food plant, with willows and vari- 

 ous members of the Rosaceae also frequently attacked. Of the 

 latter, the horticultural varieties of apple are quite susceptible, the 

 insect proving a serious pest during some seasons. Here the fall 

 brood works the greatest harm. 



Distribution. The insect occurs over nearly the entire United 

 States east of Texas and Montana and is reported to be worse in 

 the southern states. In Ohio certainly it is more abundant in the 

 southern counties than in the northern. 



Natural enemies. Natural checks of a diversified nature and 

 in considerable abundance prey upon this species. Among these 

 agencies may be found insectivorous birds, egg parasites, predaceous 

 enemies and internal parasites of the larvae; and in all probability 

 the wilt disease previously referred to in the discussion of the tus- 

 sock moth, plays an important role in the control of the species. 



Contrpl. Except in the event of a widespread outbreak of ex- 

 ceptional severity, the best control measure lies in the destruction 

 of the webs containing the feeding caterpillars. At least three 

 practicable methods are available for this purpose . (1) If the 

 trees are large enough so that the loss of a branch will not seriously 

 mar their shape, pruning away the branch upon which the web 

 occurs controls it with comparative ease. (2) If the trees are small, 

 stripping away the nest and destroying it, without removing the 

 branch is satisfactory. The work is much more pleasant if the 

 hands are protected by a pair of gloves. (3) Burning the nests by 

 means of an oil torch is practiced by some with success, but in the 

 hands of careless workmen there is a possibility of considerable 

 injury to the tree. 



The final control measure, most practicable for use on large 

 trees and in instances of severe, widespread outbreaks, is spraying 

 with poisons, such as arsenate of lead at the usual strength. 



THE BAG, OR BASKET WORM 



(Thyridopteryx ephemeraeformis Haworth) 



Description. One of the most curious and interesting of the 

 shade tree pests is the bag worm. A glance at Plate XXI, Figs. 1 

 and 2, indicates more plainly than words why the creature was given 



