250 FIFTH REPORT OF THE ENTOMOLOGICAL COMMISSION. 



3-4. Ficus carica h. (Fig.) 



4. Mhiis cotinus li. (Smoke Tree.) 



4. Pinus spec. (Pine.) 



4. TaxMS spec. (Yew.) 



4. Nyssa multifloraWa.n^. (Sour Gum.) 



4. Liriodendron tulipifera L. (Tulip 



Tree.) 

 4. Magnolia spec. (Magnolia.) 

 4. Chionanthiis virginicus L. (Fringe 



Tree.) 



4. Fag us ferruginea Ait. (Beech.) 4. Ligustriim vulgare h. (Privet.) 



4. JEsculus flava, Ait. (Sweet Buck- 

 eye. ) 

 4. j^sculus glabra Willd. (Ohio Buck- 

 eye.) 

 4. Morus ruira Li. (Red Mulberry.) 

 4. Zanthoxylum americanum M. (Prickly 



Ash.) 

 4. Acer dasycarpum Ehrh. (White or 



Silver Maple.) 

 4. Acer rubrum Wang. (Red Maple.) 



4. Kalmiaspec. (Laurel.) 



4. Rhododendron spec. (Rhododendron.) 



4. Eicinus communis L. (Castor-oil 

 Plant.) 



4. Liquidambar styraciflua L. (Sweet 

 Gum.) 



4. Gleditschia triacanthos L. (Honey 

 Locust.) 



4. Gymnocladus canadensis, Lamb. (Ken- 

 tucky Coffee Tree.) 



4. Bobina pseudacacia h. (Locust.) 



Trees in the vicinity of the white poplar and cottonwood suffered most. Even 

 trees usually not injured, as, for instance, the sugar maple, are often badly defoliated 

 when in such contiguity. 



This list contains a number of plants not usually injured by these caterpillars. In 

 some cases the injury was due to the fact that twigs containing the web, with its 

 occupants, had been pruned from the tree and thrown near plants, instead of being 

 at once burned or otherwise destroyed. 



In other cases the injury is due to the peculiar position of the plant injured, i. e., 

 under a tree infested by the caterpillars. These when fully grown commence to scat- 

 ter, and dropping upon the plants underneath the tree so defoliate it without act- 

 ually making their home upon it. The great unmber thus droppiugfrom a large tree 

 will soon defoliate any smaller plant, even if each caterpillar takes but a mouthful 

 by way of trial. Thus holly, a plant not usually eaten by these insects, soon be- 

 comes denuded. Other plants unpalatable or even obnoxious to the caterpillars are 

 sometimes destroyed by the multitudes in their search for more suitable food. 



Hungry caterpillars leaving a denuded tree in search or food wander in a straight 

 line to the next tree, sometimes a distance of 25 feet, showing that they possess some 

 keen sense to guide them. If such a tree offers unsuitable food, they still explore it 

 for a long time before deserting it. In this manner two columns of wandering cater- 

 pillars are formed, which frequently move in opposite directions. 



Peculiar effect of defoliation upon some plants. — During the early part of October 

 many trees, mainly apple and pear, which had been entirely denuded of their foli- 

 age by the caterpillars, showed renewed activity of growth. Some had a few 

 scattered flowers upon them, others had one or two branches clothed with flowers, 

 while in some few cases the whole tree appeared white. It looked as if the trees were 

 covered with snow, since they lacked the green foliage usually seen with the blossoms 

 in spring. Some few flowers were also observed upon badly defoliated cherry-trees. 

 Even as late as the middle of November, owing perhaps also to the pleasantly warm 

 weather, some few flowers could be observed upon some imported plants belonging 

 to the genus Spircea and upon the Chinese red-apple. All these plants usually blossom 

 early in spring. The caterpillars having entirely defoliated the trees produced thus 

 an artificial period of rest, or winter, which was followed by unseasonable budding 

 and flowering. Such a result often follows summer denudation by any insect, and 

 we have referred to some remarkable cases in our previous writings.* 



Enemies of the Web- Worm other than insects. — The caterpillars have compara- 

 tively few enemies belonging to the vertebrate animals. This is not owing to any 

 offensive odor or to any other means of defense, but is entirely due to their hairiness. 



* See Eighth Report on the Insects of Missouri, p. 121. 



