248 FIFTH REPORT OF THE ENTOMOLOGICAL COMMISSION. 
they wen more local, and almost entirely confined to certain trees, and mainly so to 
the white poplar and the cottouwood. Along the Baltimore and Potomac Railroad 
n.uks these trees wet© defoliated as far as 5 miles from the Capitol. In George- 
town the caterpillars were equally noxious, but in the adjoining forests but very few 
•rebe could be Men. 
The proportionate injury to any given species of tree is to some extent a matter of 
Ohanoe, and In some respects a year of great injury, as 1886, is not a good year to 
study the preferences of a species, because when hard pressed for food the cater- 
pillars will feed upon almost any plant, though it is questionable whether they can 
mature and transform on those which they take to only under the influence of such 
absolute necessity. Again, the preference shown for particular trees is more the re- 
sult of the preference of the parent moth than of its progeny in a case of so general a 
feeder as the Fall Web- worm. We had a very good illustration of this in Atlantic 
City last autumn. The caterpillars were exceedingly abundant during autumn along 
this portion of the Atlantic coast, especially on the trees above named. We studied 
particularly their ways upon one tree that was totally defoliated by September 11. 
The bulk of the caterpillars were then just through their last molt, though others 
were of all ages illustrating different hatchings. There was an instinctive migration 
of these larvae of all sizes, and the strength of their food habits once acquired from 
birth upon a particular tree was well illustrated. At first the worms passed over 
various adjacent plants, like honeysuckles, roses, etc., the leaves of which they 
freely devour if hatched upon them, but as the migrating swarm became pressed 
with hunger they finally fell upon these, and even upon plants like the peach, and 
ailanthus, which ordinarily are passed over. They would pounce upon any food, 
and a rotten apple placed in their way was soon literally swarming with them and 
sucked dry. 
In a general way it may be stated that conifers, grapes, and most herbaceous plants 
are free from their attacks, and it is very doubtful whether the species can mature 
upon them. 
The list of plants which follows is arranged according to the relative damage to 
the foliage in the city of Washington. The three first named are most subject to at- 
tack, and, in fact, are almost always defoliated. 
Proportionate injury to different plants and shade trees. — The damage done in the 
city of Washington was exceptional, but so was also the general damage throughout 
the New England States, if not throughout the country. In New England the 
greater predilection which the species showed for poplar, cotton wood, and the ranker 
growing willows was everywhere manifest, and so much was this the case that the 
destruction of the first brood on these trees would have substantially lessened the 
damage to other trees. 
Plants marked 1 have lost from 75 to 100 per cent, of their foliage. 
Plants marked 2 have lost from 50 to 45 per cent, of their foliage. 
Plants marked 3 have lost from 25 to 50 per cent, of their foliage. 
Plants marked 4 have lost from to 25 per cent, of their foliage. 
Plants marked with two figures have shown the relative immunity or injury indi- 
cated by both, the variation being in individual trees. 
1. Xegundo aceroides Mcench. (Box El- 
der.) 
1. Popnius alba L. (European White 
Poplar.) 
1-2. FraxinusamericanaLi. (White Ash.) 
1-2. Fraxinus excelsior L. (European 
Ash.) 
1-2. Sambucus canadensis L. (Elder.) 
1. Populus monilifera Aiton. (Cotton- 1-2. Pyrus species. (Cultivated Pear and 
wood.) Apple.) 
1-2. Populus balsamifera L. (Balsam 
Poplar. ) 
1-2. Populus tremuloides Mich'x. (Amer- 
cau Aspen.) 
1-2. Prunus avium and cerasus L. (Cher- 
ries.) 
1-4. Sjpringa vulgaris L. (Lilac.) 
1-4. Ilex spec. (Holly.) 
