38 OUR SHACE TREES AND THEIR INSECT DEFOLIATORS. 
selecting Shade trees for the city. Each street has, in many cases, but 
one kind of shade tree; rows of them extend for miles, and the trees 
are planted so close together that their branches al mostinterlace. Thus 
there is no obstacle at all for the rapid increase and distribution of the 
caterpillars. I different kinds of trees had been planted, so as to alter- 
nate, Less trouble might be experienced. Plate I shows a view of Four- 
teenth street, taken in late September, which illustrates this point; the 
poplars on the west side being completely defoliated as far as the eye 
ean reach, while the maples on the east are almost untouched. 
“As long as the ca terpillars were young, and still small, the different 
communities remained under cover of their webs, and only offended the 
eye. But as soon as they reached maturity , and commenced to scat- 
ter— prompted by the desire to find suitable places to spin their cocoons 
and transform to pupse—matters became more unpleasant, and com- 
plaints were heard from all those who had to pass such infested trees. 
In many localities no one could walk without stepping upon caterpil- 
lars; they dropped upon every one and everything; they entered flower 
and vegetable gardens, porches and verandas, and the house itself, and 
became, in fact, a general nuisance. 
‘The chief damage done to vegetation was confined to the city itself, 
although the caterpillars extended some distance into the surroundin ¢ 
country. There, however, they were more local, and almost entirely 
confined to certain trees, and mainly so to the White Poplar and the 
Cottonwood. Along the Baltimore and Pot omac Railroad tracks these 
trees were defoliated as far as five miles from the Capitol. In George- 
town the caterpillars were equally noxious, but in the adjoining forests 
but very few webs could be seen. 
“The proportionate injury to any given species of tree is to some ex- 
tent a matter of chance, 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 caterpillars 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 
result 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 larve 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, &c., the leaves of which they freely devour if 
