108 PROMINENTS. 
or lower branches during the moulting period, when the 
whole colony can be destroyed by crushing or burning. 
There are a number of other species of the genus Datana 
which occasionally cause injury to our fruit-trees. Last 
summer (1898) two species were found in large numbers 
and were quite destructive to plums; the caterpillars had a 
somewhat different color but none could be reared to their 
winged form. All species of this genus have but one 
annual brood. 
THE WALNUT CATERPILLAR. 
(Datana angusii G. & R.). 
This species closely resembles the ministra, but is a dis- 
tinct kind, which is sometimes so destructive to our walnut 
and hickory trees, in thelatter part of summer that they be- 
come denuded of all their leaves. The caterpillars are dark 
with light stripes along the sides. They assume the same 
peculiar position whenat rest asthe other species of Datana. 
Two other species of Datana are found feeding upon the 
foliage of the apple, walnut, hickory and oak, i. e. Datana 
integerrima G. & R., and Datana contracta Walk. 
The caterpillars of all the species of this genus have the 
habit of descending to the trunk of the tree to within a few 
feet of the ground, when about to moult, and to congregate 
here in a large mass. Large numbers of their cast-off skins 
are often very conspicuous after such moults and after the 
worms have disappeared long ago. It is, of course, very 
easy to capture at such times the whole colony and to de- 
stroy it. The application of arsenical preparations is of 
little use, unless the whole tree can be sprayed. But in 
nurseries, where the trees are still small and close together, 
it is in some cases advisable to apply such insecticides that 
do not alone kill the species of Datana but also the numer- 
ous other worms that eat their leaves. 
Prof. Beutenmueller gives the following description of the 
species: 
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