124 REPORT 4, UNITED STATES ENTOMOLOGICAL COMMISSION. 
Where band -picking is followed, the pupae should not be crushed at 
once, but placed in a barrel covered with a wire screen to admit of the 
escape of the parasites, and at the same time to retain the moths and 
cause them to perish. 
Immunity of Cotton under Trees. — The immunity of cotton 
growing under single trees that are left standing in the field has long 
been noticed and attributed to the protection and attraction afforded 
to birds by such trees. We had adopted this view in the first edition 
of this work, bat the great regularity with which this phenomenon 
occurs throughout the cotton belt, and several other circumstances 
connected with it and presently to be mentioned, induced us to have the 
subject re-examined. There is no doubt in our mind that this exemp- 
tion of cotton is due to the direct influence of the tree on the plants 
growing under it, and not to the birds and other enemies of the worm. 
Mr. J. P. Stelle, during his stay in Texas, conducted an experiment 
which throws some light on the subject, and which he records in his 
diary as follows : 
August 30, 1881. It is thought by all planters that shade protects cotton from the 
work of the Cotton Worm, and it grows out of the fact that plants growing under trees 
are more or less exempt. I have attributed the exemption to the work of birds ; but 
the planters declare it to be shade. To settle the question I have to-day erected a 
temporary shed over a number of plants by stretching an old tarpaulin above them, 
on stakes in the center of a field. 
September 3. My temporary shade has proveu a protection to the plants ; the worms 
are not working under it to amount to much, though all around they have completely 
stripped the cotton. 
Other observations show that cotton growing under a dense tree is 
not only exempt from injury, but even not touched by the starving and 
migrating worms. This fact alone indicates that the presence of 
birds cannot be the true explanation. It has been further observed 
that a small tree, or a dead one, even if it has many branches, has but 
little protective influence, or none at all, on the plants growing under 
it. That this influence cannot be entirely due to the shade alone ap- 
pears more than probable, since it is exerted on all sides of the tree. 
Whatever the real cause may be that prevents the work of the worm 
under such circumstances, it likewise affects the cotton injuriously, for 
on poor soil such cotton remains very poor and small, while on rich soil 
it grows rank, and consequently bears very few bolls or none at all. 
There is no way of making any practical use of this influence of trees 
on the work of the worm. 
Preventing Oviposition of the Moth. — As a possible means of 
prevention, the idea suggested itself to apply some substance to the 
plants which, by its odor or otherwise, would drive off the moths, and 
thus prevent oviposition. This idea opens, of course, a large field ftfiac 
experimentation; but we confess that, for several reasons, we do not 
hope for important results in this direction. The few experiments that 
have been made are far from being encouraging, and are simply re- 
