182 REPORT 4, UNITED STATES ENTOMOLOGICAL COMMISSION. 
guide us. Plants that are poisonous to man and the higher animals are 
usually harmless to insects ; others may possess insecticide qualities 
only at a certain season or only when they are dried or otherwise pre- 
pared ; in still other plants only one part, e. the flower or the root, 
may prove useful, perhaps only at a certain stage of development, and 
the rest worthless. Hence experiment in this direction must be more 
or less tentative, and practical results will follow only, if at all, the 
most extensive trials. Other difficulties also present themselves. Two 
observers, while experimenting with the same material, with the same 
instruments, and under precisely similar conditions, often report vary- 
ing results ; or the same observer after a favorable result in the first trial 
obtains a quite different result in subsequent trials. In the case of 
the Cotton Worm, with its rapid development, there is, also, great risk 
of drawing false conclusions, the most frequent cause being the appar- 
ent sudden disappearance of the worms, or at least of a large portion 
of them, after the application of the "remedy." The worms may 
have simply changed to chrysalides or may have been carried away by 
enemies. Again, the presence of a number of dead worms upou and 
under the plants is often misleading, as such worms may have been 
killed by their numerous enemies. Finally, very young worms, or such 
as are just in the act of molting, are often killed by the mere force of 
a spray thrown upon them, while others that have fallen to the ground, 
and are more or less covered with soil, exhaust themselves in their 
frantic efforts to get rid of the incumbrance. 
In this connection, also, it must be remembered that experiments 
made indoors are without practical value unless confirmed by repeated 
experiments in the field. 
The plants with which we have experimented are partly such as were 
recommended by correspondents as being efficient for the Cotton Worm 
or other insects j* partly such as from their immunity from insect at- 
tacks might be presumed to possess insecticide properties. Prevalence 
and cheapness being desiderata in any plant that might prove to have 
destructive qualities, many of the weeds that by their abundance, per- 
sistency, and power of adaptation are so obnoxious to agriculture in the 
South were tested. In order to test such plants thoroughly they should 
be used both fresh and dry, and in flower, fruit, leaf, and root. This is 
a work of considerable magnitude which cannot possibly be accomplished 
in one or two seasons, and for the purpose of this investigation Ave 
deemed it advisable, with few exceptions, to first try alcoholic extracts 
and decoctions, mostly made from the fresh plants, leaving for the future 
more complete experiments with such as give promise of success. While 
the results thus far obtained seem discouraging, considering the outlay 
in money and time, and while in no case was the effect upon the worms 
such as would warrant the recommendation of any of these plants for 
* A few of these plants conld not be recognized from the popular name given by the correspondent, 
and could, therefore, not be tested. 
