LOCUST PLAGUE—UVAROV 337 
been a single sustained flight. As will be seen later, the extent of 
migrations becomes even greater when the swarms of several succes- 
sive generations are considered. 
METHODS OF LOCUST CONTROL 
It would be impossible even to enumerate here the many methods 
used, or recommended, for locust destruction. It is of interest, how- 
ever, to point out that some of them are centuries old and are still 
in use. The destruction of eggs by digging was practiced in ancient 
China and is still widely recommended, though it is effective only in 
some special cases. Beating of hoppers by branches and driving 
them into trenches were the methods enforced by the Romans in 
North Africa, according to Pliny, and are still practiced in spite of 
being of little value and involving the use of forced labor in astro- 
nomical quantities. 
In more recent times, endless new methods have been proposed and 
tried against locusts, such as the use of flame throwers, poison gases, 
bacterial diseases, steam rollers, balloon barrages, smoke screens, and 
even artillery. Lately, the method of poison baits has come into 
almost universal use. Bran, moistened with sodium arsenite solution, 
is scattered thinly on the ground and proves to be more attractive to 
locusts than green food. When the low dosage of poison, sufficient to 
kill locusts but not grazing animals, is strictly adhered to, there is 
no danger from baits, but it would obviously be an advantage to 
eliminate all risks. This may eventually be achieved by investiga- 
tions, now in progress, with dusts which would kill locusts by contact 
and which could be sprayed from aircraft. 
However, even some of the relatively primitive methods may be 
of use for destroying locusts. Indeed, it is definitely not the lack of 
the proper technique which hampers the solution of the problem. 
ANTI-LOCUST POLICY OF THE PAST 
The main stumbling block in the way of a solution of the locust 
problem is the fact that locust depredations do not recur annually 
but in cycles of several years, separated by clear intervals. When a 
country is invaded, no effort is spared to organize defense, which is 
rarely effective, since the organization usually lags behind the inva- 
sion. As soon as the immediate danger is over, the anxiety gives 
way to wholly unjustified hopes that perhaps the invasion will not 
recur, or at least not in our time, and nothing is done until the next 
catastrophe, which again occurs unexpectedly. It is this unfounded 
optimism that should be considered as the first cause of the continual 
recurrence of locust plagues over the centuries. 
