BITING AND NOXIOUS INSECTS OTHER THAN MOSQUITOES 47 



a sheltered place where it can be sieved, and thus separate the eggs and egg masses from the 

 dirt. This method is probably too elaborate for most districts, but might be tried in some. 



The collected eggs are to be destroyed by burying in deep pits, taking care to have 

 the earth packed hard on the surface. 



(c) Destnictioii of the Younq or Unfledged Locusts. This may be done by : 



1. Burning. 4. Catching. 



2. Crushing. 5. Use of destructive agents. 



3. Trapping. 



1. Burning is useful in a grass country. Where there is no cover for roosting, grass 

 bundles may be laiil down into which the locusts will gather at night. These can then 

 be burned. 



A simple burning method is to have a stout wire, say 40 feet long, enveloped in rags 

 which are soaked in oil. A slender wire is then wound round to fix the rags in position. 

 These are set alight, and two men drag this contrivance to and fro until the fuel is exhausted. 

 It is not necessary to pass over the same ground more than once or twice, so that a large 

 field of grain can be thus protected during the half-hour or so that the rags burn. 



2. Crnshinff. This is only of use where the ground is smooth and hard. Short of 

 crushing, beating with palm or other branches is useful, as the smallest injury to a locust 

 will prevent its obtaining maturity. 



3. Trappiiiij. Various kinds of traps have been devised. Simple ditches and trenches 

 are useful, 2 feet wide by 2 deep and with perpendicular sides. They have to be carefully 

 dug to be effectual. 



As regards traps, reference must be made to the Sudan Instructions of 1901. The same 

 applies to : — 



4. Cdtrhiiuj. Screens and bags are described in the Instructions. 



5. Use of destructive iiijeiits. Coal oil is very deadly to young locusts. It may he 

 employed in conjunction with irrigating ditches. The following useful notes are quoted as 

 being possibly applicable to some districts in the Sudan. 



" The method consists essentially in pouring, or better, dropping coal tar or coal oil on 

 the running water with which the irrigating ditches are supplied. It is only necessary to 

 sprinkle a few drops of coal tar on the stream, when the oils contained in the tar are diffused 

 over the surface of the water, and coming in contact with the insects, cause their speedy 

 death. The toxic power of coal oil upon the insects is very remarkable ; a single drop of it 

 floating on the water is capable of causing the death of a large number of insects. A simple 

 and ingenious mode of keeping up a constant supply of the tar to a ditch is as follows : — • 



"A three-quart can is perforated on the side close to the bottom, a chip loosely fitting the 

 aperture is inserted therein, and the can is then immersed in the ditch. Three-quarts or 

 less of tar, trickling out drop by drop from this slight vent, are sufficient to keep a great 

 length of ditch supplied \vith coal oil for 36 hours. The precise extent of ditch which may 

 thus be rendered toxic to the locusts cannot, of course, be exactly stated. It is in fact quite 

 indefinite, for the reason that the quantity of oil necessary to kill one of the insects is almost 

 infinitesimal, and for the further reason that a single drop of oil will cover quite a large 

 surface when dropped on water, so that taking these two facts together, it is easy to see that 

 a very small quantity of tar or oil will serve to guard, by means of ditches, a large tract of 

 territory from the ravages of the young (unwinged) locusts." Creosote oil prepared with 



