Published online by Cambridge University Press: 10 July 2009
A method of marking adult locusts, particularly useful when numbers are low and hand marking would be difficult, is described. It involves the use of a small hand spray gun from which a jet of paint can be directed at the locusts in spurts at ranges up to about 15 ft. The paints tested consisted of suspensions of pigments in light oil.
The paints are of low toxicity and the marks remain visible for many weeks. By the use of this method far more locusts can be marked in a given time than could be marked by hand. The efficiency of the method is reduced by high winds and dense vegetation, and it is more costly than hand marking. Most of the marked locusts cannot be recognised as such without being captured.
Some results obtained with this method in the French Sudan are given. In two months more than 50,000 locusts, Locusta migratoria migratorioides (R. & F.), were marked with a red paint; four were recovered 60 kilometres or more from the area in which they were marked, and the paint was clearly visible after five weeks.
Ways of improving the technique, and other possible methods of marking, are discussed.