NOTE ON THE DISAPPEARANCE OF DEAD GRASSHOPPERS FROM SITES OF APPLICATION OF CONTROL MEASURES

Extract

For some years it has been evident to workers conducting research on grasshopper control methods that those dead grasshoppers which can be found at the scene of application of a control measure do not necessarily represent all the grasshoppers which have succumbed to the treatment. Often, dismembered remains are considerably in evidence and usually only the more resistant parts, such as head capsules, remain to be found. It is reasonable to suppose that many of the dead bodies of grasshoppers may disappear entirely, before sufficient time has elapsed for the final observations on the treatment. It is important, therefore, in relation to the appraisal of the efficiency of control measures in the field, such as baiting, to know to what extent this is true. It is particularly important in the study of baits because, where arsenites are used, at least three days may be required for the poison to take full effect after ingestion and before the appraisal can be made. Meanwhile, a considerable period of time has elapsed during which grasshoppers that died 1 or 2 days after feeding could be removed. Under these circumstances it would obviously be erroneous in appraising the results, to take into consideration only the counts or estimates of numbers of dead on the ground, particularly if compared with the estimated population prior to baiting.