LOCUSTS AND GRASSHOPPERS (ACRIDIID.E). in 



them away, and lie rotting in one huge mass for days. 

 Fish die from the poisonous effects, and float on the 

 surface, adding to the already existing mortality, and 

 so powerful the effluvia produced, no one dare venture 

 near to gaze on the scene of desolation. 



Locust swarms do not visit the places that are subject 

 to their visitations every year, but, as a rule, only after 

 intervals of a considerable number of years. It has 

 been satisfactorily ascertained that both in Algeria and 

 North America, the noted locust years occur usually 

 only at considerable intervals. There is, however, no 

 certainty in the migrations, no law of periodicity 

 governing destructive flights, these only occurring at 

 irregular intervals. Nevertheless, it may be pointed 

 out, the history of the most noted locust years, both 

 in North America and in Europe, shows a tendency 

 to their recurrence about every eleven years. From 

 the respective areas of their most abundant develop- 

 ment, the European and Asiatic, the African, and the 

 American species swarm in exceptional years, to ravage 

 adjacent regions in which they are not found per- 

 manently. 



These interims between migrations seem at first 

 unexplainable, for it would be supposed that as locusts 

 are capable of excessive increase, when once they were 

 established in any spot in large numbers, there would be 

 a constant development of superfluous individuals which 



