PRESIDENT'S ADDRESS. Ixxxix. 



filled with their accounts of them. The earliest record of their 

 ravages as one of the plagues of Egypt shows how much they 

 were dreaded at that remote time, and also brings forward one 

 or two points in their habits which still specially characterise 

 them. One is that they often travel for very considerable 

 distances before settling down anywhere, and, therefore, come 

 suddenly without notice. Another is that they are much under 

 the influence of the wind, and are liable to be carried along by 

 it and perish in the sea, if it should take them in that direction, 

 much as the swarms of Aphides seen on the Poole coast. 



Pliny and other ancient authors speak of the swarms of 

 locusts, and the records increase immensely in number as we 

 approach our own times. Their habits have been most carefully 

 investigated in Algeria and North America. As we shall see a 

 little later on with regard to the Lepidoptera, some locusts have 

 the remarkable habit of migrating, not only in the perfect state, 

 when they are furnished with wings, but their larvae, which 

 resemble the imagines except in being destitute of these organs 

 (just like our ordinary grasshoppers), undertake most extensive 

 migrations upon their own account. These have been watched 

 in Algeria, and it is found that with regard to the species 

 Schistocerca peregrina the larvas continue the migratory movement 

 started by their parents, which generally come in vast swarms 

 from the south, flying by day, and laying their eggs in a suitable 

 locality. The larvae move onwards slowly at first, devouring as 

 they go, and when about 35 days old, and nearly ready to assume 

 the perfect state, cover as much as three miles in the course of a 

 day, and may travel altogether 25 miles or more from the place 

 where they were hatched. After they have acquired their wings 

 they continue to eat with still greater voracity, and after a time, 

 when food becomes scarce, start on a fresh migration which 

 generally takes place southwards. 



From other accounts it would seem that locusts are not 

 usually so regular in their habits, but are much more uncertain 



