16 LETTERS ON ENTOMOLOGY. 
as they extended their flight, fell before them. 
They first appeared in Long Island, from whence 
they proceeded inland at the rate of fifteen or 
twenty miles annually. Nothing intercepts their 
career; they were seen to cross the Delaware 
like a cloud ; and their numbers were so great, 
that in the wheat harvest, five hundred were 
counted in a single glass tumbler, exposed to 
them a few minutes with some beer in it. When 
laid up in the barn or granary, the grain is often 
attacked by the Weevil, in its perfect as well as 
grub state; and this pest increases incredibly, 
for a single one will produce in one year 6000 
descendants. 
Another very destructive species to plants in 
general (and which, indeed, comes next to the 
locusts), are the aphides, or plant-lice, which 
multiply so prodigiously as to cause great injury. 
In five generations one aphis may produce 
5,904,900,000 descendants, and Reaumur sup- 
poses that in one year there may be twenty ge- 
nerations. Pease and beans are greatly injured by 
them, and in the year 1810, the produce was not 
much more than the seed sown : however, by 
being sown earlier, the pease have some chance 
of escaping. 
How dull would our beautiful meadows look 
