BUTTERFLIES AT SEA. 



Some insects have the power of boring into de- 

 caying trees, which they do to a great length with 

 considerable skill and perseverance.* Others pe- 

 netrate into the earth, or drop their eggs in the 

 water, while many live in communities, defending 

 themselves and their young with so much courage, 

 that even the largest animals have been obliged to 

 yield to their united assaults. 



It is evident, that the great multiplicity of in- 

 sects would be attended with injury, if various 

 causes did not serve to dimmish their numbers, 

 when there was an undue proportion of them. 

 Birds devour them, and so do the larger tribe of 

 insects, such as spiders, wasps, &c. Another 

 cause of preventing a superabundant proportion 

 of them, and of keeping down the numbers of 

 certain insects, is the migratory principle which 

 pervades certain species, during the progress of 

 which vast numbers are destroyed. For instance, 

 when the Beagle was off the shores of Northern 

 Patagonia, and about ten miles from the Bay of 

 San Bias, Mr. Darwin tells us, that vast numbers 

 of butterflies, in bands or flocks of countless my- 

 riads, extended as far as the eye could range. 



* Much has been said and written on the subject of the injury 

 done to the elm trees in Hyde Park by a particular grub. I am, 

 however convinced, that if the injured trees had been properly 

 examined, either positive or incipient decay would have been 

 found to have existed in them before the grubs attacked them. 

 N2 



