10 
thus the insect, having no place to deposit its eggs where its young 
could be nourished, has become measurably ‘starved out.” But 
that this opinion is erroneous, is I think evident from one or two 
facts. During this entire period, since notice was first altracted to 
the wheat-fly, there are some farmers who have every year con- 
tinued the cultivation of wheat with very fair success, their crops 
having been in no one of these years so severely injured as to dis- 
hearten them ; and their respective situations are so dissimilar, that 
this immunity can with no plausibility be attributed to any pecu- 
liarity in the locations of their farms. Now if the swarms of these 
insects which for a time pervaded every neighborhood through this 
entire section of country, and which possess a power of wing capa- 
ble of bearing them from twenty to fifty miles in a single season, 
had been in the “ starving” condition supposed, how have the fields 
alluded to escaped destruction? Certainly these myriads of tiny 
creatures could not have been reduced to such straits for want of 
the appropriate repository for their eggs, until after these crops 
had been utterly consumed. And, with the insect not exterminated, 
but still everywhere common, now that the culture of wheat has 
been gradually returned to with such success that it has again be- 
come general, why has not the fly again increased?’ Why have the 
considerable crops of the past and the abundant ones of the present 
year in this (Washington) county, been so little injured ? I am 
firmly persuaded, therefore, that the speedy diminution in the num- 
bers of the wheat-fly, which soon follows a season in which it has 
been extremely annoying, can not be truly assigned to the cause 
above stated ; but that it is rather to be attributed to that beautiful 
provision of nature, long since observed, and additional instances of 
the truth of which are brought to light by the investigations of every 
year, to wit, that an undue increase in any of the species of the 
animal or vegetable world never takes place, without being speedily 
succeeded by a corresponding increase of the natural enemies and 
destroyers of that species, whereby it again becomes reduced to its 
appropriate bounds. 
Whenever once introduced, it is probable the wheat-fly will ever 
after continue in limited numbers, laying the wheat crop annually 
under a moderate contribution for its support. Isolated fields will 
occur where its devastations will be quite serious, whilst the crop 
of the district generally will suffer but little, and many fields none at 
