500 
Observations on the various Insects 
" The first operation can be done at the time of weeding or of 
clearing the corn of thistles : the young swelled and yellow plants 
are easily enough known. The second operation ought to be per- 
formed a fortnight or three weeks before harvest-time, when it is 
much more easy to execute, as the stems attacked by the Chlorops 
are very easily distinguished, even at a distance, because of their 
short height, more considerable thickness, and deep green colour 
of the head ; and, lastly, because the ear always remains sheathed 
and enveloped by large leaves. IVIoreover, these plants thus 
altered are almost always found situated at the lower side of the 
beds or furrows, so that in passing between two ridges one can 
easily reach them with the hand, from one side or the other, with- 
out causing any damage to the corn. 
" Another of the most certain means, the most economical, and 
the most advantageous, which can in general be employed to 
destroy the insects injurious to our crops, is to vary the culture by 
alternate courses, so that corn-crops may be succeeded by others 
which are weeded or fed off, and vice versa. It will follow that 
the noxious larvae deposited in the fields, not finding at the period 
of their hatching the novn-ishment which is suited to their organ- 
ization, are not able to subsist, and infallibly perish." * 
He is also disposed to attribute the apparent exhaustion of the 
soil from over-cropping, as much to the presence of, and the ex- 
cessive propagation of, certain injurious insects, as to the land 
being actually tired ; and thus the rotation and changing of culture, 
whenever they are not called for by other powerful reasons, ought 
yet to be adopted and put in practice, to hinder and prevent the 
too great multiplication of certain species of noxious insects. 
Mr. Arthur says, "Perhaps the most efficient preventive would 
be to detect the insect fly when it appears to deposit its eggs, and 
keep it from lighting on the field by the appHcation of some repul- 
sive perfume, such as soot, guano, or sand that has been immersed 
in gas- water, &c., dried and sown over the field." f 
As the larvae of tliese flies have caused considerable alarm on 
many occasions, and have no doubt done extensive miscliief, we 
will take a general review of their economy before we dismiss the 
subject. It is now evident that tliere are many species of these, 
flies to whose larvae wheat, barley, and rye arc equally acceptable, 
and we cannot l)e certain that they are not bred in grasses also ; 
indeed, from the swarms of the Chlorops' lly that are found in 
the meadows, and the myriads that enter dwelling-houses, often 
not surrounded by corn-fields, it seems to be very probable. There 
are also, it will be observed, two broods of the Chlorops annually ; 
* Herpin's Memoir, pp. 11 and 12. 
i- Gardener s Chronicle lor 1844, p. 3G5, 
