affecting the Tiirnip-Croj).?. 
113 
There seem to be very few, if any. Intervals of the year, when 
some of these surface-grubs are not at work ; they consequently 
become very formidable enemies to the turnip-crops where they 
abound : in the summer it is evident that they destroy the young 
plants by separating the crown from the root, and in the autumn 
and in mild winters they eat large cavities in the bulbs, which, 
besides making them less wholesome food for stock, reduce their 
weight, and render them more subject to decay, from the alternate 
effects of wet and frost : those caterpillars, likewise, which live 
through the winter and come out to feed in the spring, are ready 
to attack any young crop that may be conveniently reached by them. 
I shall now lay before the agriculturist the various methods 
that have been suggested for the destruction of these caterpillars, 
for whilst in the egg state, which appears to be seldom earlier 
than midsummer, the fields are producing their crops ; it is there- 
fore at least inconvenient to attempt, if not impracticable, to do 
any good, except perhaps on fallows, by ploughing, harrowing, 
and working the soil, which must be one of the most effectual 
means of rendering the attacks of most, if not of all, insects 
abortive, at least after the first assault, for nowhere do they in- 
crease and luxuriate more than on neglected and slovenly cul- 
tivated lands. Like many other wild animals they will multiply 
greatly in a favourite spot if unmolested ; but when harassed and 
disturbed, they will depart for a more eligible locality. Neatness 
therefore, and constant attention to the crops, are as essential 
in the field as in the garden, and they will be attended with the 
same beneficial results as care and cleanliness ensure in the fold 
and stable when bestowed upon our stock and teams. There is 
likewise little doubt, from the astonishing sagacity which insects 
exhibit, that the females would only lay their eggs in fields 
where there was a fair prospect of the young caterpillars finding 
at once the food necessary for their sustenance ; for so perfect is 
their instinct, that a butterfly will traverse a wood in every direc- 
tion to find a leaf of the tree on which alone her caterpillars will 
feed. This is very astonishing, for what impulse can lead the 
butterfly, which for her own nourishment only extracts nectar 
from flowers, to a certain kind of tree, there to deposit her eggs 
upon the most sheltered part of the foliage?* It is undoubtedly 
* I was in an extensive wood last April where I saw only one tree of the 
Alder-Buckthorn, Rhamnus Frangula ; hovering about it I observed a 
female Brimstone Butterfly, Gonepteryx Rhamni, the larva of which feeds 
only upon that and the common Buckthorn : she seemed to have some diffi- 
culty in selecting a proper leaf, but, having done so, she bent her body and 
deposited an egg on the underside ; and although I went within a few 
inches of her to witness the operation, nothing could divert her from her 
purpose, but immediately after she flew away. 
VOL. IV. I 
