15 
pillar changes its skin every six or seven clays ; but unless 
it has previously fixed itself firmly to the edge of a leaf 
or some substance by means of its sucker-feet, it cannot 
free itself from the old tight-fitting coat, and it perishes 
within. This is one reason why, in bad attacks of this 
pest, sometimes known as ‘^Niggers” or ‘‘Black 
Palmers,” any method of brushing the Turnip leaves 
has been found serviceable. Pine boughs fixed in front 
of a scuffler, heating the plants with a light bough held 
in the hand, or the use of a rope dragged by any means 
which will keep it a little above the ground, are all 
useful in this way, besides the obvious benefit to us of the 
numbers that are crushed, bruised, and otherwise pre¬ 
vented from getting back to their food-plant. The 
principle of shaking or beating injurious larvae from 
bushes and fruit-trees might very desirably be carried 
out much further than it is at present in this country. 
Many kinds of caterpillars will fall at once on a smart 
shake, “jarring,” as it is termed in American cultiva¬ 
tion, and, as almost all larvae have only a special range 
of food plants, if they are prevented crawling back by 
throwing anything they cannot cross round the stems, 
all that are not on the point of turning to 'puixe must 
perish. A few of our injurious insects are general 
feeders, but the greater pairt of them are limited in their 
diet, or especially frequent certain orders of plants; and 
this point is an important one for consideration, not only 
regarding rotation of crops, by which the maggots (or 
insects in any stage) which may have remained in the 
ground after any one kind of crop may be fairly starved 
out before it comes round again, but also with regard to 
destruction of weeds allied botanically to the cultivated 
plants. The Turnip Ply feeds also on wild plants of the 
Cabbage order, notably on Charlock, which, therefore, is 
a most undesirable weed; the golden patch, where its 
yellow flowers show it has been left to thrive in careless 
neglect, shows a centre for fly which sometimes infects a 
whole district. The Aphis fjranaria ot our Corn is to be 
found also on several of the common grasses which grow 
