( ICO ) 
IX. — Observations on the Natural Hbtory and Economy of 
various' Insects ajfecthnj the Turnip-crops, incUiding the Sur- 
face-Caterpillars, the Turnip-gall Weevil, and the Dipterous 
Flies and Rove-Beetles infesting Anbury. By John Cxjrtis, 
F.L.S., Corresponding INIember of tlie Imperial and Royal 
Georgofili Society of Florence, &c. 
Paper V. 
Having fully discussed the various insects wliich destroy the 
foliage, flowers, and seeds of the turnips, I shall now treat of" 
those which principally affect the roots. Some of these may seem 
to do little more than disfigure the bulb, yet it is far froin impro- 
bable that the most harmless of them, by first injuring the rind, 
may thus lead to the decomposition of the bulb, which once begun 
is speedily accelerated by more active agents. Among this por- 
tion of noxious insects are many large caterpillars, called by 
farmers and gardenei's Surface-grubs, that commit very extensive 
depredations upon the turnips, and likewise the Wireworm, which 
is the most troublesome, I believe, of all insects to the agricul- 
turist, and will shortly form the subject of a separate memoir. 
The Surface-grubs or Surface-caterpillars. 
Of these there are several different sorts, some less injurious 
than others, owing perhaps more to the paucity of their numbers 
than to the want of individual power to do mischief. One of our 
greatest philosophers was well aware of this when he said, 
" Insects act upon a smaller scale, but by their united energies 
sometimes produce great effect ; the Ant, by establishing her 
colony, and forming her magazines, often saps the foundations of the 
strongest buildings, and the most insignificant creatures triumph, 
as it were, over the grandest works of man."* It is a fact which 
I particularly wish to impress upon the mind of the agriculturist, 
that any insect feeding upon his crops may prove a great loss to 
him when it multiplies to excess, and this renders it most essen- 
tial that he should be able to detect the first appearance of his 
enemies, and watch their progress ; which he cannot do with 
certainty, unless he will make himself master of their habits, and 
become so well acquainted widi the insects affecting his crojis as 
to be almost able at the first glance to detect them. When this 
is accomplished, he may hope to learn how to deal with the enemy 
opposed to him, and instead of suffering a small number of 
destructive insects to pass unheeded, which, as we have already 
shown, may muhij)ly hy millicms in a few weeks, he may employ 
his best energies to crush immediately the worm in the bud. 
* Sir H, Davy's Last ]3ays of a Philosopher, p. 250. 
