112 
Ohscrtations on the varioui Inscctx 
rounding: the bulb of a well -grown turnip in the autumn, ten or 
twelve will often be found congregated in fields that are much 
infested. 
5. There is still another kind of these surface-grubs which I 
have frequently received with the others ; but I cannot ascertain 
the species of moth it would change to, never having been able 
to rear one ; indeed, persons living in a city, and constantly engaged 
in literary or scientific pursuits, have neither time nor opportunities 
to carry on these useful and interesting investigations with much 
chance of success ; but those who reside in the country would be 
doing great service, even to science, if they would devote a little 
attention to the breeding of insects injurious to man ; and the better 
to enable them to accomplish this, 1 will give some instructions at 
the end of this paper for the rearing of the surface-grubs. But to 
resume the subject. These caterpillars (fig. 12) are full grown the 
beginning of September, and feed upon the roots of turnips in 
fields : they ate off the crown close to the top, as shown at fig. 8, 
and in the garden they injured the roots of the cabbages, it was 
said, by gnawing all round the stem just below the surface. One 
was found in earthing up celery : this was left upon the ground a 
few seconds, when it disappeared, and on digging it was ascertained 
to have buried itself in that short space of time about a foot deep. 
This surface-grub is very ravenous, for two that were confined in 
a pill-box, where one changed its skin, were eating the soft part 
of the exuvia when I chanced to look at them ; they even appeared 
to be disjiuling for it, and in a short time the whole was entirely 
devoured : I afterwards gave them a cabbage-leaf, which they ate 
very readily. They were of a pale-green colour, somewhat flesh- 
coloured on the back and liglitly freckled, with a double line 
down tlie centre, the space between the lines whitish, a similar 
line extending along each side near the base of the thighs; the 
spiracles are black, and on the back of each segment are four 
black dots, the first pair approaching : the head is horny and 
ochreous, with a black spot on each eye, near the base of the jaws, 
which are rusty, and a black furcate mark on the crown ; there is 
no horny covering to the first thoracic segment, which distin- 
guishes it at once from the foregoing species ; the feet are sixteen, 
as usual in this family : these cater})illars are as thick as a goose- 
quill, and about 2 inches long ; they can walk backward with 
perfect ease, a power which enables them to sally from their 
burrows more readily, and when touched they coil themselves u]). 
In the month of March following I examined the mould and found 
they had formed thick oval cases of earth, with a cavity inside 
(fig. 13), in which they had changed to bright-brown puj)ai ; the 
tail terminate^ by two slender spines, with heads like pins, and a 
row of spiracles or Ijreathing pores down each side (fig. 14). 
