affecting the Turnip-Crops. 
127 
to fly well ; .mtl towards sunset multitudes are roving about, and 
apparently enjoying, on the wing, the decline of day. Indeed 
they may be said to be found everywhere, and at all seasons. 
They are able to emit an acid, or some acrid liquor, from the 
mouth when irritated, which causes great pain when they fly into 
our eyes; and it lasts until the poison becomes diluted by tears 
from the lachrymal ducts. 
Lastly, we come to several two-winged flies, which, by deposit- 
ing their eggs either in the crown of the turniji or close to the 
young bulb, cause the destruction of that plant. My attention 
was first called to this enemy of the farmer a few years since by 
Edward Bennet, Esq., of Rougham Old Hall, in Suffolk. We 
found many of the turnip-plants in that parish which had a mag- 
got either in the young crown or just inside, at the base of the 
tap-root, which was indicated by a yellow tint on the leaves, the 
flagging of the plants in the heat of the day, and their dropping 
off : this was during the first week of August; in a few days after 
the maggots changed to pupze, and in about three weeks two male 
flies and one female hatched from them. The Rev. C. Clarke 
also showed me some white maggots at the roots of the cabbages 
about the same period, which destroyed his plants earlier in the 
year, by eating off the fibrous roots and excoriating the stem 
below the surface. When I saw them they were living under the 
rind of the stem ; and he informed me that the same or a similar 
maggot sometimes does great mischief to the Swedish turnips. 
These maggots were identical with broods reared from cabbages 
by another friend in Surrey ; but in that instance the maggots 
were feeding the beginning of June, and the flies emerged the 
end of the same month. 
These maggots are somewhat like those of the flesh-fly, but 
smaller : they are yellowish-white and shining, composed of 
eleven visible rings, tapering very much to the head, which is 
pointed, and terminated by two black horny claws, and there is a 
dark spot on the first segment : the rump is the thickest, and cut 
off abruptly, with two brown tubercles in the centre, and several 
short teeth on the lower margin : when full-grown they are about 
4 lines long (fig. 30) ; they then change below the surface of the 
earth to reddish-brown pupae (fig. 31) : these are cylindrical and 
elliptical, with a few black tubercles on the head, and short spines 
on the rump, similar to those on the maggots ; for these brown 
cases are, in fact, their indurated skins, which are not cast off in 
the penultimate transformation, as they are in the caterpillars of 
butterflies and many other larvae ; neither do maggots change 
their skins as they grow, which is unnecessary, as they are ex- 
tremely thin, and stretch so readily, that as the animal increases 
in bulk so does its skin expand. In three weeks at the utmost 
