9070 Insects. 
cylindrical, and consists of twelve segments, each of these being sub- 
divided into several folds. It is quite bare, having no pubescence on 
any part. The upper surface, as far as the spiracles, is black or deep 
blackish green; then follows on either side a longitudinal slate- 
coloured stripe; then a row of black, mostly double, oblong spots; 
the legs, together with the ventral surface, are all slate-colour. There 
are twenty-two legs; namely, three pairs of horny thoracic legs, black 
marbled with gray, seven pairs of gray abdominal legs, and a pair of 
anal prolegs, so that the fourth segment only is destitute of organs of 
progression. 
Many of my larve after their last moult assumed a much paler dull 
gray lint, as represented at fig. 4 of our plate. The head is black, 
and the gray near the head somewhat darker than on the middle 
of the back. These larve were a little smaller than the black 
ones. 
On comparing our figure with that of Curtis, in plate B of ‘Farm 
Insects,’ a considerable difference will be perceived. His larve are 
more or less brown on the dorsal surface and yellowish on the sides ; 
however, we can assure our readers that our drawings were made from 
life, and we must therefore suppose that Mr. Curtis, usually so accurate, 
or at all events the artist who coloured his plates, has been mistaken 
in this instance, for in the description the colour of the back is given 
as slate or gray, and that of the sides is called a pale line. 
These larve repose somewhat curled up on the upper surface of the 
leaves, and, in contrast with the habits of some other sawfly larve, 
appear to luxuriate in the hottest sunshine. They mostly eat holes in 
the leaves, feeding, however, sometimes along the margins, to which 
they generally keep themselves attached by the six thoracic legs. 
When feeding they slightly elevate the abdomen. 
According to the views of Mr. Wttewaall, there must be three 
generations of this insect in the year in this country ; the first living as 
larve in May and June on the wild radish and wild mustard; the 
second in July and August, subsisting on the summer turnip crop; 
and the third in September and October on the autumn crop. Never- 
theless it is most probable that very many individuals of the second 
and third generations will be found on wild plants of the rape family. 
When full grown the larva descends to the ground, and, burrowing 
one or two inches below the surface, makes a little oval cocoon of 
grains of earth, as represented at plate 9, fig. 5; this it lines with a 
white satiny material, so that the walls inside are quite smooth and 
shining. In this receptacle it changes to a white pupa (fig. 6). The 
