274 Mustard Beetles. 
is the Phaidon hetulx, Linn., formerly known as Chrysomelo) 
betulee (Fig. 1, natural size and magnified). It is oblong-oval^ 
Fig. I.— Mustard Beetle (PhEedon betulse).. 
1, 2, 4, larva (natural size) on leaf ; 5, larva (magnified) ; 6, beetle, natural 
size ; 1, beetle, magnified. 
hardly the sixth of an inch in length, of a full blue or deep 
greenish colour above, and so brightly shining as to be of an 
almost glassy lustre. The legs, horns, and body beneath are 
black. The thorax or fore-body is very minutely punctured, the- 
wing-cases having punctured striae, with the spaces between- 
the striae also punctured. 
These beetles pass the winter in a torpid state, in any con- 
venient shelter near the fields where they have been in the 
autumn. In the spring they become active again, and spreading 
to whatever food-plant may be near, they lay their small eggs 
and die. 
The grubs, or larvae, which hatch from these eggs,* are of the 
shape shown in Fig. 1, and are from about three-sixteenths to a 
quarter of an inch in length when full grown, slightly hairy, of 
a smoky colour, spotted with black, with black heads and stout 
black conical horns, lighter at the base. They have three pairs 
of claw-feet, and a caudal foot, or proleg, at the end of the tail,, 
and a row of tubercles along each side, from which the grubs 
have the power of protruding a yellow gland. These voracious 
grubs devour far and wide, until when full fed they go into 
the ground to change to chrysalids. In this state they are said 
to remain about fourteen days, and from these chrysalids the 
summer brood of beetles comes out which often spreads devas- 
tation over the mustard crop, then in an advanced state. 
• I Lave identified the grub from specimens kindly procured for me by 
Mr. George Moore, of Wisbocli from mustard plants near Ely, which enabled 
me to trace the insect from larval condition up to its perfect stuto, and confirm 
the figure and descrii>lion given (doubtfully) by John Curtis in bis ' Farm 
Insects' as being certainly that of the larva of the J'hxdon Ictuhv. — E. A. O. 
