74 
MUSTARD. 
Mustard Beetle. Phcedon betulce , Linn.; P. Cochlearice , Fab.* 
Mustard Beetle, nat. size and mag. f 
On June 6th I received the following note from Mr. 0. Caswell, of 
Peterborough, regarding the Mustard Seed Beetle, with specimens 
accompanying:—Are you aware of the existence of a great pest in 
the shape of a beetle called by the farmer the Black Jack, that infests 
the Fen district between Peterborough and Ely, especially round 
Wliittlesea ? They feed upon White and Brown Mustard plants, 
Cress, Bape, or Cole, and are so destructive that in six or seven days 
they will completely destroy a field of twelve acres, and leave nothing 
but the bare stalks. 
For the last two or three years the farmers have been afraid to 
sow White Mustard, of which the insect makes first choice. This was 
a most profitable crop, and hundreds of acres used to be grown in this 
district. The insect will live through the most severe winter in the 
pipe of the reeds and rushes in ditches and drains. Two or three 
years since they were so numerous that many acres of nearly ripe 
seed were burnt in the fields to destroy the beetle, but this was not 
effective, as they drop before the flame and bury themselves in the 
soil. 
We have found the beetles alive in sacks of the seed for two years 
after it has been threshed. 
Mr. William C. Little, of Stag’s Holt, near March, mentions that 
for some years past immense damage has been done by the Mustard 
* This beetle is sometimes injurious to Horse Radish, Cochlearia Armoracia, 
Linn. 
t The beetle figured above, nat. size and magnified, is the Plicedon (Ghrysomela) 
Betulce , commonly known as the Mustard Beetle, and the larvre are of some species 
of Chrysomela, considered by John Curtis to be probably, but not quite certainly, 
those of Betulce. As I have not had any opportunity as yet of figuring the grubs 
myself, I give the good representation of John Curtis of the beetle with his further 
observation. 
