102 MODERN CLASSIFICATION OF INSECTS. 

and quince, in the United States. Its history has been completely 
detailed by Professor Peck, in the memoir above noticed, and who 
reared one of the Encyrti (?) from it. 
The 22-footed larva of Athalia spinarum, according to Dahlbom 
and Drewsen (Clav. Nov. Hym. Syst. p.16.), is gregarious, and 
feeds upon various species of Brassica, which it completely strips 
of its leaves, leaving only the stronger nerves. ‘There are two ge- 
nerations in the course of the summer; and the larva does not form 
any cocoon, but merely encloses itself in an oval cell in the earth, of 
which it plasters the sides with a glutinous secretion, mixed with the 
earth. 
The 22-footed larva of Athalia centifcliae has periodically, in 
this country, proved to be one of the most obnoxious of our insect 
enemies. It is of a greenish black colour, whence it has obtained 
the name of the nigger, or black caterpillar, of the turnip, to which 
plant it is chiefly detrimental, by devouring the leaves, and thus totally 
destroying the crop in an incredibly short space of time. Albin, in his 
Nat. Hist. of English Insects, 1720, pl. 62., first figured this insect in its 
different states, observing that whole fields were occasionally destroyed 
by it; and an instance is recorded in the Philos. Transact. for 1783 
(vol. Ixxiii. p. 317.), by Mr. Marshall, in which their destruction was so 
great that many thousand acres were obliged to be ploughed up. In 
1835, 1836, and 1837, it was exceedingly abundant and injurious. The 
appearance of the blacks is preceded by that of the imago, a pretty 
yellow and black species, which first appears about the middle of May 
or beginning of June, depositing its eggs within the parenchymatous 
tissue of the leaf, introducing her saw between the edges of the cu- 
ticle; and from which, in five or six days, the larve are hatched. 
