LEPIDOPTERA. 
301 
Fig. 360 .—Plusia simplex. 
number of individuals in the later broods which infest the 
cotton. 
The genus Plusia (Plu'si-a) includes a large number of 
species in which the fore wings are 
marked with metallic-colored scales. 
The most common form of this 
marking is a silvery spot shaped 
something like a comma near the 
centre of the wing. Plusia simplex 
(Fig. 360) is a well-known illustra¬ 
tion of this genus. About sixty species of this genus have 
been described from North America. In some of the 
species the metallic markings cover a large proportion of 
the fore wings, and in others they are wanting. The larva 
of Plusia brassicce (P. bras'si-cae) feeds on cabbage and other 
Cruciferce. 
In the cotton-growing States the most important insect 
pest is the Cotton-worm, Aletia argillacea (A-le'ti-a ar-gil-la'- 
ce-a). The adult of this insect (Fig. 361) is a brownish 
moth with its fore wings crossed 
with wavy lines of darker color and 
marked with a bluish discal spot 
and two white dots as shown in the 
figure. This moth is found in the 
Northern States and even in 
Canada in the latter part of the 
summer and in the autumn. But this occurrence in the 
North is due to migrations from the South, as the insect can¬ 
not survive the winter north of the Gulf States. The larva 
feeds on the foliage of cotton ; and as there are five or six 
generations in a year, the multiplication of individuals is 
very rapid, and the injury to the cotton great. Detailed 
descriptions and colored figures of this insect in its different 
stages are given in the works cited above in the description 
of the Boll-worm. The best known way of combating this 
pest is by the use of Paris green. 
Fig. 361 .—Aletia argillacea. 
