LEPIDOPTERA. 30 1 



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 



. \ 111 -11 FlG - 36o- Plitsia. simplex. 



(Fig. 300) 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 brassica (P. bras'si-cse) feeds on cabbage and other 

 CrucifercB. 



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 



FlG. 361. Aletia argillacea. ~ . . . . . . 



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. 



