LEPIDOPTERA 747 



fifty gallons of water. Chemical analysis of sprayed plants has shown 

 that there is practically no danger from eating cabbages that have 

 been treated in this way. 



The gray -veined white, Pleris 71dpi. — In the most common form 

 the wings are white above and below, with a scarcely perceptible tinge 

 of greenish yellow. Sometimes there is a dark spot in cell M3 of the 

 fore wings, "but usually the wings are immaculate. The base of the 

 wings, however, and the basal half of the costal margin of the front 

 wings, are powdered more of less with dark scales, and the veins of 

 the wings, especially on the lower side are grayish. The wing-expanse 

 is from 42 to 50 mm. 



This species occurs throughout Canada and the more northern 

 portions of the United States. It appears in many different forms ; 

 eleven named forms are now recognized in the United States, and still 

 other forms are known in Europe. This pol^onorphism is partly 

 seasonal and partly geographical. 



The checkered white, Pleris protodice.- — ^The two sexes of this 

 species differ greatly in appearance, the female being much more 

 darkly marked than the male. The wings are white, marked above 

 with grayish brown. There is a bar of this color at the end of the 

 discal cell; beyond this there is in the male a row of three more or 

 less distinct spots, and in the female an almost continuous band of 

 spots. Besides these there is in the female a row of triangular spots 

 on the outer margin of both fore and hind wings, and on the hind wings 

 a submarginal zigzag bar. 



The larva of this species is colored with alternating stripes of 

 bright golden yellow and dark greenish purple, upon which are nu- 

 merous black spots. It feeds upon cabbage and other cruciferous plants, 

 and occurs in nearly the whole of the United States. Both this and 

 the preceding species seem to become greatly lessened in numbers by 

 the increase of the imported Pieris rapes. 



II. THE ORANGE-TIPS 



These, like the butterflies comprising the preceding group, are 

 white, marked with black. Their most 

 characteristic feature is the presence 

 on the lower surface of the hind wings 

 of a greenish network, or a marbled 

 green mottling. This usually shows 

 through the wing so as to appear as a 

 dark shade when the wings are seen 

 from above (Fig. 955). Many species 

 have a conspicuous orange spot on the 

 apical portion of the front wings. This 

 has suggested the common name orange- Fig. gss.—Eiichloe a usonides. 

 tips for the group. But it should be 

 remembered that some species lack this mark, and that in some others 



