296 APPLIED ENTOMOLOGY 



each hind wing. In the female the black wing border has yellow spots in it. 

 Sometimes the orange color in the female is replaced by whitish. The cater- 

 pillar is brown at first but later becomes dark-green with a white stripe on each 

 side (Fig. 316). Alfalfa, clovers, vetches and other legumes are fed upon. 

 The number of generations seems to vary in different parts of the country 

 from two in the North to six or possibly more, in the far South. The colder, or 



FIG. 316. Caterpillar of the Alfalfa Butterfly, about three times natural size. (From U. 



S. D. A. Bull. 124.) 



in the Southwest, the dry months may be passed either as larva, pupa or adult. 

 Treatment is by cultural methods such as pasturage, or early and close cutting of 

 the crop, followed if necessary by rolling or brush dragging. 



The spreading of an insect introduced into a country is always of 

 interest, even if no financial factor is involved, and several of the species 

 considered in this chapter supply good examples of this. Its method of 

 introduction; its establishment; the rapidity with which it spreads, and 

 the final limits of its distribution, are all topics for investigation. 



In the case of the Gypsy Moth its introduction was apparently inten- 

 tional, though it was far from the plan of the scientist who brought it to 

 this country that it should escape. It is stated that this scientist had in 

 mind testing the silk-producing possibilities of various Lepidoptera and 

 imported a number of species for that purpose. Unfortunately in some 

 way, some of the Gypsy Moth specimens escaped and as he could not 

 find them, he issued a notice calling attention to the fact, and warning 

 the public of the possible menace they might become. 



The Brown-tail Moth appears to have been brought to this country 

 as a winter tent containing young caterpillars, on an importation of 

 roses from Europe. This occured before the inspection of nursery stock 

 imported into this country was required by law. How the Cabbage 

 Butterfly arrived, is not known, but it was probably the chrysalis on 

 some material brought as freight. 



It is evident that in any case, either an adult female able to deposit 

 fertile eggs, or else several individuals at least, in some early stage, 

 must be imported at about the same time, if the species is to obtain a 

 start. Then with an individual ready to lay its eggs, suitable food 



