234 BULLKTIN 133, 



called the " army-worm" because whenever it appears in injur- 

 ious numbers, after destroying the vegetation in one field, the 

 caterpillars always march like an army to other fields. The 

 parents of army-worms are moths (see figure 69) which belong to 

 a great family of insects known as Noctuids or owlet-moths. Most 

 of the moths or "millers" that fly into our houses at night, 

 attracted by the lights, are members of this family. 



The Caterpillars and their Parents Described. 



When full-grown, army-worms measure nearly an inch and a 



half in length. They are of a general greenish -black color, 



much lighter on the venter which is more or less mottled with 



blackish, and each side bears several distinct stripes. 



Along each side of the body extend three stripes of about the same width ; 

 the one just below the spiracles is of a light greenish-yellow with whitish 

 edges ; the one bordering on the dorsum is a little darker with a mottled 

 greenish-black center and narrow white lines along its edges ; the central 

 stripe, or the one with the spiracles in its lower edge, is black, sometimes 

 lighter along its center. The dorsum is finely mottled with greenish-black 

 and closely resembles the dark stigmatal stripe in color ; along the middle 

 line of the dorsum there extends a narrow white stripe, usually quite indis- 

 tinct except on the thoracic and anal segments. The six true legs are light 

 brown in color, and each pro-leg is marked with a large, shiny, blackish 

 spot. The head is of a greenish-brown color, rather coarsely mottled with 

 black which merges into distinct blackish stripes along the sutures. 



There is considerable variation in general color among the 

 caterpillars, some being much lighter than others, due to differ- 

 ences in the intensity of the stripes and the mottlings on the 

 body. In some cases this difference was so great as to lead to 

 doubts of the specimens being true army-worms. Two extremes 

 of variation are illustrated in figure 70 ; in one instance all the 

 army-worms received from one locality were like the one in the 

 upper part of the figure, while those sent in from another army 

 were all dark like the lower one. 



The parent insect — the moth — is shown natural size at rest at 

 a^ and with wings expanded at b, in figure 69 ; at <: in this figure 

 the moth is represented twice natural size. As these figures indi- 

 cate, the adult insect is a very plain little "miller." Its princi- 

 pal characteristic markings are the distinct white spot near the 

 center, and the dark shade or stripe in the upper outer angle, of 



