81 



of Colimil)ia of a secoiul brood of caterjiillars produced in late fall. A 

 full-grown larva taken Sejiteniber 2 in Illinois entered the ground for 

 pupation Sei)teiul){n- !) and emerged ()c(o])er KJ; another, taken b}' m 

 on clover August 18, entered the ground August 26 and emerged Sep- 

 tember 12. In warm weather the pupal stage ordinarily lasts about 

 two weeks. The earliest appearances of the moths in our local collec- 

 tions have been May 29, June 12, and July 11, after which no more have 

 occurred until August 15, when they became common. 



THE GRASS-WORM OR FALL ARMY-WORM. 



Laphjgnia frugiperda Sm. and Abb. 

 This caterpillar, occasionally and locally very destructive, appears 

 so infrequently in threatening numbers as to be virtually unknown at 

 each of its appearances to ordinary observers of insect life. The facts 

 of its occurrence and its life history in the 

 Southern States point to the conclusion that it 

 does not winter in our latitude, all remaining 

 here after one of its destructive periods seem- 

 ingly perishing before the following spring. As 

 it lives continuously in the Southern States, its 

 appearance in Illinois is probably due to the 

 migration of the parent moths from the South 

 in spring and early summer. 



The caterpillar (Fig. 59) is about an inch 

 and a half in length, blackish or grayish in 

 general color, with three narrow whitish lines 

 the entire length of the back. The head (Fig. 

 60, o) is black or dark brown, with a white 

 A-shaped mark on the face. The skin is 

 smooth, with rather- prominent tubercles, each 



bearing a single hair. This caterpillar resembles the common army- 

 worm and the corn ear-worm both in habits and in appearance. From 

 the ear- worm it is readily distinguished by its smooth skin (Fig. 60, b), 

 the skin of the former (Fig. 60, d) being finely but roughly granulate,' 

 and from both it may be told at once by the white face-mark (Fig. 

 60, a), which is present in neither of the other species (Fig. 60, c; 63, b). 



This caterpillar is not a common corn insect, but, nevertheless, occa- 

 sionally does considerable injury to that crop, eating down into the 

 growing tip of the young plant, and later in the season feeding upon the 

 leaves, entering the ears like the ear-worm, and burrowing among the 

 kernels beneath the husk. In 1889 it did considerable damage in 

 broom-corn fields in Douglas county, Illinois, in one case diminishing 

 the crop by fully a third. Later in this season it became generally 



Fig. 59. The Grass-worm, 

 Laphj/ffma frug-iperda: a, larva, 

 natural size; 6, face of larva; 

 c, d, an abdominal segment, 

 top and side views. 



