86 



INSECTS INJURIOUS TO STAPLE CROPS. 



about ten days. The exact time required for the growth 

 of the larva or the time occupied in the pupal stage does 

 not seem to have been definitely observed. ''Present 

 knowledge indicates that the number of generations that 

 are normally produced each year is two in the most 

 northern range of the species (in years Avhen it develops 

 northward), three for central localities like central and 

 southern Illinois and the District of Columbia, and prob- 

 ably four for the extreme South. We know, however, 



Fig. 53. — Yall Army -worm {LnpJiygma frugiperda S. & A.). 1,2, 

 moth; 3, pupa; 4, 5, larva. (After W. D. Hunter.) 



practically nothing of the development of this sjDecies in 

 the Gulf States."* 



Prof. Morgan states that this insect often makes its 

 appearance in damaging numbers in the States around the 

 Mississippi Delta, in sections behind the levees immediately 

 after an overflow or crevasse. This seems to be largely 

 due to the predaceous ground-beetles (see page 36), which 

 usually prey upon the army-worms in such numbers as to 



*F. H. Chittenden, "The Fall Army-worm," Bulletin 29, n. s., 

 Div. Ent , U. S. Dept. Agr. 



