i 



CUTWORMS, ARMYWORMS, AND RELATED SPECIES 3 



alence of dry seasons during that period. Conversely, excessive soil 

 moisture favors the increase of Agrotis ypsilon, and this species, 

 usually scarce in Kansas, appeared in destructive abundance after 

 the floods of 1935, This species tolerates more moisture than any 

 of the others observed, and it can develop in saturated soil. 5 



Many species in this region are at the outward limits of their normal 

 range of destructive abundance. Thus, the pale western cutworm is 

 near the eastward limit, the variegated cutworm at the westward 

 limit, and the fall armyworm at the northern limit of its range. The 

 fall armyworm is actually beyond its range of complete development, 

 since, so far as is known, it is unable to pass the winter in the central 

 Great Plains, but invades this region annually from infestations 

 originating farther south. 



Crumb (5) points out that the metropolis of most multiple-brooded 

 species is in the warmer latitudes, owing largely to their low resistance 

 to cold and their tendency to hibernate as pupae; that single- brooded 

 species tend to be of northern distribution but, as they advance south- 

 ward, higher average temperatures shorten the cycle of development; 

 and that in order to make the life cycle occupy a full year, a quiescent 

 period, which becomes more prolonged as a species advances south- 

 ward, is interpolated. Thus, with the pale western cutworm in 

 Kansas, development is retarded in the larval stage and the summer 

 is passed in a quiescent state within the pupal cell. The army cut- 

 worm estivates in the adult stage. Other species having a period of 

 retarded development include Agrotis gladiaria, A. venerabilis, and 

 Feltia subgothica in the larval stage, and Anicla badinodis and Orthodes 

 incincta in the pupal stage. 



Powerful repressive factors must be operating to limit the abundance 

 of most species. During 1934-37 nearly 300 species of Phalaenidae 

 were taken in light traps operated at several places in Kansas and 

 Nebraska (Walkden and Whelan (21)). Many were of the cutworm 

 type. It is noteworthy, therefore, that so few species have developed 

 into major economic pests. 



KEY TO LARVAE OF SOME SPECIES OF PHALAENIDAE 



Many species of cutworms resemble each other so closely that 

 structural characters (figs. 1-7) for distinguishing them are diffi- 

 cult to find. To facilitate identification of the cutworms and army- 

 worms likely to be encountered in the central Great Plains, the writer 

 has prepared a key to the larvae for use in separating the species taken 

 in the many collections made during this investigation. It is based 

 on existing keys, but includes additional species taken in the region 

 and the months in which some of them were found. The arrangement 

 and size of the setigerous tubercles on the abdominal segments of the 

 larvae are useful characters for separating the species. A diagram of 

 the arrangement and numbering of the setae of a typical cutworm 

 larva is shown in figure 3. The setae and markings of the head are 



5 MANNIS, H. J. MOISTURE TOLERANCE OF THE BLACK CUTWORM. 1937. 



[Unpublished master's thesis, copy on file at Kans. State Col. Agr., Manhattan.] 



