CUTWORMS, ARMYWORMS, AND RELATED SPECIES 47 



bunchgrass, probably Andropogon sp. In captivity they bored into 

 the crowns of bluegrass. 



Seasonal history. — There is but one generation of this species a 

 year. It evidently passes the winter as a partly grown larva. Lar- 

 vae taken on April 3 appeared to be nearly mature, but continued 

 feeding until the last of June. After constructing pupal cells within 

 their tunnels in the crowns of the host grass, they remained inactive 

 until they pupated late in August. Adults emerged in September. 

 Adults were taken at light traps in September and the first half of 

 October. 



Papaipema nebris (Guenee) 



Stalk Borer 

 (Figs. 4, R; 6, B; 7, L) 



Distribution. — The stalk borer is widely distributed in the United 

 States east of the Rocky Mountains. It has been reported from 

 southern Canada to the Gulf of Mexico. 



Economic status. — It is of minor economic importance in the central 

 Great Plains, occasionally becoming abundant locally. 



Food plants and larval habits. — This species feeds on a wide variety 

 of plants, 176 host plants having been recorded. In their younger 

 stages the larvae bore into the stems of plants, showing a preference 

 for bluegrass, timothy, and orchard grass. They soon outgrow the 

 small stems of these grasses and migrate to a new host to complete 

 their development, provided the stem is large enough to accomodate 

 them. If not, they migrate to still another host. In their later stages 

 the larvae prefer the giant ragweed (Ambrosia trifida L.). 



Seasonal history. — There is but a single generation of this species 

 a year. The eggs are deposited in the fall in dead grass and hatch 

 in the spring. The larvae become full-grown early in August, and 

 usually pupate within the tunnel made by the larva. Adults emerge 

 during September and deposit eggs. 



Reproductive capacity. — When 16 reared females were dissected, 

 they contained 1,324 to 2,560 eggs, averaging 1,987. 



Natural enemies. — A total of 267 larvae, taken mostly from the 

 stalks of giant ragweed, were reared individually. Of this number, 

 0.4 percent were parasitized by Hymenoptera and 6 percent by 

 Diptera. The parasites reared from these larvae were as follows: 



Hymenoptera — Apanteles papaipemae Mues. 



Diptera — Achaetoneura melalophae Allen, Lydella nigripes Tns., Sarcophaga 

 sp. near cimbicis Tns., and Megaselia sp. near aletiae were reared from 

 puparia found in tunnels made by the larvae of Papaipema nebris. 



CONTROL 



Natural Control 



Parasites, predators, disease, and climate are important factors 

 in limiting cutworm and armyworm populations. Because of their 

 tremendous reproductive capacity most of the species are able, 

 under favorable conditions, to build up large populations quickly. 

 No satisfactory method of evaluating the effectiveness of various 



