16 CIRCULAR 8 49. U. S. DEPT. OF AGRICULTURE 



The larvae make burrows into which they drag their food. They are 

 very pugnacious and on being touched will strike and bite viciously, 

 exuding a green fluid from the mouth. Some of the larger larvae will 

 pinch severely, but in the writer's experience, none can pierce the 

 skin. The larvae are strongly cannibalistic when confined. When 

 eight nearly full-grown larvae, collected in the field, were left over- 

 night in an 8-ounce salve tin. only one remained the next morning. 

 This species exhibits the highest tolerance to moisture of any observed, 

 and prefers moist or wet soil. An outbreak frequently appears in 

 land that has been flooded recently. For this reason the black cut- 

 worm is called the overflow worm in some localities. 



Seasonal history. — In the central Great Plains adults have been 

 taken every month except December, January, and February. The 

 overlapping of life cycles makes it difficult to determine the number 

 of generations a year, but apparently there are four complete genera- 

 tions and sometimes a partial fifth. A heavy flight of adults usually 

 occurs during September and October, but stragglers are present into 

 November. Attempts to carry these late-emerging adults through 

 the winter have failed. Crumb (5) states that in the latitude of 

 Clarksville. Tenn.. the pupa is the normal overwintering stage. In 

 Kansas it is probable that this stage carried the species through the 

 winter, although in cages all attempts failed. The larvae are most 

 abundant during May and June. 



Reproductive capacity. — When 14 field-collected females were dis- 

 sected, the number of eggs ranged from 477 to 2.257. with an average 

 of 1.367. Three reared females contained 1.219, 1,692. and 2.032 

 eggs, respectively, averaging 1.648. Obviously a species with such a 

 high reproductive capacity can increase rapidly to destructive abun- 

 dance under favorable conditions. 



Life cycle. — Spring generation: Eggs deposited on May 10 on alfalfa 

 foliage produced adults on July 16. The eggs were 0.6 to 0.7 mm. in 

 diameter and 0.4 to 0.5 mm. in height. The larval instars were not 

 observed in this generation. 



Summer generations: Eggs deposited on July 22 hatched 6 days 

 later and those deposited on August 5 hatched 3 days later. The 

 periods required in the various stages and the width of the head 

 capsule in the different larval instars were as follows: 



EGGS DEPOSITED JULY 22 



Stage: Period Width of head 



Instar: (days) capsule {mm.) 



First 2 to 3 



Second 1 to 2 



Third 1 to 2 



Fourth 2 to 4 



Fifth 2 to 4 



Sixth 2 to 15 



Seventh 4 to 15 



Eighth i 4 to 7 



Total 28 to 34 



Pupa 12 to 15 



Egg to adult 46 to 52 



1 2 specimens. 



