sept. 4. 1916 Life History of Army Cutworm 879 



in each of the boxes and the eggs hatched within a few hours. It seemed 

 to be clear that incubation had been completed some days earlier in 

 some of the lots, but that the young caterpillars had been prevented 

 from issuing until sufficient moisture was present. Thus, some hatched 

 in 9, while others hatched in 21 days. Those in the outdoor shelter 

 hatched as soon as those inside. It is probable that 9 or 10 days is 

 about the correct incubation period. 



No field data on the incubation period are available. Repeated 

 searching revealed no newly hatched caterpillars in fields where numerous 

 eggs were known to have been laid. It is very interesting to note also 

 that no larvae could be found this spring in the field on the college farm 

 where the eggs are known to have been laid last fall. 



-t>e>- 



LARVAL FEEDING IN THE FALL 



Only scattering records of larvae in the fall are available, but these are 

 of considerable interest. In the fall of 1906 the very small larvae of this 

 species did some damage in the northern part of Gallatin Valley. Several 

 lots of the larvae were received at the Experiment Station in November, 

 and reports of their occurrence had reached it in October. One lot was 

 reared to the adult condition. This is the only case known here in which 

 the larvae have attracted the attention of the farmers in the fall, and in 

 this case the knowledge of their presence served as a useful warning of 

 their coming in destructive numbers the next spring. The fall of 1906 

 was unusually dry and warm, the mild weather continuing until late. 

 The larvae continued feeding until December 6. 



On November 4 and 5, 191 5, an assistant was able to find larvae in 

 nearly every field of grain examined in Fergus County. They were not 

 very abundant, but were easily found by the holes eaten in the leaves. 

 At this time the worms were very small, probably in the second instar. 

 Cold weather occurred soon afterward and larval feeding must have 

 ceased. On April io, 1916, some of the same fields were visited again 

 and the larvae were still very small. They certainly were very much 

 smaller than on the same date in 191 5. It is clear that there is a con- 

 siderable variation in the size reached before winter sets in and, hence, 

 in the size of the larvae in the spring. 



HIBERNATION OF THE INSECT 



From the foregoing and from Johnson's observations ! it is clearly 

 evident that the insect hibernates as a partly grown larva. 



It has been stated above that in the fall of 1906 the larvae fed until 

 December 6. The feeding of the caterpillars ceased with the coming of a 

 snowstorm. A field which had been visited only a few days before and 

 which was known to contain many larvae was examined after this storm. 

 The snow was swept away with a broom, and the larvae were found on 



1 Johnson, S. A. Cutworms. In Colo. Agr. Exp. Sta. Bui. 98, p. 18. 1905. 



