302 Journal of Agricultural Research voi. xxn, no. t 



Porosagrotis orthogonia moths were seen laying eggs in the open at 

 Willow Creek on September 5, 1920. Just before dark moths were seen 

 flying over a freshly worked, summer-fallowed field, being most abun- 

 dant on the higher knolls and along the ridges where the soil was soft 

 and loose. One moth was followed for some distance. She would fly a 

 few feet, never getting over 10 inches above the ground, and would then 

 crawl a short distance, continuously feeling the surface with her ovi- 

 positor. On reaching soft dirt she stopped and laid eggs for six minutes, 

 going through the same actions as the moth observed in the cage. When 

 she left the ground she flew straight away for at least X ^^^ ^t a height 

 of 20 to 30 feet above the ground and was finally lost to view. Five eggs 

 were recovered from this oviposition. Other moths were seen flying to 

 the ridges and knolls, but it was too dark for further observations on this 

 date. A few days later another moth was observed laying eggs on a 

 knoll in the same field. One oviposition was made which lasted 23 min- 

 utes, during which time the moth was not in the least disturbed by any 

 movements of the observer. When the ovipositor was finally with- 

 drawn the moth swung around X iiich and started in again, this time 

 remaining quiet for 1 7 minutes, after which she crawled under a clod to 

 hide. This moth had oviposited for 40 minutes, and 12 eggs were re- 

 covered from the two holes. Moths were seen ovipositing along the 

 knolls and ridges in this field for several days. 



Moths in egg-laying show their preference for spots in the field where 

 the soil is softest and also indicate a preference for freshly worked fields 

 over those which have become caked and hard. Across the road from 

 the freshly worked, summer-fallowed fields in which egg laying was 

 observed was another summer-fallowed field which was spotted with 

 Russian thistles and in which the soil was caked on the surface, due to a 

 rain some two weeks earlier. Moths were continually observed flying 

 into this field, but they usually flew on across it to the knolls in the 

 freshly worked field, even though it was ]4 mile farther. Very few 

 moths flew to similar knolls in the caked field, and those that alighted hid 

 under the thistles or clods of dirt and made no attempt to lay eggs. 

 Further evidence of this preference for mellow fields will be brought out 

 later in this paper. 



ATTRACTION OF THE MOTHS TO LIGHTS 



Our first experiments in attracting the moths to lights were conducted 

 at Wilsall on the evening of August 26, 19 19. A large Coleman gas lamp 

 was placed on the ground in the field where the grain had been destroyed 

 the previous spring. As soon as it grew dark Porosagrotis orthogonia 

 moths began to come to the light at the rate of one every two or three 

 minutes. The lamp was placed upon bare sandy soil and the ground was 

 well lighted for several feet on all sides. The moths usually struck the 



