20 



THE REPORT OF THE 



No. 36 



the moths emerged at almost the exact rate at which they emerged from identical 

 material left lying in the field, which was later sown to oats. 



General pupation in the field started about June 7th and reached its maxi- 

 mum about June 25th, although the first pupa found occurred on May 31st. 

 Last year the first pupa was found on June 2nd. The daily count in 1922 showed 

 that a high point of pupation was reached on June 16, which was the date on 

 which the first moths were found in the field in 1921. Although pupation was 

 fairly uniform all over the oat field kept under observation, it was found that 

 the emergence of moths from the lowest and dampest areas was considerably 

 delayed. In fact in this low, damp north corner of the field, many borers died 

 after pupating and the moths did not emerge. This was the only instance found 

 where larvae that had pupated failed to come through to moths unless the pupae 

 were eaten by ants. 



Emergence of Adults. The emergence of adults started this year about 

 June 26 in the oat field and by July 12, 80 per cent, of the moths had emerged 

 from the corn debris and stubble in this field. 





1921 



1922 



Period of Max. Emergence 



June 26-July 1 

 June 28 



July 2-18 



Zenith of Emergence 



July 8-12 





This later date July 12, 1922, for emergence in the field, coincided with the 

 result obtained from material kept in cages in the open, exposed to the elements. 



Oviposition Records. There was a slight difference this year, compared 

 to last, in the number of eggs laid per moth and in the fertility of the eggs. 

 This is summed up by the following figures: 



1921 



1922 



Pre-oviposition period 



Egg-laying capacity per moth 



Longevity of females 



Fertility of eggs 



Mortality of embryos 



3-9ds. Av. 4 ds. 

 95-988. Av. 442. 

 10-31 ds. Av. 15.4 ds. 

 100%. 

 nil. 



l^-8ds. Av. 3.5ds. 

 37 to 1,210. Av. 642.07. 

 7-28 ds. Av. 17.07. 

 99%. 



About 1% just before 

 time to hatch. 



Habits of Moths. This year's observations confirmed those of last year, 

 when it was found that most moths emerged from the pupae between 5 a.m. 

 and 9 a.m. In some cases they emerged before 5 a.m., but generally they did 

 not begin to appear above the top of the stalks in the cages until that time. 

 The process of emergence was watched in several cases between 7 and 9 a.m.; 

 it occupied only a few minutes and in less than half-an-hour they were able to 

 fly. Occasionally moths come out later in the day, and but rarely in the after- 

 noons or evenings. One would expect that nocturnal insects such as these are, 

 would emerge at dusk, but such seems not to be the case in this instance. 



If the moths are confined in wire cages exposed to wind, they must have 

 water to drink soon after emerging or else they die. We have reared them better 

 on water alone than on sugar solutions. Moths have been kept alive for from 

 two to four days without food in tightly closed cans, but in open cages they must 

 have food or else they die. As soon as they take flight after emergence, they 

 seek cover on the under side of leaves and will remain there all day unless dis- 

 turbed, or unless the sun should happen to strike them, when they will move 

 into shade. 



