98 JOURNAL OF ECONOMIC ENTOMOLOGY [Vol. 10 



We have no records to show just how early egg-laying begins in the 

 field. Larvae have been found in abundance in Yellowstone County 

 in the middle of April. Allowing a week for incubation and a few 

 days more for feeding, since incubation, it is clearly indicated that 

 egg-laying may begin early in April. 



During two seasons we have carefully observed egg-laying in the 

 insectary in large Riley type cages, which had about four inches of 

 soil in the bottom. In 1911 this insect was kept under daily observa- 

 tion in the insectary from May 13 to July 25 and was occasionally 

 examined until October 31. Adults brought in on May 18 began 

 depositing in a few days and continued irregularly until July 10, many 

 eggs being laid up to June 22. 



In 1915, sixteen single females were kept isolated for egg-laying 

 records. The experiment began on April 13 and continued until 

 May 31 when one was still laying. From these records as well as 

 from observations in the field, it is clear that the egg-laying period is 

 long drawn out. 



Number of Eggs Laid 



As stated above, individual egg-laying records were made. The 

 largest number laid in any one day was six, while two or three was the 

 usual number. In many instances none were laid during a twenty- 

 four-hour period. The largest total number laid by a single female 

 while in confinement was seventy-five and the average was thirty-nine. 

 These beetles were captured rather early in the season, but it is almost 

 certain that they had laid some eggs before being brought to the 

 insectary. 



Increase in Size of Eggs During Incubation 



During the course of this investigation we have had a large number 

 of the insects in all stages under observation. The writer in some wd,y 

 had a suspicion that the eggs increased in size after being laid. Accord- 

 ingly, individual eggs of which we had certain knowledge of the approx- 

 imate time of being deposited were measured under a microscope with 

 the aid of a filar micrometer soon after being laid and set aside to be 

 measured again from time to time. It had been learned that it was 

 necessary to keep the eggs in moist earth to prevent them from shrivel- 

 ling. Accurate measurement records were made on fifteen eggs. 

 Most of the eggs were measured four times. Some were measured 

 seven tinies and a few only twice. Disregarding two eggs, which were 

 allowed to go two days before the first measurement was made the 

 increase in size ranged from 0.18 mm. by 0.25 mm. to 0.46 mm. by 

 0.48 mm. In a number of instances the eggs increased in size until 

 ■ the shorter diameter became as great as the longer diameter had been. 



