juneio, i9i8 Nysius eHcae ^yj 



To secure data on the seasonal variation in oviposition, females were 

 collected and confined with males, and a record kept of the egg pro- 

 duction and of the length of life of each female. The experiment was 

 begun on May 6 and continued until September i8. Fifty -four females 

 collected during May deposited 260 eggs in 295 days of life; 48 females 

 collected during June deposited 231 eggs in 166 days of life; 39 fe- 

 males collected during July deposited 28 eggs in 216 days of life; 10 

 females collected during August deposited 17 eggs in 55 days of life, 

 and 21 females collected during September deposited 113 eggs in 119 

 days of life. This is at the rate during May of i egg per female in 1.13 

 days; during June, i egg per female in 0.718 days; during July, i egg per 

 female in 7.86 days; during August, i egg per female in 3.235 days; and 

 during September, i egg per female in i .05 days. 



These figures coincide with the reproductive activity of the species 

 as observed in the field. During May and June and again during Sep- 

 tember and October the females mate and oviposit frequently. Begin- 

 ning in July and continuing into August they are much less prolific, it 

 being sometimes difficult to secure sufficient eggs for rearing experiments. 

 This decreased activity is exhibited only by the adults, there being no 

 lengthening of the incubation period or nymphal instars. 



EFFECT OF TEMPERATURE ON DEVELOPMENT 



With an average temperature of 79.78° F. at Garden City, Kans., eggs 

 hatched in about 4 days, and the average nymphal period (calculated 

 from the averages of the largest number available in each instar) is 20.35 

 days. The average time, therefore, from oviposition to maturity is 24.35 

 days. 



With an average temperature of 74.75° at Wichita, eggs hatched in 

 3.5 days, and the average nymphal period was 20.69 days. This gives 

 the time from oviposition to maturity as 24.19 days. 



Of 6 eggs deposited October 16 and 17, 1914, two hatched November 

 25, one November 28, and one November 30, making the shortest possible 

 incubation period 39 days and the longest 44 days. Twenty-six times 

 during this period the temperature was below 32° F., the minimum 

 being 18° and the average 49.8°. This shows an average difference of 

 1 . 1 6 days in the length of the incubation period for each degree of dif- 

 ference in average temperatures. 



From the data in the preceding paragraphs it appears that develop- 

 ment at a temperature of 74.75° requires only 0.34 of a day longer than 

 development at a temperature of 79.78°, but at 79.78° incubation re- 

 quires only 4 days, while at a temperature of 49.8° 39 days are required, 

 or i^ days for each degree of difference in temperature. 



Of the 6 eggs under observation at a temperature of 18° four sur- 

 vived, and it is not certain that the other two were killed by the cold. 



