158 



ASSOCIATION" OF ECONOMIC ENTOMOLOGISTS. 



From the above table can be deduced the approximate effect within 

 the limits of these observations of a single degree of daily mean tem- 

 perature on the period of incubation. If we consider only the three 

 batches of eggs which matured with the lowest average daily mean 

 temperature and the three batches which matured with the highest 

 average daily mean temperature, we find that the former average was 

 62.3° F. and the latter 72.7° F., while the period of incubation is 

 shortened with the increase in temperature from 8.6 to 5.3 days. In 

 other words the decrease of .10.1° F. represents an increase of 3.3 days 

 in the incubation period or 0.32 day for each degree of temperature. 



The average number of eggs deposited per day by the female 

 during the entire adult life was 9.3. Omitting the first eight days 

 during which no eggs were laid, the number of eggs after the begin- 

 ning of the egg-laying period averaged 11.2 per day. The rate of 

 production of eggs as well as the length of incubation period was 

 affected in a marked degree by the daily temperatures. The last 

 fifteen days of the month of August were cooler than the first 15 : the 

 5 warmest days of the month occurred consecutively from August 1 

 to 5, inclusive, and the 5 coolest days occurred consecutively from Au- 

 gust 16 to 20, inclusive. The relation of temperature to the produc- 

 tion of eggs is shown in the following table, although allowance 

 should be made for the influence of minor factors, the experience with 

 one insect being too limited for anything more than general con- 

 clusions. 



Relation of temperature to prod net ion of eggs. 



Period, August, 1902. 



Average 

 daily 

 mean 



temper- 

 ature. 



Number 



of egg 

 batches. 



Total 

 number 

 of eggs. 



Per cent 

 of total 

 number 

 of eggs 



per 

 month. 



Average 

 number 

 of eggs 

 per day. 



1-15 .. 



° F. 

 67.9 

 63.9 

 73 

 59.3- 



9 



271 



73 

 27 



37 







18.6 



16 30 



3 j 102 

 5 1 139 



6.8 



1-5 .... 



27.8 



16-20 











It is worthy of note that the longest incubation period of ihe 17 

 records included the 5 coldest days of the month, while the shortest 

 incubation period included 44 of the 5 warmest clays. 



OBSERVATIONS ON DURATION OF NYMPH STAGES AND LENGTH OF ADFLT 



LIFE. 



The duration of the nymph stages depends for the most part on the 

 temperature and perhaps more or less on food supply. Of the 18 

 batches of eggs obtained from the female under observation, the 

 nymphs from only 1 — Xo. 12 — were bred to maturity in the labora- 

 tory. Thirty-four nymphs hatched on August 18 from egg batch No. 



