36 



PLANT-BUGS INJURIOUS TO COTTON BOLLS. 



number of intervening calendar days has been taken as the basis and 

 the additional periods approximated by a plan which has been fol- 

 lowed throughout and which is believed to have produced very 

 nearly correct averages. To the number of intervening calendar days 

 has been added the known additional hours and one-half the hours 

 between observations during which egg-laying or hatching might 

 have occurred. In many cases the exact time of the egg-deposition 

 or of hatching was noted, consequently lessening the chances for 

 error. For example, a female was observed in the act of depositing 

 an egg-batch at 4 p. m., July 16. This batch had hatched when the 

 record was taken at 3 p. m. on July 23. The number of intervening 

 calendar days in this case was six. The known additional period is 

 8 hours, 4 p. m., July 16, to 12 midnight. The period preceding the 

 time the eggs were first noted as having hatched, during which no 

 observations were made, was 23 hours, one-half of which is added to 

 the known period of 8 hours, making practically five-sixths of a day. 

 This added to the intervening calendar days gives 6f days as the 

 approximate incubation period. 



Table XIV. — Relation of temperature to period of incuhation of eggs of the conchuela. 





Period. 



Num- 

 ber of 



batches. 



Num- 

 ber of 



eggs. 



Range. 



Average. 



Place. 



Inter- 

 vening 

 calen- 

 dar 



days. 



Approxi- 

 mate in- 

 cubation 

 period. 



Average 

 daily mean 

 temperature 

 for interven- 

 ing days. 



Daily 

 mean 

 tem- 

 pera- 

 ture. 



Approxi- 

 mate incuba- 

 tion period. 



Tlahualilo, Du- 

 rango, Mexico. 



Do 



Dallas, Tex 



Do 



1905. 



July 14-23 



July 22-30 



Aug. 6-Sept.l5.. 

 Sept.l6-Oct.5... 



Julyl4-Oct.5... 



3 



5 



11 



7 



99 

 234 

 350 

 313 



6 to 6 



5 to 4 

 3 to 2 



6 to 4 



Days. 

 7h to 6| 

 6,1^ to 5^ 

 41 to 3^ 

 7 to 5 



°F. 



75. 4 to 76. 1 

 79.1 to 79.5 

 80. 1 to 86 

 73.7 to 75 



75.8 

 79.4 

 82.8 

 74.3 



Days. 

 6 

 5 

 3 

 5 



Hours, 



19 



9 



15 



23 







Summary with 

 averages 



26 



996 



2 to 6 



3^ to 7i 



73.7 to 86 



78 



5 



8 



From the last three columns of the above table can be computed 

 the average effect of 1° of temperature on the duration of the 

 incubation period within the limits noted. 



Table XV. — Effect of 1° of temperature on incubation period of eggs of the conchuela. 



Place. 



Range, average 

 daily mean 

 temperature. 



Number of 



degrees 

 represented 

 by range. 



Increase or decrease in incu- 

 bation period correspond- 

 ing to 1° of temperature. 



Tlahualilo, Durango, Mexico . 

 Dallas, Tex 



75. 8 to 79. 4 

 74. 3 to 82. 8 



3.6 

 8.3 



0. 39 days or 9 hrs. 30 min. 

 . 27 days or 6 hrs. 30 min. 



The average of the Tlahualilo and Dallas records shows that between 

 the limits of 74.3° and 82.8° the average increase or decrease in the 

 incubation period corresponding to a single degree of temperature is 



