42 BULLETIN 173, U. S. DEPARTMENT OF AGRICULTURE. 



Table IX. — Length of egg stage of the pear thrips, San Jose, CaL, 1910 — Continued. 



Cage 

 No- 



Date de- 

 posited. 



Date 

 hatched. 



Number ; Length X ^F 

 of eggs of egg tem ;^ a 

 hatched. | stage. ! fjfj 



Prevailing 

 weather. 



VLT 



VIII 



IX 



X 



XI 



xn 



Mar. 29 

 Mar. 29 



Mar. 29 



Apr. 6 

 Apr. 6 

 Apr. 6 



Apr. 3 



8 



Apr. 7 



8 



9 



10 



Apr. 2 

 6 



7 

 8 

 10 

 14 



Apr. 12 



Apr. 13 



Apr. 13 



1 

 1 



1 

 7 

 3 

 4 



1 

 1 



1 

 4 

 4 

 1 



1 



1 



2 



Bays. 

 5 

 10 



9 



10 

 11 

 12 



4 

 8 

 9 

 10 

 12 

 16 



6 



7 



7 



° F. 

 56 

 56 



56 

 56 

 56 

 56 



57 

 56 

 56 

 56 

 56 

 55 



54 



54 



54 



Clear. 

 Do. 



Clear. 

 Do. 

 Do. 

 Do. 



Clear. 

 Do. 

 Do. 

 Do. 

 Do. 

 Do. 



Cloudy. 



Cloudy. 

 Cloudy. 



SUMMARY. 



X umber eggs deposited. 



Time 

 required for 

 incubation. 



Xumber eggs deposited. 



Time 

 required for 

 incubation. 



1 



1 



66 



44 



49 



61 . 



Bays. 



4 

 5 

 6 

 7 

 8 

 9 



34.'. 



Bays. 

 10 

 11 

 12 

 13 

 14 

 16 



7 



24 



4 



4 



1 





For the 296 eggs under observation, the maximum length of the 

 egg stage was 16 days, and the minimum 4 days, making 8.3 days 

 the average time required for incubation. 



The eggs of the pear thrips are undoubtedly affected by tempera- 

 ture conditions, but rainy weather as compared with clear weather 

 seems to make no difference when the mean temperature is the same, 

 as all eggs are embedded in the moist plant tissue and do not require 

 additional moisture from the atmosphere. 



It is evident that all of the eggs are not in the same stage of develop- 

 ment at the time they leave the abdomen of the female, since eggs 

 deposited upon the same day ranged from 4 to 16 days in the length 

 of the egg stage. An examination of the average mean temperature 

 for the various cages shows usually several degrees less mean tem- 

 perature for a long egg stage in comparison with a short egg stage. 



The maximum and minimum temperatures influencing the different 

 lots of eggs are given in Table X. 



