THE PEAR LEAF-WOEM. 



13 



Table V, 122 eggs were marked on the trees. Thirty eggs died 

 before hatching or were infertile. The remaining 92 hatched and 

 16 iarvse disappeared and 3 died before molting. Thus 73 larvae 

 cast their first skin under observation. Of these, 6 disappeared and 

 2 died before casting the second skin. Thus 65 larvse molted a second 

 skin under observation. Of these, 5 disappeared and 5 died (1 being 

 destroyed by a coccineUid larva) before shedding the third skin. Of 

 the 55 larvas which cast the third skin, 8 subsequently disappeared 

 before they were ready to drop to the ground. The larvae under 

 observation were taken into the laboratory insectary after their 

 third molt, but were not inclosed in cages, so that those which desired 

 to move away could do so. On the trees most of the larvae which 

 disappeared were dislodged during the operation of molting. 



Table VI. — Summary of Table V. 



Instar. 



Maximum. 



Minimum. 



Average. 



1 



Days. 



8 



7 



7 



10 



Days. 

 3 

 2 

 2 

 4 



Days. 

 5.3 

 3.4 

 4.2 

 6.6 



2 



3 . . . 



4. .. 



Total larval period on trees 



23 



16 



18.4 



The data in Tables V and VI are in striking contrast to those 

 recorded from San Jose (Table IV) , in which the average period spent 

 by the larvae in vials was 31.6 days. It would appear that the San 

 Jose individuals were retarded by reason of the abnormal character 

 of their food as a result of the feedmg of cut leaves. It might be 

 added that the temperature during the period of larval growth in 

 1913 at Walnut Creek was higher than the mean average for that time 

 of year, and toward the end of April great daily fluctuations occurred; 

 for instance, on Aprd 24 and on May 3 there was a range of 48° F. 



Tables VII and VIII give the larval life history at Wenatchee, 

 Wash., in 1915. 



