78 



DECIDUOUS FRUIT INSECTS AND INSECTICIDES. 



Table LXXV. — Larval instars of the codling moth; head measurements in millimeters 

 for each instar; duration' of instars. Summary of Table LXXIV. 



1 Winter. 



The head measurements were all made by an ocular micrometer 

 of a compound microscope. It was necessary to bring the larvae to 

 a perfectly quiet position before the readings could be made. In 1910 

 tlxis was accomplished by placing a cover glass over the larvae during 

 the early stages. The larger larvae were held in place between two 

 broken pieces of glass and by a small glass cover placed above. The 

 results of these readings are given in Table LXXIV. Four larvae 

 out of 10 reached maturity and entered their winter cocoons. Three 

 of these passed through six instars and one larva passed through five 

 instars. A summary of these readings has been brought together in 

 Table LXXV. The average length of the entire feeding period was 

 evidently prolonged beyond that of the normal. The records for the 

 minimum length of time of each instar represent more nearly the 

 normal. 



In 1911 similar observations w r ere again made for both first-brood 

 and second-brood larvae. To quiet the larvae for the necessary read- 

 ings they were held over a piece of ice under the microscope. The 

 exposure of the larvae to the ice was made as brief as possible and in 

 most instances extended to a few seconds. It was found that the 

 larvae would resume their normal activities within a minute after the 

 exposure, and this treatment seemed to have no material effect upon 

 the larvae so far as altering the normal numbers of molts, since the 

 results of these tests are identical with those of 1910. 



