405 



These velocities, when used to calculate standard time for the period in 

 the apple from Glenn's Olney data, were divided into 650, which was regarded 

 as an approximately correct suhstitution-quotient, though the average time 

 calculated on that basis was 1.3 per cent higher than the actual time. (See 

 Table XI.) 



A substitution-quotient of 100 was tried for the time in the cocoon. This 

 gave an average calculated time 0.4 per cent lower than the average actual 

 time. When 750 was tried for the total larval life, it gave a mean calculated 

 time 1.6 per cent higher than the actual average time (Table XI). A substi- 

 tution-quotient of 73S would make the average calculated time agree with the 

 average actual time for Glenn's data. In view of the small series of observa- 

 tions and the striking variation in time, it was deemed unnecessary to change 

 the quotients used. 



It will be noted that 750 and 73S are materially smaller than the 763 used 

 in plotting Glenn's data (circles Fig. 24). This is to be accounted for by the 

 fact that the period of the stage under variable temperature is longer because 

 of the inclusion of temperatures at which development is slower or even at 

 a standstill. Glenn's corrected sum calculated on this basis was 744. His 

 correction, which amounted to 2.5 per cent for mean temperatures between 

 6S° and 78° F., apparently should be 3.4 per cent. For the higher temperatures 

 there are even greater differences between the substitution-quotient and the 

 uncoiTected sums. 



Turning again to the meagre experimental data, to consider them in the 

 light of the results with the Olney records, we find them in keeping with ex- 

 pectations based on other stages. When plotted on 650 as the substitution- 

 quotient, the curve should fall a little below the curve for variable temper- 

 atures, because constant temperatures give slightly slower development. (This 

 difference amounted to 7 per cent in the case of the pupae.) Since the ex- 

 perimental data are so meagre, all are plotted on a 650 basis, and only mean 

 points are shown. With the exception of the 81° point, all data are in the 

 straight-line limits (where means are correct). The 81° point, apparently, is 

 only slightly outside. The mean value of all experimental temperatures and 

 all velocities calcuated on the 650 basis falls on 74.2° F. and velocity 24.65 

 (see Fig. 24). The variable-temperature velocity line passes through 26.7, 

 and an increase of 8 per cent places the mean of experimental data approxi- 

 mately on the line which is within the range of expectations. The marked 

 variability of the experimental data is, in part, due to differences in kinds of 

 apples (see Table XXI). 



Hibernated Larvae. 



It has not been pos.sible to make a careful investigation of the period 

 of dormancy, commonly called hibernation, into which the mature larva 

 of the codling moth lapses in the month of August or even earlier, and 

 in which it remains until it has passed the winter or has received special 

 treatment in the laboratory. Many experiments were tried, but the restilts 

 were inconsistent. 



In a large series of experiments on the length of the pupal stage conducted 

 during the summer of 1917. very few of the larvae collected after July pupated; 

 of those collected on August 18th, only 15 per cent pupated; and none of those 

 collected later. The larvae failing to pupate in the August experiments, to- 

 gether with those collected early in September, after being left until October 

 19th under the experimental conditions supposedly suitable for pupation, were 

 subjected to various treatment.* 



• Stocks used in the experiment.^ nn the length of the larval and pupal periods 

 received better treatment. See pp. 374-.3S0. 



