413 



1919 and 1920 larvae (see Tables XXIV to XXVII), the curves shown 

 in Fig. 26 were drawn, and on the basis of these curves the velocity chart 

 (Fig. 27) was constructed. It is a provisional attempt, but it summarizes 

 our experience with hibernated larvae. The method described for the 

 pupae was used with this chart. All two-hourly readings of temperature 

 and humidity above 40° F. from January 1st to the first pupation were 

 entered on the chart. A curve was drawn with alpha as 47.3° and the 

 recorded temperatures were corrected ; the substitution-quotient proved 

 to be 197 for the first pupation; mean for the first thirty, 227; first maxi- 

 mimi, 265 ; mean of first modal group, 283 ; second maximum, 441 ; mean 

 of second modal group, 443 ; mean of third modal group, 725 ; mean of 



Table XXIV. Hibernated larvae at approximately constant temperature, 191S. 



Air flow was 8 mm. per sec. for all cages except AW^. which was 10. 



last group to first blank day. 758. The figures are quite close to those 

 predicted from the constant-temperature experiments. It was not possible 

 to check over other years, as hygrothermograph records were wanting. 



In working over these data, a new method was devised. The weather 

 data were plotted on the chart only once ; and the sum and mean were 

 determined for temperature, humidity, and velocity from January 1st to 

 May 20th, when the last larva pupated. The data were carried forward 

 from day to day in tabular form. This saves time, but the other method 

 with overlapping of plotting on the charts, generally has the advantage of 

 showing the distribution of the two-hour readings associated with the 

 various groups. 



