390 



drawn; while it did not purport to be extremely accurate, it was an 

 approximation serving to check the data available. 



With a view to further corrections and adjustments of the chart, 

 the readings of temperature and humidity were taken for representative 

 pupae of spring and summer groups from Glenn's 1915, 1916, and 1917 

 data, and plotted on the chart in the manner shown in Fig. 17, a dot 

 being placed on the chart for the temperature and humidity of each two 

 hours during the pupal period for each group. The dots between each 

 pair of heavy velocity lines (representing 5 velocity units, except at the 

 low temperatures where the first interval is 2 units and the second is 3 

 units) were taken together, and mean humidities, H, mean temperatures, 

 P, and mean velocities, V, were computed for numbers of dots, N, as 

 shown at the right of Figs. 17, 19, 21, and 22. The mean velocities were 

 then plotted on the mean temperatures to make a curve similar to Fig. 18. 

 When temperature substitutions were made, it was found that the sub- 

 stitution-quotients were too large for those groups of pupae subjected 



Fig. 16. The long curve is the full-length velocity curve for the experi- 

 ment DD made by plotting the velocities crossed by the line DD in Fig. 15, on 

 the corresponding temperatures. The curve in the upper left-hand corner is 

 a curve of correction for reducing temperatures outside the staight-line limits 

 to a value with the same velocity on the straight line. Read from the right- 

 hand side of the curve, 109° equals 59.8° on the straight line, etc., as shown 

 in figures at the right. Follow the arrows and broken line beginning on 108° F. 



Note: The curves in this article are not drawn with the straight-line portion 

 making an angle of 45° with the base line, as all are trial curves. Figures 16, IS, 

 and 20 were intended to be so drawn, but the draftsman made the vertical scale 1.1 

 times the horizontal instead of 1.07 (see page 383). The values in Table I, when 

 plotted for average daily variations, make a 45° angle within the sliaded area of 

 Fig. 15 when the scale is such tliat one developmental unit equals one degree of 

 temperature. 



