A. GLENN RICHARDS 



151 



find anything critical or limiting in the hatching process of Oncopeltus 

 failed; del)ilitatcd young hugs died before, during or after hatching with 

 no discernible rclationshij) to the hatching process itself. 



Since no specific explanation of results was located in tests such as those 

 itemized in the above paragraph, we returned to an analysis of the time- 

 temperature curves. No useful ideas came from curves such as those shown 

 in figures 1-3. Expressions concerning them seem no more than juggling 

 algebraic or arithmetric terms — even though they have practical use for 

 forecasting they give no clue as to what is added or how it is added. The 

 situation can hardly be as simple as the mere summation of similarly ac- 

 tivated chemical events because this would leave unexplained the >10% 

 discrepancy at the end of curve B in figure 2. A clue is forthcoming if we 



Fig. 6. Comparison of oxygen 

 consumption of recently 

 hatched Oncopeltus larvae 

 {solid circles) with the develop- 

 mental rate of Oncopeltus eggs 

 (open circles). The develop- 

 mental rate curve is drawn as a 

 broken line for the calculated 

 values at subthreshold tempera- 

 tures. Actual rates of develop- 

 ment available in fig. 1 ; O2 con- 

 sumption at 30°C is 0.39 mmV 

 larva/hr. 



tr 



5i 



4- 



3- 



32 



36 



re-plot the developmental rate data as an Arrhenius-type plot and compare 

 it with a similar plot for oxygen consumption (fig. 6). (No attempt will be 

 made to justify the drawing of a series of straight lines through the points 

 for developmental rate — it is so drawn here for illustrative purposes.) 

 Whether one draws straight lines or smooth curves through these points, 

 the fact remains that oxygen consumption, which is linear throughout 

 more than the viable range, nearly parallels developmental rate in the 

 range 20°-30° but deviates widely from it below 20°C.- It follows from 

 these curves that progressively more and more energy should be required 

 to complete development as the temperature is lowered further below 20°C. 

 The above is substantiated by measurement of weight losses following 

 incubation at 25°, 17° and 15°C (fig. 7 and table 1). Ignoring the variation 



■If one calculates from the straight lines drawn, the developmental rate has a fi 

 value of about 13,600 from 20° to 30°C, and about 46,000 below 20°C. 



