A. GLENN RICHARDS 153 



what sticky eggs. This reasonable interpretation is supported by the better 

 paralleling of curves in figure 7D where the weighed egg lots were divided 

 into two parts for incubation at the two temperatures, whereas the ex- 

 tractions being performed necessitated the use of separate egg lots for the 

 curves in figures 7A-C. (See also 8A.) 



It is well known that the oxygen consumption of insect eggs increases 

 gradually through development and then rises sharply at the time of 

 hatching. It seemed unnecessarily laborious to determine total oxygen con- 

 sumption throughout development at various temperatures. The values 

 given in figure 6 are based on recently hatched larvae. Making the assump- 

 tion that the shape of the curve for oxygen consumption versus develop- 

 mental stage will be similar for all temperatures, the values from the 

 recently hatched larvae can be used to obtain ratios of expected energy 

 utilization at various temperatures.'^ These ratios are calculated in table 

 2 both on the basis of a /x value of 10,000 for oxygen consumption (this is 

 the line drawn in fig. 6) and on the basis of a /x value of 14,000 (the value 

 obtained in an earlier independent determination plotted in fig. 10) . Since 

 the water content remains constant (measured values 68%-71%) one would 

 expect agreement between ratios of dry weight losses and oxygen con- 

 sumption. Agreement is closely approximated at constant incubation tem- 

 peratures if the oxygen consumption has a yu, value of 14,000; less closely 

 but still approximately if the /x value is 10,000. The data suggest that when 

 incubation is at constant temperatures, the day-degree accumulation will 

 be equivalent to calorie-counting. 



Since we have at present no way of estimating how much loss of dry 

 weight can be tolerated, more interest centers on fractionation of the dry 

 weight loss. The average amounts of ether extract are 26-30 ;u.g/egg for 

 eggs with live weight averages of 225-240 fig. Somewhat less than half of 

 this ether extract is lost in incubation at 25°, about half at 17°, about two- 

 thirds at 15° and by extrapolation nearly complete loss would be expected 

 at 14°. But a Soxhlet extraction does not distinguish between fats which 

 are present as available food reserves, and fats of structural importance 

 such as cuticular waxes, nerve sheaths, etc. To a first approximation it 

 seems reasonable to conclude that on the average the fat reserve available 

 for energy is nearly exhausted following incubation at 15° and would be 

 inadequate for incubation at 14°. At the lower temperatures there are also 

 significant losses in the ether residue fraction but we have at present no 

 data to show whether this is due to loss of carbohydrate or protein or some- 

 thing else. 



Further support for the preceding interpretation comes from a consider- 



^ The energy expenditure to produce a larva can be calculated approximately from 

 the measured weight losses. It is only a few tenths of a gram calorie at 25°C. 



