Similar stocking and treatment procedures were used in 

 temperature-delayed feeding-growth experiments. Food was witWield from one 

 group at each temperature, and one group at each temperature was given food 

 at the beginning of the experimental period. Initial dry weight measurements 

 were made on a sample of 20 larvae at the beginning of the experiment. At the 

 time each group was given its first food, a sample of 10 larvae from the unfed 

 lot was weighed. At the end of the observation period all of the larvae in each 

 treatment were measured and weighed. In cases where an intermediate growth 

 observation was made between the time of first feeding, and before the end of 

 the experiment, a sample of 10 larvae was used to establish growtli of the 

 population to this point. 



RESULTS 



Figure 16-1 shows the effect of delayed initial feeding on groups of larvae 

 maintained at four temperatures. The survival time of tlie unfed control 

 decreased with increasing temperature. The time to 50 percent mortality for 

 unfed groups was 19, 21, 25 and 27 days after hatching among groups 

 maintained at 24, 21, 18 and 15°C, respectively. Survival among early fed 

 groups was generally higliest in each temperature treatment. Among groups in 

 which food was provided for the first time after up to 50 percent of the 

 population had died, a portion of those remaining alive survived through the 

 end of the observation period. A "point-of-no-return" beyond which survival 

 could not occur even when food was provided, was nowhere in evidence in 

 these experiments. In each temperature treatment the longer food was 

 withheld, the greater the total mortality each group suffered. In cases where 

 some additional mortality was observed after food was presented, there was 

 generally evidence that the dead larvae had captured at least some food before 

 expiring. 



Figure 1 6-2 shows the result of an experiment in which initial feeding was 

 progressively delayed in a series of experimental groups of larvae held at five 

 test temperatures. Changes in dry weight were used here to measure the rate of 

 growth or shrinkage in fed and unfed groups at each temperature. Among 

 starved lots, longevity increased and the rate of weight loss decreased at lower 

 temperatures. Growth in dry weight increased rapidly once food was provided. 

 In general, the effect of delayed initial feeding was to defer the attainment of a 

 temperature-specific rate of growth of which larvae fed to satiation were 

 capable. 



Larvae receiving their first food at day six after hatching at 15*^C, had 

 scarcely recovered their initial weight at hatching by the end of the 25-day 

 observation period. Other groups which received their first food at day six after 



240 



