i 7 8 



COLORATION IN LEPTINO'fARSA. 



and those of others is that a special effort has been made to change one factor 

 only in the environment. In this I have been successful. In most of the 

 experiments that have been recorded no attention was paid to relative humid- 

 ity. When pupae are inclosed in a dish or box in an atmosphere in summer 

 where the relative humidity is 60 to 70 per cent, and are then placed in an ice 

 box, the temperature is lowered, but the relative humidity is increased, and 

 thus two important factors are changed. Or if pupae are placed free in an 

 ice box the temperature is lowered, and the humidity is also increased almost 

 to saturation. On the other hand, in high-temperature experiments in which 

 an incubator is used the temperature is increased and the relative humidity 

 decreased to a point below that of the driest deserts. In such experiments 

 two or perhaps more factors are changed, so that the results are due to 

 changed complexes, and not to deviations in any single factor. In these 

 experiments a special effort has been made to change the one factor of tem- 

 perature alone, the relative humidity being kept between 65 and 70 per cent. 

 The general conclusions derived from these experiments accord well with 

 those of Fischer working upon Vanessidae, as also with those of a like nature 

 that have been made by others upon Lepidoptera. In the set of experiments 

 which follows the procedure has been quite different from that just described, 

 the animals having been reared throughout the entire generation under the 

 conditions of the experiment. In these experiments it was necessary that 

 much smaller numbers of insects be used, but the results are nevertheless 

 equally as conclusive as those of the preceding set. 



Experiment 8. To determine the effect of increased temperature upon the color and 

 color pattern of L. decemlineata when applied throughout life. 



Conditions. Temperature on the average 5.33 C. above that in nature, 

 with other conditions normal. 



Apparatus. Glass breeding tanks, as in experiments 1 and 2. 



In these experiments, which were conducted in the years 1898 to 1904, 

 2,000 larvae were used. The eggs were taken from a state of nature within 

 eight or ten hours after being laid, and placed in the conditions of the experi- 

 ment. From the 3,200 eggs used 2,000 larvae were hatched. These were 

 kept under the best of conditions as regards food and cleanliness. The tem- 

 perature records in the experiments are as follows : 



Table 58. Temperature conditions. 



