120 



JOURNAL OF ECONOMIC ENTOMOLOGY 



[VoL 3 



10° 



30- C. 



Weeks 



case the coefficient of velocity is greater, being about 3 between 16 

 and 21°C. and about 2.2 between 21 and 26°C. 



The eggs of Samia cecropia also failed to hatch at the low tempera- 

 tures, but hatched at 32° C. though the latter temperature is seen to 

 be above the optimum from the fact that the time did not decrease 

 above 26° C. See figure 9. 



The eggs and pup^e of Tenetrio molitor were handled in the same 

 manner. The larvae have also been used, but as yet we have no 

 definite results, owing to difficulty in rearing them under the arti- 

 ficial conditions. The eggs and pupas 

 both failed to transform at 9° or 

 10° C. though they did so at 12 °C., 

 showing that the minimum temper- 

 ature for growth is slightly below the 

 latter temperature. The curves, fig- 

 ure 10, for the egg and pupa are of 

 interest as they are based on a large 

 number of individuals and show a 

 similarity which is to be observed in 

 other species, indicating that the eggs 

 and pupa^, Avhere they exist under 

 similar conditions are similarly af- 

 fected by temperature, while the ac- 

 tive larvffi is much more quickly in- 

 fluenced by changes of temperature. 

 The eggs of Leptinotarsa decemlin- 

 eata were similarly studied and the 

 results are shown in figure 11. The 

 time at 12° C. is questioned because of 

 inaccuracy in the records. The major portion of the curve is of in- 

 terest when compared with the work of Girault and Rosenfeld in 

 which the time of incubation was determined in Georgia and Ohio 

 under natural conditions, using the average mean daily temperature 

 for the period. It will be noted that the curves between 23.5° and 

 28° C. are very similar, but that in Georgia the time is prolonged at 

 29°C., while in our incubators it continued to shorten up to 32.5°C. 

 This may possibly be due to dryness of the atmosphere in Georgia at 

 the time of the observations, of which we have no records. It is 

 known that lack of moisture at high temperatures very quickly lowers 

 the optimum for development. In our own work we have not used 

 apparatus by which we could maintain a constant degree of moisture, 

 but vessels of water have been placed in the incubators and fairly 



Fig. 12. Relation of tempera- 

 ture to life cycle of Cidex pipiens 

 according to data of Kerschbau- 

 mer (original). 



