114 PROCEEDINGS ENTOMOLOGICAL SOCIETY 



of moisture contained therein. Furthermore, it is obviously 

 necessary, in order to get a perfect formula, to consider the 

 sex of the developing weevils. The question has been put to 

 a mathematician who has given considerable study to biono- 

 metrics and he stated that the only way that a formula could 

 be derived for this condition and the only way that a curve 

 could be plotted would be by the use of the three dimensions. 

 This paper has been introduced in order to warn other en- 

 tomologists against coming to hasty conclusions about laws of 

 development, and to urge those who have the time and in- 

 clination to make thorough studies of the various factors in- 

 fluencing the development of the insects which they can 

 study. 



During the very full discussion of this paper Mr. Pierce 

 added that the minimum fatal temperature of the boll weevil 

 seems to be 12 F. and the maximum fatal temperature 123 F. 



In reply to Dr. Howard's question as to whether the weevil 

 was not now able to stand colder temperatures than formerly 

 Mr. Pierce stated he could not say definitely, but thought 

 that certain apparent discrepancies in statements about mini- 

 mum temperatures would be accounted for by the law of alter- 

 nating temperature. It is well known that sudden alternation 

 of otherwise harmless temperatures is frequently fatal. 



Mr. Pierce stated that the minimum isotherm of 14 almost 

 corresponded with the line of winter control of the boll weevil. 



In reply to Dr. Howard's inquiry as to the extent of the 

 use of 43 as the zero of effective temperature, Mr. Pierce 

 stated that it first came into the literature of botany in France, 

 but was adopted by Merriam in his study of life zones. Later 

 on this zero was accepted without research for the codling 

 moth, boll weevil, bollworm, cattle tick, and many minor in- 

 sects. It is very important to understand the law of effective 

 temperature. In the case of the cattle tick the recommenda- 

 tions were based on 43 where the zero should be nearer 50, 

 and this is a very important point. 



Dr. Hopkins spoke of the difference in seasons, and said he 

 had abandoned temperature records and now relied on the 

 conditions of certain plants to indicate real time for action; 

 that the temperature law governing insects also governs the 

 plants, a striking example being Chermes, which is immune to 



