360 ENTOMOLOGY 



A 



(i) "The relation between the temperature and the velocity of pupal 

 development in Tenebrio cannot be expressed in terms of Van't Hoff's 

 formula, but between 18.5 and 28 the relation is algebraic and the curve 

 representing it is a straight line. (2) Beyond these limits the curve 

 is not straight, but bends upwards at the lower temperature and down- 

 wards at the higher. Normal development is still possible at tempera- 

 tures between 15 (13.5) and 33. (3) In the metabolic activity of the 

 chrysalides of Tenebrio three stages are recognizable, corresponding 

 roughly to periods of disintegration of larval tissues, comparative rest 

 and formation of imago tissues. The metabolism in the tissue disin- 

 tegration period is practically of the same intensity as in the tissue for- 

 mation period. (4) The total amount of CO 2 produced during the pupal 

 life is the same at all the temperatures examined (21 33). There is 

 no optimum temperature with regard to metabolism. The relation be- 

 tween the temperature and the average CQz production per hour 

 follows the same curve as that found for the velocity of development. ' ' 



Sanderson found that pupae of the meal worm, Tenebrio molitor, 

 failed to transform at 9 or 10 C. but transformed at 12 C.; and that 

 pupae of the codling moth underwent little development below 55 F. 

 As a rule, the length of the pupal period is* rapidly shortened by 

 increase of temperature. In Michigan, in spring, pupae of the codling 

 moth developed in an average of 18.4 days at an average mean tempera- 

 ture of 66 F. (A. G. Hammar.) The boll weevil in summer had a pupal 

 period of 5.1 days at an average mean temperature of 74.3 F. (Hunter 

 and Pierce.) 



Life Cycle. The total life cycle of the boll weevil, as obtained by 

 adding egg, larval, and pupal periods, was found to be 17.65 days, at 

 an average mean temperature of 77.8 F.; or an average of effective 

 temperatures of 34.8 degrees; the total of effective temperatures being 

 614.2 degrees. As found by continuous observations on the same indi- 

 viduals, the life cycle was 17.7 days, with average mean temperature 76.9 

 F.; average of effective temperatures 33. 9 degrees, and total of effective 

 temperatures 600 degrees. (Hunter and Hinds.) Here, again, 43 F. 

 was assumed to be the " zero of development." 



Acclimatization. A few insects have become adapted to survive and 

 thrive under extremely high temperatures. Larvae of a fly, Stratiomys, 

 have been found in a hot spring in Colorado with a temperature of 69 C. 

 A water beetle in India was found in a warm spring at 44.4 C. Few 

 organisms, however, resist temperatures over 45 C. (Dr. C. B. Daven- 

 port.) Probably in successive generations of the ancestors of these forms 



