176 DR. V, E. SHELFORD ON THE LIFE-HISTORIES AND 



Lamp chiumeys containing larva3 that had been in the cool moist conditions 

 were transferred to the warm moist conditions. The larvse at once excavated 

 their burrows to dei3ths comparable to those o£ the larvae kept for some time 

 in the loarm conditions. One individual whose burrow was only 2 cm. deep, 

 dug to a depth of 6*25 cm. in 28 hours, and to 10 cm. in 48 hours. 



The pupal cells of purpurea limbalis are made by enlarging and sometimes 

 shitting the inner end of the burrow (PL 24. fig. 18). In the construction 

 of the pupal burrows the same relations to temperature are shown as in the 

 depth of burrows. Actual statistics were not preserved in the case of other 

 species subjected to experimentel conditions, but observations on scutellaris 

 and tranqueharica show that they respond to temperature in the construction 

 of the pupal cells in the same way as purpurea limbalis. Under experimental 

 conditions in which about 15 cm. of soil are heated (bottom 33°-39° C. ; 

 top 36°-41° C.) from above so as to give a difference of about one degree 

 for each 7' 5 cm. of depth, these species almost always constructed cells 

 as near the bottom as possible. In cool conditions (bottom 22° ; top 18°) 

 cells are usually constructed near the top; none have been noted at the 

 bottom. In view of these responses it is evident that marked differences in 

 the depth of pupation may be brought about in a given brood of the same 

 species by alternating short periods of warm and cool weather during the 

 time of preparation of the cells. Individuals at different depths would be 

 subjected to very different conditions during their quiescent stages. 



In the habitat of scutellaris the temperature of the soil at 2.00 p.m. on a 

 warm sunny day when the surface is dry, is about as follows : — Surface 47° C; 

 at a depth of 375 cm., 38° ; 7-5 cm., 35° ; 10 cm., 33^° ; 12-5 cm., 32° ; 

 17*5 cm., 30°. The surface of the soil is subject to the greatest extremes ; 

 the conditions become more constant, both in temperature and moisture, as we 

 go downward. 



Few observations have been made on the depth of pupation in nature ; 

 one pupa of C. scutellaris was found at a depth of 10 cm., while C. trancpie- 

 barica has never been observed. C. punctidata, which can be subjected to a 

 temperature of 47° C. during the quiescent stages without fatal results or 

 modification of the adults, pupates at a depth varying between 2*5 and 

 7-5 cm. 



The length of the prepupal and the pupal stages is related to temperature. 

 The process of development is probably most rapid when the temperature 

 during the day averages about 28°-30° C. (the temperature at which most of 

 the records here presented were made). At this temperature the length of 

 the combined quiescent stages has been noted as usually from four to six 

 weeks. If the temperature is lowered to 20° or 22° it is six to eight weeks, 

 and if lowered to an average of 15° to 17° it will be increased to ten or 

 twelve weeks. If the temperature be kept between 36° and 38° the time is 

 increased to eight weeks. 



