65 



only in the hypodermis (Jouvenaz and Hazard, 1978) , I attempted 



to answer the following questions: 1) If MB spores do 



not develop at all temperatures at which NMB spores develop, 



is it because sporulation is inhibited in the fat body? 



Or, 2) do NMB spores develop in lieu of MB spores in the 



fat body? And 3) are the effects of heat and cold the same 



in this respect? Resolution of these questions was attempted 



by histological examination of diseased pupae reared at 



high or low temperatures. 



Materials and Methods 



Ratios of Spore Types 



Fourth-instar larvae were removed from a heavily infected 

 laboratory colony and held in miniature nest cells at the 

 desired temperature (20, 22.5, 28, 32, and 35 C) overnight. 

 The temperatures in the incubators were monitored by hygro- 

 thermographs and mercury thermometers. Humidity was main- 

 tained close to 100% by the design of the cells (see General 

 Materials and Methods). Larvae that pupated during the 

 first 16 hr were discarded, as were those that had not pupated 

 during the next 24 hr. A contingent of nurses (young workers 

 primarily care for the immatures) captured from the brood 

 piles was introduced to care for the immatures. These were 

 removed shortly before the end of pupal life (at that time 

 they were no longer needed to groom the pupae) to facilitate 

 the examination and harvest of specimens in advanced disease. 



