66 



The uninfected pupae served as controls to monitor the rate 

 of maturation at the different temperatures. Infected pupae 

 were harvested only after eclosion of the controls, when 

 the disease had progressed to near the point of cuticle 

 rupture and spore production was essentially complete. The 

 completeness of spore production was judged by the percentage 

 of immature spores seen in phase-contrast microscopic examina- 

 tion. Spore ratios were determined only for those pupae 

 in which > 98% of the NMB spores appeared to be mature. 



The initial rearing study indicated that the develop- 

 ment of MB and NMB spores of B. dimorpha is inhibited by 

 both high and low temperatures. Therefore, an additional 

 study was conducted to determine the maximum age of the 

 host at which MB spore inhibition can be effected by raising 

 or lowering the temperature. Immature workers were divided 

 into five age groups and half of each group were incubated 

 at 20 C and the remaining half at 32 C. The age groups 

 were 1) fourth-ins tar larvae; 2) larvaform pupae; 3) early 

 pupaform pupae (eye development not yet evident); 4) pupae 

 whose eyes had developed sufficiently to permit diagnosis 

 of infection; 5) pupae slightly older, having first evidences 

 of clearing in the occiput. These groups were reared and 

 examined as described above. 



Spore ratios were determined by homogenizing individual 

 pupae in ca 1 ml distilled water in a 3 ml glass tissue 

 grinder, and examining this extract by phase-contrast 



