30 



pupae of ^. geminata (ingestion of the pupae was confirmed 

 by observation) , and spores mixed with their regular diet. 

 In addition to examining pupae for pathognomonic signs, 

 aqueous extracts of pupae were examined by phase-contrast 

 microscopy for spores in case external signs were not evident. 



Larvae of H. zea and their rearing media were obtained 

 from Mr. D. W. Anthony, Agricultural Research Service, USDA, 

 Gainesville. The protocols for conducting infectivity tests 

 with B. dimorpha included those used by Anthony et al. (1978) 

 to infect H. zea with H. algerae for mass production of spores. 

 Twenty larvae 4-5 days old were held in isolation without 

 food or water for 24 hr , fed 0.1 ml of a suspension containing 

 ca. 10 spores per ml, and then placed on fresh media. Twenty 

 larvae 8-10 days old were allowed to consume one diseased 

 S^. geminata pupa each, and an additional 20 larvae 8-10 

 days old were injected with 2-10 ul of spore suspension. 

 The adult moths were examined by phase-contrast microscopy 

 ca one month after they had ingested or been injected with 

 spores . 



Results 

 The B. dimorpha did not persist in S^. invicta or S. 

 richteri for more than a few generations (Table 1) . Three 

 weeks after the final feeding of B. dimorpha spores, the 

 S^. invicta colonies were infected at the rates of 6% (colony 

 #1), 44% (colony #2), and 4% (colony #3). The colony of 



