32 



S^. richteri had an infection rate of 5%. One month later 

 (day 49) , however, infection could be detected only in S^. 

 invicta colony #2, and the infection rate in this colony 

 had declined from 44% to 8.5%. One month later (day 80), 

 only one infected pupa (out of 786 pupae in the age group 

 that exhibits pathognomonic signs) was found in the colony. 

 By day 110, all of the 1,000 pupae that were examined were 

 free of disease. All four colonies remained free of B. 

 dimorpha on all subsequent examinations. In contrast, the 

 colony of S^. geminata from which the diseased pupae (those 

 fed to the test colonies) were taken maintained an infection 

 rate of ca 50% for 14 months. 



None of the other species of ants tested were susceptible 

 to infection by B. dimorpha (Table 2) . The H. zea was 

 not susceptible to infection either per os or by injection. 



Discussion 

 The B. dimorpha is host specific for S^. geminata . Although 

 S^. invicta and S^. richteri may be readily infected, the 

 parasite does not persist in these factitious hosts beyond 

 a few generations. The 9 species (representing 8 genera) 

 of ants other than Solenopsi s spp . proved refractory to 

 infection. While this is a very small sample of the living 

 species of ants, it is highly improbable that a parasite 

 that cannot maintain itself in factitious species of the 

 genus of its host would be able to infect species of other 

 genera. 



