25 



had extruded their polar filaments. The 51 (2.9%) NMB spores 

 that had not extruded their polar filaments were probably not 

 quite mature, as they were very slightly less refractile 

 or less deep amber internally than mature spores. 



Membrane bound spores did not appear to be infective 

 per OS for S_. geminata . Examination of meconia showed that 

 few if any MB spores had extruded their polar filaments 

 while in the larval gut. A total of 274 mature, nonextrud- 

 ed MB spores were seen in the 20 meconia, but only one body 

 was seen which strongly appeared to be an extruded MB spore. 

 Five additional bodies were seen that resembled extruded 

 MB spores but almost certainly were not. The meconia con- 

 tained occasional empty walls of ingested or gut unicellular 

 fungi, some of which superficially resembeled extruded MB 

 spores; extruded NMB spores were distinct. 



Discussion 

 The cycle of B. dimorpha infection within an ant 

 colony may be summarized as follows: NMB spores develop 

 in the hypodermis, producing clear areas in the heads, 

 petioles, and gasters of pupae. As the infection 

 progresses, the cuticle becomes very fragile and eventually 

 ruptures. The adult ants cannibalize these ruptured pupae 

 but do not ingest the spores. Instead, the spores, together 

 with other particulate matter, are diverted to the infra- 

 buccal cavity and formed into an infrabuccal pellet. This 



