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parasite as a dimorphic species on the basis of light micro- 

 scopy studies of the life cycle, and the statistical improb- 

 ability of a dual infection occurring at high frequency, 

 but they were not able to experimentally demonstrate by 

 feeding tests that both spore types were produced by the 

 same microsporidium. 



Adult fire ant workers feed liquid food to larvae in 

 all instars, but solid foods to f ourth-instar larvae only 

 (Petralia and Vinson, 1978). A pellet of solid food is 

 expelled from the infrabuccal cavity and placed on the prae- 

 saepium of a larva by a worker, and the pellet is consumed 

 by the pupa. This method of feeding larvae suggested a 

 cycle of infection from ruptured pupae to f ourth-instar 

 larvae vectored mechanically by adults via the infrabuccal 

 pellet. This study was conducted to 1) determine the mode 

 of intracolonial transmission of infection, 2) to determine 

 whether one or both spore types are infective, and 3) to 

 verify that B. dimorpha is a dimorphic species. 



Materials and Methods 

 Boiled egg yolk wetted to a paste consistency with 

 a suspension of spores was offered to a small, healthy colony 

 of S^. geminata , which was allowed to feed for 24 hr. A 

 sample of workers trapped immediately after feeding was 

 held one hour, killed by freezing, sectioned into the three 

 body parts, and examined by phase-contrast microscopy to 



