61 



The fat body is diminished in infected pupae, as is 

 evident in Figs 23 and 24. Several MB spores may be seen 

 in the latter electronmicrograph. 



The tissue specificities of the two spore types are 

 shown at increasing magnifications in Figs 25-27. The MB 

 spores are confined to the fat body; NMB spores are confined 

 to hypodermal and connective tissues, including that in 

 the deeper parts of the body such as the tissue encasing 

 the brain. The tissue section in Fig 25 is only 0.5 mu 

 thick; therefore, MB spores are seen in groups of 2-4 rather 

 than octets. The tissue sections in Figs 26 and 27 are 

 ca 6-8 mu thick, and thus show the octosporous pansporoblasts 

 better. 



Discussion 

 The pathognomonic signs of B. dimorpha infection in 

 S_. geminata reflect damage or destruction of the developing 

 adult cuticle. In the pupal stage of development, the integu- 

 ment of the adult ant forms under the integument of the 

 fourth- instar larva. During this period, the larval integument 

 is transformed into a protective sheath that adheres closely 

 to the developing adult integument and is moulted when the 

 development of the latter is complete (eclosion). Over 

 most of the body, the adult cuticle of pupae infected by 

 B. dimorpha appears to be damaged or inhibited only to the 

 extent that tanning is inhibited (Fig 26; also, the adult 



