232 DISEASES OF FLIES 



knowledge of the complete cycle of development, methods of 

 infection, and the conditions which determine the persistence 

 of the vitality of the fungus from the end of one fly season to 

 the beginning of the next is necessary" (Bernstein, 1910, p. 41). 



Knowledge on all these points is, however, very incomplete. 

 Before the disease can be artificially reproduced on a large scale 

 artificial cultures of the fungus must be obtained. Owing to 

 the overgrowth of common harmless species of fungi on the 

 bodies of flies dead of empusa great difficulty has been met 

 with in attempting to grow E. vmscce on artificial culture media, 

 and until recently little success has been reported. 



Recently, however, Morgan (19 12) very briefly reported that 

 he had succeeded in cultivating the fungus " directly from the 

 fly in liquid horse serum three months old, from which it can be 

 subcultured on to blood agar." All the cultures were grown 

 at 37"" C. Hesse (29, Xl, 19 12), who lately published a short 

 popular article on the subject, also believes that he has suc- 

 ceeded. In a letter to the writer he made the following statement. 

 In May 191 2 he contaminated the bodies of recently killed flies 

 with a fly that had died of empusa in the previous autumn. 

 Within four days a fungus of the mucor t}'pe appeared. The 

 spores obtained from this growth he cultivated on egg-yolk in 

 a jar containing sufficient water to maintain a saturated atmo- 

 sphere. He later succeeded in infecting flies in a cage b}' 

 allowing them to feed on a paper smeared with syrup containing 

 spores. By the same means flies in a workshop and in an open 

 room were also apparently infected. Experiments on larvse 

 were inconclusive ; larvae bred in manure, infected with spores 

 from cultures, pupated but the imagines failed to appear. 



Hesse therefore appears to have cultivated a fungus, which 

 produces an empusa-like disease in flies, but further observations 

 are necessary before its identity with E. imisca, or its capacit}- 

 for producing disease, is fully established. Should it be found 

 that both adult flies and larvai can be easily killed with this 

 organism, a very effective means of reducing the number of flies 

 will have been obtained. 



