To compare ihe degree of toxicily of the different moulds series 

 of experiments under like conditions, number of l)ees (laken from 

 Ihe same hive in all instances), quantity of fungous material fed 

 etc. were started on July 23. The results are given in the ahove. 

 O.i gram of Penicillium conditaneum given in 10 c.c. honey to 12 

 bees killed the bees within 4 days. Next in toxicity comes Mucor 

 Mucedo, which, the quantity being identical, killed the same number 

 of bees in 5 days, Penicillium sp. y Penicillium stoloniferum and 

 Cladosporium herbarum seem to have about the same degree of 

 toxicity to bees, and were all inferior in virulence to Penicillium 

 conditaneum and Mucor. 



The question of the difference in toxicity in different species of 

 moulds is very interesting. Species will likely be found which are 

 far more toxic to bees than those recorded in the above. The vi- 

 rulence of Penicillium puberulum, investigated by Alsberg and Black 

 (1) and discussed more in detail below, is slight compared with 

 toxic extracts obtained from species investigated by Sturli (23) and 

 others. Even different strains of the same fungus have been shown 

 to possess different degrees of toxicity. Penicillium stoloniferum 

 probably includes several »physiological varielies» some of which 

 are toxic and some nontoxic (Alsberg and Black 1). Otto (20) 

 found the Italian strain of Aspergillus fumigatus, more toxic than 

 the German, and the American strain of this fungus investigated 

 by Turesson (24) was likewise found to be superior in virulence to 

 the German. The climate has undoubtedly something to do with 

 the different degrees of virulence in the moulds, those of warmer 

 climates being far more toxic than those of temperate climates. 

 This would also explain why bee-paralysis is much more prevalent 

 and virulent in warm than in cold climates. 



Controls. 



During the time the feeding experiments were run conlrol cages 

 were used in every series. Four such series corresponding to the 

 series of feeding experiment with the different fungi were set up, 

 namely from June 27 — July 3; July 12 — 17; July 17 — 23; July 

 23—30. 



Serie s I. 



June 27. 15 bees were caged (taken from the same hive 

 as those used in the experiments with Penicillium sp. and Peni- 



