34 TECHNICAL BULLETIN 14 9, XT. S. DEFT. OF AGRICULTURE 



of conditions. Some of them occur regularly on brood combs under 

 proper conditions for their growth, whereas others are rarely found 



The specific descriptions have not been included, since they are 

 obtainable in standard works on mycology. 



The Aspergilli are widely distributed, and the various species 

 develop under widely different conditions. They are most com- 

 monly met with as saprophytes growing upon rotting fruits and 

 other food products in which there is a high concentration of sugars. 

 During dearths of nectar, spores of Aspergilli may be gathered by 

 bees with juices of fruit or other juices which contain sugar. They are 

 often found on the brood combs under certain conditions of moisture 

 which exist in weak colonies, or in hives in which colonies have died 

 out during winter or spring. Wet extracting combs when stored in 

 damp rooms may also be attacked by a number of the species. Many 

 of the species of Aspergillus, however, reach their typical develop- 

 ment under dry conditions. Grain in storage, dried fish, foods, and 

 herbarium specimens are frequently attacked by these. Some forms 

 are typical inhabitants of the soil. Still others are capable of be- 

 coming active animal parasites, attacking insects, birds, and mam- 

 mals, including man. 



Of the several hundred isolations of Aspergilli from bees affected 

 by mycosis, more than half were yellow -green spored forms of the 

 Aspergillus-f.avus-oryzae group. The greater number of these in 

 turn were of the A. flcwus series with comparatively long conidio- 

 phores. This may probably be accounted for by their virulent patho- 

 genic nature, their abundant spore production, and their widespread 

 saprophytic growth on a variety of natural substances including 

 extracting and brood combs. All of the organisms belonging to this 

 group isolated from bees from the chief beekeeping sections of the 

 United States and from Canada and Europe have been found to be 

 pathogenic when tested. Tests with a considerable number of races, 

 strains, or species of the group, obtained elsewhere than from bees, 

 seem to indicate that there is considerable difference in the degree of 

 virulence. Intermediate strains, all Imown as A. -fla/ous-oryzae^ have 

 been isolated from bees on but few occasions. These organisms, when 

 tested, attacked both bees and brood. Intermediate forms from other 

 sources have also given positive results, but the death rate among 

 bees was generally lower than Avith A. flavus. Other strains failed 

 to attack bees under similar conditions. 



A. oryzae was not isolated from bees, but at least one strain, A. 

 oryzae (113 L), obtained from the Thom and Church collection, 

 attacked a few bees in cages and an occasional larva when spores 

 were shaken over a brood comb containing uncapped brood. It is 

 only among the A. flaws series of this group, however, that patho- 

 genic organisms are found that are of importance as causing bee 

 diseases. 



The deep-green strains, which produce acid most abundantly are 

 the ones that attack bees most readily. On the other hand, the thick- 

 ness of the spore wall, which in A. flavus is about twice as thick as in 

 A. oryzae, may l3e a determing factor in protecting the spores from 

 the digestive fluids of the bee until germination can take place. 



