FUNGOUS DISEASES OF THE HONEYBEE 39 



pathogenic fungi grow. Infection from this source, however, is not 

 liliely to become epidemic. 



Infection from molded combs, equipment, and dead bees can be 

 considerably reduced by care about the apiary. During the winter 

 ample provisions should be made for the escape from the hives of 

 metabolic \Yater vapor. The bottom board should be cleaned of 

 molded bees as early in the spring as weather conditions are suitable 

 for manipulating the bees without danger of chilling them. Brood 

 combs and extracting combs, when not in use, should be stored in dry 

 rooms to prevent pathogenic fungi from growing on them. 



In order to prevent the possible occurrence of disease, all badly 

 molded combs and equipment used inside of the hive should be 

 dipped for a few minutes in a 20 per cent solution of formalin 

 in water or exposed to formaldehyde gas in an air-tight chamber for 

 two or three days. Molded hive bodies, bottom boards, and covers 

 which can not be dipped readily should be washed with the same 

 solution. 



SUMMARY 



This investigation of the fungous pests of bees shows that para- 

 sitic fungous species occur on bees and brood, that they may cause 

 quite virulent diseases, that some of these forms reported as patho- 

 genic in Europe also occur in North America, and that there are 

 additional pathogens not heretofore reported. Certain other myco- 

 logical and biochemical data have been obtained and presented ; and 

 the effects of the invading fungi on the bees, their development, and 

 the disturbances caused within the body of the bees and larvae, have 

 been worked out in considerable detail. 



The fungi shown to be pathogenic include species of Aspergillus 

 and Mucor, and the Saccharomycetes. Several species of Aspergillus 

 and one of Mucor are most important. 



Members of the Aspergillus flaims series were shown to attack bees 

 more frequently than otiier forms of Aspergillus, but A. fwmigatus 

 is also virulently pathogenic. In addition, A. nidulans, A. niger, 

 A. glomaws^ and A. ochraceus attack bees in nature. 



Bees are attacked when spores of pathogenic fungi are taken into 

 the alimentary canal. They can be artificially inoculated by mixing 

 spores of the fungi with their food or by causing them to come in 

 contact with mature cultures. Infection also results when spores 

 ^re placed in the blood of bees by puncturing the exoskeleton. 



The spores germinate within the food contents of the alimentary 

 canal. The hyphae penetrate the wall, and under favorable condi- 

 tions all of ^Q softer tissues are attacked by the mycelium. The 

 spores of nonpathogenic fungi do not germinate within the ali- 

 mentary canal of healthy bees, but with some species they remain 

 viable and germinate after the death of the bee. 



Germ tubes were found not to penetrate the exoskeleton of healthy 

 adult bees. They may be induced to penetrate the skin of larvae, 

 but this rarely, if ever, occurs in nature. 



Before death the gross symptoms of mycosis are not distinct from 

 those of other disturbances in adult bees. At the time of death, or 

 soon thereafter, positive diagnosis can be made microscopically from 



