FUNGOUS DISEASES OF THE HONEYBEE 17 



kept in cages were attacked and killed within from two to four days. 

 With less virulent species the bees lived somewhat longer and a vary- 

 ing percentage of the inoculated bees escaped infection. At times, 

 with species not ordinarily found on bees, only about 5 or 10 per cent 

 of the inoculated bees died of infection. 



The results obtained in colonies were quite similar to those obtained 

 with bees in cages. When colonies were infected with one or two 

 brood-comb cultures of virulent species of Aspergillus, all, or nearly 

 all, of the brood and bees of the colony were killed by the fungi. 

 Illustrations A and B of Plate 2 show brood combs from infected 

 colonies after most of the field bees had died from infection with 

 AspergiJIiis favus. 



With less virulent organisms the death rate for the first day was 

 considerably lower, and at times only part of the population of the 

 colony Avas killed. In the latter case the activity of the colony 

 returned to normal after the infected combs had been cleaned and 

 the dead brood removed from the brood combs. 



When the inoculations were made by placing spores of pathogenic 

 Aspergilli in the blood of bees through needle punctures, disease and 

 death usually resulted. A few larvae were attacked as a result of 

 direct penetration of the skin by germ tubes. (PI. 1, D.) 



Symptoms of Mycosis in Adult Bbiis 



The first noticeable sjonptoms of infection by Aspergillus in adult 

 bees is their weakening and restlessness, and the continued effort on 

 the part of the sick bees to escape from the cluster of healthy ones. 

 In cages the earliest affected bees can be picked out from among those 

 not yet infected by selecting bees that continue to crawl at a time 

 when the greater number of bees are quiet. Crawling continues for 

 several hours, accompanied by a gradual weakening and loss of 

 definiteness in the movements. In from one to four hours the crawl- 

 ers become too weak to stand or crawl normally and move with a 

 staggering motion. They frequently fall and eventually become 

 unable to right themselves. During the crawling period bees some- 

 times lose the use of one or more legs. The affected legs are dragged 

 or used ineffectively in crawling. Weakness increases until the in- 

 fected bees are capable of only feeble movements of the legs, mouth 

 parts, and abdominal segmente.' 



Bees that are naturally infected or are artificially infected within 

 the colony show the same symptoms of disease as are shown by bees 

 kept in cages. As soon as attacked by the fungus, field bees fly or 

 crawl from the hive and usually die at a considerable distance from 

 the entrance. During weather favorable for flight probably not 

 more than 5 or 10 per cent of the infected bees die within or directly 

 in front of the hive. Most of these die at night and are young bees 



'These obserTations are comparable to tbose made by Turesson (26) on the toxicity 

 of molds to the honeybee and the cause of bee paralysis. As a result of his experiments 

 Turesson concluded that paralysis among bees Is caused by the eating of fungous spores 

 and mycelium. He claims to have found very little difference in the toxicity of the 

 different species that he tried and believes that toxic substances are present in most 

 fungi. He speaks of observing the germination of spores and development of mycelium 

 within the alimentary canal, but apparently did not suspect any of the organisms 

 capable of parasitizing bees. The writer's conclusions differ from the conclusions of 

 Turesson on this point. 



59850°— 30 3 



