18 TECHISriCAL BULLETIN 149, U. S. DEPT. OF AGEICULTUEE 



that were infected before their first flight. These young bees avoid 

 the light and consequently remain in the hive imtil the disease is 

 well advanced. In artificially infected colonies the first crawlers 

 appear in from one to three or four days, depending largely upon 

 the virulence and rate of growth of the fungus, and the quantity of 

 inoculum used. Bees were seen to leave the hive and fly heavily. 

 Some fly for only a short distance, then fall to the ground as if too 

 weak to maintain flight. Several such short flights may be made by 

 diseased bees while sufficient strength remains. When too weak to 

 fly, they crawl and frequently attempt to take wing from the tops 

 of grasses or stems, but fall to the ground only to try again. Death 

 usually occurs within a few hours after they have come to the stage 

 where they are no longer able to fly. When not too weak, the crawl- 

 ers taken from the shade into bright sunlight or a warm room may 

 recover sufficient strength to take wing again. This apparent re- 

 covery lasts for only a short time", and death occurs as soon as if the 

 bees had remained exposed to the lower temperatures. Cowan 

 (9, p. 189) attributes the loss of flight in bees infected with Miwor 

 mucedo to pressure exerted by developing mycelium and the con- 

 sequent inability to distend the air sacs. In the case of Aspergillus 

 infection, however, a general weakening as a result of disease seems 

 to account for their inability to fly. 



No important changes in appearance occur at death. The body 

 of the bee retains its normal color and shape. The abdomen may or 

 may not be distended, since this depends upon the quantity of food 

 consumed by the diseased bee just previous to death. The body ap- 

 pendages retain their normal position in relation to the body, which 

 may lie in any position. A slight increase in the hardness of the 

 abdomen may have occurred at death, though this harderiing has 

 been immediately preceded by a softening of the infected tissues. 

 Soon after death, if the original infection was heavy and the sapro- 

 phytic development of putrefactive bacteria is not too rapid, the 

 abdomen becomes noticeably harder than in normal bees or in bees 

 dead of disturbances not of a fungous nature. The muscles of the 

 thorax, on the other hand, usually become considerably softer soon 

 after death, as can be noted by crushing them between the fingers or 

 under a cover glass. This character is of little diagnostic value, 

 however, as the same symptom is present in bees dying of other 

 causes. The increase in firmness of the abdomen at this time is, 

 therefore, the only distinctive external symptom of fungous infec- 

 tion. After death the firmness remains or increases, and the tissues 

 of the abdomen may become quite hard. The thoracic muscles, after 

 first softening, also increase in rigidity, and then upon drying 

 become of chalklike gonsistency. 



When the abdomens of these dead bees are dissected for micro- 

 scopic examination the digestive tract and surrounding tissues are 

 found to be tough in texture and are less easily crushed than in the 

 case of healthy bees or of bees dead of other diseases. While the 

 ventriculus of the healthy bee spreads evenly when pressed under a 

 cover glass, the ventriculus of a bee dead of mycosis offers consider- 

 able resistance to pressure. Teasing it apart with needles is often 

 necessary to prepare mounts that will transmit sufficient light for 

 satisfactory examination. 



