. Diseases of bees. Bees. 28 CIRCULAR 3 92, U. S. DEPARTMENT OF AGRICULTURE die outside. When large numbers of infested bees crawl from the hive at about the same time, the condition is known as mass crawling. Bees often continue to work for weeks after they have become infested by mites, and acarine disease may be well advanced in a colony before symptoms are noticeable. The most commonly rec- ognized symptoms are crawling and the loss of ability to fly. Crawl- ing may come on gradually when the disease spreads slowly within the colony, or it may develop rapidly and result in mass crawling. A
. Diseases of bees. Bees. 28 CIRCULAR 3 92, U. S. DEPARTMENT OF AGRICULTURE die outside. When large numbers of infested bees crawl from the hive at about the same time, the condition is known as mass crawling. Bees often continue to work for weeks after they have become infested by mites, and acarine disease may be well advanced in a colony before symptoms are noticeable. The most commonly rec- ognized symptoms are crawling and the loss of ability to fly. Crawl- ing may come on gradually when the disease spreads slowly within the colony, or it may develop rapidly and result in mass crawling. After mass crawling has occurred, the colony is freed of most of the diseased bees and may appear to recover temporarily. Mass crawling often follows a period of unfavorable weather. Crawling is frequently accompanied by retention of feces, swollen abdomens, and unjointed PiGUEE 18.—Acarine disease. Discolored trachea taken from the thorax of an infested bee. The mites that cause acarine disease can be seen through the tracheal waU. Mag- nified 75 times. (Photograph by J. Rennie.) DIAGNOSIS IN THE APIARY In healthy bees the tracheae are always pure white. In heavily infested bees the tracheae become bronzed or blackened in irregular spots. The presence of these spots is used as a symptom in diagnosis. With the aid of a lens that magnifies 6 or 8 times, the dark-colored spots can be distinguished. They may be few in number, or there may be so many that the trachea appears black (fig. 18). In making examinations for acarine disease in the apiary it is best to use crawlers. The tracheae of bees killed by other disorders often. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original
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