Diseases of bees / Ministry of Agriculture and Fisheries.

Date:
1948
Catalogue details

Licence: Public Domain Mark

Credit: Diseases of bees / Ministry of Agriculture and Fisheries. Source: Wellcome Collection.

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    anterior part of the tracheal system. Infection takes place through the migration of a gravid female mite into the thoracic tracheal system of a young, healthy bee. Infection has been shown to occur only during the first four or five days of a bee’s adult life. The mites can live only for a few hours when separated entirely from a living bee and only for a few days in the tracheal system of a dead bee. Soon after effecting entrance into the tracheal system of a young bee the gravid female mite commences to lay eggs. The nymphs emerge from these a few days later and, after a number of moults, assume the adult stage. The adult mites and their nymphs both feed upon the tissues of the bee. The damage that they do to the bee is probably due to three causes. First, multiplication of the mites in the thoracic tracheal system rapidly causes a partial blockage which impedes the proper diffusion of air within the system; secondiy, they weaken the host by the destruction of its tissues; and ee the by-products of the metabolism of the mite are toxic to the host. The strength of infected bees is thus impaired, their lives shortened, and the efficiency of the colony reduced. All this frequently occurs before any signs of disease have been observed by the bee-keeper. Those bees which survive until the thoracic breathing tubes have become packed with mites, in all stages of their life history, lose the power to fly, but are still able to crawl. Such crawlers are often seen in front of the hive, sometimes in considerable numbers, after a period of confinement due to unfavourable weather conditions. If breeding is going on apace and large numbers of young bees are emerg- ing from their cells, the rate of spread of this disease both within the colony and from one colony to another, can take place very rapidly. The disease is spread in the following ways: (1) From bee to bee within the colony, by migration of the adult gravid female mites from old infected bees to young bees. (2) By drifting. This drifting of bees from hive to hive in an apiary, owing largely to errors in home finding, may be reduced by placing the hives a reasonable distance apart, say 12 ft., and when manipulating hives, by taking care not to cause undue disturbance and confusion. The placing of hive parts in front of the entrance to the hive may be mentioned as one of the ways of causing confusion and consequent drifting. Landmarks, such as bushes, near the hives are very useful as they enable the bees to trace their own homes more readily. (3) By natural swarming, which affords opportunities for the mingling of bees from different colonies, bees from infected colonies sometimes joining a swarm from a healthy colony. (4) Possibly from colony to colony by robbing. It is, of course, the duty of all bee-keepers to take every precaution to prevent an outbreak of robbing and, should one occur, to take immediate steps to end it. (5) From apiary to apiary by the introduction of infected queens, colonies or nuclei, swarms and driven bees. The introduction of a truant swarm of unknown origin into an apiary is a most risky undertaking.