Currently two species of Tropilaelaps mites have been identified (Tropilaelaps clareae and Tropilaelaps koenigerum). Their natural host is the giant honey bee, (Apis dorsata), but it has also been found in other Asian honey bees, including the Himalayan honey bee Apis laboriosa, the Asian hive bee Apis cerana and the little honey bee Apis florea. They can also infest colonies of the western honey bee (Apis mellifera). Although their exact geographical range is not fully known it is thought to be restricted to tropical and sub-tropical parts of Asia at present. However, with the globalisation of the beekeeping industry there is significant potential for this parasite to be spread worldwide by movement of bees in a similar manner to the Varroa mite.
Tropilaelaps mites seriously affect developing brood. They cause the death of both brood and bees which leads to colony collapse, often causing any remaining bees to abscond. The reddish-brown mites are about 1mm long and 0.6mm wide and visible to the naked eye. They are very mobile moving about easily and quickly in the hive. All stages of the mites feed on the haemolymph of the honey bee larva causing serious damage to it during its development and with the potential to introduce viruses into the larval body. Because Tropilaelaps mouthparts are not strong enough to penetrate the coating of the adult bees the mites rely solely on brood for their food. Because of this they are not thought to be able to survive for very long in colonies where there is no brood present. This understanding of their life history can be used to reduce the infestation of Tropilaelaps in managed colonies by inducing a broodless period.
Where mite levels are high, Tropilaelaps infestation will cause damaged brood with an irregular brood pattern and stunted and deformed adults. Although the life cycle is similar to the Varroa mite there are some differences. Tropilaelaps has a shorter life cycle than Varroa and a faster development time so it produces more offspring. Mite reproduction takes place in the sealed cell and while they will reproduce in both worker and drone cells they have a preference for drone cells similar to Varroa but not as marked. Forty eight hours after the cells are capped the female Tropilaelaps mite lays 3-4 eggs which will hatch after 12 hours. The larvae pass through a number of nymphal stages before reaching adulthood and mites are fully developed in 6 days. Mite infestation levels can be quite high with as many as 14 adults and 10 nymphal stages recorded in a single cell.
Because the mites cannot suck 'blood' (haemolymph) from the adult bees the time period that the mites spend on the adult bees is very short. Females carrying eggs will die within 2 days if they cannot lay their eggs on larvae so they are poorly adapted to survive in colonies where there are long periods without brood. Mites move to other colonies using the movement of adult bees during drifting, swarming and robbing giving a slow natural spread of the mite. However, the movement of infested combs and colonies by beekeepers the most important means of rapid spread of the parasite between colonies and into previously uninfested areas. Regular collection and examination of floor debris or uncapping drone brood is the best method of detecting infestation in managed colonies.
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- Author Bees for Development
- Publisher Bees for Development
- Published Date October 2016
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