How do varroa mites harm honey bee colonies?
- By transmitting viruses
- By increasing the bees’ susceptibility to diseases
- By destroying the colonies’ food reserves
- By reducing the lifespan of worker bees
- By decreasing the quality of the food produced by nurse bees
- By causing varroosis, which gradually weakens the colonies
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Correct answers: 1–2–4–5–6
The action of the varroa mite has numerous consequences for honey bees.
Injury:
To feed, the varroa pierces a hole in the cuticle of the larva and the adult bee. This perforation constitutes an entry point for bacteria and viruses.
Loss of body mass:
Parasitized bees emerge with a body mass deficit of approximately 10%. This deficit is never compensated for in the imago.
Increased susceptibility to diseases:
By feeding on the bee’s fat body, the varroa removes a large proportion of the components required for proper functioning of the bee’s immune system.
Deformation:
Approximately 10% of bees parasitized at the nymphal stage emerge with atrophied/deformed wings and a shortened abdomen. These bees die a few hours to days after emergence. The bee may also die in the cell before emergence.
Reduction in the size of the hypopharyngeal glands:
Bees parasitized at the larval stage will be poor nurse bees. The brood food they produce is of lower quality, which has consequences for rearing the next generation.
Reproductive disorders:
Parasitized drones are smaller and weakened. They no longer have the physical capacity to fertilize virgin queens during the nuptial flight.
All these aggressions by the varroa mite, collectively referred to as “varroosis,” result in a reduced life expectancy of bees. At the colony level, this leads to progressive weakening, reduced honey production, and increased winter losses.
► see also: Varroa destructor