Social grooming of Apis mellifera
In social grooming (allogrooming) bees search each other’s fur and free each other from pollen rests and perhaps also from parasites. The more than 160 different shots of the grooming actions can be divided into three different groups depending on the trigger. All three variants can be observed significantly more frequently on days with flight activity (and the following day) than on days without flight activity.
Most often I was able to film this form of grooming. For no apparent reason, a bee suddenly starts grooming a neighboring bee. The bee’s activity or resting phase is suddenly interrupted. She probably notices pollen remains in the bee’s fur and begins to collect them. As in the other grooming variants, the cleaned bee willingly spreads the wings.
I have filmed this form of grooming almost as often. Here are the triggers for the social grooming violent shaking and grooming movements of a bee, which obviously wants to free itself from pollen rests and/or parasites in this way. Land/Seeley describe these movements in their 2017 work as “Grooming Invitation Dance”. I will not adopt this formulation. I do not consider the shaking movements to be a dance, but simply an intention to free oneself from pollen. The movements do not follow a certain choreography, the bees shake themselves only with presumably maximum intensity and interrupt this in irregular distances by grooming movements. As with the above variant, a neighbouring bee becomes active, which wants to collect pollen remains from the fur of the shaking bee.
Also with this variant the goal is probably the collection of pollen remains. Individual bees make it at least periodically to the task to search one bee after the other and to groom them. All grooming bees were only active from the late afternoon. It is quite possible that the same bees collect pollen during the day outside the hive.
Varroa mites with fatal injuries on the screen bottom board
It is a fact that in some colonies Varroa mites with massive injuries are found on the control board. Since the control boards are protected from the bees by a grid and no other known inhabitant in the hives can be considered for the injuries (I can exclude this due to the frequency of the controls), the injuries can only have been inflicted by bees outside the control board.
Now the question arises where the Varroa are attacked by the bees. Are they stripped and attacked by the bee itself? Are perhaps only the mites moving on the honeycombs attacked? Do they fall victim to bees that open the capped brood? Or do neighbouring bees attack Varroa mites on bees, perhaps during social grooming?
Current IR images from the beehive cast doubt on social grooming as the cause of the injuries. Even bees that have physical contact with the varroa during social grooming obviously don’t recognize them as pests and don’t bite the mites. Apart from that varroa move amazingly fast and safe on the bees, they evade the cleaning bee.