> That I understand,  but that’s robbing,  not drifting....  if that’s what the researchers were eluding to it would be extremely poorly worded for a bee paper.  Drifting would be moving into and takeingup some sort of residence in the wrong hive.   Not going into a crashing hive and taking food.

What they said is this:

Horizontal inter-colony transmission of honeybee pathogens can take various routes,
including: (1) contact between infected individuals or infectious materials during robbing (robbing
bees invade another colony to steal food resources); (2) contact between infected and
uninfected individuals from different colonies during foraging; (3) contact with infectious
material from the environment; and (4) "drifting" of an infected bee from its own to another colony.

Genotyping of workers collected from colonies
allowed us to identify genuine drifted workers as well as source colonies sending out drifters
in addition to sink colonies accepting them. We then used network analysis to determine
patterns of drifting. Only colony infestation with Varroa was associated with significantly
enhanced drifting. More specifically, colonies with high Varroa infestation had a significantly
enhanced acceptance of drifters, although they did not send out more drifting workers.

* * *

So, they distinguish between robbing and drifting. They state: "Only those passing guard bees and directly entering the hive on a straight flight path were sampled," so they do not think they are robbers at all. That was _my_ suggestion, looking for some explanation that fits with bee behavior.

Upon re-reading the paper, it seems clear that they are talking about conventional drifting in the sense that it is usually described, where bees wind up in the "wrong" hives. They found many more drifted bees in varroa infested hives than varroa free hives. This seems to imply that the varroa infested bees are drifting more than healthy bees.

The whole thing raises more questions than answers, I know. What we have observed is an influx of mites at certain times of year, and seeing that, we are looking for explanations. After all, mites spread very fast when they arrive in a new area. They must have very efficient ways of moving them about. 

PLB

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