How does varroa know the difference between a drone cell and worker cell.

[Gwr]

We know that Varroa prefers drone brood to worker brood but how do they know the difference?

Do they simply enter the cell at a certain stage in brood development and thus recognise something different in the brood lava between Drone and Worker or is it the cell size they recognise?

 

[B+.]

Do they simply enter the cell at a certain stage in brood development and thus recognise something different in the brood l

Yes

We know that Varroa prefers drone brood to worker brood but how do they know the difference?

I don't believe they do.
The longer development cycle of the drone gives the foundress mite more time to raise daughters (the first egg is male and subsequent eggs are female). This means more of her daughters will make it to adulthood before the cell is opened (males and immature females don't survive outside the cell)
if there is a preference, it may be due to a difference in the pheremone given off by the larva when it is ready to pupate.

 

[Uncle Betty]

We know that Varroa prefers drone brood to worker brood but how do they know the difference?

Do they simply enter the cell at a certain stage in brood development and thus recognise something different in the brood lava between Drone and Worker or is it the cell size they recognise?

A couple of quotes from the link below...

Drone cell preference is partly influenced by the properties of the brood cells

Rather than the shape of the cell, the time and construction effort needed for capping might be the relevant factor in determining the degree of mite infestation. In addition, stimuli from the larvae are involved. Drone comb preference was not influenced by the number of infesting mites or the absolute number of available cells (Fuchs 1990).

http://www.beeculture.com/a-closer-look-varroa-mite-orientation/


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[mazzamazda]

I don't believe they do.

I agree, I think it depends lots on the colonys too. Last year I had colonies with huge varroa loads, every drone I pulled out was varroa free. Random worker cells were loaded with varroa.

 

[domino]

Yes



I don't believe they do.

I read a few studies which have proven that varroa will select raised brood cells (i.e. drone) over other cells.

For example https://link.springer.com/article/10.1023/A:1007784130228?LI=true

The key appears to be the distance between the cell rim and where the larva is in the cell.

When a worker cell has its rim extended a varroa mite will enter that cell in preference to all the other cells on that comb.

 

[ShinySideUp]

I read a few studies which have proven that varroa will select raised brood cells (i.e. drone) over other cells.

For example https://link.springer.com/article/10.1023/A:1007784130228?LI=true

The key appears to be the distance between the cell rim and where the larva is in the cell.

When a worker cell has its rim extended a varroa mite will enter that cell in preference to all the other cells on that comb.

But why don't queen cells get infested then as they too have different cell heights? Unless the mite senses a different pheromone there is surely no way it can know it hasn't gone into a drone cell and although the cell time for a queen is less there is still the possibility of one or two mite offspring making it through.

 

[domino]

But why don't queen cells get infested then as they too have different cell heights? Unless the mite senses a different pheromone there is surely no way it can know it hasn't gone into a drone cell and although the cell time for a queen is less there is still the possibility of one or two mite offspring making it through.

Natural selection in action https://hal.archives-ouvertes.fr/hal-00890955/document

Essentially the Queen grows too fast for the baby varroa to mature before the cell is uncapped.

 

[Finman]

.
The basic instincts come from Apis cerana, the original host of varroa.
Asian bee has mites only in drone pupae.

I have seen a research, where dark worker cells invited better mites than new white drone cells.

 

[Barbarian]

Chemical Attractant

I have read that varroa are attracted by a chemical in drone cells.
Memory fails but I think it was a phallate used in paper manufacture.

There was info about it in a back issue of Bee Culture. Someone designed a sticky trap baited with the chemical.

 

[B+.]

I agree, I think it depends lots on the colonys too. Last year I had colonies with huge varroa loads, every drone I pulled out was varroa free. Random worker cells were loaded with varroa.

A lot of the reports talk about numbers of mites (which is due to the longer pupation period). The real question is: how many foundress mites enter drone vs worker cells? I've seen nothing that talks about the age profile of the mites in cells.

 

[Finman]

The real question is: how many foundress mites enter drone vs worker cells?

I've seen nothing that talks about the age profile of the mites in cells.

How are you going to use that data?
.

I try to find out before next summer, how I am going to do my hives broodless in July.
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[Beefriendly]

I have read that varroa are attracted by a chemical in drone cells.
Memory fails but I think it was a phallate used in paper manufacture.

There is a pdf of a talk by Mark J. Carroll that can be found here.
Carl Hayden Bee Research Center
USDA-ARS Tucson, AZ,
detailing his experiments with varroa attractants. Very readable.
Essentially a Capping Attractant CA is produced by brood as they are being capped and this volatile odour is extremely attractive to mites. Not sure if drone cells produce more of it or they emit it for longer.
When he floods the hive with CA it confused the mites as they don't now know where to go.

 

[B+.]

How are you going to use that data?

The number of foundress mites indicate the number of mites that actually went into the cells (protonymphs/deutonymphs were born there and inflate the number). If there is a preference for drone/worker brood, it is in the number of foundress mites that went into those cells.

 

[Finman]

.
There is a detailed article about varroa Orientation/Bee Culture. No need to invent it. For example new born works worker attracts mite.

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[Gwr]

But why don't queen cells get infested then as they too have different cell heights? Unless the mite senses a different pheromone there is surely no way it can know it hasn't gone into a drone cell and although the cell time for a queen is less there is still the possibility of one or two mite offspring making it through.

That’s a good point. I’d not thought of about the queen not being infested for one reason or another ( unless she is?).

It makes you think if the mite is clever enough to have worked out that if they affect queen, then indirectly it will affect its self by killing of the only thing it really does need, which is a good healthy queen to lay as many of the eggs to make the brood that the mite actually has to have to succeed.

 

[pargyle]

SO .... The honest answer (as in a lot of beekeeping questions) is ... we don't really know !

And ... even if we did ... at beekeeper level there's very little we could do about it. Best apply thoughts to those things that help our bees that we can influence. Finny was right for once ...

 

[mbc]

Interesting thread, I'd always assumed it was pheromones that attracted varroa preferentially to drone cells, weren't there attempts at varroa traps loaded with drone larvae pheromones at one time? obviously didnt work that well or they'd still be around.

 

[gregior]

Has anyone here ever seen mites in a Queen cell I haven;t?

 

[Hivemaker.]

Has anyone here ever seen mites in a Queen cell

Yes.

 

[foghornleghorn]

Has anyone here ever seen mites in a Queen cell I haven;t?

Yes