Final month I confirmed how we arrange a area research to attempt to reply a variety of questions on mite drift from collapsing colonies. Let’s proceed.

The Donor Colonies

We had arrange two mite-free Management Donor hives, and 9 high-mite Donor hives meant to break down (the tenth collapsed earlier than we had been prepared). Colony strengths averaged 9 frames coated with bees (vary 7-13). Beginning varroa mite infestation charges of the high-mite Donors (decided by alcohol wash) averaged 26 mites (vary 11-55, per degree half cup of bees [[1]]).

Tagging

Initially of the research on 17 September, we glued color-coded metal tags onto 50 non-flying bees in every hive, after which later tagged extra cohorts of bees (100-250 at a time) when their colony’s mite depend exceeded 30, or we noticed indicators that collapse was imminent (lack of power, deformed wings, or dying pupae). In some Donors that collapsed slowly, we tagged extra bees in the course of the course of. In all, we tagged a complete of 6230 bees, averaging 585 per hive.

Outcomes and Dialogue

Did the Tagged Bees Behave Usually?

I confirmed final month how we frivolously anesthetized and tagged the bees. A important query to think about is whether or not the method of tagging these bees modified their behaviors. So I watched them intently afterwards (Determine 1).

Fig. 1 We tagged staff shaken from brood combs, after which behaviorally-sorted to acquire non-flying, presumably “younger” bees. Checking again within the days after making use of the tags, the tagged bees gave the impression to be behaving like “regular home bees” on the combs, as on this picture.

What was placing was that within the first days after the preliminary tagging, we didn’t see any tagged bees on the entrances or flying. However after round 10 days, we had been shocked by seeing tagged bees all of a sudden seem en masse on the entrance — presumably as they shifted from nursing habits to guarding and foraging (Determine 2).

Fig. 2 What a shock to come back out to the Donor yard someday and see the tagged bees all of a sudden exhibiting themselves, exhibiting “regular” development in habits. It was actually conspicuous and spectacular! This confirmed that we had been tagging cohorts of bees of comparable behavioral “age.”

After which a couple of days later, we seen tagged bees performing as foragers (Determine 3)

Fig. 3 I watched a single red-tagged bee present up at some pollen that I had spilled, after which apparently recruit different foragers with the identical tag coloration. I additionally noticed tagged bees foraging upon spilled syrup the place we fill our feeder jars. All indications had been that the tagged bees had been behaving utterly usually.

Progress of the Colonies

The Donors: The 2 mite-free Management Donor colonies retained their power and well being all through the 74 days of information assortment.

All of the high-mite Donor colonies save one, sooner or later collapsed (D7 solely dwindled a bit). Some started collapsing in September, however most did so throughout mid-October. Some colonies collapsed comparatively shortly, others extra slowly.

The Receivers: All Receiver colonies remained in good well being. These within the residence yard with stickyboards maintained mite wash counts of zero all through the research, aside from 4 that had counts of 1 in the course of the peak of bee drift on 15 October.

Answering our Questions

We had a variety of inquiries to reply; let’s go over them one after the other.

Query: What proportion of staff from collapsing colonies drift to different hives?

This is among the major questions that this research was designed to reply.

Observations from the Donor Hives

It shortly turned clear that staff drift freely between close by hives (the Donors had been a number of ft aside from one another) (Determine 4).

Fig. 4 There was appreciable drift of tagged bees between the Donor hives, as evidenced by bees with completely different tag colours exhibiting up on the combs, as within the picture above. However since these hives didn’t have magnetic traps, we couldn’t quantify the complete quantity of drifting happening.

At remaining cleanup on the finish of the research, we recovered 44 drifted tags from the underside boards or floor in entrance of the Donors (2-13 tags per hive, with the drifted tags typically from probably the most closely-adjacent colonies). That works out to twenty% of all tags recovered, confirming that there’s a number of drift between close by hives.

Experimental limitation: These 44 recovered tags will be thought-about as a gross underestimate of what number of tagged bees really drifted into close by Donors, for the reason that Donor hives didn’t have magnetic traps. Any drifted bee would probably have later flown out to die with out leaving a tag behind (as evidenced by the very fact that there have been only a few tagged bees or dropped tags remaining within the Donor hives on the finish of the research).

Earlier research have discovered that charges of employee bee drift between close by hives will be as much as 40% [[2]^{, [3], [4], [5], [6]}], however has been extra usually been discovered to be within the 3-10% vary. On this research we recovered drifted tags from 3.6% of our tagged bees (Desk 1), however I’ll clarify in a second why that may be assumed to be an underestimate of the particular quantity of drift that occurred throughout this research.

Desk 1. Of the 6430 tags that we glued onto younger staff, we recovered 3.6%, principally from the magnetic traps of the Receiver hives, but in addition some from the underside boards and floor in entrance of the Donor hives. I’ll go over this knowledge graphically additional alongside.

It’s an open query as to the place the 6000 unrecovered tags (and their bees) wound up. The tagged bees might have drifted to colonies not concerned within the research, or simply finally died within the area, as do the overwhelming majority of staff.

We will justifiably assume that our depend is an underestimation of precise drift, is since we had magnetic traps on solely 3 of the 30 hives in every of our surrounding outyards, so would solely anticipate to recuperate 10% of the drifted bees to these yards. Equally, we don’t know what number of of every cohort of tagged bees drifted into unknown hobbyist or feral colonies within the neighborhood.

Conclusions: Bees did certainly drift from collapsing colonies, but in addition from mite-free hives. Our quantified 3.6% drifted tag restoration charge will be safely assumed to be a considerable underestimate of the particular share of tagged bees that drifted from our Donors to different colonies.

Correlation With Varroa Infestation

Query: Does the varroa-virus complicated improve the speed of bee drift into different hives?

Even though a variety of parasites have been proven to have an effect on host habits with a view to improve transmission, there’s little or no proof up to now that both varroa or DWV [[7]] induce elevated drifting of honey bees [[8]].

So since this wasn’t a major query to reply, in designing this research I included solely two mite-free Management Donors, erroneously assuming that their drift charges could be comparable. I couldn’t have been extra improper! (Determine 5).

Fig. 5 It turned out that of all of the Donors, the 2 mite-free Controls exhibited not solely the bottom, but in addition the very best charge of drift! The charges of drift from the 9 varroa-collapsing Donors all fell between that of the 2 mite-free Controls.

On reflection I want that I had run a bigger variety of mite-free Controls, and thank my fortunate stars that I didn’t run just one, since drawing conclusions from the info of both Management alone would have been very deceptive. Thankfully, these two Donor hives confirmed us how significantly the speed of bee drift can fluctuate between wholesome colonies.

Nonetheless curious, and since we did take periodic mite washes from the Donor colonies, I additionally regarded to see whether or not there was a correlation between the depth of the varroa infestation charge, and the diploma of drifting (Determine 6).

Fig. 6 I didn’t plan particularly to create this graph, so used mite wash knowledge taken from our 15 October washes, or the mid-September mite counts from two Donors that had already largely collapsed by that later date. Once more, there was no obvious correlation between varroa infestation charge and the speed of bee drift.

I’m not about to make any statistical declare primarily based upon an “n” of solely two hives within the Management group, however our outcomes exemplify the kind of “ugly info” that Thomas Huxley was referring to in his well-known quote: “The nice tragedy of science — the slaying of an attractive speculation by an unpleasant reality.”

Conclusions: It will make “complete sense” for the varroa-DWV complicated to trigger contaminated bees to float to different hives. However, as discovered by others, our area knowledge don’t assist that beguiling speculation.

Tag Restoration by Date

Even when the varroa-DWV complicated isn’t the trigger, that doesn’t essentially imply that employee bees don’t have a tendency to extend their quantity of drifting as their colony collapses. Free [[9]] discovered that:

A person bee is extra more likely to drift from a small to a big colony than vice versa.

We noticed that two Donors collapsed shortly after the beginning of the research, whereas a lot of the relaxation collapsed in mid-October. Let’s see whether or not that’s mirrored by tag restoration (Determine 7).

Fig. 7 The restoration of tags correlated fairly intently with the collapses of two colonies in late September, after which with the remainder of the Donors in in mid-October.

The above knowledge definitely counsel that bee drift correlates with the timing of colonies collapsing, so let’s take a more in-depth take a look at our restoration of drifted tags, Donor-by-Donor.

Timelines of Restoration of Drifted Bees

My quandary when designing and executing this research

Remember the fact that this research was about mite immigration, and we’re bee drift within the context that immigrated mites would wish to have caught rides on both drifting or robbing bees [[10]]. From different research, in addition to my very own observations, I suspected that substantial mite immigration attributable to drifting bees would possibly happen from September by way of November in my space. That covers a 90-day timespan. However employee bees throughout that point of season stay for a mean of solely about 35 days [[11]^{, [12], [13]}], so I didn’t need to mark all 500 bees at first of the research, since many won’t nonetheless be alive by the point that their colony really collapsed.

An alternate design would have been to arrange equal numbers of mite-free and high-mite Donors, and on the identical day of every week, tag 50 bees in every hive, concurrently grading every colony for power, after which search for a correlation between lack of power and bee drift. However since I don’t have grad college students at my disposal, the logistics would have been robust. Of better significance, there would have been smaller numbers of tagged bees in a hive at time of collapse, and my goal was to focus upon acquiring probably the most potential knowledge on the drifting of staff in the course of the time of precise collapse. That stated, I strongly encourage somebody to run the research described!

Did the act of tagging bees trigger them to float?

One other query arises comes from observations by a variety of different researchers that bees marked shortly after emergence might exhibit excessive charges of “loss” throughout the first days after being marked. This made me curious as as to whether these “losses” are an artifact of one thing do with the method or marking them (which might have confounded our knowledge), or whether or not that early lack of tagged bees was merely attributable to them getting confused and drifting throughout their first defecation flights.

On this undertaking, in the course of the 5-day interval between 17 and 21 September, we glued tags onto over 3000 staff, checking the magnetic traps on the Receivers every day. Throughout this time interval we recovered solely a single tag the day after our preliminary tagging of 550 bees, and solely 2 extra drifted tags by way of the twenty first. We then took the weekend off, and checked the traps on 24 September, after we recovered 17 drifted tags.

Conclusion: The above findings counsel that the style during which we tagged bees didn’t provoke speedy drifting.

Relevance to Mite Immigration

I’ve confirmed that shaken non-flying “home bees” (corresponding to we tagged) are inclined to exhibit a better charge of mite infestation in comparison with “flyers” [[14]]. That is presumably as a result of commentary that nurse bees are most tasty to varroa, and thus have the very best infestation charge of any staff within the hive.

So at what age would we anticipate bees to are inclined to drift? Once more returning to King’s observations in 1932:

The ages at which drifting gave the impression to be most prevalent had been between the fifth and tenth days, which corresponds relatively intently with the age at which younger bees present an inclination to shift from actions throughout the colony to area work.

Free [[15]] adopted up on this in 1958, discovering that:

A lot of the bees which drift achieve this throughout their orientation flights and earlier than they change into common foragers.
Bees rising in August and September drift lower than these rising earlier within the 12 months.
Drifting varies significantly in several circumstances, and could also be intensive.
Drones drift two to 3 occasions as incessantly as staff.

And at last, Bordier [[16]], monitoring 1000 tagged bees with a receiver hive positioned to both aspect, discovered that 10% of them drifted to a different hive, principally once they had been over 10 days of age.

We didn’t particularly arrange this research to find out age of drift, however since we solely tagged bees that didn’t fly off after shaking them from the combs, we will doubtless assume that they had been younger “home bees.”

Sensible software: For the reason that problem of curiosity is switch of varroa by way of drifting, if we’re making an attempt to correlate mite immigration with bee drift, it’s essential to know the behavioral “age” of these drifted bees. Is it primarily younger staff getting misplaced throughout cleaning or orientation flights, foragers coming back from their first exploratory flights, or older foragers that both received misplaced, disoriented, confused, or unable to withstand the alluring scent of one other colony?

So with the above caveats and purposes defined, let’s see what we will tease out of our knowledge. I’ve created graphs of tag software and restoration for every particular person Donor colony, with the date and variety of bees that we tagged in blue columns (on the left hand y axis), and the variety of their tags magnetically recovered in Receiver hives in pink columns (on a special scale on the precise axis). The columns don’t embody drifted tags later recovered from Donor hives.

Query: At what age do bees are inclined to drift?

We tagged bees within the mite-free Management Donor hives solely within the first few days, which provides us a possibility to get an thought of at what ages these bees drifted from these wholesome colonies (Determine 8).

Fig. 8 These first two graphs are for the 2 mite-free Management Donor hives, during which we tagged bees solely within the first few days (the blue columns). As I’ve already stated, C2 then exhibited much more drifting (the pink columns) than did C1 (and a better quantity shortly after tagging). Colony-to-colony variation is at all times the bugaboo of area analysis!

Interpretation: The quantity of drifting of bees from the 2 Management Donor colonies was as completely different as evening and day, however the total timing of bee drift was nicely unfold out for each colonies — indicating that the tagged bees drifted in any respect completely different ages. Surprisingly, we recovered a tag from every colony on the 70^th day after first tagging, which signifies that even very previous staff might drift.

Now let’s transfer to the high-mite Donors.

Query: Does bee drift correlate with the collapse of a hive?

Observe: This research was designed to quantify the diploma of drifting as colonies collapsed, not the correlation between collapsing and drifting. In these colonies, the correlation of drift with age or collapse could also be confounded by our tagging of extra bees over time. On reflection, if I had been to run this research once more, primarily based upon the unevenness of drift from the Controls above, I would solely tag bees in the course of the first week, relatively than ready for his or her colonies to start collapsing.

That stated, I nonetheless discover it of curiosity to look intently on the knowledge. Versus the mite-free Controls above, all however one of many high-mite Donors did collapse. In every of these Donors, we tagged 50 bees initially, however then waited, if essential, for indicators that the colony was collapsing (reducing power, deformed wings, or dying pupae) to tag one other 450 (or extra) bees. You possibly can inform after we thought that collapse regarded imminent by the timing of the extra blue columns.

Because of the issue in making a three-axis graph in Excel, I’ll present beginning and different acceptable mite wash counts within the captions. Take your time in analyzing the graphs under (and the data within the captions), as they inform us loads concerning the drifting of bees throughout a colony’s collapse attributable to varroa.

Fig. 9 Remember the fact that the scales for the blue and pink columns are completely different. D1 began with a excessive mite depend (30) and we anticipated it to break down shortly, but it surely didn’t begin to take action till mid-October, after which did shortly. D2 began with a comparatively low mite depend (19), and was nonetheless robust on 1 October, however then was collapsing shortly by 15 October, with a mite depend of 51. D3 began with excessive mites (33), and likewise crashed by mid-October. Of curiosity, it graded at solely 1 / 4 body of bees on 31 October, but three of its tagged bees drifted throughout November (maybe from a second drifting from one other Donor?). D4 began with a low mite depend (11), was nonetheless robust on 1 October with a wash depend of 29, however then collapsed slowly.

Interpretation: The clumpings of the pink columns for these colonies counsel that bee drift was related to collapse, though some colonies collapsed extra shortly than others.

Fig. 10 Mite counts elevated shortly in D5 (from 15 to 53 by 15 Oct) and it collapsed over the past half of October, whereas D6 was a robust hive with a really excessive beginning mite depend (55) that we rushed to tag because it began collapsing in September. D7 (beginning depend of 13) by no means collapsed, so we tagged solely about half as many bees as for the remainder of the Donors. D8 (beginning depend 38) collapsed pretty early, whereas D9 began robust and with a comparatively low mite degree (17) that elevated significantly by mid-October (45) , inflicting indicators of PMS (whereas it nonetheless contained 6 frames of bees). Due to its extended collapse (3 frames of bees remaining on 31 Oct), we tagged one other 500 bees on 2 November.

Conclusion: Though our knowledge didn’t assist that mite-infested bees essentially drift greater than “regular,” it does seem that elevated drift typically coincides with the timing of collapse. It’s not clear whether or not that was simply an artifact of our timing of marking, or attributable to bees tending to float out of weakening colonies “with issues” into extra engaging colonies.

I’ve solely simply begun — subsequent month we’ll check out the impact of distance upon drifting bees, the “attractiveness” of some colonies to drifted bees, after which on to our knowledge on the immigration of mites into the Receiver hives, relative to incoming drifted bees. I’ll then proceed with quantifying the precise quantity of mite immigration, and whether or not there was a correlation with robbing. As I stated, this was an formidable research, and we will be taught loads from it!

Acknowledgements

Due to my helpers Brooke Molina, Anna Mudd, Sandy Honigsberg, and Brion and Alice Dunbar, with out whose assist I might by no means have pulled off this research. And Dr. Norman Gary for his useful session. And naturally to these beekeepers whose donations allow me to pay for doing this kind of analysis.

Citations and Notes

[1] All mite counts on this article are for the variety of mites recovered by a mechanically-agitated alcohol wash of a degree half cup of bees

[2] King, GE (1932) Drifting bees might make manufacturing data of little worth. Am. Bee J. 72: 141-142.

[3] Nelson, DL & SC Jay (1989). The impact of colony relocation on loss and disorientation of honeybees. Apidologie 20(3): 245-250.

[4] Jay, SC (1969). Drifting honeybees in industrial apiaries v. Impact of drifting on honey manufacturing. Journal of Apicultural Analysis 8(1): 13-17.

[5] Pfeiffer, Ok & Ok Crailsheim (1998). Drifting of honeybees. Insectes Sociaux 45: 151-167.

[6] Goodwin, R, et al (2006) Drift of Varroa destructor-infested employee honey bees to neighbouring colonies. Journal of Apicultural Analysis 45:((3) 155-156.

[7] Deformed Wing Virus.

[8] Citations in Half 1 of this sequence.

[9] Free, JB (1958) The drifting of honey-bees. The Journal of Agricultural Science 51(3): 294-306.

[10] Ignoring for now that from drifting drones. Throughout the course of this research, there have been only a few drones in any of our colonies.

[11] Lloyd Harris, in prep.

[12] Free, J & Y Spencer‐Sales space (1959). The longevity of employee honey bees (Apis mellifera). In Proceedings of the Royal Entomological Society of London. Sequence A, Normal Entomology 34 (10‐12):141-150.

[13] Sakagami, S& H Fukuda (1968) Life tables for employee honeybees. Inhabitants Ecology 10(2): 127-139.

[14] https://scientificbeekeeping.com/re-evaluating-varroa-monitoring-part-4/

[15] Free, JB (1958) op cit.

[16] Bordier, C, et al (2017) Ought to I keep or ought to I’m going: honeybee drifting behaviour as a operate of parasitism. Apidologie 48(3): 286–297.

A Research on Bee Drift and Mite Immigration: Half 3

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