Contents
Distance that Employee Bees will Drift 1
Impact of Distance upon Bee Drift 4
Hive-to-Hive Variation in Captured Tags 7
Mite Immigration: Outcomes of the Stickyboard Counts. 10
Cumulative Mite Immigration. 11
A Examine on Bee and Mite Drift:
Half 4
Randy Oliver
ScientificBeekeeping.com
First printed in ABJ Might 2023
The outcomes that I introduced final month urged that maybe 5-10% of our tagged bees drifted to different colonies within the neighborhood, and (surprisingly) that drifting didn’t seem like essentially correlated with both the diploma of mite infestation of the bees, nor the timing of collapse. So let’s transfer on to what else we discovered.
I left off final month with quite a lot of yet-unanswered questions. So let’s begin off with certainly one of nice curiosity to beekeepers:
Distance that Employee Bees will Drift
Query: How removed from collapsing colonies will bees (and hitchhiking mites) drift?
As a way to reply this query, we had positioned magnetic entrance traps on 24 Receiver hives at distances from 15 ft to 3 miles from the Donor hives (Determine 1).
Fig 1 The approximate structure of the Receiver hives. The Donor hives had been on the middle of the golden star. Drifted tag restoration is indicated within the inexperienced bins. We recovered the overwhelming majority of the tags from our House yard, but in addition 13 tags (6% of the overall) from two of the outyards.
Though we began tagging bees on the seventeenth of September, we didn’t recuperate our first tag in an outyard (a half mile distant) till 9 days later (Determine 2).
Fig. 2 Bingo ― our first tag in a distant outyard! It wasn’t till 9 days after we initiated tagging that we recovered the primary tag from an outyard (the white dot on the tip of my thumb) — proof that bees can certainly drift over a large neighborhood. The arrow signifies the route to the Donor colony again house ― a half mile distant (and over two valleys). Regardless of inserting magnetic traps on solely three of the 30 hives on this outyard, we nonetheless recovered, over the course of the research, 11 tags from drifted bees (from seven completely different Donor colonies), indicating that substantial employee drift at this distance was “regular.”
How substantial? Since we solely tagged roughly one bee out of 30 staff in every Donor hive, and positioned magnetic traps on solely three hives out of thirty at this yard, we will extrapolate that these 11 recovered tags recommend {that a} whole of roughly 3000 bees drifted from the 11 Donor colonies to this yard a half mile distant!
Take into account that this experiment was run in an space with various landscapes, vegetation, and elevations (Determine 3), so we don’t understand how this discovering would apply to flatlands.
Fig. 3 This map exhibits the panorama between the Donor colonies at my place on the high, and our apiary to the south the place we recovered the tags from 11 drifted bees. The highway is on the backside of a valley. We had been amazed by the quantity of drift to this location, not solely as a result of distance, but in addition as a result of it concerned flight over forest, two valleys, throughout a hayfield, and into an apiary hidden by oak forest. Why the heck would so many bees drift to unusual colonies so far-off?
We additionally recovered one other two tags from three hives (out of thirty), these hives had been well-hidden by bushes and a fence, at a distance a full mile in the wrong way, indicating that there was considerable bee drift occurring even at that distance. This leads us to a different query:
Impact of Distance upon Bee Drift
Query: How does the drift of bees to close by hives evaluate to that to these extra distant?
Determine 4 exhibits common tag restoration per Receiver hive by distance from the Donors.
Fig. 4 What actually shocked us was how nice the drift was to the hives 500 ft distant, in comparison with these in plain sight of the Donors at 60 ft. Not solely had been these Receivers situated uphill, there have been a number of buildings, bushes, and different obstacles and landmarks between them and the Donors.
The above distribution of drifting bees was fully surprising, and definitely wouldn’t be anticipated by likelihood. Have a look again at Determine 1 — for every distance from the Donors, the floor space of the panorama will increase by the sq. of the radius [[1]]. Thus the probability of a drifted bee randomly touchdown close to one other hive decreases exponentially with distance.
So I ran some calculations, primarily based upon two assumptions: (1) since there was minimal nectar stream going down throughout this time interval, there can be no purpose to count on {that a} drifted bee can be extra more likely to fly close to any specific Receiver hive location than one other, and (2) the presumably false assumption (since we all know that staff are inclined to forage as near their hive as doable) {that a} drifted bee can be as more likely to land a mile from its hive as it will to land extra intently (which might underestimate the calculated disparity between the anticipated and noticed values (Desk 1 and Determine 5).
Fig. 5 The blue plot signifies the probability by likelihood of a drifted bee touchdown inside 10 ft of a Receiver hive relative to the floor space of the panorama encompassed by that distance (the chance rapidly approaches zero). The purple plot is our precise p.c tag restoration. The boldface numbers point out the proportional improve over what can be anticipated by likelihood. As defined above, the fold-increase numbers are probably underestimations.
Our knowledge clearly point out that the drifted bees didn’t simply randomly wind up in distant hives by likelihood — one thing clearly drew them to these hives.
Interpretation: The above was essentially the most surprising (and attention-grabbing) discovering (to me): that our tagged bees drifted into extra distant hives at a charge disproportionally far higher than anticipated by likelihood. Each scientific literature and area observations point out that honey bees exhibit remarkably correct navigation and homing means. I can perceive how a returning bee would possibly drift to an adjoining hive, however why would the speed of drift to distant hives be so disproportionately excessive?
Maybe foragers usually tend to get misplaced, disoriented, or confused as they get farther from their properties. Might it have been as a result of throughout my research — resulting from little nectar or pollen stream going down — that the foragers had been exploring farther from their hives than they’d have been had close by forage been extra ample? One explanatory speculation can be that that when a bee will get disoriented, that it merely flies upwind towards the scent of the closest hive. Or are some foragers merely unable to withstand the alluring scent of one other colony? It is a query crying for extra analysis — which might be simple to do with these magnetic tags and traps.
The above dialogue brings up one other certainly one of our questions:
Hive-to-hive Variation in Captured Tags
Query: Are some colonies extra (or much less) enticing to drifting bees (and thus mites) than others?
This topic was raised on this very journal clear again in 1932 by George King [[2]], who described the outcomes of his research (on the College of Illinois) on the drifting of marked bees:
It was discovered that the quantity of drifting between colonies was typically over 30 p.c of the overall variety of bees. [His test colonies were in a row, spaced 4-8 feet apart].
He famous that:
There are components aside from the space of colonies from one another which affect drifting.
King wrote that:
Regularly one colony seems to outyield different colonies close to it, and so the queen in it’s chosen as an acceptable mom to requeen the apiary. She ought to be a selection queen if she is accountable for the additional exhibiting made by her colony. Nevertheless, if staff reared in neighboring colonies have drifted into her colony with out an equal drift again into them, the queen can’t be credited with the outcomes proven.
Dr. Jerry Bromenshenk (pers comm), utilizing entrance counters, additionally discovered that some colonies gained power resulting from persistently having extra bees getting into than exiting — indicating that drifters had been frequently including to the populations of some hives in an apiary (the reverse was additionally true). Jay [[3]] and Pfeiffer [[4]] discovered that with hives positioned in a row, these on the ends could decide up further drift, however Bromenshenk discovered that it may be unbiased of relative placement.
King’s concluding remarks had been prophetic:
There are such a lot of issues to contemplate in beekeeping of which so little is thought that extra info is definitely fascinating. One of many issues which is able to bear appreciable investigation is drifting.
Ninety-one years later, I couldn’t have mentioned it higher myself! Now again to our findings …
In Determine 6 we will see that among the house yard Receivers gave the impression to be extra (or much less) enticing to drifting bees (I’m not clear whether or not guarding conduct made a distinction, since a drifted bee solely wanted to make it to the doorway to be snagged by the magnetic lure).
Fig. 6 I’ve color-coded the hives by their distances from the Donor hives (the nonmagnetic seize from the Donor hives shouldn’t be proven). Observe that in any distance group, some colonies gave the impression to be extra (or much less) enticing to drifting bees than others (regardless of all hives being identically sized and coloured, principally of the identical bee inventory, and of roughly equal power).
So how about my haphazard decisions for the three hives to which I utilized traps out of the thirty in every outyard? I do not know as to whether or not they had been individually enticing or unattractive to drifting bees ― so they might have over- or underestimated common drift to these yards.
The query then arises as as to whether colonies that entice or permit extra ingress of drifting bees additionally undergo extra vastly from mite immigration. So let’s transfer on to what we discovered in regards to the affiliation between employee drift and mite immigration:
Validating our Methodology
As a way to quantify mite immigration, we needed to preserve Receiver colonies that had been just about freed from mites (and mite copy). We did this by use of continuous miticide remedy. We began taking formal stickyboard counts on 17 September — later than I’d hoped for, since we had been already seeing substantial mite drop in our preliminary checks. This made me wonder if our Receiver colonies had been actually mite free. So we carried out alcohol washes on two dates to substantiate (Desk 2).
Regardless of all colonies nonetheless exhibiting very low infestation charges of the grownup bees (which may have been from recently-immigrated mites), I used to be nonetheless curious whether or not R5 and R7, which exhibited persistently excessive sticky counts, had been producing their very own mites. So on 17 October I dissected 100 cells of white-eyed pupae to pre-emerging adults from R5 (Determine 7). There have been zero mites. R7 was fully missing sealed brood — no larvae had been previous third instar, indicating that the Carniolan colony had shut down brood rearing a while in the past, solely to restart a number of days earlier than inspection (so no mites may have been within the brood). These findings strongly supported that their stickyboard counts had been apparently due solely or no less than primarily to incoming mites.
Fig. 7 I didn’t discover proof of a single mite within the hundred pupal cells that I dissected, confirming that little or no mite copy was going down within the colony with the very best every day mite drop.
Area analysis observe: It’s essential for a researcher to repeatedly query not solely their interpretation of their knowledge, but in addition the validity of their methodology.
Nonetheless, I questioned whether or not, regardless of my repeated zero mite wash counts, brood dissections, and the ultimate November wet days test, whether or not our stickyboard counts actually mirrored mite immigration, versus surreptitious mite copy throughout the colony. So in 2019 I replicated treating receiver colonies and taking stickyboard counts from six colonies in the identical yard over roughly the identical time interval. This time the climate was much more useful! Check out Determine 8.
Fig. 8 This time there have been three flight-suppressing climate occasions, which once more confirmed that the mite drops in handled Receiver hives was resulting from drifting bees.
O.Ok., now that I’m comfy with our methodology and knowledge, let’s see what we discovered.
Mite Immigration: Outcomes of the Stickyboard Counts
The collapsing Donor colonies had been rife with mites on the employees (Determine 9).
Fig. 9 By 15 October a number of Donor colonies had been clearly collapsing — most with loads of marked bees nonetheless on the combs. Observe the excessive varroa infestation charge on this photograph from a collapsing colony — right here you may see two staff with a mite on their again (remember the fact that most mites experience on the stomach).
So let’s reply some extra of our questions, beginning with two that we will reply on the similar time:
Cumulative Mite Immigration
Query 1: How many mites truly immigrated into our Receiver hives in late summer season and fall?
Query 2: Do all colonies undergo equally from mite immigration?
We recorded semi-weekly stickyboard counts from the Receiver hives, and counted a complete of practically 3000 mites, the overwhelming majority of which had been probably immigrants. So let’s check out the cumulative counts (Determine 10).
Fig. 10 Receivers R5 and R6 (at roughly 60 ft from the Donors) had the very best immigration totals, whereas the adjoining R3 and R4 had the bottom ― go determine! And it’s clear that the quantity of mite immigration differed vastly from hive to hive, no matter placement. General, the Receiver colonies obtained a mean of 245 apparently-immigrated mites over this time interval (R5 obtained over 500).
Sensible utility: On the identical property, with 9 collapsing colonies, there was big hive-to-hive variation within the variety of mites that hitchhiked into Receivers as much as 550 ft distant. Surprisingly, the quantity of immigration wasn’t associated to their proximity to the collapsing hives.
The 160 tagged bees that we all know drifted to the 12 House Receiver hives could not appear to be a big quantity, however remember the fact that we solely tagged an estimated 1/thirtieth of the overall variety of staff in every donor hive (which began at common cluster sizes of higher than 9 frames lined with bees), after which recovered tags from solely 2.7% of these. So we will extrapolate that on common, every House Receiver had a mean of 360 Donor bees drift into it, the overwhelming majority of which might have been untagged.
Sensible utility: Even with 9 colonies collapsing from varroa within the House yard, the above calculated quantity of heavily-infested drifting bees may solely account for a mean of about 70 out of the common 245 mites that confirmed up on the stickyboards. It is a nagging query to me — did most of these mites come from elsewhere, or did our restoration of tagged bees not absolutely signify the precise diploma of bee (and mite) drift from the Donors that truly happened? We could possibly reply this with a deeper evaluation of our knowledge.
Subsequent Month
Within the subsequent installment, we’ll take a deeper look into our knowledge, and handle our remaining questions:
Query: Is mite immigration regular or episodic?
Query: How intently did mite immigration correlate with the drifting of tagged bees?
Query: Did mite immigration correlate with robbing at my location?
Acknowledgements
Thanks once more to my helpers Brion and Alice Dunbar, Sandy Honigsberg, Anna Mudd, and Brooke Molina.
Citations and Notes
[1] Floor space = 
[2] King, GE (1932) Drifting bees could make manufacturing information of little worth. Am. Bee J. 72: 141-142.
[3] Jay, SC (1969). Drifting honeybees in industrial apiaries v. Impact of drifting on honey manufacturing. Journal of Apicultural Analysis 8(1): 13-17.
[4] Pfeiffer, Ok & Ok Crailsheim (1998) Drifting of honeybees. Insectes Sociaux 45: 151-167.
