Contents
Why Would Mites Want Drones?. 12
Drones and Varroa, Section 2
Randy Oliver
ScientificBeekeeping.com
First Printed in ABJ November 2023
Within the Would possibly factor of this magazine, Dr. Zac Lamas offered some findings of serious pastime, in regards to the distribution of varroa mites on drones as in comparison to that on staff. Aha, I assumed – this may lend a hand to provide an explanation for why mite wash counts after the honey movement from time to time build up extra strongly than anticipated. So I dove into some hives to resolve to what extent the superiority of drones within the hive might be concerned.
If you happen to haven’t already watched it, take a look at Dr. Lamas’ video [[1]], wherein he is going into a lot higher intensity than in his Would possibly article. He explains that the drones serve as as a “protecting cushion” for the colony, because of the mites preferentially feeding upon them moderately than the employees. Since drones aren’t focused on shifting meals to different bees, nor in brood rearing, they’re extra expendable than the crucial nurse bees, and their presence would possibly lend a hand to cut back the have an effect on of mites upon the nurse bees, in addition to cut back varroa-mediated virus transmission inside the hive, particularly early within the season, when the reasonably few mites provide at the grownup bees in a colony could also be driving (and feeding) predominately on drones.
Sensible query: The biotechnical way of the use of drone brood to lure and take away varroa can cut back the choice of mites in a hive, however it could additionally take away the “protecting cushion” that the ones drones would have supplied had they been allowed to emerge. This tradeoff can be a captivating topic of analysis.
What particularly intrigued me about Dr. Lamas’ presentation have been two intriguing hypotheses:
- That for the needs of varroa tracking early within the season, sampling drones would possibly higher mirror a colony’s general infestation charge than sampling bees shaken from the combs, and
- That the post-flow disappearance of drones from the hive would reason an considerable build up the varroa infestation charge of the employee inhabitants.
I discovered either one of the above hypotheses to be believable and price trying out.
In regards to the first speculation, Dr. Lamas identified the issue with the use of a sampling technique in line with the belief of a random distribution of the parasite at the bees, when the parasite in truth happens in an aggregated distribution – suggesting that hand-plucking of drones could also be a greater way than a wash of a 1/2 cup of staff. Closing month I confirmed my very own effects, evaluating the mite counts from employee samples to these of plucked samples of 25 drones from the similar combs.
This brings us to the second one speculation, which to me was once of a ways higher pastime, since it could lend a hand me to enhance my varroa mannequin [[2]]. Dr. Lamas’ proposed speculation was once that once the drones “disappear” after the honey movement, the consequent shift of mites only onto the employees may lend a hand to provide an explanation for why mite wash counts unexpectedly build up, resulting in viruses overwhelming the colony.
I discovered the above speculation to be believable, and in all probability explanatory for why my varroa mannequin from time to time underestimates the seen fast build up in mite wash counts in employee samples taken in overdue summer time. So I made up our minds that I’d higher examine.
Trying out Speculation #2
First let me specify the query to reply to:
Would the post-honey movement “disappearance” of drones from a colony lead to an considerable build up within the infestation charge of the grownup staff?
It befell to me that this could be a simple arithmetical calculation. So for our calculation, let’s consider a hypothetical case wherein all of the drones in a colony have been to unexpectedly fly off, leaving a few of their mites in the back of.
To accomplish the calculation, we want to know:
- The whole choice of grownup bees within the hive previous to drone fly off.
- The proportion of the ones bees that have been drones.
- The mite infestation charge of the drones relative to that of the employees.
- The choice of mites that the drones can be anticipated to hold out as they exited the hive.
We usually pay attention that colonies achieve populations of as much as 60-80 thousand bees. However I used to be stunned via how tough it was once to search out laborious knowledge supporting the ones numbers. So I made up our minds that we must roll up our sleeves and depend simply what number of staff and drones there have been in a few of my very own hives in overdue June and early July (on the finish of our honey movement).
Since I sought after to get counts for each the employees and the drones, I couldn’t simply weigh the hive sooner than and after shaking out the bees – I had to first shake all the bees right into a cage and weigh them (this phase was once reasonably simple), then separate out the drones, and weigh them by myself (that grew to become out to be just a little tougher than I was hoping) (Figures 1 & 2).
Fig. 1 I used an overly to hand battery-powered instrument from China to shake the bees from each and every comb. Simply pull the cause, and in two seconds all of the bees are falling throughout the funnel (I used a typical bulk bee funnel). I constructed a unique hive physique “cage” to carry them for weighing.
Via weighing the cage sooner than and after shaking the bees into it, I may just resolve the online weight of the bees. I additionally took a pattern (on ice) of a minimum of 100 staff for later weighing. After the primary hive, I first situated and caged the queen previous to shaking.
Fig. 2 A view of the combs after shaking off the bees. The small quantity of bees you notice have been returned foragers (which we then additionally shook into the cage).
It was once reasonably simple to resolve the load of the grownup bee inhabitants. The difficult phase was once then to split the drones from the employees. I had put in a queen excluder over the cage, in order that after weighing, I may just permit the employees to go out (Determine 3).
Fig. 3 Younger staff keep away from gentle; older staff fly against it. I discovered that what labored best possible was once to first substitute the queen again into the empty hive (with its brood combs), then position the cage queen excluder facet of the cage down, and make allowance the more youthful staff to climb thru it onto the combs. Then I’d turn the cage over, and make allowance the older staff to go out up and out against the sunshine, leaving the drones nonetheless trapped inside of.
Sadly, some staff stubbornly stay in the back of within the cage (there was once a considerable hive to hive distinction), combating me from merely weighing a cage stuffed with simplest drones. I attempted shifting the rest bees to a bucket to smoke the employees down throughout the excluder (Determine 4).
Fig. 4 Looking to smoke the employees down. Didn’t paintings.
So how about knocking them out? (Determine 5).
Fig. 5 I attempted anesthetizing the drones and staff with CO2, however they recovered too temporarily to split them via hand.
What I sadly wound up having to do was once to drench the drones (and any ultimate recalcitrant staff) with detergent answer, and bag them for later drying, hand sorting, and weighing (Figures 6 & 7).
Fig. 6 We tediously hand taken care of and weighed 1000’s of drones and staff.
Fig. 7 Via counting out 100 staff or drones and as it should be weighing them, shall we resolve their moderate weights, after which calculate what number of of each and every have been within the hive.
We shook the bees from 5 reasonably robust double- and triple-deep hives. This was once on the finish of our honey movement, and we simplest shook out colonies wherein I noticed a large number of drones. I highlighted the outline “reasonably robust” because it was once based totally upon my overview of “cluster dimension” via taking a look down on the most sensible bars – the colonies gave the impression to be “stuffed with bees.” What was once eye-opening for me have been simply how few bees have been unfold out over the combs of the colonies that we shook (Desk 1).
Sensible be aware: A few years in the past, Dr. Eric Mussen had commented to me that our colonies in California by no means reached the power of the ones in Minnesota. So my effects won’t mirror what you’d see in different places.
I put out a request for different beekeepers to shake a few of their hives. Invoice Elliot from Alabama did so from a 1½-story hive round 20 days after his honey movement ended, and I incorporated his discovering. None of our shaken colonies have been any place close to the usually mentioned 50-60,000 bee vary. In the summertime warmth, the bees weren’t as packed at the combs as they’re when it’s cool.
My unhealthy: In my varroa mannequin, I incorrectly assumed that there have been as many bees on a comb all the way through summer time as there are when it’s cooler. That mistake ends up in beneath calculating the predicted mite wash counts all the way through summer time. I’ll deal with this in my subsequent article.
Anyway, we’ve now were given a determine for the overall inhabitants of bees in post-flow hive. We now desire a determine for the proportion of the inhabitants that have been drones. Currie and Jay [[3]] mentioned that “Colonies with 24,000 – 27,000 staff comprise roughly 1800 drones,” which fits out to them constituting just a little greater than 7% of the inhabitants. We didn’t in finding any place close to that prime a proportion, with one of the crucial hives containing simplest 2-3% drones. Anyway, for our calculation, let’s use the absolute best drone proportion (5%) that I discovered in my hives.
The following determine that we want for the calculation will be the mite infestation charge of the drones relative to that of the employees – happily one thing that I already had from the drone sampling that I described ultimate month (Desk 2).
I colour coded the employee infestation charges in blue, and the ones of the drones in purple. In black boldface beneath I calculated the “multiplier” – how time and again upper the infestation charge of the drones was once, relative to that of the employees.
In all of the hives, the infestation charge of the drones was once upper than that of the employees. For our calculation, let’s use the whole moderate multiplier of five.5% (that means that the common infestation charge of the drones was once 5 and a 1/2 occasions upper than that of the employees).
The ultimate determine that we’d want for our calculation can be what number of mites the exiting drones would take with them. E.J. Steed gathered flying (and thus possibly) older drones at drone congregation spaces, and located that they have been infested via mites at about two-thirds the speed of staff sampled from brood combs in close by hives [[4]]. This means that drones that go out the hive take their mites with them. Dr. Lama’s knowledge point out that drones sufficiently old to fly have been more or less as sexy to mites as have been staff of the similar age, so for my calculations I’ll think that once a drone exits a hive, its infestation charge will be the identical as that of the employee moderate (versus staff sampled from the brood combs).
Let’s Do the Calcs!
OK, we’ve now were given all of the data that we want to calculate to what stage a hypothetical fly-off of drones would build up the mite wash depend in a pattern of staff. So (as I’m at risk of do) I took a while (in truth a large number of time) to create a calculator [[5]] to look (Determine 8).
Fig. 8 Within the above calculation run, I arbitrarily assumed that previous to drone fly off, the employees had reached an infestation charge of 10 mites in line with half-cup pattern (a three.2% infestation — a usually approved motion threshold). The calculation signifies that even within the hypothetical case of the drones (infested at 5.5x that charge) unexpectedly leaving the hive, their go out would simplest lead to a minimum build up within the infestation charge of the employees. Any other tantalizing speculation bites the mud.
Conclusions
Even though the speculation that submit honey movement drone disappearance would lead to a significant leap within the mite infestation charge of the employees was once compelling, my knowledge and calculations don’t toughen it.
The reason for the fast build up within the infestation seems to be principally because of a mix of 4 components:
- The exponential build up within the mite inhabitants, which doubles more or less each and every month [[6]].
- The relief of the grownup employee inhabitants, that means extra mites in line with bee [[7]].
- A lower within the quantity of sealed brood, which leads to a better share of mites at the grownup bees.
- And conceivable immigration of mites because of employee flow or robbing.
Sensible software: My measuring of the particular bee counts of my hives has opened my eyes to the truth that my varroa mannequin wishes adjustment. I’ll pass into higher intensity subsequent month.
Why Would Mites Want Drones?
I need to thank Dr. Lamas for his spectacular physique of analysis. His findings at the choice via mites for drones (which my knowledge ascertain) are of serious pastime, and I’m curious as to why, since their fats our bodies (varroa’s goal meals) aren’t as evolved as the ones of non-foraging staff. Haydak [[8]] discovered that the fats our bodies in drones consisted of simplest “a couple of aggregations of cells, tough to search out,” and that “no fat-body was once present in drones 3 days previous or extra.” On the other hand, the hemolymph of freshly emerged drones incorporates reasonably extra glycogen (an power molecule) than in same-aged staff, and the protein and vitellogenin content material of drone hemolymph “will increase abruptly inside the first days after emergence, attaining a top on the third day and lowering after the primary week” [[9]]. So what’s it about drones that mites in finding so sexy?
We clearly nonetheless have so much to be informed about varroa and their affinity for drones! I look ahead to studying Dr. Lamas’ research once they transform to be had.
Acknowledgements
Thank you for the sector lend a hand from Corrine Jones, Kamon Reynolds, Victoria Knight, and Rose Pasetes.
Citations and notes
[1] Hidden in simple sight: Varroa mixture on grownup drones https://www.youtube.com/watch?v=mAsXFPakumU
[2] https://scientificbeekeeping.com/randys-varroa-model/
[3] Currie, R & S Jay (1991) The affect of a colony’s queen state at the drifting of drone honey bees (Apis mellifera L.). Apidologie 22: 183–195.
[4] Steed, EJ (2023) Parasites and pathogens at honey bee mating websites, and the consequences for tracking colony well being. M.S. Thesis, The College of Waikato.
[5] I’d feel free to proportion a duplicate when you’re .
[6] See mobile AG62 at the Present Model tab of my varroa mannequin.
[7] https://scientificbeekeeping.com/ipm-3-strategy-understanding-varroa-population-dynamics/
[8] Haydak, MH (1957) Adjustments with age within the look of a few inner organs of the honeybee. Bee Global 38: 197–207.
[9] Hrassnigg, N & Ok Crailsheim (2005) Variations in drone and employee body structure in honeybees (Apis mellifera). Apidologie 36(2): 255-277.