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Observations on Pollen Subs: Half 4- Nectar, Water, and Humidity

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Observations on Pollen Subs:  Half 4

Nectar, Water, and Humidity

First revealed in ABJ January 2022

Randy Oliver


Final month I identified that there’s something about even a light-weight pure pollen circulation that appears to extend a colony’s response to fed pollen sub. However a light-weight pollen circulation is usually additionally accompanied by a light-weight nectar circulation maybe not sufficient to be noticeable by the beekeeper, however sufficient to have an effect on the humidity inside the broodnest. Might or not it’s that the moisture from a nectar circulation (unbiased of pollen) permits colonies to higher make the most of synthetic diets?

On this sequence I’m nonetheless attempting to determine why I couldn’t get my check colonies to develop, regardless of continuous feeding of pollen sub, usually together with sugar syrup.

Doug Somerville, in his handbook on bee vitamin, [[1]] observes that:

The lack of the stimulating impression of nectar will even equate to a discount within the space of brood being cared for by the colony. The availability of nectar continues to maintain the brood space “open” and inhabitants substitute at a excessive or increasing stage. This stimulus will be artificially created by the supply of sugar syrup.

My check colonies all placed on loads of weight from the fed syrup, so that they definitely weren’t missing for sugar stimulation (the continually-fed patties have been additionally half sugar). So might or not it’s the water in nectar that’s stimulating?


It was not solely unusually sizzling throughout the experiment, but in addition drier (decrease humidity) than “regular” (no matter that’s these days). Through the trial I assumed that we had supplied the colonies with sufficient 1:1 sugar syrup to keep up broodnest humidity. However might difficulties in sustaining water homeostasis have been the explanation that the relatively-small colonies didn’t increase their broodnests?

Water necessities of colonies

Throughout situations of sizzling climate, colonies require water for at the very least 5 causes:

  • To exchange the water misplaced from the bees’ our bodies throughout respiration.
  • To dilute saved honey in order that the bees can use it as an power supply.
  • To carry out evaporative cooling to forestall overheating of the hive.
  • To take care of humidity within the broodnest to forestall desiccation of the eggs and younger larvae.
  • To permit nurse bees to supply the water-rich jelly (>70% moisture) essential to feed the larvae

Contained in the hive, broodnest humidities are sometimes held (based mostly upon a scan of the sparse literature on this topic) between 40 and 70% RH, which isn’t stunning, since ripened honey comes into equilibrium with air at a relative humidity (RH) within the 50-60% vary. At greater humidities, honey will take up water and presumably ferment, at decrease humidities water will slowly evaporate from the honey. These combs of honey, nevertheless, seem to exhibit little precise buffering of the humidity between them, indicating that the bees actively regulate the humidity inside the cluster [[2], [3]], probably primarily for the good thing about the desiccation-susceptible eggs and larvae. So far as the grownup bees, Abou-Shaara [[4]] discovered that prime temperatures coupled with low humidity cut back their longevity, so it’s not stunning {that a} colony would keep a “snug” humidity in its residence.

Experimentally, Harbo [[5]] discovered that the water requirement of clusters of round 1500 caged bees, saved at a relentless 55% RH, elevated tremendously because the temperature elevated from 77-104°F, whereas their want for sugar plummeted.

Sensible utility: Harbo’s discovering definitely signifies that employee bees require much more water at greater temperatures, however I’m stunned by his discovering that sugar consumption decreased, since a number of research have discovered that the resting metabolism of honey bees will increase with excessive temperature [[6]].

It has been usually seen that colonies will desperately forage for water in winter if they’re rearing brood [[7]]; this although in chilly climate they produce an extra of metabolic water within the strategy of burning honey for power. Now couple that requirement for water with the necessity to cool and humidify the broodnest below sizzling/dry situations. If there’s a nectar circulation on, the colony might receive sufficient water from that supply. However in lots of arid areas (akin to my location in California), not solely is there no rain throughout summer time, however no considerable nectar circulation late within the season.


How bees forage for water, and use it to adapt to thermal stress, is an enchanting topic, which I’m solely going to cowl briefly. The quick model is that colonies can get determined for water, because of lack of ability to forage, or to warmth waves. After they do get thirsty, mid-age home bees begin to beg “water collector” foragers for water. The water collectors then reply by speeding out and bringing water again to the hive [[8]]. As soon as within the hive, that water will get trophallactically handed between bees, and deposited inside cells surrounding the brood nest, in addition to on the highest bars of Langstroth hives [[9], [10]] (Determine 1).

Fig. 1 A photograph of the highest bars in considered one of my hives on a sizzling day. It’s straightforward to see the glistening water within the burr comb, and to shake water, or very diluted nectar, out of combs.

A landmark examine on how a colony makes use of water was revealed in 1955 by Martin Lindauer in, [[11]] who concluded that:

The actions essential to control the temperature on overheating are carried out in accordance with the precept of division of labour. There are separate teams of bees for carrying water, for receiving and distributing it within the hive, for spreading it, for working it with their tongues, and for fanning. The person teams work in concord collectively; a direct relationship between overheating and the exercise of the water carriers has been established.

Lindauer noticed that water foraging elevated when a colony was rearing brood, and in addition discovered that the identical bees that foraged for water for brood rearing have been those who introduced again water for cooling the hive.

Then in 1997 Susanne Kühnholz and Dr. Tom Seeley adopted up with a examine [[12]] on how a colony delegates the duty of water reception (from the water foragers) to mid-age bees, and confirmed Lindauer’s suggestion they have been those who managed the quantity of water foraging by how eagerly they beg for or refuse water supplied by returning foragers. The water receivers then transport the water contained in the hive, sharing it with mid-aged employees or smearing it on the partitions of cells.

Permit me to cite from the paper:

Apparently, a colony adjusts the variety of water receivers by way of bees switching to water reception from each nectar reception and different duties, in accordance with the colony’s water want … The outcomes of this experiment present that after we heated the remark hive, the colony strongly elevated its water assortment however didn’t lower its nectar assortment. These outcomes additionally present that our focal nectar collector didn’t expertise larger difficulty in unloading a concentrated sugar resolution when the colony boosted its consumption of water, and in consequence was in no way discouraged from accumulating a wealthy sugar resolution all through the interval of extreme warmth stress.This helps the concept that a colony can elevate its water assortment with out concurrently reducing its nectar assortment. [Boldface mine]

Because the colony’s want for water elevated, the bees that had beforehand labored as water collectors have been more and more begged for fluid by their nestmates. This outcome means that being begged extra usually stimulates the inactive water collectors to renew their water assortment work.

Dr. Seeley adopted up on this analysis with Madeleine Ostwald and Michael Smith in 2016 [[13]], confirming that hive bees saved water not solely of their crops, but in addition within the combs close to the place water collectors returned from their flights.

Interested in how the Arabian bee offers with water, I corresponded with Dr. Abdulaziz Alqarni, who talked about three observations by beekeepers in Saudi Arabia:

  1. The native honey bee (m. jemenitica), collects water throughout sizzling midday instances whereas European bees don’t.
  2. Jemenitica place extra water drops on prime of the frames than do Europeans.
  3. Additionally they place small water droplets within the space between the brood cells.

Surprisingly, Abou-Shaara [[14]] discovered that his colonies in Saudi Arabia ignored a dish of water with floats positioned subsequent to the combs.


Standifer [[15]] discovered that in Arizona, the place they managed the water supply for an apiary, that after accounting for evaporation, that weekly common consumption of water by a colony was within the 5-9 liter vary (roughly a liter a day), whereas throughout winter it was round a liter every week.

Sensible query: The above observations made me curious as as to whether I would encourage brood rearing throughout sizzling, dry climate by providing colonies water contained in the hive.

So I ran a small experiment with three colonies, putting an empty field on prime, and providing the bees a alternative between heavy syrup (77% sugar) or contemporary water, throughout a July warmth wave, by which every day highs reached 105°F (Figures 2 & 3).

Fig. 2 There have been loads of foragers eagerly accumulating water throughout the experiment. I’ve just a few devoted bee water sources at my residence yard (this one with water dripping onto a cinder block). On sizzling days there are freeways of water foragers between the hives and the water sources.


Fig. 3 On this experiment I gave the bees a alternative between plain water (left) and 77% sugar resolution (proper), positioned on the highest bars (surrounded by an empty hive physique and canopy). I refilled the jars within the morning (so the bees could be already skilled to their location, and took this picture in late morning because the colonies began fanning loudly on the entrances as they desperately tried to chill their hives. By that point there was a column of water foragers beelining to a close-by pond.

Just like Kühnholz’s observations (and to my nice shock), regardless of the warmth and dryness, the bees took the heavy syrup extra quickly than water each time. Nevertheless, they did ultimately take the water too, though there was by no means a hoop of bees across the trough with their proboscises within the water. They consumed a mean of two/3 quart of water a day (after accounting for evaporation from the trough) — much like the quantity consumed in Arizona.

Sensible query: The dearth of curiosity is such a readily-available water supply (much like Abou-Shaara’s observations) made me ponder whether I used to be lacking one thing — did the colony deal with water supplied in a feeder in a different way than water introduced again by water collectors? How might I inform the place they positioned the syrup or water taken being fed on the prime of the hive?

So I ran a second experiment, providing a single-deep colony, once more in sizzling, dry climate, with two dishes every of two decisions of liquid — one heavy syrup (tinted with purple meals coloring), the opposite plain water (tinted blue). Then I waited just a few hours (at which level all liquid had been taken) and pulled each body to see whether or not and the place the bees had positioned both liquid. I used dozens of Q-tips to search for coloured liquid by inserting them into cells all through every comb (Determine 4).

Fig. 4 On this picture I’m pouring the red-tinted heavy syrup right into a dish. I might then sprinkle items of pine needles, as proven within the dishes of blue-tinted plain water, to forestall drowning. I then changed the hive cowl over the 1.5” rim, and let the bees suck the trays dry.

Fig. 5 The above is typical of how a Q-tip regarded as I withdrew it from a cell containing saved red-tinted syrup. The tactic clearly differentiated between purple syrup and blue water, and labored very nicely for a fast evaluation of the distribution of both liquid within the hive. Only a few Q-tips confirmed blue water, probably as a result of the water had already evaporated or been consumed.

Fig. 6 On this outer body of partially-drawn basis I detected solely blue coloration, with the water already evaporated. Not proven is that there have been additionally blue stains alongside the underside and higher surfaces of the highest bars all throughout the hive.

Findings and sensible utility: I discovered blue coloration (indicating water) scattered solely within the outermost frames and close to the highest bars — all within the periphery of the cluster. I discovered purple syrup (indicating syrup) in far larger quantity, however solely inside (and extensively all through) the broodnest and within the open cells of uncured honey inside the cluster. It appeared that the bees that took the water drank some, and used the remainder for evaporative cooling on the fringe of the cluster. Backside line: Sure, a colony seems to make the most of water supplied inside the hive much like the way it makes use of water introduced again by foragers.

On this experiment, I didn’t discover any proof of plain water being positioned within the brood space, however which may be as a result of it dried with out being saved — Stabentheiner [[16]] exhibits a thermal picture of how bees cool the broodnest by evaporating droplets of water, which can cowl as much as 7% of the brood space [[17]]. Then again, there was loads of heavy syrup saved across the brood, however at 77% sugar, one wouldn’t anticipate there to be a lot evaporation of moisture.

So I made a decision to return to my unique query.


Sensible query: Might the explanation that my check colonies late final summer time did not increase their broodnests have been because of the colonies’ lack of ability to keep up broodnest humidity throughout the sizzling, very dry climate?

Eggs and younger larvae require excessive relative humidities to keep away from desiccation [[18]]. There’s not an entire lot of revealed information on how intently colonies regulate broodnest humidity below varied situations. However by success, I used to be in a position to receive broodnest humidity information from two beekeepers who shared recordings from hives of their very own with me. Evaluating broodnest humidity measurements from colonies from very completely different temperature and humidity environments would possibly enable us to tease out the minimal and most broodnest humidity targets that colonies intention for.

Etienne Tardif recorded information throughout a cool, humid summer time within the Yukon. Underneath these situations, a colony can comparatively simply regulate its “most well-liked” minimal relative humidity [[19]] (Determine 7).


Fig. 7 Regardless of cool temperatures (largely within the 40s to 50s F) and excessive ambient relative humidities (usually above 90%), Etienne’s colony maintained a broodnest RH within the 55 to 70% vary (averaging 65% over the course of the summer time). The above information counsel that bees “desire” a minimal broodnest RH of round 60%.

Then again, in a heat, humid local weather it’s troublesome for bees to decrease broodnest humidity beneath ambient humidity, so we are able to discover their most “most well-liked” restrict. Russ Litsinger supplied information from his hive in Kentucky (Determine 8).

Fig. 8 Though ambient temps and RHs have been usually within the 80s, Russ’s colony was in a position to keep broodnest RH in the identical 50-70% vary till greater summer time temperatures and RH prevented them from with the ability to drop the inner RH by warming the air across the brood combs, leading to a summer time common RH of 72%. This implies the higher restrict for “most well-liked” broodnest humidity.

Sensible utility: The 2 graphs above affirm what different researchers have discovered — that regardless of greatly-varying ambient situations, colonies try to keep up the relative humidity within the broodnest between the 50 and 75% RH setpoints, with the “most well-liked” vary showing to be 60-70% (maybe a bit greater close to eggs) [[20]].

So might relatively-small colonies in my sizzling and dry summer time surroundings keep broodnest RH within the 50-70% vary? With a view to see, I purchased some humidistat/thermometers, and for preliminary testing measured the situations between frames of colonies of various strengths and configurations.

My preliminary observations recommended that humidities tended to be greater in higher brood chambers than in decrease. So for a worst-case state of affairs, I monitored the RH and temperature (for a number of days) of a single-deep weak colony in a dark-colored hive, in 100°F climate with no noticeable nectar circulation. The RH subsequent to their brood ranged from 60-80%, indicating that even a weak colony being blasted by the solar was in a position to keep broodnest humidity below sizzling, dry situations.

Shocked, I needed some extra detailed data. So I then arrange a colony in the identical configuration because the colonies within the trial final October (double deep, honey within the higher chamber, seven frames coated with bees, three frames within the decrease chamber containing brood). I positioned eight sensors, one outdoors the hive, the remainder between frames within the decrease chamber — three between the brood frames, the remainder between honey frames, and recorded their readings hourly over the course of three heat days in October (Fig. 9).

Fig. 9 Cheapskate that I’m, quite than utilizing information loggers, I crudely took images of the readings each hour. There was a really gentle nectar circulation on, and the complete solar hit the hive round 11:00 every morning, then gentle shade occurred once more round 2:00 pm.

Etienne and Russ supplied me with every day averages information, which can be greatest for indicating goal humidities, since a examine by Hannelie Human [[21]] indicated that broodnest humidities might enhance throughout the evening. What I used to be actually focused on was how low my colony would enable broodnest humidity to drop hour-by-hour throughout daytime. So I recorded hourly readings over the course of three days, with nighttimes indicated by grey columns (Fig. 10).

Fig. 10 First notice that ambient temperature and humidity (heavy stable strains) have been inversely proportional — because the air warmed, relative humidity decreased. Not so inside the cluster. The colony simply maintained the brood at a near-constant temperature (purple dashed strains), and positively appeared to have the ability to keep humidity between the brood frames (blue dashed strains) within the “regular” 50-70% RH vary (total daytime broodnest RH averaged 57%). At almost all instances throughout these three days, temperature and humidities between the frames have been greater and extra moderated than these outdoors the hive.

The one odd remark was that the RH subsequent to unsealed honey (skinny stable blue strains) was at all times greater on the east aspect of the hive (triangle markers). This can be the place they tended to retailer and evaporate incoming nectar or water.

One other stunning speculation slain — it seems that throughout sizzling, dry climate even weak colonies are in a position to keep broodnest humidity within the 50-70% vary. However that doesn’t imply that such upkeep doesn’t come at a price — Yildiz [[22]] discovered that it takes much more power for bees to chill their hive than to warmth it.

Sensible utility: So I can’t blame the climate or lack of moisture for the shortage of progress of those continually-fed colonies. I thus wrap this sequence up with what I discussed in my final installment — that I think that the stimulation for brood rearing, is not only about putting protein patties someplace within the hive, however is quite about offering the proper cue(s) to the nurse bees to stop “brood trimming” and as an alternative rear each laid egg to maturity, thus leading to colony progress. These cues probably have one thing to do with the location of incoming nectar or pollen immediately into the middle of the broodnest, which thus informs the nurses {that a} circulation is on, and it’s time for the colony to develop. We clearly have to be taught extra about one of the best placement of pollen sub inside the hive.


A really fascinating article got here to my consideration after writing the above.  It was written by Henry Pirker, a beekeeper in Alberta, Canada, who paid shut consideration to his indoor-wintered colonies.  He noticed that colony habits when in winter cluster was all about humidity.  Even when supplementally fed gentle sugar syrup to offer moisture, when colonies would sporadically “heat up” their brood space, and the queen would fill it with eggs, the nurse bees then eat these eggs quite than produce jelly to feed larvae.

Pirker experimented with elevating the humidity in his storage room, and located that doing so would lead to a lot of observable colony behaviors, in addition to the humidified colonies instantly participating in rearing massive quantities of brood.

Pirker concluded that: Maybe in attempting to grasp the character of our bees, we ought to be reminded that they developed within the lands across the Mediterranean Sea.  Drought durations posed at the very least as nice a problem because the cool seasons.  It isn’t merely a coincidence of nature that the defensive mechanism of Apis mellifera capabilities equally in opposition to drought and chilly.  Should not, certainly, our winter with its minute out there humidity seem to the bees primarily as a protracted, extreme drought season?

Pirker, H (1978) Steering issue humidity. ABJ Dec 1978: 786-789.


Maybe I used to be too hasty in letting lack of moisture off the hook.  “Moisture” is not only about humidity – it’s additionally in regards to the quantity of water required for the nurse bees to supply jelly.

In his wonderful guide “Fats Bees, Skinny Bees”, Doug Somerville notes:

.Ample out there nectar within the subject additionally acts as a stimulus to the colony, encouraging growing curiosity by the colony for pollen and an enlargement of the areas of brood inside the colony.

Following upon this, I ran a tough calculation as to how a lot incoming water a colony truly wanted (from both nectar or water foragers) to supply the high-moisture jelly essential for rearing larvae.


Due to Etienne Tardif and Russ Litsinger for information and dialogue, Dr. Alqarni for his observations, and to Peter Borst for library help.


[1] Somerville, Doug (2005) Fats Bees Skinny Bees, A handbook on honey bee vitamin for beekeepers. Rural Industries Analysis and Improvement Company, Australia.

[2] Ellis, M, et al. (2008 Hygropreference and brood care within the honeybee (Apis mellifera). Journal of Insect Physiology 54(12):1516-21.

[3] Li Z, et al. (2016) Drone and employee brood microclimates are regulated differentially in honey bees, Apis mellifera. PLoS ONE 11(2): e0148740.

[4] Abou-Shaara, H, et al. (2012) Tolerance of two honey bee races to numerous temperature and relative humidity gradients. Environmental and Experimental Biology10: 133–138.

[5] Harbo, J (2000) Heating grownup honey bees to take away Varroa Jacobsoni. Journal of Apicultural Analysis 39(3-4): 181-182.

[6] Kovak, H, et al. (2007) Respiration of resting honeybees. J Insect Physiol. 53(12): 1250–1261.

[7] Chilcott, A, & T. Seeley (2018) Chilly-flying foragers: Honey bees in Scotland search water in winter. ABJ 158(1): 75-77.

[8] Bordier, C, et al. (2017) Colony adaptive response to simulated warmth waves and penalties on the particular person stage in honeybees (Apis mellifera). Sci Rep 7: 3760.

[9] Park O (1923) Water saved by bees. ABH 63: 348-349.

[10] Nicolson, S (2009) Water homeostasis in bees, with the emphasis on sociality. The Journal of Experimental Biology 212: 429-434.

[11] Lindauer, M (1955) The water economic system and temperature regulation of the honeybee colony. Bee World 36(6): 105-111.

[12] Kühnholz, S., Seeley, T. (1997) The management of water assortment in honey bee colonies. Behav Ecol Sociobiol 41, 407–422.

[13] Ostwald, M, et al. (2016) The behavioral regulation of thirst, water assortment and water storage in honey bee colonies. Journal of Experimental Biology 219: 2156-2165.

[14] Abou-Shaara, H (2012) Notes on water assortment by honey bees. Bee World 89(4): 86-87.

[15] Standifer, L, et al. (1973) Supplementary feeding of honeybee colonies in Arizona. ABJ 113: 298 -301.

[16] Stabentheiner, A, et al. (2021) Dealing with the chilly and combating the warmth: thermal homeostasis of a superorganism, the honeybee colony. Journal of Comparative Physiology A207(3): 337-351.

[17] Their Determine 7c, and Desk S1.

[18] Doull, Ok (1976). The consequences of various humidities on the hatching of the eggs of honeybees. Apidologie 7(1): 61-66.

[19] Obtain a psychometric chart: (https://www.engineeringtoolbox.com/docs/paperwork/816/psychrometric_chart_29inHg.pdf

At 50°F at a RH of 90%, a pound of air holds 50 grains of moisture. But when the bees heat that air to broodnest temperature, its RH drops to solely 20%. Thus, they would wish to add moisture, so Etienne’s information would counsel the lowest broodnest RH restrict focused by bees. Conversely, Russ’s information would counsel the highest broodnest humidity allowed.

[20] Li, Z, et al. (2016) Drone and employee brood microclimates are regulated differentially in honey bees, Apis mellifera. PLoS ONE 11(2): e0148740.

[21] Human, H, et al. (2006) Do honeybees, Apis mellifera scutellata, regulate humidity of their nest? Naturwissenschaften 93: 397–401.

[22] Yildiz, C & M Özilgen (2019). Thermodynamic evaluation of the impression of the local weather change on the honeybees. Worldwide Journal of World Warming17(2): 185-218.



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