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Don’t miss the Varroa train

This post, bound to be wildly unpopular, is a reminder about Varroa mites. At this time of year, when colonies are large without a mite in sight, it’s easy to underestimate them. But like a terrorist cell, they work in secret. They know their time will come.

During spring build-up of honey bee colonies, the bees out-produce the mites. But come late summer when drone production stops and worker production slows, the mites will out-produce your bees. If you are not ready for the reversal, your hive may not survive till spring.

It is hard to make winter preparations in the heat of the summer. But if you wait until October to think about overwintering, you will have already missed the Varroa train. In fact, there will be no seats left on the train after August—they will be claimed by hoards of mites doing their best to kill your colony.

If you want a reasonably good chance of seeing your bees in spring, you need to finish your winter preparations in just a little over three months from now—about 14 weeks.

“How can that be?” you wonder. Well, here’s the thing to remember about Varroa mite treatment: How you treat is up to you, but when you treat is not. Here’s why:

Summer honey bees live four to six weeks, but winter bees can live six months or more. The winter survival of your colony is directly dependent on the health and vigor of those winter bees. If they are weakened by mites or viruses, your colony has little chance of survival.

But it’s your summer colony that has to raise the winter bees. To produce a healthy winter population, they must raise winter bees in an environment free of both Varroa mites and the diseases they carry. The winter bees will be raised in September or October, which means that in most of North America, your colony needs to be virtually mite-free by the first of September.

Now is the time to decide on a treatment regimen. Many options are available from powdered sugar to organic acids to commercial pesticides, as well as various management strategies such as drone trapping and hive splitting. I urge you to read about the pros and cons of each and to avoid commercial pesticides whenever possible.

Regardless of the option you choose, you must make a plan. For example, using powdered sugar alone requires weekly applications from now till winter, so you need to get started. If you plan to use one of the organic acids, you may need to order the product and accumulate the necessary equipment and know-how. If you are going to trap drones or restrict egg laying, now is the time.

So yes, I know it’s only May, but if you want to derail the mites before they rule your winter hive, it’s not too soon to start.

Rusty
HoneyBeeSuite

What they didn’t teach you in bee school

In bee school you learned that the sex of a bee is determined by the fertilization status of the egg. A fertilized egg becomes a female; an unfertilized one becomes a male (or drone). You may have also learned that this phenomenon is called haplodiploidy, and that all the hymenoptera (bees, wasps, and ants) are haplodiploid organisms.

What they didn’t tell you was that some of the fertilized eggs become diploid drones. This happens because the thing that actually determines sex is not the presence or absence of fertilization but the presence or absence of heterozygous alleles at the sex locus. Don’t go away yet; this isn’t difficult.

You see, instead of having an entire chromosome that determines sex (like the X and Y chromosomes in humans) bees have one gene on one chromosome that determines sex. Specific places on chromosomes are called loci (the singular is locus), so the “sex locus” is just the place (think location) on the chromosome where the sex gene is found.

The European honey bee species has about 18-20 different alleles of the sex gene. An allele is just a variation of a gene. All the sex alleles do basically the same thing, but the genetic coding is a little different in each one. Compare this to having 18 different recipes for chocolate cake—the end products are similar but the instructions for getting there vary.

Haplodiploidy is a sex-determination system in which males develop from unfertilized eggs and are haploid, and females develop from fertilized eggs and are diploid.


One of two or more alternative forms of a gene that arise by mutation and are found at the same place on a chromosome.


The specific location of a gene or DNA sequence on a chromosome.

So different bees are running around with different alleles (or instructions) for the sex gene. If an egg is not fertilized, there is only one set of instructions and the bee becomes a drone. If an egg is fertilized and has two different sets of instructions, the bee becomes a female. But—and here’s the rub—if the egg is fertilized but receives two identical sets of instructions (two identical sex alleles) the bee becomes not a female but a diploid drone. Think of it like this: one set of instructions twice is not the same as two different sets of instructions.

These diploid drones do not survive. In colonies of social insects such as honey bees, the worker bees eat the diploid drones soon after the eggs hatch. Many diploid drones in a colony result in “shot brood” or “scattered brood”—brood combs that have lots of empties or brood of many different ages. In solitary bees, the diploid male may die in the cell, or may emerge, mature, and produce sterile offspring.

The chart below shows what would happen when a honey bee queen (with two alleles) mates with five different drones, each with one allele. In this case, two of the drones have the B allele and the rest have different alleles.

Drones Queen Allele A Queen Allele B
Drone Allele A AA BA
Drone Allele B AB BB
Drone Allele C AC BC
Drone Allele B AB BB
Drone Allele D AD BD

Wherever you have homozygous alleles for the sex gene (two of the same alleles), you get a diploid drone. This chart shows an extreme example because it has a small number of alleles and a small number of matings, but it illustrates how homozygous alleles happen.

In real life, honey bees have about 18 alleles for the sex gene and a queen may mate twelve or more times, both of which lessen the likelihood of diploid males. But inbreeding decreases the number of alleles in a population and thereby increases the occurrence of diploid drones. Large numbers of diploid drones weaken a colony because the nurse bees waste resources raising these bees only to kill them later, and because the presence of so many drones reduces the number of worker bees that the colony can raise.

Large numbers of diploid males hasten a species toward extinction. Studies have shown that when population sizes of haplodiploid organisms become small, they go extinct more quickly than other species (Zayed and Packer 2004, 2005). With feral honey bee populations declining and inbreeding becoming even more common, the presence of diploid drones is a major concern to honey bee breeders.

Rusty
HoneyBeeSuite

Shot brood often signals high numbers of diploid drones.
Shot brood often signals high numbers of diploid drones.

The mystery of the dead drones

I wasn’t going to write about this until I figured it out, but I’m coming up blank. On July 5, I checked my top-bar hive and saw a massive pile of dead bees on the ground just outside the entrance. My first thought: pesticide kill. I’ve seen pesticide kills before and it looked just the same.

But the hive was churning with bees. With my hive tool, I sifted through the mound of dead bodies and discovered it was all drones—thousands of them. Not drone pupae, but fully–formed adults. Heaps of dead drones are not unusual as fall approaches and drone eviction is well under way, but this was the beginning of July. What was going on?

Unlike the rest of the country, the Pacific Northwest coast had a cold and wet spring. In fact, now that July is more than half gone, I am still wearing a jacket on most days. Up through July 5 we were still having days in the 60s and nights in the 40s. The bees couldn’t possibly think it was summer, but did they think it was fall? Were they evicting drones prematurely based on the temperature?

There is no dearth as of yet, the forest and fields where I live are laden with wildflowers producing both nectar and pollen. And since the rainy season wasn’t over by July 5—and it still hasn’t quite given up—water was plentiful.

Someone suggested the hive might be queenless. I’m not sure I follow: Do queenless hives eject drones? I’ve never heard of that. But I checked anyway. Although I didn’t find the queen, I found young brood, sealed brood (including more drones) and scads of honey and pollen.

Now almost two weeks later, nothing has changed. The hive is abustle with bees that are bearding on the front and underside of their home every day even though the days are mild and the nights are chilly. They remained camped outside during several days of thunderstorms, and they were even festooning in long strings from the landing board. I didn’t see any evidence of swarming or swarm preparation.

As far as I can tell everything looks normal except the boneyard out front. I thoroughly checked my other hives—all Langstroths—and found no dead drones anywhere. So, I’m looking for theories. Does anyone have a thought?

Rusty
HoneyBeeSuite

Dead drones under the top-bar hive. All the dark material you see laying around is composed of dried and crispy drones as well.
Dead drones under the top-bar hive. All the dark material you see laying around is composed of dried and crispy drones as well.
Bearding on the top-bar hive. You can barely see the three hive openings.
Bearding on the top-bar hive. You can barely see the three hive openings.
You can see bees bearding under the top-hive as well as in front. They have a screened bottom board that they are hanging from.
You can see bees bearding under the top-hive as well as in front. They have a screened bottom board that they are hanging from.

Essence of dead drone

If you detect a reeking, putrefying, gagging odor near your beehives this time of year, it could be the aroma of dead drones. Phillip at Mudsongs.org and I both detected it yesterday, and we both went through moments of self-doubt when we wondered what was happening to our hives.

Having forgotten the lessons of the past, I scurried to open the “offending” hive only to be met with the intoxicating scent of honey and wax, and that wonderful, indescribable odor of busy beehive. Then, confident the smell was coming from outside the hive, I searched until I found a dead mouse.

For a while I blamed the mouse, but then I realized he was too dead to be causing the problem. Too dead, meaning desiccated and crispy. At that moment I visualized the scent—dead drones.

It makes sense (scents) when you realize this is the season when adult drones and drone pupae are evicted from the hives. Although the workers make an effort to carry off the corpses, they often drop them only a few feet from the hive. In large colonies this turns into a big pile—a mound that rots in the summer heat and reeks to high heaven. Nothing smells more dead than dead pupae.

All of this reminds of an incident several years ago. At that time I was taking advice from another beekeeper about culling drones for mite control. I took frames of drone pupae from my hives, froze them over night and then, using a garden hose at an oblique angle, flushed the pupae from the cells. Naively, I did this near the back patio of our home five days before having guests for the July 4 holiday.

After about three days, I was met with a gut-writhing stench every time I entered the backyard. It took me a while to figure it what it was, but eventually I realized it was the drone pupae. Meanwhile, my husband was trying to get the place spruced up for the holiday. He kept asking, “What is that smell?” And I would shrug and say, “What smell?”

“It must be a dead deer,” he said, thrashing through the bushes looking for the offending carcass. “It could be a raccoon,” he added, “but it smells big, like a deer . . . or maybe a coyote.”

“You’re right,” I concurred, not wanting a lecture on my choice of drone burial grounds. Not that he probably ever thought about it.

Every time he was out of sight for an instant I flooded the area with more water, trying to hose the effluvium into the ground. It was strange because the pupae had fallen down into the grass where you couldn’t see a single one, but there was no doubt about their presence.

In the end, it took about two weeks for the smell to dissipate. My husband apologized to the guests for the dead animal smell and explained that since we live next to a state forest, all kinds of animal things happen here. I smiled politely and agreed.

That was years ago and I never said a word about it. I no longer hose out drones, I just feed them to the chickens. Now there’s just one problem remaining. Since my husband reads my blog every day . . .

Rusty

Bee abortion

When food sources run low, such as during a summer nectar dearth, the workers in a honey bee hive will often expel both drones and drone pupae. Since drones eat plenty of food but don’t collect any, it is a way for the colony to conserve stores for the winter. Later on, in the fall, nearly all the drones will be removed from the hive. In warmer climates a few may be allowed to remain throughout the winter, but in cold latitudes every last drone will be discarded.

A small percentage of worker bees in every colony are known as undertaker bees. Their job is to remove the corpses from the hive. They usually fly the bodies several meters away from the hive before dropping them, and sometimes two bees can be seen carrying one body. If the bodies are dropped close to the hive, predators may be seen working over the meat. Sometimes those predators, like the bald-faced hornet shown below, get bold enough to eat corpses right on the landing board.

The landing board shown below held a hornet eating a drone pupa. Because I think like a beekeeper and not a photographer, I killed it before I remembered to take a picture. Sorry. These photos were taken in the morning when the landing board was damp with dew and bodies had accumulated overnight. About an hour later, the board was cleared of all carnage.

 

Undertaker bee working among dead drone pupae
Undertaker bee working among dead drone pupae

 

Bald-faced hornet (Vespula maculata) in a mason jar
Bald-faced hornet (Vespula maculata) in a mason jar