Navigate / search

Why are my bees crawling in front of the hive?

We call them crawlers. They can appear any time of year but are most prevalent in the fall. They inch along the landing board, cling to blades of grass, or struggle among twigs and small stones. On close inspection they look normal, but they can’t fly. You may see a few, a handful, or hundreds. What does it mean?

The tracheal mite connection

In years gone by, tracheal mites were often blamed for causing crawlers. You can still find many references that link crawling to tracheal mites, but they no longer seem to be the major cause. For one thing, tracheal mites have largely disappeared in many areas because of the widespread use of acaricides to treat varroa mites.

Over the past six or seven years I’ve heard from dozens of beekeepers who’ve had their crawlers tested for tracheal mites, and all but one came up negative. And while tracheal mites are less common than they used to be, reports of crawlers seem to be on the rise.

Furthermore, not everyone agrees on the relationship between tracheal mites and crawling. Way back in 1969, L. Bailey wrote:

There are no reliable symptoms for the diagnosis of the common infections of adult bees. Nosema apis and Malpighamoeba mellifica do not cause crawling, and sickness of bees infested with A. woodi cannot be unreservedly attributed to this parasite. Paralysis virus is the most probable pathogen for causing crawling and early death of bees and these often are the only signs the virus causes in nature.[1]

Or maybe pesticides

Pesticides have also been blamed for causing crawlers, and I believe pesticides could be a cause in some cases. However, the signs of pesticide poisoning are often more dramatic and include piles of dead bees with extended tongues or dying bees that are shivering, quivering, or spinning.

The trouble with crawling is that it’s a common sign of a sick bee. Many things can weaken a bee and render it unable to fly. Diseases, poor nutrition, environmental stress, and genetics are all potential sources of weakness. Those possibilities coupled with the fact that old and wing-worn bees may also crawl, make it hard to diagnose.

Viral disease and varroa mites

In recent years, however, I’ve become convinced that crawling bees are often infected with one or more of the viruses commonly carried by varroa mites. Although deformed wing virus is frequently cited, a number of other viruses could cause crawling.

Anecdotal evidence indicates that crawlers are often seen in the fall just as the mite-per-bee ratio inside the hive spikes, often beginning in late August or early September. Also, some beekeepers report actually seeing deformed wings among the crawlers. Others have reported to me that in the weeks following an increase in crawlers, their colonies died of varroa mites, as evidenced by guanine deposits, shredded brood caps, and varroa among the hive debris.

In fact, Stavely et al (2014) wrote:

The causal criterion of specific symptoms experienced by colonies suffering from the combination of Varroa and viruses is convincingly supportive. These symptoms include reduced colony development, the presence of malnourished, deformed, and underweight bees, or crawling bees that are unable to fly or that have crippled wings.[2]

On its website, Extension.org also suggests a strong correlation between varroa mites and viral disease:

… controlling Varroa populations in a hive will often control the associated viruses and finding symptoms of the viral diseases is indicative of a Varroa epidemic in the colony. Viruses are, however, the least understood of honey bee diseases. Emerging information of honey bee viruses continues to alter our understanding of the role viruses play in honey bee colonies.

Recall that long before varroa mites appeared in the US, Bailey [above] suggested that paralysis virus was the most likely cause of crawling. The current list of viruses carried by varroa mites includes several of those identified as paralysis viruses, including acute bee paralysis virus, Israeli acute paralysis virus, chronic bee paralysis virus, and slow bee paralysis virus. It makes me wonder if perhaps tracheal mites carry the same viruses as varroa mites and distribute them in similar fashion.

That said, I do not believe there is a one-to-one correspondence between crawling bees and mites. As stated above, crawling has multiple causes.  However, I am convinced that if you have an abundance of crawlers, you should begin your diagnosis by doing a varroa count. With so much apparent correlation between varroa and crawlers, it seems like an easy and logical place to start looking.

A word about visual observations

Remember that it is easy to be fooled by casual observations. Sometimes a beekeeper will say, “I saw no deformed wings and no varroa, so I can eliminate that problem.” But in truth, it’s not that simple. In the first place, varroa are good at hiding. Even a phoretic mite hitching a ride on an adult bee can easily slip into the space under an abdominal plate where it is nearly impossible to see.

We’ve all seen photos of clearly visible varroa mites clinging to adult bees. But those photos are on the Internet for a reason: it’s an uncommon sight. I’ve been carrying my camera around for the last ten years trying to get one of those photos, and I never see phoretic mites, even in colonies with high mite counts. So please, don’t rely on visual inspections of adult bees. Do a real mite count with powdered sugar or alcohol so you have solid information to work with.

Remember, too, that a bee can be infected with deformed-wing virus whenever it is bitten by a varroa mite carrying the disease. If the bee is bitten in a developmental stage before the wings appear, the wings may become deformed. However, a bee that is infected after the wings are fully formed will not show that symptom. So a bee with perfect wings is not necessarily free of deformed-wing virus. There are plenty of other consequences of the virus that are harder to see, including lack of vitality, shortened life span, and depressed immune response.

Implications for the beekeeper

Nothing I’ve read so far convinces me that a particular virus causes crawling, However, there seems to be a strong association among crawling, viruses, and varroa. With that information, the appearance of crawling bees—which are often easier to detect than either deformed-wing virus or varroa mites—can signal the need for further investigation into a possible varroa infestation.

Rusty
Honey Bee Suite

[1]Bailey, L. (1969). The signs of adult bee diseases. Bee World, 50(2), 66-68. Chicago

[2]Jane P. Staveley , Sheryl A. Law , Anne Fairbrother & Charles A. Menzie (2014) A Causal Analysis of Observed Declines in Managed Honey Bees (Apis mellifera), Human and Ecological Risk Assessment: An International Journal, 20:2, 566-591

Please note: Although the conclusions drawn in this post are my own, I wish to acknowledge the kind assistance of Peter L. Borst in locating some of the quoted material.

Bees crawling may be due to deformed-wing virus.
A honey bee infected with deformed-wing virus. By Xolani90 – Own work, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=26406168

Save

Save

Save

Comments

Terri Brantley
Reply

Thank you! This is some very good, timely information. Since treating for varroa and tracheal mites, I have almost completely stopped seeing crawling bees in front of my hive. I am still waiting to hear back from the inspector what he finds in the sample of bees I provided.

Kathy Pallos
Reply

Here in Pa we are having 75-80° days, and nights are way too warm for this time of the year. I noticed today that my girls are hanging on the front of the hives bearding. I have never seen this before in the fall. Could they be getting ready to swarm? We still have full fields of wildflowers and tons of goldenrod and wild aster among other plants and they have been hauling it in without letup. Do I have something to worry about? Thanks All, I love this site it is so helpful.

Kathy

Rusty
Reply

Kathy,

First, whenever you are outside of swarm season, the chance of swarming is low. And when you are far outside of swarm season, it is even lower. You do see them on occasion, of course, but the probability of any one colony swarming out of season is low. The worse problem, of course, is that most of the drones have been tossed, so there may be few, if any, mating choices for a virgin queen.

Lots of people confuse bearding with swarming, but they are not at all alike. Bearding and swarming are entirely different activities caused by different conditions. We think bees beard to help keep the brood nest from overheating in hot weather. There is no harm in bearding, so you can just let them do it.

Not so uncommon in fall is absconding, but unless their life is miserable where they are, they will probably stay put.

Brian T
Reply

Excellent as always Rusty. Glad PL Borst is a collaborator, he’s a rockstar on Bee-L. As you are here!

I have crawlers this time time of year, near all hives. Not many, but enough to be noteworthy.

I have just completed a full course of OAV treatment of all hives but still see a few bees ‘in the grass’. Mite drops are very low so I assume that previously infected (with virus) bees will continue to manifest for some weeks. Is there danger of bee-to-bee virus transmission or are the viruses dependent on mites to vector transmission?

Brian
115W, 53N, El. 850 M

Rusty
Reply

Brian,

Once infected, the bees will die off slowly, so you will continue to see them for several weeks as they emerge from the brood cells. I did some research on viruses a while back, and I remember reading that most of these viruses have been around for a long time, causing very little trouble. Without varroa, they are more-or-less background noise, similar to cold viruses in humans. The virus is always there, but we usually resist it.

But since varroa actually inject the virus into the bee, it’s a whole different level of infection, almost guaranteed.

It may have been in the master beekeeper course that we had a discussion of lateral and vertical infection of virus when no varroa are present. It seems there is some lateral transmission between siblings, usually from workers to larvae through the feed (if I remember correctly). There is also some transmission vertically from infected queen through the egg. But neither of these are very common.

What was interesting to me is that many of these viruses were unknown until varroa came along, but now researchers can go back and look at preserved samples in museums and laboratories and actually find them. So many, at least those not recently imported, have been here for a while, but they weren’t pernicious enough to cause trouble.

Another interesting item was that now that the viruses are so common, some researchers believe the incidence of spontaneous mutation is beginning to skyrocket, leading to strains that are much more virulent than they used to be. This theory is used to support the observation that many beekeepers used to be able to treat for varroa once a year, then twice, and now some treat three times. In other words, it doesn’t take a lot of virus to take down a colony.

Catherine Stobie
Reply

Hi Rusty,

In my main hive, when my bees start crawling it has been because they have been parasitized by the tiny zombie fly and are nearly dead. They will usually die within the next 12 to 24 hours. Just another possibility.

Rusty
Reply

Catherine,

I’m curious, did you grow out the larvae from your bees and have them identified?

Jeffrey S.
Reply

Rusty,

Unfortunately I have this problem with two of my Italian hives. We had a very wet summer here in NEPA this year so I left my honey supers on longer than I should have to try to squeeze out a few more capped frames of honey. Which in turn had me treating for mites in mid to late August instead of in mid to late June. Now I am doing a second knock down in October to hopefully get enough health winter bees to make it through winter. Don’t get me wrong, these hives were rocken big but now are dwindling slowly due to the daily death of newly hatched bees. These hives are still heavily populated and will hopefully have large clusters this fall but if the bees aren’t healthy that won’t mean jack.

What I find strange is that I have two Carniolan hive side by side with these Italian hives and they don’t have any visible problems at all. I am going to treat them too just to be safe and I will see what happens. If the Italians don’t make it I will be getting Carniolans to replace them in the spring. I just hope they are strong enough to bounce back because they were rock stars this year and I will feel terrible if they die due to my stupidity. I won’t make this mistake again, off with the supers in mind June and treat!

Also for the past three nights I have had to turn of my auto sensor lights due to a few honey bees flying around the sensor and keeping the light active. They seam to actually be attacking the light bulb, very strange behavior. I talked with a Master Beekeeper in our area and he said he hasn’t heard of Zombees ever in our area. I seam to be a magnet for strange anomalies.

Take care and happy beekeeping.

Rusty
Reply

Jeffrey,

Have you checked the map for Zombee sightings?

Tony Weller
Reply

Hi Rusty,

As a 3rd season beekeeper, I thank you for all the information you have provided. I am currently experimenting with your suggestion, i.e., with foundationless frames, with success with no burr comb.

Just an observation, this season, I have identified bald faced hornets, (I think are actually wasps). I have never seen these critters before, however, they catch my girls in mid-air, in front of the colony, cut a couple of legs off, then wrestle them to the ground or to my spruce tree, cut their head off, then fly off with them. I have seen a couple of my bees walking in circles, very fast, and agitated. Closer observations revealed their middle legs were gone. Bald face hornets were in the vicinity hovering over my wild strawberry patch. Just thought I’d mention, since this is a different cause and effect. I did observe 2 of my bees crawling around in front of the hive a few days ago, all looking normal, all legs, no deformed wings, crawling up blades of grass, fall down, and repeat over again. It definitely got my attention as did your article.

Rusty
Reply

Tony,

Bald-faced hornets, Dolichovespula maculata, are definitely wasps in the family Vespidae. I have them every year, but this year was crazy. They were everywhere. Each day, I could go out in front of my hives and net a couple dozen in a few minutes. As morbid as they are, I find their hunting techniques fascinating, especially how they tail a bee in the air. Moving like fighter pilots, once they get in the right position behind the bee, that bee is toast.

Anyway, you are right. They wrestle the bees to the ground and dismember them. Even when I catch them with prey in the net, they won’t let go of their prize. They are crazy mothers.

I try to catch the queens in spring. This year I saw an enormous queen in my garden. I tried for her, but missed. Right then I know I would be in serious trouble this year and I was right. Never did find the nest.

Steven
Reply

Hi Rusty, I believe we have crawlers here in Australia too (I spot up to a dozen around my hive every day without really looking – they still have their wings), but we have neither tracheal mites nor varroa. I always thought they were just older, weak bees ready to die. Aren’t hundreds if not thousands of bees dying every day? In a hive of 50-60,000 bees, you would see a lot of weakened bees around the hive area. Bees that couldn’t quite make it back to the hive. Just a thought. Comments welcome!

Rusty
Reply

Steven,

Even without mites, any hive is going to have a certain number of crawlers, but not necessarily hundreds or thousands. These bee viruses are in any colony of bees, regardless of mites, and have been for ages. It’s just that varroa actually inject the virus into the bees making the infection rate much, much higher.

Most foragers die out in the field; they just never make it home. The average size hive loses about 1000-1500 bees per day, which is why the queen has to churn out that many eggs just to stay even.

Steve Riley
Reply

Dear Rusty,

No one is quite sure of the extent that mites vector viruses and more scientific analysis is required here. It’s likely to be a moving target as mites evolve to develop resistance to the insecticides that currently knock them back; of course, the varroa that survive potentially generate the “super mite”.

In the meantime, our honeybees aren’t allowed to evolve to develop their own “resistance” whilst we chemically treat, but most of us beekeepers can’t face the colony losses whilst that evolution takes place.

It is time for a “third way”…… Reducing varroa to tolerable levels without using insecticides. Thinking caps on.

Steve

Rusty
Reply

Steve,

In this post I advocate neither treating nor not treating. I simply recommend counting, something any beekeeper should be okay with. Knowledge is power, and knowing what’s going on in your hive is important for any management style.

Wendy
Reply

Timely article! After no signs of varroa over the summer on my oiled tray under the hives, the other day I was horrified to see 2 bees, one in front of each hive, with deformed wings. A mite could clearly be seen attached to one of the girls. I was devastated. I’d treated in August on the instruction of my mentor (I’m a first year beekeeper) and he said I must have made a mistake with the treatment. I treated them again with oxalic acid, the go-to treatment here in Italy. We have no other hives near us and we live up in the mountains over 1000m, so I was carrying on about how my bees were healthy. In the end though, they were brought up from the less healthy lowlands, and undoubtedly infected. I was convinced their infestation was low, now I’m worried sick they won’t make it through the winter, as well as feeling awful about those poor sick girls I saw.

Debbie
Reply

Very good article Rusty. I have seen thousands of bees walk out of a hive and just walk away to die due to varroa. There are so many viruses that varroa give to the bees and they are so insidious anymore, you don’t even know you have them. This year we have been seeing the varroa levels hidden … it’s like, one does a check and sees and gets very few varroa, but when one closely inspects the cells, the larvae is melted or already dying from varroa. One has to stay vigilant no matter what time of year it is. It was weird seeing hardly any varroa this year, and then BOOM, fall came, and the numbers shot up. Thanks for this post, Rusty, I’m sure it helped a lot of people.

Elena
Reply

Thank you, Rusty. You’ve compiled a wonderful synopsis of info in one place here that a person would otherwise have to find in multiple sources. The info is somewhat alarming, but what we all need to understand it. I have seen a single ‘crawler.’ I thought that, particularly given this time of year, it is normal to see an attrition of the workers that have foraged for 6 weeks and are now on their last flights. What does happen naturally to old bees? Where do they go to die? Do they go back to their colony, or do they just never go back home?

Rusty
Reply

Elena,

Yes, it is perfectly normal to see a certain number of crawlers. It’s not disturbing until you begin seeing large numbers. Normally, old bees die in the field. I find them dead inside flowers sometimes, or just on the sidewalk or patio. Old bees are easy prey for bee wolves, robber flies, wasps, birds, frogs, or whatever is hungry. Old bees are often caught in storms or cold weather. Sometimes they just leave the hive and die in flight.

BeeHappy
Reply

So does any anyone have memories of whether hives with heavy amounts of crawlers tend to not make it thru winter? Would heavy amounts of crawlers be an indication of shaking out these “unhealthy” hives and making the best of a bad situation. It seems at this point the winter bees need be hatching, and if there are issues one might cut the losses early and extract all the honey and freeze the combs for spring expansion.

Any ideas here?

Rusty
Reply

Keith,

If you get rid of the varroa, the virus will clear out. If lots of bees remain, I would try to save the colony.

Pedro
Reply

I wonder what are the ages of the crawling bees. Do colonies in early autumn have an inverted population pyramid, with the highest percentage of older foraging bees in the year? Could old age be a cause for decreased immunological condition? Could bees from different colonies be meeting more often due to reduced food sources and speeding the spread of viruses among them? Just some thoughts.

Rusty
Reply

Pedro,

Most of the crawlers I’ve seen in the past were not old. In fact, they’re often quite furry and soft. Also, no tattered wings, which means they weren’t old at all. Then again, I haven’t seen that many in the past few years. There is not much horizontal transfer of viruses between honey bees, so it’s not likely they are passing disease between hives unless the mites are doing it for them.

Still…all good questions. I will try to be more observant in the future.

Pedro
Reply

Thanks for your reply. I haven’t seen crawlers myself – yet… – or at least if I did I didn’t identify them as such. Good to know that horizontal transfer between bees is not a big factor. I think swarming really helps the colony to control mites. I have so far totally failed to prevent swarming in my hives but I guess that’s not all bad!

Rusty
Reply

Pedro,

Since I’ve let mine swarm when they want, my mite numbers have gone way down. I can hardly believe the difference.

Debbie
Reply

Something to note re: oxalic treatments … we have found that it doesn’t work as well if the hive has more than two brood boxes. You have to use more oxalic to get up to the supers. I know you are supposed to remove supers first, but a lot of people do not because it’s ‘after flow’, but it appears the hives we do w/the supers on don’t get as good a treatment as when the supers are off. Go figure. just thought I would share that so people who wonder why the oxalic didn’t work well might have left the supers on and didn’t account for more oxalic. Also, it’s important to keep track of the drop on the white board. Usually the first drop will be heavy and subsequent drops should lighten up as the mites die off. Some of the people here treat their hives for three weeks in a row during the brood break period, that way, the oxalic gets each subsequent brood emergence.

Also, September is not too late to save the hive and make winter bees. You figure, these bees will be dead by November anyway, so if you have a heavy mite load, or virus load, get them hives treated, and feed protein patties and sugar water to get them fattened up. Things seem to work out better for the bees if one feeds them after these treatments since supers have already been processed.

I have had several huge hives over the years get virus and lose tons of bees, but after treating and feeding, they spring right back up and make it till spring. Bees are rather resilient if the bee keeper keeps vigilant and finds things early enough to help them out.

Great post here to discuss ……. so many viruses!

Jeffrey S.
Reply

Rusty,

I didn’t know about the Zombee map, thank you for the information. Upon viewing it I found a confirmed infection in White Haven, that is only 15 miles from me. If any more of my bees show this strange behavior I will capture them and attempt to let them hatch to confirm. Is there any way to keep this fly from infecting my bees? Is this a large problem for a hive or small apiary? Wow, between mites, virus, bad weather, poor nectar flow, animal attacks, zombee fly, hive beetles, dysentery, nosema, foul brood, chalk brood, wasps, etc… its a wonder there are any honey bees left.

Rusty
Reply

Jeffrey,

I don’t think zombee flies are much threat to honey bee colonies. I think they’ve probably been around all along, but we never noticed them. After one confirmed sighting in my apiary, I never saw them again.

Pat
Reply

I’m in western NY state, and it’s been crazy hot here too. It’s unusual for it to be this hot this late, so I’m sure it’s just the usual summer bearding, only in the fall instead. Many of my bees also spent the evening on the front of the hive yesterday.

steve
Reply

I’ve also been puzzled by lots of bees on the landing board. They appear to be very healthy and super energetic going back and forth as if they are cleaning the board. They have done this for a month and they did this last year. There are maybe 20 bees on a 4″x6″ landing board going back and forth all day long as if they were an army of housekeepers vacuuming a banquet hall after an out of control wedding reception. Any ideas about this O. C. behavior? I look forward to your blog! thank you. Steve

Rusty
Reply

Steve,

It sounds like they are washboarding.

Bill
Reply

Really have appreciated the discussion about crawling bees as this is the first year I noticed them (doesn’t mean they weren’t there in previous years but I’m a hobbyist and just this summer noticed them while simultaneously not seeing signs of wing deformity). Not great numbers of crawlers but it was still worrisome, so a relief to hear others’ observations and analysis.

Regarding treating for mites as basic all purpose approach, I do this and use the oxalic acid vapor treatment. I’ve heard that three successive treatments about 5-6 days apart is generally sufficient, but I’d like to know if carrying on the treatment for additional sessions might be of further benefit, and if is there a downside to added treatments. I’m not seeing heavy mite counts (using mite trap board under hive), but after three treatments I still see a few. Any thoughts about calling it good after three treatments or keeping at it?

Rusty
Reply

Bill,

It’s not great for your bees and can cause brood mortality. If treatments were extended, I wouldn’t be surprised to see absconding at some point. Give them a break.

Dieter
Reply

Rusty,

You commented, re. excessive oxalic vapourizer, “… It’s not great for your bees and can cause brood mortality …”. Oxalic acid does not kill varroas in brood cells, likely because of the capping it can not get inside the cell. If so, how then could it cause brood mortality?

Rusty
Reply

Dieter,

According to what I read, some amount of OA diffuses across cappings, not enough to hurt the mites but enough to damage the very soft-bodied brood. Plus, the mites are protected by the bee bodies.

The US EPA official label for OA says this, “Use only in late fall or early spring when little or no brood is present. Oxalic Acid Dihydrate might damage bee brood. Oxalic Acid Dihydrate will not control Varroa mites in
capped brood.”

Charles
Reply

Hi Rusty,

I haven’t done research on the subject, but I’ve seen “crawlers” and their presence generally correlates with the mite infestation rate. When I note an increase in the number of crawlers, it typically means I’m going to see an increase in the number of mites on my next sugar roll test. I live in the SF Bay Area where mites are a big problem.

I’m curious about the crawler bees. They depart the hive almost like forager bees, crawling in the same general direction as the majority of fliers are headed. Do you know if the crawlers are foragers or younger bees? Might they be like infected cells in multicellular organism and essentially committing an act of self-destruction much like apoptosis in an organism.

It’s a bit of an esoteric question about the nature of eusocial insects.

Thanks,
Charles

Rusty
Reply

Hi Charles,

It’s called altruistic suicide. Bees that are sick sacrifice themselves to reduce the pathogen load in the colony. Of course, they don’t think of it like that, but something in their genetics tells them when it’s time to leave.

I don’t know how important age is. In your case, it is probably the result of deformed wing virus carried by the varroa mite. That is why you see the correlation between the number of mites and the number of suicides. As you know, only a small portion of bees with DWV actually have deformed wings, so you may not see that in the crawlers. A lot depends on their age when they contracted the virus. If their wings were already formed, they won’t show deformities.

Other diseases are associated with crawlers as well, including tracheal mites and nosema.

Leave a comment

name*

email* (not published)

website

Feeding a New Package of BeesHow Long?
+