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The slippery life of the small hive beetle

Alfred Hitchcock would have loved the small hive beetle, Aethina tumida. If he had only known, he might have scrapped his movie The Birds in favor of The Beetles. Small hive beetles lead a horror story life, fraught with mystery, intrigue, and destruction. The beetles, aided by their partner in crime—a symbiotic yeast—produce slime, mimic pheromones, and ferment honey.  And if that’s not odd enough, an adult hive beetle can coax a honey bee worker into feeding it. Even the larvae are creepy. Reminiscent of fictional lemmings that leap from cliffs, beetle larvae of a certain age travel in packs and dive from the hive entrance to the ground below. Weirdness knows no bounds.

In its homeland of sub-Saharan Africa, the small hive beetle is only a minor pest. Having evolved together with the local honey bees, Apis mellifera scutellata and A. m. capensis,1 the small hive beetles are kept in check and do not normally destroy colonies of honey bees.2 However, once it crossed oceans, the small hive beetle found a vulnerable host without a ready defense. The European sub-species of honey bees are easy prey, partly because they abscond less frequently than the African bees. In addition, they leave more resources behind for the beetles to consume when they do abscond.3

This article first appeared in American Bee Journal, Volume 158 No 1, January 2018, pp. 39-42.

Widespread Damage

Since the small hive beetle was first spotted in North America in 1996, it has spread rapidly, defying predictions about its inability to survive in colder climates. It was first reported in both Canada and Australia in 2002 and has since scattered throughout other regions as well.

Damage to colonies infected by small hive beetles can be severe, potentially causing colony demise. In the early years after its introduction, the small hive beetle seemed to be a problem limited to weak or small colonies, or to unguarded honey houses and stored equipment. But more recently, beekeepers have reported that even large and robust colonies can be destroyed by the beetles. Elevated beetle populations, especially those that approach 1,000 adults per hive,4 are especially problematic.

An adult small hive beetle may enter a hive along with a nucleus colony, a package, or a split. Or, left to its own devices, a beetle may discover a colony by detecting honey bee pheromones or other attractive hive odors.5

Imagine Life in their Shoes

To better understand the life cycle of these creatures, suppose for a moment you are one. Let’s say you, Bonnie the Beetle, emerged from the soil a week ago.  Before doing anything else, you mate with the handsome dudes in your area. After a week or so,6 you go for a nice long flight to look for a place to live and raise your young. There’s no point in staying too close to home because lovely, habitable hives are everywhere.

You find a suitable domicile by sniffing the air. Honey bee alarm pheromone smells inviting, as do the odors of pollen, ripening honey, and bee brood. Your ability to fly about six miles (10 km) makes this an easy task.1 Once you find a hive you like, you simply fly in. What a relief to be out of the light!

Laying your Eggs

Where you lay your eggs depends on how welcoming your hosts decide to be. If the host bees are friendly, you may lay your eggs atop stored pollen or directly on bee brood. To reach the brood, you chew a tiny hole through the wax cappings or make a small slit in the side of a brood cell. With your long and flexible ovipositor, you can reach deep into protected places. You drop your clutch of eggs—a dozen or two—in the tight space and then move on to another. With a little luck, you may lay 1000 eggs, or maybe double that, in your lifetime.4

If the host bees are not so benevolent, you may decide to leave your eggs in cracks and slits along the edge of the brood nest. Unprotected eggs may be eaten by worker bees, so site selection is important. You want to avoid ornery bees, so you seek tiny out-of-the way crevices where they can’t quite reach you. If in doubt, you try the secluded spaces between the top bars, in feeders, in the corners of the bottom board, or up on top of the inner cover. It’s a world of choices.

Avoiding the Jailers

Still, caution is necessary. Sometimes an army of cranky nurse bees will corral you and your friends into a corner, denying you food and preventing access to the brood nest. With no get-out-of-jail-free cards, you are incarcerated behind a line of guards that watches you 24/7.

At such times, you must be devious. Play nice. If you stroke the bees’ mandibles with your antennae, they will eventually feed you. When she receives just the right touch, a nurse bee will extend her proboscis into your waiting mouth and, in a process called trophallaxis, share regurgitated nectar from her honey stomach.4 How sweet it is. And remember, patience pays. You can play this waiting game for 180 days or more.2

Meanwhile, while you’re marking time behind bars, your eggs begin to hatch. Within 2-4 days, hungry larvae emerge and promptly begin a search for food.2 The menu includes pollen, nectar, honey, and brood, and the larvae will burrow through combs and cappings to get it. And like creatures everywhere, the more they eat, the more they defecate. But this larval feces is special, loaded with the spores of a yeast called Kodamaea ohmeri.7 The yeast spores love the moist environment of the hive, and soon germinate and mature into a slimy mat that coats the combs with a glistening and slippery mantle.

The yeast can bloom quickly. A pristine frame of honey can transform into a slimy mess in as little as 30 hours. The shimmering, gelatinous sheet weakens the wax cappings that cover the honeycomb, causing the honey to leak from the cells and then ferment. In severe cases, the ruined honey will drip down through the hive and run out the entrance.

The Wandering Stage

After about 13 days of gorging in the hive,8 your offspring are ready to rock and roam. The larvae gather together near the hive entrance and wait for the witching hour. Just after dusk, under the cover of darkness, the larvae wriggle from the hive and drop to the ground. This group exit from the colony has been described as a “mass exodus” or a “larval regiment.” As soon as they hit terra firma, these wandering larvae begin to look for a place to burrow into the soil. Most find a spot within three feet (90 cm) of the hive entrance.

Small hive beetle larva. By USGS Bee Inventory and Monitoring Lab from Beltsville, Maryland, USA [Public domain], via Wikimedia Commons. Courtesy Sam Droege.
Small hive beetle larva. By USGS Bee Inventory and Monitoring Lab from Beltsville, Maryland, USA [Public domain], via Wikimedia Commons. Courtesy Sam Droege.
But worry not. Wandering larvae are resilient and strong. If soil conditions under the hive are not perfect, the larvae will take off in search of something better. Such vagabonds have been known to travel 220 yards (200 m) in search of better soil. Their primary concern is soil moisture, especially summer moisture.9 Relentless in their pursuit of ideal conditions, larvae have been known to wander for up to 48 days and still manage to pupate successfully.10

Pupa to Adult Beetle

Once they find a suitable place, the larvae dig down 4-8 inches (10-20 cm) where they prepare a smooth-walled cradle for themselves in which to pupate. Pupation is usually complete in three to four weeks, although it may take anywhere from 8 to 78 days, depending on conditions.9 The adult then emerges from the soil, just like you did. When all goes according to plan, one year can yield six generations of beetles.

Okay, enough of being Bonnie the Beetle. You can hang up your wings now and come back to real life.

A Close Relationship

Although the small hive beetle life cycle is strange, the yeast-beetle relationship is crazier still. It turns out that when the yeast, K. ohmeri, grows on top of pollen, it produces an odor that mimics honey bee alarm pheromone.5 Since small hive beetles are attracted to alarm pheromone in a big way, the growing yeast attracts more and more beetles. Like a siren call, the yeast odor announces that small hive beetles have successfully colonized this hive. “Come join us!” the odor seems to say. And join they do. A hive that had few beetles may suddenly attract hundreds.

Contrary to early accounts, small hive beetles prefer to lay their eggs directly in brood comb. Beetle larvae that emerge within a brood cell have a ready supply of protein and other nutrients in the form of a honey bee pupa.  Multiple beetle larvae may spill from a single brood cell and begin burrowing through combs and honey as they search for more food. Beekeepers have reported cutting open brood cells to find a dozen or more beetle larvae actively consuming a dead pupa.

Sometimes the exoskeletons of bee pupae can be seen on the landing board or on the ground beneath a hive, their interiors completely sucked dry by the beetles. Such skeletons, often accompanied by leaking honey, may be a beekeeper’s first sign of trouble.

Oddly enough, honey bees do not pursue small hive beetle larvae. While a phalanx of guards imprisons the adult beetles, the beetle larvae freely roam through the brood nest and honeycombs, eating and defecating as they go.

Adults can overwinter in the hive as long as the bees feed them, and heat from the cluster keeps them warm.11 Egg laying is suspended during the winter months but can resume as the weather warms in spring.

How Yeast Spores get into the Hive

It is still unknown how the yeast spores get into the larvae. It is possible that the spores survive within the larva during metamorphosis into an adult beetle, even though the digestive tract gets completely reorganized in the process. Alternatively, the larva may shed yeast spores in its feces as it digs into the soil prior to pupation, only to become re-infected as an emerging adult. Others speculate that the spores may reside in pollen, which in turn is carried into the hive by foraging bees and then eaten by the larvae.12

Underside of adult small hive beetle by USGS Bee Inventory and Monitoring Lab from Beltsville, Maryland, USA [Public domain], via Wikimedia Commons. Courtesy of Sam Droege.
Underside of adult small hive beetle by USGS Bee Inventory and Monitoring Lab from Beltsville, Maryland, USA [Public domain], via Wikimedia Commons. Courtesy of Sam Droege.
Hayes et al.13 grew slime in the laboratory by placing small hive beetles, water, brood comb, and honeycomb in plastic bags. They found “the best slime (with the highest yeast production) was obtained when a combination of honeycomb and brood comb was used.” Honeycomb alone did not produce beetles or slime, brood comb alone produced beetles but minimal slime, but in combination, brood comb and honeycomb produced numerous larvae within a viscous mantle of slime.

They also found that the slime became more attractive to small hive beetles as it aged, possibly due to an increasing amount of ethanol. Ethanol is attractive to many insects, helping them locate rotting fruit and similar foods. In addition, other compounds such as isobutanol, isopentanol, and isopentyl acetate were produced by the slime.7 Isopentyl acetate is the well-known main component of honey bee alarm pheromone.

Many beekeepers have reported seeing little or no slime in a hive and then, several days later, seeing masses of it covering many frames. The slime seems to materialize out of nowhere, far exceeding the expansion of the beetles themselves. This sudden appearance occurs because the yeast can multiply much more quickly than the beetles.

Severely infested honey bee colonies are unable to remove the slime.  As the slime spreads the bees tend to move up into the supers, trying to get away from the mess. Egg laying drops or may cease altogether. At some point the colony may abscond or collapse.1

Pairs of Pests

Many parallels exist between the varroa mite-virus association and the small hive beetle-yeast association. In each case, it is probably the unseen partner that causes the most damage. It is possible that honey bees could live with varroa if it weren’t for the viruses. Likewise, perhaps the bees could live with small hive beetles if it weren’t for the yeast.

And just as mites are getting harder to control, small hive beetles are getting harder to control as well. Simply maintaining strong and healthy colonies may no longer be enough. Since controlling an insect on an insect is tricky business, we may well have to begin looking at the yeast as the potential weak spot in the beetle life cycle.

Looking back on it, perhaps Alfred Hitchcock could have written his movie about The Yeasts. Now that’s creepy.

Rusty
Honey Bee Suite

Small hive beetles in a hive with honey bees. CSIRO [CC BY 3.0 (https://creativecommons.org/licenses/by/3.0)], via Wikimedia Commons.
Small hive beetles in a hive with honey bees. CSIRO [CC BY 3.0 (https://creativecommons.org/licenses/by/3.0)], via Wikimedia Commons.

References

  1. Annand N. 2011. Investigations on small hive beetle biology to develop better control options (Masters thesis). Retrieved from http://handle.uws.edu.au:8081/1959.7/507741.
  2. Lundie AE. 1940. The small hive beetle, Aethina tumida. South Africa Department of Agriculture & Forestry. Science bulletin 22.
  3. Spiewok S, Pettis JS, Duncan M, Spooner-Hart R, Westervelt D et al. 2007. Small hive beetle Aethina tumida populations I: Infestation levels of honey bee colonies, apiaries and regions. Apidologie 38: 595-605.
  4. Pettis JS, Chen YP, Ellis J, Evans JD, Rennich KD et al. 2015. Diseases and Pests of Honey Bees. In JM Graham (Ed.) The Hive and the Honey Bee (pp 856-859). Hamilton, Illinois: Dadant & Sons, Inc.
  5. Torto B, Suazo A, Alborn H, Tumlinson JH, Teal PEA. 2005. Response of the small hive beetle (Aethina tumida) to a blend of chemicals identified from honeybee (Apis mellifera) volatiles. Apidologie 36: 523-532.
  6. Ellis JD. 2004. The ecology and control of small hive beetles (Aethina tumida Murray). (Doctoral dissertation). Retrieved from http://hdl.handle.net/20.500.11892/21265.
  7. Benda ND, Boucias D, Torto B, Teal P. 2008. Detection and characterization of Kodamaea ohmeri associated with small hive beetle Aethina tumida infesting honey bee hives. Journal of Apicultural Research and Bee World 47 (3): 194-201.
  8. Stedman M 2006. Small hive beetle: Aethina tumida Murray (Coleoptera: Nitidulidae). Primary Industries and Resources for South Australia. Factsheet 03/06.
  9. de Guzman L, Prudente J, Rinderer TE, Frake AM, Tubbs H. 2009. Population of small hive beetles (Aethina tumida Murray) in two apiaries having different soil textures in Mississippi. Science of Bee Culture 1(1): 4-7.
  10. Cuthbertson GS, Wakefield ME, Powell ME, Marris G, Anderson H et al. 2013. The small hive beetle Aethina tumida: A review of its biology and control measures. Current Zoology 59 (5): 644-653.
  11. Schäfer MO, Ritter W, Pettis J, Teal PEA, Neumann P. 2009. Effects of organic acid treatments on small hive beetles, Aethina tumida, and the associated yeast Kodamaea ohmeri. Journal of Pest Science 82:283-287.
  12. Conklin TA. 2012. Investigations of small hive beetle-yeast associations (Doctoral dissertation). Retrieved from https://etda.libraries.psu.edu/catalog/15226.
  13. Hayes R, Rice S, Amos B, Leemon D. 2015. Increased attractiveness of honey bee hive product volatiles to adult small hive beetle, Aethina tumida, resulting from small hive beetle larval infestation. Entomol Exp Appl, 155: 240–248. doi:10.1111/eea.12304

Comments

Richard Caton
Reply

Hello Rusty,

Good article. I learned a bit more from you about this nasty pest. I have a six-colony apiary in my backyard here in Dayton, MN that was clean of these beetles until I purchased a couple of nucs. It was my second year of beekeeping and I was excited to get them. What a nightmare they turned out to be. They were Minnesota Hygienic bees that were overwintering in Texas from a local pollinating service up here. Along with them came the beetles that I didn’t see when I installed them. I didn’t recognize them at first, ignoring them as just another yard bug walking through the hive. After seeing more of them I took a sample and hit the books and videos and found out I had beetles. I installed beetle traps and got them under control. The infected hives died out over the winter and so did the beetles. I didn’t see any in my hives last summer. Those MN Hygienic bees never took off and the brood cappings were sunken in and had a little hole in the middle. I did the rope test and they roped out so now I also had AFB. I burned the two hives of the MN Hygienic bees. These were very mean and aggressive bees and in a way I was glad to see them go. I look at the money I lost on these failed nucs as paying for an education. You can open the books and read about these things but when you live the words you learn.

Rusty
Reply

Such a deal, Richard. You paid extra (I’m sure) for the MN hygienics but you got free beeltes, AFB, and bad temperaments! How discouraging. As you say, it’s the price of an education.

Granny Roberta in nw Connecticut USA
Reply

This is completely disgusting, fascinating, and amazing.

Also, thank you, because small hive beetles are spreading toward Connecticut and I should get ready. (They’ve already reached New Jersey.)

(Also also, would wax moths support an equally disgusting and fascinating article?)

Rusty
Reply

Roberta,

I’ve started a review of wax moths, although they are not nearly as entertaining as small hive beetles.

Jenny W - Central Michigan
Reply

I battled SHBs this summer (in my largest and strongest colony) seemingly alone, as no one in our large beekeeping club admitted to problems with these pests. I have read a few books on the topic, discouraged that there seems to be no real fix to eliminate them. I will be trying variegated plastic squares wrapped in dry Swiffer pads placed on my bottom boards this year…at least with varroa I can test for mite loads and treat to kill…would love to read a post regarding treatment options for SHB. The most frustrating aspect for me is not knowing if my honey was ruined by small amounts of yeast…no slimy frames noted, but at small amounts, there may not be slime present as a warning. Thanks Rusty!

Rusty
Reply

If you don’t see any slime, I wouldn’t worry about it.

Rusty
Reply

If you don’t see any slime, I wouldn’t worry about it.

Alice
Reply

Great study review on SHB, Rusty, although I did have deja-vu while reading it for some reason.

Rusty
Reply

Alice,

That happens with the ABJ articles, but I think they are worth running regardless.

Patrick Purcell
Reply

Thank you Rusty, I am now horrified and paranoid. Please follow up with an article on prevention.

All beekeepers should read this article.

Rusty
Reply

Patrick,

I may do that. In the meantime, people should check their packages. I know for sure they often come that way—no extra charge.

Lloyd Seested
Reply

For the past two years I have spread diatomaceous earth about three feet wide around the hive stands. as you said they dive off the ipm board or fall thru the screened bottom board to get to the ground. I also put rolled up swiffer sweeper dry sheets (10”x 8”) in several corners. They either like the corners because they can hide there or the bees drive them there or both. tThis seems to work as I find some beetles in the cloths and haven’t had any problem.

Debby Williams
Reply

These are great ideas. I think the diatomaceous earth would help with ants too.

Jim Jamieson
Reply

How far into Canada has the small hive beetle advanced?

Rusty
Reply

Does anyone know? I’ve heard it is more in the east, but that may be old news.

Larry T
Reply

Can you stop these beetle pests or draw them to a trap they cannot escape from…As a kid I trapped regular bettles by taking an olive jar dig a hole put it (the jar full length into the ground) put a little sandwich meat in the bottom of the jar…the beetle would smell and follow the scent…fall into the bottle where it couldn’t escape and I would have to show a science class.

Rusty
Reply

Larry,

There are many different types of oil trap available that fit into different places within the hive and below it.

Sean Govan
Reply

Since the damage occurs so quickly, is it wise to use preventive measures to keep a hive from being infested in the first place, or is it a rare enough problem that I shouldn’t worry about it unless it happens? I am in Kansas. (First time beekeeper here.)

Rusty
Reply

Sean,

They are certainly not rare, although they may be rare in your area. I don’t know. It seems like the soil type is often the deciding factor. The larvae have to be able to pupate in the soil, so some soil types are better than others.

Debby Williams
Reply

In your opinion, are the hive beetle traps worth the effort? I have been using the one that sits as a frame, next to the sidewall, of the top box. After reading this, I am not sure why it is supposed to be in the top most box. I have found the beetles on my sticky boards, never in the traps, and so far only a few.

Rusty
Reply

Debby,

The adult beetles frequently go up to the top and hide between the bars or under the cover. People who have a lot of beetles report good success using traps of different types. They are not very expensive to you can experiment with different brands.

Pat Ratliff
Reply

Here in SE Oklahoma, we have battled SHB from the first package I installed 3 years ago. The queen was producing only drones, and by the time the package workers superceded her, it was too late. I saw honey draining out the front entrance and all the comb was covered in thousands of what appeared to be maggots! [shudder] Beetles were in high numbers in the next set of hives, too, though no more sliming at least. I have finally found the ways to keep their numbers low. I installed screen-bottom boards with oil-filled trays slid just under the screen. This catches adults as they run from the bees and larvae en route for pupation. We tried the in-frame Beetle Blaster traps but they weren’t catching enough. We put our last set of hives in the sun instead of shade (bright light + drier ground), and I salt down the ground all around the hives to decrease pupation success. There’s just a few beetles at most in each colony instead of the 100s I used to find.

Rusty
Reply

Pat,

It sounds like you’re doing a good job.

Larry T
Reply

Just so I understand how this pest works…as an adult and after mating it flies to a nest…enters looking for nectar, honey, and brood…bees may or may not aggressively herd the pest especially if the hive is small in numbers….If they herd the pest by patience it may live because the pest can trick the bees into feeding and caring for it by not being aggressive itself…the eggs become larva that go out of the hive onto the ground looking for proper soil to burrow and develop into and adult beetle to complete the cycle. If this is correct I need to see where can we prevent the start of the adult getting into the hive (preferred), but doesn’t seem that is possible????

Rusty
Reply

Larry,

If it was an easy problem to solve, it would have been solved by now. Instead, they just keep spreading.

Chet
Reply

Great info and writing.

Sandy Richey
Reply

Another witty and educational article. Thanks for sharing.

Larry T
Reply

Rusty, are these bees regional, for example I live in Central Texas and enjoy some clover honey from North and South Dakota. These location are of course very northern climates with much shorter summer periods, and would seem not favorable for a beetle.

My climate on the other hand has already started to warm and act like we are very near start of an early summer while the majority of the country is still suffering winter weather conditions and would seem favorable to such a beetle?

Rusty
Reply

Larry,

At one time it was assumed the beetles would stay in the south, but now they are already up in Canada. It seems the soil type is more important that the temperatures.

Richard Rurup
Reply

Hello all.

I live in central AR (zone 7b). I have converted my screened bottom boards to a closed unit with a removable panel in the rear to slide out my pan which contains diatomaceous earth. My only entrance to the hives are 5×3/4 inch openings in summer and 1 1/2 x 3/4 in winter at the regular place. Beetle blaster and beetle jails do a little good, but Swiffer just seems to give them a place to hide. Leave as much propolis as possible and smash as many SHBs as you can during inspections. Control the amount of space the bees have and don’t give them more than they can patrol. I have never had sliming yet, but some members of my club has and they lost the hives. Sun or shade doesn’t seem to matter with my hives, it’s always shady inside and they fly to the hives mainly at dusk.

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