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James E. Tew
Wax Moths and Honey Bees
An Old Combative Relationship
By: James E. Tew
At First Glance…
Our old frenemy, the wax moth, is clearly a pest to both beekeepers and their bees. But for just a moment, consider the restrictive lifestyle that the moth has evolutionary chosen and the long coexistence that they have had with our bees.
Theirs have been a unique path. Just like ants, another longtime pest of honey bees, wax moths have been a part of the bees’ lives for millions of years. Yet, I only discovered “the moth” to be a pest of honey bees when I began in beekeeping about fifty years ago. That’s not even an eye blink in evolutionary time. As a foe of the wax moth, beekeepers only recently came on the scene. The actual relationship has always been between bees and moths – we are only interested bystanders.
The reality is that moths are very good at infiltrating the bee nest. The greater wax moth (Galleria mellonella) is known to mimic some of the pheromones of honey bees. This mimicry allows the moths to infiltrate bee colonies without being detected. The moths produce chemicals that closely resemble the pheromones bees use for communication, which helps them avoid detection by the bees and facilitates their entry into the hive. Bottom line, wax moths have been coming and going in the bees’ nest a long, long time. This is not a new relationship.
Figure 1. A streamlined, highly evolved hive invader.
On occasion, I have watched an adult wax moth dash around on a frame inside the colony. I would expect to see the bees rabidly attack the moth. Usually, they did nothing to punish the pest intruder. The moth was generally ignored. Bummer. That was disappointing.
The Two Teams That Are Involved
Wax moths and honey bees are distinct species that have evolved specialized interactions, particularly in the context of honey bee colonies. This close relationship did not develop quickly (apparently).
Taxonomic Classification
- Honey Bees (Apis spp.):
Family: Apidae (Eusocial bee)
Genus: Apis - Wax Moths:
Family: Pyralidae (Snout moths)
Genera: Galleria (Greater wax moth) and Achroia (Lesser wax moth)
Evolutionary Relationship and Game Plans
While both honey bees and wax moths belong to the class Insecta, their evolutionary paths deviated significantly. Honey bees are part of the Apocrita suborder, characterized by a narrow waist (petiole) and a division between the thorax and abdomen. Wax moths, on the other hand, are part of the Lepidopteran order, which includes butterflies and moths. Both bees and wax moths are insects, but they are very different insects. The relationship between wax moths and honey bees can be seen as a form of coevolution, where both species have developed adaptations in response to each other and continue to modify those adaptions as time passes.
Honey bees (genus Apis) are believed to have evolved around 30 to 40 million years ago. The specialized relationship between wax moths and honey bees, where the moths have adapted to live and feed within bee colonies, suggests a co-evolutionary process. This relationship likely developed over a considerable time frame, potentially over millions of years, as both species evolved behaviors and adaptations in response to each other.
Wax moths are essentially parasites of honey bees. Wax moths have evolved to exploit the resources within honey bee colonies, particularly beeswax, which serves as a food source for their larvae. The ability of wax moth larvae to enzymatically digest beeswax, which is a complex mix of long-chain alkanes, fatty acids and esters, demonstrates a highly specialized adaptation. This capability likely evolved as an opportunistic strategy to exploit the rich and somewhat protected environment within beehives.
Factors Influencing Evolution
If living and eating within a bee hive was such a great idea, why have only two moths made the evolutionary transition? I don’t know that there is a clear answer to that question and, of course, I am not including the microscopic pests that have adapted to living within the bee nest. However, a couple of possible reasons are presented below.
- Environmental Changes: Climate shifts and changes in vegetation and ecosystems could have impacted the availability of resources and the distribution of bee species, influencing the evolution of wax moths.
- Bee Evolution and Diversification: The diversification and spread of honey bees and other bees could have provided new ecological opportunities for wax moths, promoting their adaptation to different bee species and environments
Figure 2. Greater and Lesser Wax Moths eliminating a bee colony.
A Long-term Battle
The damage caused by wax moth larvae can leave the weak hive more susceptible to infections and infestations by other pests and pathogens. The accumulation of frass (larval waste) and silk can provide breeding grounds for bacteria and fungi, further compromising the health of the bee colony.
But bees have not behaviorally given up. They have developed various defense mechanisms to protect their nests from wax moth infestations. These include:
- Propolis seals and barriers – Bees use propolis to seal cracks and crevices in the hive, temporarily preventing wax moths from accessing the colony.
- Hygienic behavior – Some bee species have developed behaviors to detect and remove wax moth larvae or pupae from the hive.
- Maintenance – not prevention – it appears to me that bees have long since given up trying to keep wax moths out of the hive. Instead, they consistently monitor the hive interior for invading moth activities and deal with them as they occur. This is an example of host-parasite interactions.
- An arms race – Over great expanses of time, wax moths have evolved to exploit the specialized niche provided by honey bee nests, while – also over great lengths of time – honey bees have developed various ways to defend against the moth invaders. This longtime, fluid relationship demonstrates the ongoing evolutionary race between these species, where each adapts in response to the other. Punch – then counterpunch. This evolutionary battle is far from over.
Wax moths, in turn, have developed mechanisms to avoid detection and predation by bees, such as spinning protective silk cocoons and producing pheromones that may mimic bee behavior. The silk cocoons are particularly adept at snagging an attacking bee and restraining her while the moth makes a getaway.
A Small Bit of Wax Moth Benefit
From my perspective as a beekeeper, there is precious little reason to want wax moths around. Given that biased opinion, I should say that there actually are a few areas where the moths’ activities can be viewed in a more positive light.
Natural Hive Maintenance
In the wild, wax moths can play a role in the natural maintenance and recycling of old and abandoned hives. They help decompose and break down old combs, which could otherwise harbor diseases and pests that might affect other bee colonies. By cleaning out these old hives, wax moths can facilitate the natural decay process and make space for new colonies or other inhabitants.
Indicator of Hive Health
Wax moth infestations are often a sign of a weak or declining colony. Healthy, strong bee colonies are typically able to forestall wax moths. Therefore, the presence of wax moths can serve as an indicator to beekeepers that their hive may be under stress due to disease, a lack of food or other environmental factors such as pesticide effects. This allows beekeepers to take timely action to support and strengthen the colony before the balance tilts in favor of the attacking moths.
Research and Pest Control Innovations
Wax moths are often used in scientific research, particularly in studies related to pest control, insect physiology, and microbiology. For example, the wax moth larvae are used to study insect gut microbiomes and the digestion of complex substances like beeswax. Research into wax moth biology and behavior can lead to the development of better methods for controlling their populations, thereby reducing the impact on honey bee colonies.
Biological Control Agents
In some contexts, wax moth larvae have been explored as biological control agents for other insect pests. For example, their ability to digest beeswax and other organic materials has led to research into their potential for managing various types of waste products.
Supplemental Protein Source
In some cultures, wax moth larvae are considered a food delicacy and are consumed as a source of protein (Mexico, China, Thailand, India, and Uganda). While this does not directly benefit bees or beekeepers, it offers an alternative use for wax moths, potentially providing beekeepers with an additional revenue stream by harvesting and selling the larvae. To support this notion, human and animal consumption of insects is currently a trending topic in popular media outlets.
Educational and Training Tool
Wax moths can also serve as a practical tool in beekeeping education and training. By studying the life cycle and habits of wax moths, beekeepers can learn about pest management and the importance of maintaining strong, healthy hives. This knowledge can lead to more effective beekeeping practices and improved colony health overall.
Figure 3. Not much that I can positively say about this situation.
Adaptation to a Specialized Niche
Wax moths have evolved to occupy a specialized ecological niche, exploiting the resources found within honey bee colonies. The key adaptations that facilitate this lifestyle include:
- Beeswax Digestion: Wax moth larvae have developed the ability to digest beeswax, a complex substance composed of long-chain alkanes, fatty acids and esters. This ability is rare among insects and likely evolved as a specialized adaptation to utilize the abundant wax in beehives as a food source. The larvae secrete enzymes that can break down the wax, allowing them to derive nutrients from it.
- Toleration of Hive Conditions: Wax moths are adapted to the warm, humid and protected environment of beehives. This adaptation allows them to thrive in conditions that might deter other insect pests.
- Physical Attributes: Wax moths are very streamlined. They hold their wings in a tentlike position. Therefore, the wings are not a hindrance within the crowded hive. Moths fold their antenna tightly against their body and only extend them when needed. Finally, wax moths are fast runners and will dash about the comb. Within the hive community, they only fly short distances.
Wax Moth Life Cycle Adaptations
Wax moths have a life cycle that is closely tied to their bee host environment:
- Eggs: Laid in crevices within the hive or on old combs. Eggs hatch into tiny first stage (instar) moth larvae can readily squeeze through cracks in hive equipment and flagrantly enter the nest to begin developing. Eggs are not always laid inside the colony.
- Larvae: The larvae are the primary destructive stage, feeding on beeswax, pollen, honey and debris in the hive. They also spin silken tunnels through the comb, providing protection from bees and a conducive environment for growth.
- Pupation: Larvae pupate within the hive or in nearby sheltered locations, eventually emerging as adult moths.
- Alternative Hosts: Wax moths can complete less successful life cycles on bumblebees, some solitary bees tropical stingless bees, and occasionally wasp and hornet nests. But clearly, their best food source is found in honey bees’ nests.
Geographical and Ecological Distribution
Wax moths are found worldwide, particularly in regions where honey bees are present. They have been inadvertently spread by human activity, mainly through the movement of honey bee colonies and beekeeping equipment. The maintenance of millions of non-natural hives and the general movement of bee colonies have provided wax moths with abundant new habitats and new opportunities to provide for population spread.
But there is a catch. In general, moths do not withstand cold temperatures well. Some areas may happily be wax moth-free during Spring months until moth populations can migrate back from warmer climates. But it is possible for adult moths to occasionally Winter in a healthy colony that provides warmth, food and shelter for their mortal enemy.
The Battle of the Wax Moths
Both the Greater Wax Moth (Galleria mellonella) and the Lesser Wax Moth (Achroia grisella) larvae rely on similar resources within the hive, primarily beeswax, but also pollen and honey. This overlap in dietary needs can lead to competition between the two species, especially when resources are limited. However, the feeding behavior of these two closely related moths is different.
- Galleria mellonella: The larvae of the Greater Wax Moth are larger and more aggressive feeders compared to those of the Lesser Wax Moth. They can cause extensive damage to hive structures, creating large tunnels and galleries as they consume wax.
- Achroia grisella: The Lesser Wax Moth larvae are generally smaller and less destructive, but they still feed on wax and other hive materials. They tend to inhabit the same areas as Galleria mellonella larvae, particularly targeting combs that are already weakened or damaged. For example, Achroia grisella might exploit finer, less structurally significant parts of the comb, while Galleria mellonella tackles larger, more robust areas.
However, both species can coexist in the same hive, especially in conditions where there is ample food supply. The presence of both species can exacerbate the damage to the hive, as they may collectively consume more resources and create more structural damage.
Management Considerations for Beekeepers
Beekeepers must manage both species of wax moths to protect their hives. Control measures typically include:
- Maintaining Strong Colonies: Strong, healthy bee colonies are better able to defend against wax moth infestations. Obviously, strong colonies are not always possible.
- Regular Hive Inspections: Frequent inspections can help detect early signs of wax moth presence, such as webbing, visible larvae or Gallarasis.
- Hive Sanitation: Removing old combs and maintaining clean hive and apiary conditions can reduce the likelihood of infestations.
- Use of Traps and Treatments: Beekeepers may use traps, biological control agents or chemical treatments to manage wax moth populations.
- Exposing combs to air and light: In NE Ohio, I have had good luck stacking beeless boxes with drawn combs on their ends and allowing them to sit in the bee yard. This only works if the moths have not already invaded the equipment. At least, this is easy to do.
So There – Moths and Bees
Bees and moths have had a relationship for a long, long time. In some ways, beekeepers have made life easier for the moth. But we these performed these assisting procedures for all the right bee management reasons. But as the bees have shown us, beekeepers will need to expect to deal with moths for eons to come. It’s an old relationship.
In a future article, I will discuss “Gallarasis” or the condition in which developing bees are trapped in their cells by wax moth webbing. I am out of space for this month. Thank you so much for reading this piece. I truly hope you continue to enjoy beekeeping.
Dr. James E. Tew
Emeritus Faculty, Entomology
The Ohio State University
tewbee2@gmail.com
Host, Honey Bee
Obscura Podcast
www.honeybeeobscura.com
