Eristalis tenax, commonly referred to as the common drone fly, is a notable member of the hover fly species.
Distributed globally, this insect plays a significant role in various ecosystems.
Its resemblance to certain bee species, coupled with its unique behaviors, makes it a subject of interest for both entomologists and insect lovers.
In this article, we will look at the drone fly life cycle and other attributes of this intriguing insect.
Classification and Appearance
Falling under the Insecta class, the Drone Fly is a member of the Diptera order, specifically belonging to the Syrphidae family.
Within this family, it’s classified under the Eristalis genus and is identified as the species E. tenax. In simpler terms, its binomial name is Eristalis tenax.
In terms of appearance, both male and female drone flies are robust and stocky.
Their eyes exhibit a marbled pattern in black, and they often engage in hovering displays, especially the males.
On average, their wings measure between 9.75–13 mm in length, with an overall wingspan of approximately 15 mm.
The abdomen of these flies can range in color from a deep brown to a more vibrant orange.
One of the distinguishing features of the drone fly, which sets it apart from honey bees, is its two wings.
In contrast, bees possess four.
Additionally, the drone fly lacks the constricted “waist” observed between the thorax and abdomen of honey bees, further differentiating it from its bee counterparts.
Distribution and Habitat
The common drone fly boasts a vast global distribution, making its presence known on every continent with the exception of Antarctica.
Within the United States, its range extends from the northern reaches of Alaska down to the warmer climates of California and Florida.
The adult drone fly is often spotted in areas abundant with flowers, given its reliance on nectar and pollen.
However, its larval form, known as the rat-tailed maggot, has a distinct preference for aquatic habitats.
These larvae thrive in stagnant or polluted water sources, such as drainage ditches, sewage pools, and even around manure piles.
The high levels of organic matter in these waters provide an ideal environment for the larvae, as they feed on the bacteria that flourish in such conditions.
Behavior and Territoriality
Male drone flies, especially during the warmer summer months, are known to be territorial.
They stake claim to specific areas, guarding them diligently against intruders.
These territories are not just for show; they play a pivotal role in the drone fly’s life cycle.
By establishing and maintaining a territory, a male drone fly ensures he has access to resources essential for mating, feeding, and grooming.
The significance of these territories extends beyond mere resource access.
They also serve as arenas where males can display their dominance, engage in mating rituals, and ensure the continuation of their lineage.
Interestingly, the behavior exhibited within these territories can vary based on their location.
For instance, a drone fly guarding a territory near a water source might exhibit different behaviors compared to one near a flowerbed.
The availability of resources, potential threats, and even the presence of females can influence how a male drone fly behaves within his claimed territory.
Drone Fly Life Cycle and Development
The life cycle of the common drone fly is a systematic progression through four distinct stages: egg, larva, pupa, and adult.
Egg Stage
The initial stage of the drone fly’s life cycle begins with the egg. These eggs are white, elongated, and covered in a sticky substance.
Females lay these eggs near the surface of stagnant or polluted water sources or close to decaying organic material.
This strategic placement ensures that the emerging larvae have immediate access to suitable habitats and food sources.
Larva
Upon hatching, the drone fly enters its larval stage, commonly referred to as the rat-tailed maggot.
These larvae are aquatic and possess a cylindrical shape segmented by horizontal folds.
A distinguishing feature of the rat-tailed maggot is its posterior siphon, which functions as a respiratory mechanism, allowing the larva to breathe while submerged.
The primary habitat for these larvae includes water sources rich in organic matter, where they feed on bacteria.
Pupa
Following the larval stage, the drone fly undergoes pupation. The pupal form retains some resemblance to the larva but is notably shorter and thicker.
This stage is characterized by limited movement, as the insect undergoes significant internal transformations.
Pupation typically occurs in drier environments, often just below the soil surface, and lasts for approximately 8-10 days.
Adult Drone Fly
Emerging from the pupal stage, the fully developed drone fly is ready to begin its adult life. Adult drone flies are robust, with a length of about 15 mm.
Their primary diet consists of nectar and pollen, sourced from various flowers.
The adult stage is also when reproductive activities occur. Males establish territories to attract females, and after mating, females lay clusters of eggs to begin the life cycle anew.
Here is a table comparing the various stages of the drone fly’s life cycle.
| Life Stage | Description | Duration |
| Egg | White, elongated, covered in a sticky substance. Laid near stagnant water or decaying material. | Few days (varies based on environmental conditions) |
| Larva | Aquatic, cylindrical shape with a respiratory siphon on the posterior end. Feeds on bacteria in stagnant waters. | Approximately 18 days |
| Pupa | Resembles the larva but shorter and thicker. Undergoes transformation below the soil surface. | 8-10 days |
| Adult | Robust fly, about 15 mm in length. Feeds on nectar and pollen. Engages in reproductive activities. | Varies (several weeks to months, depending on conditions) |
Diet and Feeding Habits
The diet of the common drone fly is primarily plant-based. As adults, their main sources of sustenance are nectar and pollen, which they obtain from a variety of flowers.
Nectar serves as a primary energy source for the drone fly, providing the necessary carbohydrates that fuel their daily activities.
Pollen, on the other hand, is a rich source of proteins and other essential nutrients vital for their reproductive processes and overall health.
The process of pollen consumption is quite methodical.
Drone flies have specialized mouthparts that allow them to efficiently extract pollen grains from flowers.
Once ingested, the pollen provides the necessary nutrients that contribute to their growth, development, and reproductive capabilities.
Role in Pollination
Hoverflies, including the drone fly Eristalis tenax, play a crucial role in the pollination process.
As they move from flower to flower in search of nectar and pollen, they inadvertently transfer pollen grains, facilitating the reproductive process of many plants.
While bees are often recognized as the primary pollinators, hoverflies like the drone fly are equally efficient in this role.
In fact, in certain environments and under specific conditions, hoverflies might even surpass bees in terms of pollination efficiency.
This is particularly true in areas where bee populations are declining or are under threat.
Comparatively, while bees tend to be more methodical in their approach to visiting the flowers of a single species during a foraging trip, hoverflies are less selective.
This non-discriminatory approach to foraging means that hover flies can potentially pollinate a broader range of plants during a single trip.
In conclusion, the role of hoverflies, including the common drone fly, in pollination is significant.
Their contribution to maintaining biodiversity and ensuring the reproduction of various plant species is invaluable, emphasizing the importance of their conservation and protection.
Mimicry and Defense Mechanisms
One of the most fascinating aspects of the common drone fly is its remarkable resemblance to certain species of bees and wasps.
This is not a mere coincidence but a result of a phenomenon known as mimicry.
Morphologically, the drone fly shares several features with honey bees. Its robust body, coloration, and even the way it moves and hovers can easily be mistaken for a bee by the untrained eye.
Behaviorally, too, the drone fly exhibits certain patterns that are reminiscent of bees, further enhancing this illusion.
The primary benefit of this mimicry is defense. By resembling species that are known to sting or pose a threat, the drone fly deters potential predators.
Many predators, having had unpleasant experiences with bees or wasps, tend to avoid any insect that looks similar.
Thus mimicry offers the drone fly a level of protection that it wouldn’t have if it were to rely solely on its own defense mechanisms.
Interaction with Humans and Common Misconceptions
Given their resemblance to bees, it’s not uncommon for people to wonder: Do drone flies bite or sting? The answer is straightforward – no, drone flies do not bite or sting.
This is a common misconception, primarily because of their bee-like appearance. In reality, drone flies are harmless to humans and pose no direct threat.
However, their larval form, known as the rat-tailed maggot, has been associated with certain health concerns.
There have been rare cases of human intestinal myiasis caused by the ingestion of water contaminated with these larvae.
In such cases, the larvae can survive within the human intestine, leading to discomfort and other symptoms.
It’s essential to note that such occurrences are extremely rare and usually result from consuming untreated water from sources where the larvae thrive.
To summarize, while the adult drone fly is harmless and plays a beneficial role in ecosystems, it’s crucial to be aware of the potential risks associated with its larval form.
Proper water treatment and hygiene can effectively mitigate these risks.
Conclusion
The common drone fly, Eristalis tenax, is a remarkable insect that plays a pivotal role in various ecosystems.
Its life cycle is a testament to the adaptability and resilience of this species.
From the egg’s strategic placement near nutrient-rich waters to the larva’s unique respiratory mechanism that allows it to thrive in stagnant waters, each stage of the drone fly’s life is intricately designed for survival.
As adults, these flies not only contribute to the pollination of various plants but also exhibit fascinating mimicry patterns, resembling bees and wasps for defense.
Their diet, primarily consisting of nectar and pollen, underscores their importance in maintaining biodiversity.
However, like many species, the drone fly is not without its misconceptions. While the adult is harmless, its larval form, the rat-tailed maggot, has been associated with rare health concerns in humans.
Proper understanding and awareness can ensure that we coexist with this species, appreciating its contributions while mitigating potential risks.
Reader Emails
Over the years, our website, whatsthatbug.com has received hundreds of letters and some interesting images asking us about Drone Flies and Rat tailed maggots. Scroll down to have a look at some of them.
Letter 1 – Unknown “Bug” found in home
Location: NC
January 26, 2016 8:46 pm
I have only found one of these. He has to be the strangest insect I’ve ever seen. I didn’t kill it ! I found him this way . It was on our living room floor near the propane fireplace.
Signature: Lost in the woods
Dear Lost in the woods,
Though you have provided several images, we have no idea what they depict. You mentioned finding it near the propane fireplace. Do you burn wood in the fireplace? Was there a stack of firewood nearby?
Many insects infest wood, including the larvae of beetles in the families Cerambycidae and Buprestidae, but this doesn’t look like either a Round Headed Borer which is pictured on BugGuide or a Flat Headed Borer which is also pictured on BugGuide.
No sir , WE do not use wood . Actually have only turn it on one or two time. Funny looking little guy ! It look like it has a possum tail.
Lost in the woods
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