The rat-tailed maggot is a distinctive larva with a fascinating life cycle. This article explores its characteristics and transformation from an aquatic dweller to its adult form.
Identifying the Rat-Tailed Maggot
The rat-tailed maggot is the larval stage of certain hoverfly species, most commonly the drone fly (Eristalis tenax). These larvae have whitish bodies, around 1.9 cm (3/4 inch) long, and a long, telescopic breathing tube extending from their posterior end. This “tail,” which can stretch up to 15 cm (6 inches), functions like a snorkel, allowing the maggot to access atmospheric oxygen while submerged.
These larvae thrive in stagnant, oxygen-poor aquatic environments rich in decaying organic matter. Habitats include sewage lagoons, manure pits, stagnant ponds, and even the water found in tree holes or compost piles. The breathing siphon is an adaptation, enabling them to survive in conditions where other aquatic insects cannot. While feeding on bacteria and decomposing material, the maggot can extend or retract its siphon, keeping the tip at the water’s surface for respiration.
From Maggot to Pupa
Once the rat-tailed maggot has completed its larval growth, it prepares for the next stage of its metamorphosis: pupation. The fully grown larva leaves its aquatic environment, seeking a drier, sheltered location. This migration often leads them to soil, under debris, or even into basements or barns, as they search for a suitable spot.
During the pupal stage, the maggot encases itself, undergoing significant internal changes. The pupa resembles a shorter, thicker version of the larva, measuring 10–12 mm long. Although the siphon remains present, it locks into a curved position over the pupa’s back. Two horn-like bumps, called cornua, appear on the thorax of the pupa, which are thought to assist with respiration during this immobile, non-feeding phase.
Emergence of the Hoverfly
After the pupal stage, which can last approximately 8 to 10 days, the rat-tailed maggot transforms into an adult hoverfly. Adult hoverflies are often mistaken for bees or wasps due to their mimicry, but they are harmless and lack a sting.
Adult drone flies measure around 15 mm (0.6 inches) in length, with a stocky body that is dark brown to black, featuring yellow-orange markings on their abdomen. They are characterized by their ability to hover motionless in the air, a behavior that gives many species in their family the common name “hoverfly.” As adults, their diet primarily consists of nectar and pollen, which they collect from various flowers.
Ecological Contributions
Both the larval and adult stages of the drone fly contribute to ecological processes. The rat-tailed maggots, living in oxygen-deprived and organically rich waters, play a role in decomposition by consuming decaying organic matter and bacteria. Their presence can sometimes indicate high levels of organic pollution in water bodies.
Adult hoverflies are pollinators. As they feed on nectar and pollen, they transfer pollen between plants, aiding in the reproduction of many flowering plants and agricultural crops. They contribute to biodiversity and the health of plant communities.