Scorpionfly Natural History

Scorpionflies are insects in the Mecoptera order of insects, which consists of approximately 600 species worldwide. Scorpionflies are known for their segmented appearance and long tail-like appendage that gives them the appearance of a flying scorpion. Other insects in the Mecoptera order include earwigs and hanging flies.

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Scorpionfly Anatomy

Scorpionflies usually measure an inch or two long and have thin, elongated bodies. Similar to many species of fly, they have an enlarged rostrum and membranous wings. They also have slender appendages, similar in appearance to mayflies. Like all insects, they have a set of compound eyes and a pair of antennae.

Perhaps the most distinguishing feature of scorpionflies is their enlarged genitals that appear like the stinger of a scorpion, hence the name. Despite the size and stinger-like appearance, this appendage is completely harmless and cannot sting. In fact, scorpionflies have very small mouthparts and cannot bite well either.

Scorpion flies are a close relative of fleas and share a common ancestor with flies, butterflies, and moths. Despite their wings, they are not strong fliers and tend to spend most of their time situated on food sources.

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Scorpionflies and the wider Mercoptera evolutionary order are important for understanding the evolutionary lineage of insects. Two of the most important insect classifications, Diptera and Trichoptera, share a common ancestor with scorpionflies, and ancestors of the scorpionfly existed over 250 million years ago.

Scorpionfly Behavior

Despite their sometimes fearsome behavior, scorpions flys are not hunters and mostly eat vegetation and decaying plant matter. They have been observed eating dead insects and are sometimes known to raid spider webs to steal food wrapped in silk. Most species are active in the spring and summer, though some species, such as snow scorpions, appear during the winter.

Like many insects, scorpionfly mating utilizes various chemicals and courtship dances. When males meet a female, they unleash a cocktail of pheromones and may present her a gift, such as a dead bug. Males will also vibrate their wings to make a buzzing sound. In some species, males will pose as females to steal mating gifts from other males.

Once fertilized, the female lays her eggs near a source of moisture. Scorpionfly eggs require very specific levels of moisture to hatch properly, and it can take months for them to hatch if the levels are off. Normally, though, eggs hatch within a few days. Scorpionfly larvae resemble caterpillars in the early stages and undergo complete metamorphosis into their adult forms by burrowing into decaying wood. 

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Scorpionflies and Forensic Entomology

Scorpionflies are scavengers and will consume other dead organisms, including human corpses. As such, forensic investigators will use the presence of scorpionflies to date the approximate age of a corpse. Scorpionflies are typically among the first insects to start feeding on corpses, indicating that the body is at most a few days old.