Spilomyia sayi

(Goot, 1964)

Four-lined Hornet Fly

Spilomyia sayi is a common North American hoverfly and mimic, ranging from western Canada to the northeastern United States. are active from June to October and are frequently found on flowers where they feed on nectar and pollen. The exhibits remarkable mimicry of yellowjacket wasps, including visual, behavioral, and acoustic deception. Larvae develop in decaying heartwood of deciduous trees and in rot holes.

Spilomyia quadrifasciata male by Williston S.W.. Used under a Public domain license.Spilomyia sayi by Beatriz Moisset. Used under a CC BY-SA 4.0 license.Spilomyia sayi dorsal by raffib128. Used under a CC0 license.

Pronunciation

How to pronounce Spilomyia sayi: /ˌspaɪloʊˈmaɪə ˈseɪaɪ/

These audio files are automatically generated. While they are not always 100% accurate, they are a good starting point.

Identification

measure 10–16 mm. The black bears a prominent inverted V-shaped yellow mark above the margin, with additional yellow spots on the humeri and a slender line above the wings. The scutellum is black with a narrow yellow rim. The pleurae display distinct yellow markings: a large elongate spot on the mesopleuron, a rounded spot on the sternopleuron, and a smaller spot above the front . The elongate cylindrical is scarcely wider than the and bears four yellow bands: segment 2 has a strongly arcuate band continuing onto segment 3; segment 3 has a band narrowly interrupted in the middle; segment 4 has both a median interrupted band and a posterior band. The is yellow with a wide median black stripe and nearly straight profile. are elongate, with the pedicle nearly twice as long as the scape. Male are and bare, with a brown color pattern. Front and mid are strongly swollen. Hind femur has an anteriolateral spur. Wings are elongate with brownish coloration along the front border, hyaline behind; R4+5 is acute and slightly , cell r1 is open, and crossvein r-m is strongly oblique.

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Habitat

frequent flowers in various . Larvae inhabit moist areas including rot holes of trees and decaying heartwood of deciduous trees.

Distribution

Western Canada to northeastern North America; recorded in Canada and the United States, including Vermont.

Seasonality

active from June to October in the northern part of the range.

Diet

feed on nectar and pollen from flowers. Larval diet consists of decaying organic matter in tree holes and rotting wood.

Life Cycle

Larvae are known as short-tailed larvae, adapted for moist environments. Development occurs in water-filled tree holes and decaying heartwood. Specific details of and timing are not documented.

Behavior

Males engage in , perching on high ground to await females. are capable of hovering nearly motionless in . The exhibits sophisticated mimicry: in addition to yellow and black coloration, individuals wave their front legs to simulate the longer of yellowjackets, and the wingbeat frequency matches that of wasp models. The portion of each wing is darkened to mimic the longitudinally folded wings of resting vespid wasps.

Ecological Role

serve as when visiting flowers. Larvae function as decomposers and nutrient cyclers in decaying wood. The contributes to indirectly through its larval preferences.

Human Relevance

are beneficial in gardens and natural areas. The is frequently encountered by naturalists and photographers due to its conspicuous -like appearance. No negative impacts on human activities are documented.

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