October 2013 Featured Paper
"The European Lesser Glow Worm, Phosphaenus hemipterus in North America" by Christopher G. Majka and J. Scott MacIvor. ZooKeys, 29:35-47 (2009).
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The lesser glow worm, Phosphaenus hemipterus, is the only firefly that has been introduced into North America. Native to much of Europe, a single specimen was reported from Yarmouth, Nova Scotia, in 1947 and again from Montreal in 1989. This present study describes a third occurrence, in Halifax, Nova Scotia, in 2009.
Of the more than 2,000 species of fireflies worldwide, P. hemipterus is the only species where both female and male adults are flightless—the females completely lack wings and the males have only rudimentary wings. Both sexes have light organs, but emit a feeble glow only when disturbed. They do not use light to attract a mate. Like other diurnal, or daytime, fireflies, a female attracts a mate by means of a chemical signal, or pheromone. Males downwind of a female can detect this pheromone from as far away as 65 feet. Males have been observed climbing a blade of grass and waving their antennae before returning to the ground in search of the female.
Larval P. hemipterus feed on earthworms. In laboratory studies they were offered a variety of snails and slugs, the preferred food of many European fireflies, but these were rejected.
In this study, a total of 122 adult P. hemipterus and four larvae were found in three neighboring sites in Halifax. Each site was similar to the fireflies’ native habitat in Europe: a mix of lawns, scattered trees, brush, and disturbed areas that included bare patches, gravel walkways, and concrete or rock walls. Each of the three sites also had a healthy population of Lumbricus terrestris, an earthworm also introduced from Europe.
P. hemipterus was originally thought to have arrived in Canada in ballast shipments—sand and gravel taken from beaches in England and placed in the bottom of sailing ships to provide stability. After arriving in Canada, the ships cast off this ballast to make way for cargo that doubled as the return ballast. Studies have since shown, however, that P. hemipterus is not found in those parts of England where the ballast would have been collected.
This study suggests an alternate method of introduction. Nineteen of the twenty-five species of earthworms found in Canada were introduced there in the soil of imported plant material, both agricultural and horticultural. The close association of P. hemipterus and these earthworms suggests that, like the worms, the fireflies were also introduced with the imported plant material. Since P. hemipterus is flightless, with limited ability to travel, it is suggested that these fireflies arrived in Canada on at least three separate occasions: a first time to Yarmouth, a second time to Quebec, and a third to Halifax.
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