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LARVA OF THE SCIOMYZID FLY PHERBELLIA ALBOVARIA PREYS ON THE LAND SNAIL ANGUISPIRA FERGUSONI

Article · January 2008

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Aydin Örstan Carnegie Museum Of Natural History

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LARVA OF THE SCIOMYZID FLY PHERBELLIA ALBOVARIA PREYS ON THE LAND SNAIL ANGUISPIRA FERGUSONI

Aydın Örstan*)

Abstract: The land snail Anguispira fergusoni is a newly recorded prey for the parasitoid larva of the sciomyzid fly Pherbellia albovaria. Key words: Mollusc, gastropod, insect, predation, North America

During a field trip in a public park in Montgomery County, Maryland, USA on 24 May 2008, I collected 6 empty land snail shells. The shells were kept in a sealed plastic bag until 15 June 2008, when I found a dead fly inside the bag. The fly was about 7.5 mm long from the front of its head to the tips of its wings and had markings on its wings (Fig. 1A). Lloyd V. Knutson identified the fly from its photograph as Pherbellia albovaria (Coquillett) (Diptera: Sciomyzidae).

The examination of all the shells from the field trip revealed that one Anguispira fergusoni (Bland) (Pulmonata: Discidae) shell had a dark object in its penultimate whorl that was about a half a whorl long (Fig. 1B). I opened a hole in the body whorl of the shell and confirmed that the object inside was an empty puparium. The diameter of the shell was 9.0 mm. Since the shells of these snails can grow almost as large as 17 mm in diameter, the shell with the puparium was a juvenile. The A. fergusoni shell was found in damp wood powder accumulated in front of a beech tree (Fagus grandifolia) near a creek in a second growth forest (39°09’55.3” N, 77°19’08.9” W). The tree had a wide rotting cavity in its trunk. 1. Pherbellia albovaria specimen (A) and the Anguispira The fly and the A. fergusoni shell containing the fergusoni shell with the fly’s puparium (B, arrows mark the ends puparium have been deposited in the of the puparium). The fly and the shell are not to scale. Department of Entomology, National Museum of Natural History, Washington, D.C.

The sciomyzid larvae prey on aquatic and terrestrial snails (Berg & Knutson, 1978; Barker et al., 2004). According to Bratt et al. (1969), the larvae of P. albovaria, a native of eastern North America, are generalist predators of several species of land snails, including A. alternata (Say) and form their puparia in the shells of the snails they consume. Anguispira fergusoni is also native to the general collection area (Örstan, 1999). This record adds one more species (and the second in the genus Anguispira) to the known gastropod preys of P. albovaria.

Acknowledgements I thank Lloyd V. Knutson for the identification of the fly, Don Harvey and Wayne N. Mathis for facilitating the identification and Megan Paustian for companionship during the field trip.

References Barker, G.M., Knutson, L., Vala, J., Coupland, J.B. & Barnes, J.K. (2004). Overview of the biology of marsh flies (Diptera: Sciomyzidae), with special reference to predators and parasitoids of terrestrial gastropods, in Natural Enemies of Terrestrial Molluscs (Barker, G.M., ed.). CABI Publishing, Oxfordshire. Berg, C.O. & Knutson, L. (1978). Biology and systematics of the Sciomyzidae. Annual Review of Entomology 23:239- 258. Bratt, A.D., Knutson, L.V., Foote, B.A. & Berg, C.O. (1969). Biology of Pherbellia (Diptera: Sciomyzidae). Cornell University Agricultural Experiment Station, Memoir 404:1-246. Örstan, A. (1999). Land snails of Black Hill Regional Park, Montgomery County, Maryland. Maryland Naturalist 43:20- 24.

*) Aydın Örstan, Section of Mollusks, Carnegie Museum of Natural History, 4400 Forbes Ave., Pittsburgh, PA, 15213 U.S.A. E-mail: [email protected]

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