Description

Taxonomy

Kingdom	Phylum	Class	Order	Family	Genus
Animalia	Hexapoda	Insecta	Coleoptera	Curculionidae	Tanysyrphus

Synonyms

Rhynchaenus lemnae

Invasion History

Chesapeake Bay Status

First Record	Population	Range	Introduction	Residency	Source Region	Native Region	Vectors
1902	Established	Unknown	Cryptogenic	Regular Resident	North America	Eurasia	Ornamental(Aquatic Plant),Shipping(Dry Ballast),Natural Dispersal(Natural Dispersal)

History of Spread

The weevil Tanysphyrus lemnae was described from Europe in 1792 and subsequently found throughout that continent, northern Asia, and Japan (Hoffmann 1954). The small size of this beetle (1.5 mm) and its life-history, in and on tiny floating plants of the genus Lemna (Duckweeds) (Hamilton 1884; Hoffmann 1954) mean that this insect is probably frequently overlooked. Recent reports of this insect are rare, probably reflecting its inconspicuousness rather than its abundance.

The first North American record we have found of Tanysphyrus lemnae is Leconte (1876) from Detroit MI. In 1884, Hamilton reported it from ponds in Allegany PA (Hamilton 1884). By 1920, this weevil was known from Canada to FL, and west to IA (Leng 1920). Currently, T. lemnae's North American range includes 23 states (VT-ID, and FL-TX-OR), and 3 Canadian provinces (British Columbia, Alberta, and Quebec) (O'Brien and Wibmer 1982). A number of authors regard this species as introduced in North America ( Mills et al. 1993; O'Brien and Wibmer 1982; Pennak 1978; Tanner 1943), while others apparently treat the species as native (Leng 1920; Hoffmann 1954). Introduction with aquatic plants is certainly a strong possibility, but as noted above, this also could be a native species which has been overlooked.

The only specific record we have for Tanysphyrus lemnae in the Chesapeake region is from the checklist of Ulke (1902) for the vicinity of Washington DC (number 2693 of 2975 beetles listed). This is apparently the basis for its occurrence in the checklists of Leng (1920) and O'Brien and Wibmer (1982). In Ulke's annotations, T. lemnae is simply listed among weevils occurring on 'palustral plants'. Since Lemna spp. (Duckweeds) are abundant in tidal fresh and oligohaline waters (Hurley 1990; Simmons et al. 1995), and this beetle is widely distributed in states to the north and south of Chesapeake Bay (e.g. PA, DE, GA, FL) (O'Brien and Wibmer 1982), we regard this species as probably present and abundant in tidal waters of Chesapeake Bay. However, recent records would be needed to confirm this.

History References - Hamilton 1884; Hoffmann 1954; Hurley 1990; Leconte 1876; Leng 1920; Mills et al. 1993; O'Brien and Wibmer 1982; Pennak 1978; Simmons et al. 1995;Tanner 1943; Ulke 1902

Invasion Comments

Invasion Status, Population Status- Since this insect is easily overlooked, and the earliest records (Hamilton 1884; Leconte 1876) make no mention of its recent arrival, we treat this weevil as cryptogenic in North America. We consider the population status of this species to be 'unknown' because of the absence of recent records in the Chesapeake region.

Residency- Tanysphyrus lemnae's status as a 'regular' or 'boundary' resident is arguable. It was reported from the Washington DC area as one of a number of weevils occurring on 'palustral plants' (Ulke 1902). T. lemnae's host plants, Lemna spp. (Duckweeds) are abundant in tidal fresh and oligohaline waters (Hurley 1990; Simmons et al. 1995), and this beetle is widely distributed [in states to the north and south of Chesapeake Bay (e.g. PA, DE, GA, FL)] (O'Brien and Wibmer 1982). Thus, we have decided to treat T. lemnae as a regular resident.

Ecology

Environmental Tolerances

	For Survival		For Reproduction
	Minimum	Maximum	Minimum	Maximum
Temperature (ºC)
Salinity (‰)	0.0		0.0
Oxygen
pH
	Salinity Range	fresh-oligo

Age and Growth

	Male	Female
Minimum Adult Size (mm)
Typical Adult Size (mm)	1.5	1.5
Maximum Adult Size (mm)
Maximum Longevity (yrs)
Typical Longevity (yrs

Reproduction

	Start	Peak	End
Reproductive Season
Typical Number of Young Per Reproductive Event
Sexuality Mode(s)
Mode(s) of Asexual Reproduction
Fertilization Type(s)
More than One Reproduction Event per Year
Reproductive Startegy
Egg/Seed Form

Impacts

Economic Impacts in Chesapeake Bay

Economic impacts of Tanysphyrus lemnae are unknown in the Chesapeake Bay region.

Economic Impacts Outside of Chesapeake Bay

While Lemna spp. (Duckweeds) occasionally reach nuisance densities in eutrophic waters (Hurley 1990), the quantitative effects of Tanysyrphus lemnae as an herbivore of this plant appear to be unknown.

Ecological Impacts on Chesapeake Native Species

The weevil Tanysphyrus lemnae is a grazer on Lemna spp. (Duckweeds), very abundant floating plants in sheltered, nutrient-rich fresh and slightly brackish waters in much of the temperate zone. The presence of the beetle can be recognized by holes in duckweed leaves, created by the feeding of the larvae within the leaf (Hamilton 1884; Hoffmann 1954). The effect of the beetle's feeding on Lemna abundance does not appear to have been studied in Europe or in North America, and its current abundance in the Chesapeake region is unknown. The only published Chesapeake Bay region record is that of Ulke (1902).

References - Hamilton 1884; Hoffmann 1954; Ulke 1902

Ecological Impacts on Other Chesapeake Non-Native Species

Tanysphyrus lemnae is a grazer on native Lemna spp. (Duckweeds) (Hamilton 1884). At least one introduced duckweed, Landoltia punctata, is present in Coastal Plain waters in Virginia (Harvill et al. 1992; Simmons et al. 1995; Wass 1972), but we do not know if the feeding range of T. lemnae extends to this genus.

References - Hamilton 1884; Harvill et al. 1992; Simmons et al. 1995; Wass 1972

References

Hamilton, John (1884) On Trogoderma ornata, Physonota unipunctata, and Tanysphyrus lemnae, Canadian Entomologist 16: 133-136

Harvill, A. M.; Bradley, Ted R.; Stevens, Charles E.; Wieboldt, Thomas F.; Ware, Donna M. E.; Ogle, Douglas W.; Ramsey, Gwynn W.; Fleming, Gary P. (1992) Atlas of the Virginia Flora, , Burkeville, VA. Pp.

Hoffmann, Adolphe (1954) Coleopteres Curculionides (Deuxieme Partie), In: (Eds.) Coleopteres Curculionides (deuxieme partie). , Paris. Pp. p 269-278

Hurley, Linda M. (1990) Field guide to the submersed aquatic vegetation of Chesapeake Bay., , Annapolis, MD. Pp.

Leconte, John L. (1876) The Rynchophora of America, north of Mexico, Proceedings of the American Philosophical Society 15: 1-470

Leng, Charles W. (1920) Catalogue of the Coleoptera of America North of Mexico, , Mount Vernon. Pp.

Mills, Edward L.; Leach, Joseph H.; Carlton, James T.; Secor, Carol L. (1993) Exotic species in the Great Lakes: a history of biotic crises and anthropogenic introductions., Journal of Great Lakes Research 19: 1-54

O'Brien, Charles W.; Wibmer, Guillermo J. (1982) Annotated checklist of the weevils (Curculionidae sensu lato) of north America, Central America, and the West Indies (Coleoptera; Curculionidea), Memoirs of the American Entomological Institute 34: 1-382

Pennak, Robert W. (1978) Freshwater Invertebrates of the United States, , New York. Pp.

Simmons, Mark P.; Ware, Donna M.; Hayden, W. John (1995) The vascular flora of the Potomac River watershed of King George County, Virginia, Castanea 60: 179-209

Strong, Mark T.; Kelloff, Carol L. (1994) Intertidal vascular plants of Brent Marsh, Potomac River, Stafford County, Virginia, Castanea 59: 354-366

Tanner, Vasco M. (1943) A study of the subtribe Hydronomi with a description of new species, (Curculionidae); Study No, VI, Great Basin Naturalist 4: 1-38

Ulke, Henry (1902) A list of the beetles of the District of Columbia, Proceedings of the United States National Museum 25: 1-57

Wass, Melvin L. (1972) A checklist of the biota of lower Chesapeake Bay, Special Scientific Report, Virginia Institute of Marine Science 65: 1-290