Cicindela macra macra LeConte, 1860
Sandy Stream Tiger Beetle
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Basis for Listing
The sandy stream tiger beetle is known historically from 5 counties in Minnesota: Winona (1920), Washington (1921), Scott (1923, 1962), Fillmore (1965, 1997), and Wabasha (1960-1972), and it was rediscovered in large numbers along the Minnesota River in Scott County in 1997, 2000, and 2001. Habitat loss due to dredging in Winona County, flood control and channel changes in Fillmore County, and trampling of larval burrows by cattle in Wabasha County threaten the species' survival in these areas. The sandy stream tiger beetle was listed as a special concern species in Minnesota in 1996.
Adult sandy stream tiger beetles are 10-12 mm (0.39-0.47 in.) long, and are dull olive-green to olive-brown with a slender, parallel-sided shape. They frequent sandy shorelines in company with the extremely abundant bronzed tiger beetle (C. repanda), which is about the same size, but which has a much more robust build. The bronzed tiger beetle is also reddish-brown. Close-focusing binoculars are useful in separating these species. The white markings on the wing covers of the sandy stream tiger beetle are much more angular than those of the bronzed tiger beetle. In the hand, the former has a pre-apical notch on each wing cover, placing it in the subgenus Ellipsoptera.
In Minnesota, the sandy stream tiger beetle prefers stream banks and sandbars of very fine sand. Suitable looking areas with coarser sand have not yet produced this species. Thus far in Minnesota, this tiger beetle only occurs in the southeastern forested corner of the state, but in states further south and west it is known to occur along riparian habitats in the prairie (Willis 1967).
Biology / Life History
Adult sandy stream tiger beetles emerge in the early summer (as early as late June), and begin hunting, mating, and laying eggs. They slowly die-off as summer progresses, seldom occurring beyond mid-August. Habitat alteration by severe spring flooding is a concern, but generally there is enough adjacent habitat along larger rivers for them to survive. Adults have been found a considerable distance up-slope from riverbanks, so they may have dispersal capabilities not yet understood.
Conservation / Management
The sandy stream tiger beetle has survived some natural flooding disasters in Scott County, but it is not known how it will respond to human- or cattle-induced disturbances or to potential mating-disruption due to lights from sandbar and/or island beach parties after dark (the species is strongly attracted to lights).
Conservation Efforts in Minnesota
There is a need for further surveys of sites where the sandy stream tiger beetle was previously found to determine whether it still survives there. Additional surveys along the Mississippi, Minnesota, and other larger rivers are also needed.