Basis for Listing

The little white tiger beetle, also known as the ghost tiger beetle, was first observed in Minnesota in 1922 in Anoka County; additional specimens were collected here until 1932. Sometime between 1932 and 1954 however, the dunes at this location were leveled for a school and housing development. There are other historic records of this species from Scott (1923), Ramsey (1924), Hennepin (1927), and Polk (1936) counties, and modern records from Wabasha (1965, 1972), Lac Qui Parle (1967, 1971), and Morrison (1997, 2004) counties. The Lac Qui Parle County site, which was formerly pastureland with a steep, open, sandy slope, was revisited in 2003 and found to be overgrown with grasses and planted with wildflowers. Given the vulnerability of its habitat, the little white tiger beetle was listed as a threatened species in Minnesota in 1996.

  Description

Adult little white tiger beetles are small, averaging 10-11 mm (0.39-0.43 in.) long. They are mostly white with brown mottling centrally on the wing covers. Their head and thorax are reddish-brown (rarely greenish) and the legs are a pale straw-yellow. In the hand, there is a slight pre-apical notch on each wing-cover, placing it in the subgenus Ellipsoptera.

Tiger beetle larvae are mostly white and somewhat grub-like (Pearson et al. 2006). The portions of their bodies that are exposed in their burrow entrances are usually the same color and texture as the surrounding soil surface, allowing them to blend in with the soil (Pearson et al. 2006; R. Dana, Minnesota DNR, pers. comm.). Tiger beetle larvae have eyes with dense photoreceptors that give them detailed focusing ability and three-dimensional visual perception (Pearson et al. 2006).

  Habitat

The little white tiger beetle is found on steep, open, blowing sand dunes.

  Biology / Life History

Adult little white tiger beetles emerge in the summer (as early as mid-June). They begin hunting, mating, and laying eggs, and slowly die-off as summer progresses. They are usually gone by the end of August.

Tiger beetles prey on small insects and other arthropods and are visual hunters. Adults will either chase their prey or wait in a shaded area and ambush prey as it wanders by (Pearson et al. 2006). They often chase their prey in fast, short bursts with brief stops in between runs. These stops are necessary for orientation as tiger beetles can run so fast that they cannot see the prey they are pursuing.

Adults have hind wings that are transparent and they are folded under the elytra (hard front wings) when at rest. When disturbed, tiger beetles may take short, low flights to escape. These escape flights and the ability to run quickly are their main defenses against predators. Tiger beetles are also usually well camouflaged in their environment.

Tiger beetle larvae dig burrows in which they live and secure prey. They are ambush predators that lie in wait in the top of their burrows with their jaws open and their heads and thorax flush with the ground surface, essentially filling the burrow entrance and disguising their presence (Pearson et al. 2006). When prey is within reach, the larvae anchor themselves to the sides of the burrow by two pairs of hooks on their lower backs, and quickly leap out and grab the prey with their mandibles. The struggling prey is then pulled back into the bottom of the burrow and eaten. When they are done eating, the larvae carry the indigestible portions of the prey to the top of their burrow and throw it backwards away from the burrow entrance. The larvae also use their burrow for protection, and will retreat into it when they sense danger. Larvae primarily use vision to detect danger, but may also sense vibrations in the ground created by large predators (Pearson et al. 2006). It is not known how deep the larvae burrow to overwinter.

  Conservation / Management

The little white tiger beetle is a habitat specialist that requires protection of dune areas. The best time to survey for this species is mid-summer (Steffens 2005).

  Conservation Efforts in Minnesota

It is not certain if the little white tiger beetle still survives in Minnesota. Further surveys of the Lac Qui Parle, Scott, Polk, and Wabasha county sites are needed to determine if the species is still present in these areas. Additional surveys should also include the Prairie Smoke Dunes Scientific and Natural Area, which Steffens (2005) reports as having potential habitat including a number of open sand blowouts.

  References and Additional Information

Dawson, R. W., and W. Horn. 1928. The tiger beetles of Minnesota. University of Minnesota Agricultural Experiment Station Technical Bulletin 56. 13 pp.

Pearson, D. L., C. B. Knisley, and C. J. Kazilek. 2006. A field guide to the tiger beetles of the United States and Canada: identification, natural history, and distribution of the Cicindelidae. Oxford University Press, New York. 227 pp. + plates.

Steffens, W. P. 2005. Rare tiger beetle surveys in central and northwest Minnesota, Fall 2004. Report submitted to the County Biological Survey, Minnesota Department of Natural Resources. 11 pp.