Salt Creek tiger beetle

Subspecies of beetle

The Salt Creek tiger beetle (Cicindela nevadica lincolniana) is a critically endangered subspecies of tiger beetle endemic to the saline wetlands of northern Lancaster County, Nebraska, adjacent to and immediately to the north of the city of Lincoln, Nebraska. It is a predatory insect, using its mandibles to catch other insects. The beetle is one of the rarest insects in North America; surveys showed that 194 adults existed in 2009, down from 263 in 2008, and 777 in 2000. However, efforts are continuing to boost the population, which in 2013 numbered 365 beetles: one beetle for each day in a regular year.

The Salt Creek tiger beetle measures, on average, 12 mm (0.5 in.) in length. The beetle has a metallic brown to dark olive green coloration, with a dark metallic green underside. Its body form and color pattern differs from other tiger beetle subspecies. Adults are sexually dimorphic where males have short white hairs on the inner tarsi of their prothoracic legs and females lack these hairs. This extremely fast subspecies can run up to 5 mph.

C. n. lincolniana are restricted to the Salt Creek banks and its tributaries, the mud flats of saline marshes of northern Lancaster County, and Arbor Lake. The eastern Nebraskan salt marsh community which encompasses the range of this species was studied which confirmed its low abundance and rareness. They prefer saline soil as the salt content stimulates ovipositioning which then impacts where the larvae will burrow. The sites selected are extremely important because larvae on the specific burrows for attacking prey that pass by. Because the C. n. lincolniana habitat is already very limited, it is that much more crucial for females to choose sites carefully. For this reason, females take into account many factors such as location, access, salinity, and more in order to determine the ideal site for ovipositioning.

The saline wetlands of eastern Nebraska are home to many sympatric tiger beetle species which leads to competition for similar resources. Thus, this species engages in niche partitioning behavior in which these species have evolved mechanisms such as thermoregulation in order to coexist. These thermoregulatory behaviors including avoiding the sun during hotter times, spending time in shallow water, and positioning their body away from the soil have reduced the competition between these related species. Research reveals that subspecies, C. n. lincolniana, C. circumpicta, and C. togata, all use oviposition for niche partitioning, but with differences attributed to soil salinity. Prey consumption is directly correlated to female fecundity and their ability to lay more eggs. Because the tiger beetle experiences high deaths in the larval stage, increased fecundity is a big advantage.

Salt flats can reach high temperatures so the evolution of mechanisms has provided ways for this species to exist in harsh environments. These mechanisms end up varying between all the related species of tiger beetles. As a result, they display different foraging behaviors correlated with temperature.

There is little known about the life cycle of the Salt Creek tiger beetle. Their lifecycle lasts 1 2 years. Adults emerge around in early June and remain active until the middle of July. After mating, the beetles lay eggs in soil with optimal salinity. Females lay around 50 200 eggs. C. n. lincolniana dipslay mate guarding in which the male latches and holds onto the female after mating in order to ensure other males are unable to copulate with her. The beetle was added to the Nebraska endangered species lists in the 1990s. On October 6, 2005, the U. S. Fish and Wildlife Service listed the beetle as an endangered species under the federal Endangered Species Act. From 1991 to 2005, the number of sites containing Salt Creek tiger beetles declined from six to three, on 35 acres. On May 5, 2014, the U. S. Fish and Wildlife Service published its "final rule" on critical habitat for the beetle in the Federal Register, designating 1,110 acres for conservation effective June 5, 2014. Established areas include saline wetlands along Little Salt Creek, Rock Creek, Oak Creek and Haines Branch Creek in Lancaster County, with a goal of supporting at least six populations. The Omaha Henry Doorly Zoo is working with the Topeka Zoo to help conserve the species. The Zoo in Omaha keeps the eggs until they hatch then will send the larva to the Topeka Zoo where Topeka will raise the larva for about a year until they travel to Nebraska to release the adults with hopes of increasing the adult beetle populations.

Habitat destruction by drainage of the salt marshes for agriculture or development, by runoff from surrounding farms and the city of Lincoln, filling, and creek rechannelization has caused a significant reduction in the population of C. n. lincolniana. There are a few new sites discovered with this rare species, however, the numbers are still low with the largest population being at the Little Salt Creek. Rechannelization was used to control erosion by straightening a part of the creek and covering it with limestone rocks. This reduced habitat space for C. n. lincolniana and decreased their population size from 115 to just 54 beetles in 1991. Since then, the beetles have been able to recolonize some soil edges, but it is important to protect the diminishing habitat this species has remaining.

It is important to explore different mechanisms of protecting this population. Since this subspecies lives predominantly in the saline wetlands of the Little Salt Creed in Lancaster County, Nebraska, investigating the optimal soil type and salinity to promote their survival is crucial. Researchers determined the best conditions to stimulate ovipositioning in females to increase larval and adult production. It was discovered in 2013 and confirmed in 2014, that there were significant differences between soil type, but no difference in salinity levels.