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GIBBON - A tiny insect described by University of Nebraska at Kearney Biology Professor Wyatt Hoback as "kind of like an aquatic butterfly" could be the fifth Platte Basin species listed for protection under the federal Endangered Species Act.

Earlier this month, the U.S. Fish and Wildlife Service included the Platte River caddisfly on a list of 29 species to be studied for possible protection. Those 29 were among 206 species on a 2007 WildEarth Guardians petition that asked the USFWS to list them as threatened or endangered.

USFWS Wildlife Biologist Bob Harms of Grand Island said the Platte River caddisfly is the only Nebraska species selected for a status assessment that could take 12 to 18 months.

"It's an evaluation of a species' life history and a lot of the focus is on the threats," Harms said, describing the process during a recent caddisfly site tour for officials of state and federal agencies and other Platte Basin interest groups.

"Our group is thinking how to proceed cautiously," he said, adding that no assessment funding has been approved yet.

Hoback said people seeing the half-inch-long insects during their short-lived adult life stage in the fall would identify them as little moths. A 12-month life cycle is one of several traits that distinguish the Platte River caddisfly from about 1,350 other caddisfly species.

The five stages begin in late September and early October when adults lay eggs in backwater sloughs near the Platte River and then die. "We think they (eggs) sink to the bottom. That's the way with most caddisflies, but we're not sure with the Platte River caddisfly," Hoback said.

The eggs quickly hatch and the larvae feed on leaves and other plant materials in the slough throughout the winter. "That means the places where they're found can't freeze to the bottom, which limits where they can be found and may tie into groundwater levels," Hoback said, which keep the water moving and maintain oxygen levels.

Larvae feed and grow in the water into the spring, until their sloughs begin to dry. "It's the only insect to form a pupa (a case developed between the larva and adult stages) under water," Hoback said.

In late May or early June, the case-enclosed larvae move to land for up to three months, hiding and feeding in moist areas under vegetation. "That's very unusual for caddisflies," he said. "Most stay in water until they (become) adults for a short time."

"They have six legs and will drag their 'case' and body along. In the water, they're pretty darn fast actually," Hoback said. He described the case as a silk sack onto which sand, sticks and other materials attach.

Researchers studying Platte River caddisflies on land from June to late September look for cases. Then the adults emerge, lay eggs and the cycle begins again.

"If it's dry too early or dry too late, that's the end of the population," Hoback said.

Researchers continue to piece together the species' basic biology and habitat needs. Platte River caddisflies first were observed in 1997 by biologists studying wetland slough wildlife for the Platte River Whooping Crane Trust on its Mormon Island Crane Meadows property south of Grand Island.

Hoback said so many Platte River caddisfly larvae were caught in those biologists' bucket traps that they covered the bucket bottoms several inches deep. It was calculated that there were 800 larvae per square meter in the slough, he said, which is an "incredible concentration."

Over the past two years, UNK graduate student researchers have monitored Platte River caddisflies at 15 sites from east of Kearney to east of Grand Island, and surveyed other locations with similar habitats.

Hoback said all current known sites have low numbers of 40 larvae or less per square meter. "At Mormon Island, there's now zero. That population is gone. We don't know why," he said, although drought could be a part of the answer.

So why does survival of the Platte River caddisfly matter?

"They have a unique life cycle, so they represent something that is different than most caddisflies," Hoback said, and conservation goals always are to maintain as much biological diversity as possible.

Platte River caddisflies benefit their slough habitats by breaking down plant material, and they are food for other species. Hoback said that includes mosquitofish, a non-native predator that's another big threat to the Platte River caddisfly's future.

Other threats include invasive plants that can take over sloughs and surrounding grasslands, and human activities - bridges, highways, dams, other construction, farming - that have forever changed the Platte River. "We know the number of sloughs changed over the years, so there aren't as many habitat sites," Hoback said.

He said Platte River caddisflies aren't good fliers, "so if adults can fly only 30 yards and if they're at sites distributed over 120 miles, then the only way for them to get to new sites is for habitat to be at least every 30 yards."

Platte River Recovery Implementation Program Executive Director Jerry Kenny told the Hub that some tour participants observed an adult caddisfly at a Whooping Crane Trust site fly the estimated length of a football field.

Because the species was unknown until 12 years ago, it's difficult for biologists to know what's normal or to determine the reasons for population declines. "We can't rule out that 1998 and 1999 were really good years for them, but we don't believe that was the case," Hoback said.

Variables at each Platte River caddisfly site aren't fully understood, he added, so researchers are trying to determine if certain habitats are preferred, marginal or just what's left.

Harms noted that the slough south of Gibbon is a woodland, not a grassland, which suggests that the Platte River caddisfly has adapted to change to some extent.

Hoback said seeing a species go from high numbers to a steep decline indicates that an ecosystem has changed. He believes that whenever it's clear that human activities play a role in the decline, it's a moral and ethical issue to preserve threatened or endangered species.

"We never really know what will happen when we lose a species," he said.

e-mail to:

lori.potter@kearneyhub.com

Lori Potter reports for the Kearney Hub.

Platte River caddisfly

Description: Moth-like insects with two sets of hairy wings that take the shape of a tent when folded against their bodies.

Size: A half-inch long or less.

Species: One of about 1,350 known species in the order Trichoptera.

Distinctive characteristics: It pupates underwater, has a one-year life cycle, and spends its entire life in and within about 25 feet of backwater sloughs along, but not connected to, the Platte River. It's unusual for caddisflies to spend any time on land.

Location: About 15 sites currently known from east of Kearney to east of Grand Island.

Numbers: Undetermined, but found in much smaller concentrations today than when first discovered in 1997.

Threats: Platte River and land use changes, non-native invasive plants, and predators such as mosquitofish.

Endangered Species Act listing: It's one of 29 species - one of two insects - selected from a list of 206 on a 2007 WildEarth Guardians petition seeking U.S. Fish and Wildlife Service status reviews. It will take the USFWS 12 to 18 months to determine if the Platte River caddisfly should be listed as threatened or endangered.

Other listed species in the Platte Basin: Migrating whooping cranes, nesting least terns and piping plovers, and pallid sturgeon.

Sources: Wyatt Hoback, UNK; USFWS