Tiger beetle coaxed off most-endangered list
HADDAM, Conn. — In row upon row, 436 tiny larvae are presumably fast asleep now, a few months after they were tucked inches deep into trenches dug along the sandy banks of the Connecticut River.
The nestled larvae represent the last chance for one of New England’s most endangered species, the Puritan tiger beetle — an insect tiny enough to fit on the pad of a thumb. The species exists in small numbers in just two spots in Haddam, and another in the Chesapeake Bay area.
“This is it for New England,” said Laura Saucier, a wildlife biologist for the state of Connecticut. “If we lose our population in Connecticut, it’s gone. The stakes are pretty high.”
Granted, the Puritan tiger beetle project — one of the largest insect reintroductions in the country — lacks the emotional appeal of protecting pandas or polar bears. “It’s not fuzzy and has a face only a mother could love, but they’re just so interesting,” Saucier said.
“They’re the top predators in this food web and the food web is down here,” she said, pointing to the sand, “so we don’t know a lot about them.”
But for an ecosystem that runs from the Canadian border to the Long Island Sound, maintaining ecological balance is crucial, said Rodger Gwiazdowski, the entomologist who is leading the project and who has been dreaming for nearly two decades about restoring the Puritan tiger beetle.
The beetles are “part of a healthy river,” he said. “When we see a stretch of healthy river, we see beetles.” So, restoring them should help support the health of New England’s longest river, whose watershed is home to more than 2 million people. “It’s powerfully naïve to think it means nothing” to allow the Puritan tiger beetles to disappear, he said.
For the winter, the beetles are in a state of torpor — essentially hibernating
— all season long. The more mature ones will emerge as adults sometime early next summer, if all goes well. They can last the winter without food, but even the larvae are predators. They will hide in their burrows, waiting for prey to walk by that they can pull down into their tunnel and consume.
Their eyesight is among the most acute of any known insect and they display a very fast muscular response time, Gwiazdowski said. “Coming and going, they’re vicious predators.”
It is unclear when the Puritan tiger beetle began disappearing. It was first named in 1871, but was not nearly wiped out until the late 1980s, perhaps as the result of development along the river.
Last summer, Gwiazdowski and his team minded 30 or so pairs of adult Puritan tiger beetles they had caught in the spring, feeding them crickets and carefully harvesting their eggs every day.
Adults are easy to catch but hard to relocate, Gwiazdowski said. With previous releases of adults, the insects were never seen again, so scientists do not think the populations survived. The plan this time was to release larvae at different stages of development, hoping some would make it.
Raised appropriately in captivity, each female can produce 100 or more offspring. But no one knew the optimal way to raise a Puritan tiger beetle — what kind of climate, prey or sand type.
So the beetle team has been figuring it out by trial and error. Each breeding pair was kept in its own shoebox-size plastic tub with a sand-filled Petri dish where researchers hoped the beetles would lay their eggs.
Every weekday, a staff member sifted through the sandbox looking for eggs to remove, adding live crickets for food and replacing water in gel form so the beetles could drink. The researchers could not put fresh water in the tubs, because the crickets — which apparently are not very smart — would drown in it.Egg-laying provided another obstacle. Because beetles exist naturally on the flat surface of a beach, they were not familiar with jumping or climbing into their makeshift sandboxes. Filling the tubs with too much sand would make the eggs difficult for researchers to find. Ramps of one type or another were too soft or too hard. Finally, the team obtained fresh clay from a quarry in Vermont. “The day we put the clay ramps in, the fecundity exploded,” Gwiazdowski said.
It takes two to three years for an egg to mature into an adult Puritan tiger beetle capable of reproduction. In the lab, scientists can speed up that process and keep adults alive longer.
In nature, each female insect will reproduce herself — leaving on average one mature offspring behind, said Joe Elkinton, a professor of environmental conservation at the University of Massachusetts Amherst, who has collaborated with Gwiazdowski and helped with the release. But in captivity, insects can multiply themselves 100-fold in one generation, suggesting just how many are lost to predators, starvation and other challenges.
It also means that reared properly in a lab, it is feasible to mature enough larvae to make a difference at the population level, Elkinton said.
Males are usually a little bit smaller than females. Researchers put a red dot on the males so they could be easily spotted and collected. From midsummer until the larvae collection was complete, the males were moved every day into a tub with a different female to promote breeding. Some females laid no eggs at all; one laid 126.
Releasing the 463 larvae on the river banks was “like kicking the kids out at 18,” Saucier joked.
Gwiazdowski remained optimistic: “It’s easy to say goodbye. I’m really happy for them.”