Back in 1986, the cobblestone tiger beetle (Cicindela marginipennis) had it all. In March of that year, the half-inch-long beetle was elected the Plainfield Town Insect, appeared on posters and T-shirts, and even became a hot topic in the national media. Reporters and photographers who descended on the Connecticut River town of Plainfield, New Hampshire, to cover the rare beetle’s story, had no idea that they were doggedly pursuing their own namesake: “paparazzi” comes from the Italian word for “a kind of buzzing insect.”
The island in the Connecticut River where the endangered cobblestone tiger beetle lives is one of only a dozen or so such places in a few select rivers in the East, including habitats in Vermont, New Hampshire, Massachusetts, and New York. The beetle prefers to dwell amid the cobblestones of islands and deltas in large rivers and streams, such as the Connecticut, White, and Winooski Rivers. Officially, the beetle is listed as “threatened” in both Vermont and New Hampshire, which means its existence is somewhat less imperiled than a fully “endangered” species.
Like many tiger beetles, cobblestones shine with a famous beauty, and insect hunters love to collect them. Their backs are olive green with a touch of bronze. Underneath they are a coppery green with a brownish-red abdomen. The upper shell has a handsome, scalloped white border.
Tiger beetle eggs hatch into larvae in mid- to late July. The predaceous larvae are terrestrial – living in holes in the sand and gravel that are slightly less than a quarter-of-an-inch wide. Strong legs anchor them in their holes and make them nearly impossible to dislodge. Here they wait in ambush; when a fly, an ant, or other prey happens by, the beetle larvae use powerful mandibles for the capture.
In the first summer, the larvae pass through one or two life stages called instars. After they overwinter, the larval instars pupate and transform into adults. Adults scavenge for dead food or hunt, capture, and consume live prey. Anything that isn’t larger than the beetles themselves is fair game.
Like the rest of us northerners, cobblestone tiger beetles endure brutal winters. During these cold and wet months, the beetles and their habitat are submerged. The erosive power of high waters and the grinding force of ice keep their beds of softball-sized cobbles free from silt and sand, which is a necessary condition of their habitat.
Come summer, and it’s the sun’s heat that defines the habitat. Alan Graham, an entomologist, photographer, and teacher who lives in Pomfret, Vermont, has noticed that cobblestone tiger beetles tend to come out only on sunny days. They regulate their temperature by making use of the varied environment of the cobblestones, crawling in and out of the spots of sun and shade. Sometimes they raise themselves up high on their legs to put space between their bodies and hot rocks.
Habitat loss is one reason that the cobblestone tiger beetle is now threatened. Large dams on rivers create deep, slow-flowing stretches of water that flood long expanses of potential beetle habitat. Another species of tiger beetle called “the Puritan,” Cicindela puritana, which once lived in the Connecticut River near Charlestown, New Hampshire, has disappeared from the region.
Overall, the status of the cobblestone tiger beetle remains a mystery. “There are more locations than we knew of 10 years ago,” says Mark Ferguson, a zoologist with the Vermont Department of Fish and Wildlife. “In 1995, a new location was found along the White River, and several have been found in other places.”
“But little money is available to monitor invertebrates,” Ferguson laments. “Monitoring is hard to do with some species, because you need to go back for many years to get data and look at the long-term trend. I hope to start a more consistent monitoring program next year.”
When asked about beetle populations, Ferguson replies, “At one of the isolated spots over the last few years, it seems to be holding good numbers. But no one has gone back to monitor the Connecticut (River) population for four years or so.”
I recently contacted Nancy Mogielnicki, who, along with husband Peter, formed the 1980s Plainfield team that brought the tiger beetle to the fore. When asked what has happened in the intervening years, Mogielnicki replied, “Not much.” Following its fifteen minutes of fame, the cobblestone tiger beetle has quietly continued to pursue its passions: stalking prey and reproducing. So far, and seemingly without assistance from people, this intrepid insect has proven a real survivor.