Rare beach beetle surprises local expert

Biologist on lower river spots imperiled insect that seeks out sand.

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3 minute read

Hairy-necked Tiger Beetle (Cicindela hirticollis), Lake St. Croix Beach, Minn. (Photo by Christopher E. Smith)

“Few groups of insects, aside from the butterflies, have proved so interesting and attractive to amateur students as the tiger beetles… The beginner, as well as the advanced student, finds the tiger beetles an attractive group for several reasons. They are neatly marked and beautifully, even gorgeously, colored. Their beauty, along with the ease and certainty with which specimens may be preserved in perfect condition, renders them more than usually satisfactory material for the building of a collection.”

– R.W. Dawson, The Tiger Beetles of Minnesota, 1928

A beetle scuttling across the sand at the very edge of Lake St. Croix one warm morning in August 2020 caught Christopher Smith’s attention. The Lake St. Croix Beach wildlife biologist was walking his dog on the beach, as he does most days. And, like usual, he was keeping his eyes on the ground, hoping to spot something interesting.

This day in 2020, he spotted a creature that hadn’t been documented in Washington County for 50 years. It was Cicindela hirticollis hirticollis, a subspecies of what’s commonly known as a Hairy-necked Tiger Beetle. It’s rarely seen, and has sensitive habitat needs. Yet here it was, mingling with much more common cousins.

“It was an exciting find, especially because it was just down the road from where I have lived for just under 10 years,” Smith said.

Subtle differences

Most people would probably not have noticed the rare species. But to Smith’s eye, even from a distance, something attracted him to the rare beetle even though it was surrounded by several bronzed tiger beetles, a common species very similar in appearance.

This one was slightly larger and had slightly wider forewings than its companions. It also tended to take shorter flights when fleeing. Smith got his phone camera to document the observation, and got up close. Then he could see the unique pattern on the beetle’s back, confirming the identification.

The insect is listed as a Species in Greatest Conservation Need by the state of Minnesota, and of “special concern” in Wisconsin. Its population numbers are believed to be declining, and it has rarely been documented in Minnesota or Wisconsin. The last confirmed sighting of the beetle in Washington County was in 1970, and along the Mississippi River, near Grey Cloud Island.

Now, Smith has added to the limited knowledge about their range.

Smith looked for the insect again at the same site in the summer of 2021, and discovered many more specimens. He thinks the historic low water created a lot of the habitat they need: damp sandy beaches, the kind right where water meets shore. But they were still limited to one approximately 400-foot stretch of shoreline.

Save the sand

People enjoyed the low water for the same reason: abundant beaches. Affinity for sand and water means tiger beetles might lay their eggs where someone will later walk, trampling eggs or the larvae, which live in the sand for at least a year before metamorphosing into their adult form.

Efforts to stabilize banks by installing boulders and other material can also obliterate their habitat. Boat wakes can erode shorelines. Unnatural water fluctuation caused by dams can also prevent reproduction and the survival of the species. Heavier rainstorms caused by climate change will disrupt flood patterns. While they are well adapted to living in areas that frequently flood, the timing and duration is changing, what Smith calls a “major threat to the species.”

He urged action to protect the species — and sandy beaches.

“Many types of wildlife, including many tiger beetles, utilize open sand habitat,” Smith said. “Creating, maintaining, and protecting open sand habitats is important and past practices to stabilize and vegetate open soils needs to be reconsidered.”

Tiger beetles are a great “gateway insect” for nature enthusiasts who want to learn more about insects, Smith adds. Most of the approximately 20 species of tiger beetles in Minnesota can be easily identified visually, and cameras used for birding are well suited to photographing them. He recommends the guidebook “Tiger Beetles of Minnesota Wisconsin & Michigan,” by Mathew Brust, published in 2020.

Smith said folks “just need to start looking down.”

Visit Christopher Smith’s website at FieldEcology.com. You can also follow him on Twitter.


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3 responses to “Rare beach beetle surprises local expert”

  1. Troy Avatar
    Troy

    Very good article!

  2. Allison Mcginnis Avatar
    Allison Mcginnis

    When I saw the title, I knew it had to be Chris! I will keep a look out this coming year while I venture on the river.

  3. Mark Hove Avatar
    Mark Hove

    Yeah, interesting content, thanks!

    Over the last four years I’ve seen tiger beetles scurrying across the sand near the Lakeland public beach, which is just upstream of Interstate 94 bridge, at the end of Quixote Ave N. Christopher Smith, if you’re interested in more info. you can contact me at mark_hove@umn.edu.