�Ӱ�ԭ��

Our large army of little green shield bugs comes and goes

The tiny flying green annoyances seemed to be in greater numbers than usual this year in late May and early June.

They wouldn’t leave me alone. I even found one sitting on the edge of a toothbrush-holding coffee cup at our house.

One day, they persisted in collecting on my four-wheeler’s windshield as I waited at the roadside for a truck to bring a load of gravel.

They also liked to settle on the metal fencing of our sled dog pens. They gathered on the surface of the water in the dogs’ drinking buckets. Dozens clung to the sides of a yellow doghouse.

“They” are the birch shield bug, Elasmostethus interstinctus. They are native to �Ӱ�ԭ�� and are about the size of a small blueberry.

I wasn’t alone in thinking this was a boom year.

“I’ve noticed that we had a huge infestation of stink bugs on our property,” someone wrote on Facebook in early June. “They were breeding everywhere ... one whole side of our house was littered with them.”

“The great 2026 stink bug locust plague of Fairbanks,” another person wrote. “They are everywhere, even up in the hills.”

Many people refer to them as stink bugs, but they aren’t stink bugs at all — scientifically, that is. Although “stink” isn’t entirely wrong.

I learned this from Derek Sikes, curator of insects at the University of �Ӱ�ԭ�� Museum of the North. He is also a professor of entomology in the Department of Biology and Wildlife at the University of �Ӱ�ԭ�� Fairbanks.

“They are very close relatives of the true stink bugs and have what are called repugnatorial glands,” he said. “And you can imagine what they do.”

Disturb one of these bugs, and you'll end up with an odor on your hands.

“Some people say it smells a little like cilantro,” Derek told me. “Maybe some people find it more offensive than other people, because I know some people like cilantro.”

So what do we know about the birch shield bug, scientifically?

They belong to the Acanthosomatidae family within Hemiptera, the group scientists call the “true bugs.” These true bugs are the real deal, defined as such primarily because they have piercing-sucking mouthparts.

They also undergo incomplete metamorphosis, meaning they skip the larval and pupal stages that insects such as butterflies and beetles go through on the way to adulthood. Instead, they develop through three stages: egg, nymph and adult. The wingless nymphs gradually mature into adults without a pupal stage.

And that relates to some birch shield bug info from Derek that sort of changed what I think of them. 

You see, bugs of the Acanthosomatidae family are commonly known as “parent bugs.” Females often guard their eggs and newly hatched nymphs, a practice uncommon among insects.

And birch shield bugs are, among entomologists, the best-known of the North American parent bugs.

“They're good parents, more so than the stink bugs,” Derek said as we looked at a tray of about 550 pinned Elasmostethus interstinctus specimens in the museum’s collections storage area. Each pin also held a small label noting where, when and by whom the bug was collected.

“The mothers, when they lay their eggs on the birch catkins, stay around when the nymphs hatch out,” he said. “They stay near them to protect them. That parental care is pretty unusual.”

So back to the birch shield bug army at my house. It’s gone now, but others will arrive in fall.

Birch shield bugs complete one generation each year. Adults that survived the winter reproduce in spring and early summer. Their offspring mature into adults by late summer or fall and then spend the winter beneath ground debris until the following year.

The bright red nymphs will show up around midsummer, feeding on birch catkins and leaves. The prior year's adults will begin to die off.

Will the next generation be as abundant as this year's? Derek said the answer may be hanging in the trees.

“Let’s keep our eyes peeled to see what's happening on the birch catkins.”

Since the late 1970s, the University of �Ӱ�ԭ�� Fairbanks' Geophysical Institute has provided the �Ӱ�ԭ�� Science Forum column free in cooperation with the UAF research community. Rod Boyce works in the Geophysical Institute public information office.