Nature News: Tracking a predatory stink bug

Anchor stink bug hauling this monarch caterpillar (already dead) around the milkweed plant Sue Pike Photo

Ever since my young cousins in New Jersey sent me photos of monarch butterfly eggs and tiny snow white monarch caterpillars with black heads (they don’t get colorful until later in development), I have been looking for the same on my milkweed plants. Unfortunately, the one and only monarch caterpillar I have found so far was dead, killed by a predatory stink bug. While great for the stink bug, this was, of course, tragic for the monarch caterpillar. We were unhappy as well since we have been encouraging milkweeds and planting all sorts of wildflowers in an attempt to create a safe haven for these beleaguered insects.

Initially, watching this menacing-looking bug drag the hapless carcass of the monarch caterpillar around, I was horrified and wanted to know who the culprit was. Identifying insects can be incredibly difficult. I tried some books and the internet, and I decided it was some sort of stink bug, perhaps an anchor stink bug. According to a “Featured Creatures” bulletin put out by the Florida Department of Agriculture and Consumer Services, the stinkbug “genus is recognized easily by the enlarged long and broadly oval scutellum (located behind the pronotum) … subapical spine on the front femora; and ventral pubescent patches on the males.” I didn’t know what any of that meant, so I resorted to iNaturalist and the awesome folks at bugguide.net for the final identification. My tiny predator did turn out to be an anchor stink bug (Stiretrus anchorago).

The red arrow points to the ‘anchor’ on the stink bug’s back. Not real obvious here. Sue Pike photo

Now that I knew what an anchor bug looked like, I decided to at least learn what one of those seemingly obscure anatomical terms referred to. I call myself a naturalist and, upon finding out what a scutellum was, realized I’m a fairly ill-informed naturalist. All true bugs have a hard plate, called the scutellum, that is usually triangular, on their backs. The anchor bug’s scutellum is unusually large and U-shaped, something like a shield with a black anchor-like pattern on it. Now that I knew what to look for, the scutellum was, indeed, a very prominent and recognizable feature.

While refreshing my memory on insect anatomy, I was reminded of some of the differences between insects that are known as true bugs (some common examples are cicadas, water striders, stinkbugs and spittlebugs) and other insects, like beetles (not true bugs). It can be difficult to identify insects down to their species, but once you know what to look for, you should be able to distinguish a beetle from a true bug fairly easily. Beetles have chewing mouthparts whereas true bugs eat a liquid diet. True bugs have a beak, which they use to suck out the contents of whatever it is they are eating. The anchor bug uses its beak to harpoon its prey and then inject digestive enzymes that first immobilizes the prey and subsequently turn its insides into goo, which they then suck up with those same beaks. If you look carefully at the photo, you can see a tubular structure attaching the anchor bug to the caterpillar — that’s the beak, firmly implanted in the caterpillar. A number of pests (aphids, for example) are true bugs that use their beaks to feed on the fluids inside plants.

The easiest way to know whether you are seeing a true bug or a beetle is the wings on the back. Beetles have hard, leathery forewings that cover up and protect the hind wings. When at rest, the hard forewings meet in the middle of the back forming a line down the middle separating the two wings. These have to be lifted out of the way when the beetle flies. Only the first part of the forewing of a true bug is hardened (hence the scientific name, Hemiptera, which means half wing). At rest, the wings cross over each other so that from above they have a triangular shape. All true bugs also have a scutellum in between the wings, sometimes it is reduced in size and sometimes it is big and obvious, like in the anchor bug.

Anchor bugs live solitary existences, roaming the landscape in search of prey and are considered to be economically beneficial insects. As generalist predators, they are good biological controls of a variety of pest species (though they really aren’t common enough to make a big dent in a pest population). Look for them in your garden or a nearby field, they are strikingly beautiful bugs with their bold patterns of black and red, yellow or white. Now that I know who they are, next time I see one, I will welcome it gladly and not judge it for killing the occasional monarch butterfly, being, as they are, important members of our local backyard ecosystems.

Nature News: The mating rituals of water striders

published May 6, 2020 seacoastonline.com, the York Weekly, Portsmouth Herald, Foster’s Daily and the York County Coast Star

The last time I wrote about water striders, it was the middle of the summer. I was sitting by a pond battling mosquitoes while watching them skate across the surface of the pond. I love how fast they move, which I didn’t understand. Are they skating and digging in their little feet for some purchase on the slick surface of the pond? Or is it a sticky surface that just looks like glass?

Water striders caught in the act of mating photo by Steve Morello stevemorello.com

Turns out not all small insects can do this – walk and skate on water. Water striders can because they have very fine hairs on the undersides of their legs that trap air and repel water. The scientific term for this is superhydrophobic. They can move so quickly because what they are doing is more like rowing, vigorously rowing, creating little swirls in the surface that help propel them forward. For their body size, they move fast, the equivalent of a 6-foot-tall person running 400 miles per hour!

I love the way their feet make little dimples in the surface of the water. Sometimes that’s how I first notice them – by the shadows those dimples cast on the bottom of the stream. As a biology teacher, I really love this, a textbook example of the high surface tension of water. They are bending the surface of the water.

I have been surprised to see water striders on my brook and along the edges of the river. I hadn’t realized they lived in flowing water as well as still water. Having never lived along a river until now, I have always made assumptions about who lives where. This was a big one. I always assumed they needed still-water, but there they were, skating upstream against the current, hanging out in the still water along the edges. And, as a wonderful sign of spring, this past weekend, while I was battling newly-hatched black flies instead of mosquitoes, I was able to catch some in the act of reproduction.

I realized these two were mating because they looked huge and on closer inspection it turned out I was seeing two, one being carried on the others’ back. So, I looked into water strider mating behavior. As you would expect, it is fascinating. As far as researchers know, there is no courtship involved. The male mounts the female. If she doesn’t fancy him, she might try to resist by deploying an extremely effective genital shield. However, the males have coevolved a behavior to prevent her from resisting, an extremely diabolical behavior. They coerce the female into mating by tapping out intricate patterns on the surface of the water. These patterns are meant to attract a predatory beetle that attacks from below the surface, the backswimmer. The female, since she is on the bottom, is more vulnerable to attack from below, so usually submits fairly quickly if the male starts tapping. This has been tested in an experiment (Han and Jablonski, “Male water striders attract predators to intimidate females into copulation,” Nature Communications, 2010) in which a small bar was glued to the back of the female. The bar raised the male up high enough that he couldn’t tap. When the male couldn’t tap, females resisted his advances for much longer periods of time.

I have been making more of a point than ever to get outside for some green time, to be in nature, to do some close and slow looking. By spending more time carefully observing water striders, my curiosity has been piqued and I have learned so much more than I would have with just casual observation. Look up slow looking. It’s something we shouldn’t have to be taught, but the art of sitting still in nature and observing what is going on around you is an art form, one that we can all participate in.

Ice is Magic

published Feb 5, 2020 in the York Weekly, Portsmouth Herald and Foster’s Daily and online at seacoastonline.com

I spent almost the entire first semester last year having my freshmen STEM class run experiments about ice. Every morning, when I walk my dog, we follow a path along the river and observe the ice, marvel at the huge slabs of ice that are carried downstream and stacked like pancakes in some places, crunch our way over the paper-thin ice that coated the hummocks of the floodplain after the last brief thaw, watch dangling orbs of ice form in the waterfall that spills down to feed the river. I, like so many others, am obsessed with ice.

If you think about it, ice formation on a pond or lake is fairly straightforward. As the water gets colder, it gets denser and starts to sink. Liquid water reaches its maximum density at 4 °C (39.2 °F), after that it continues to get colder and freeze solid, but as it freezes, it becomes less dense and floats to the surface and we end up with ice-covered lakes.

Ice slabs pile up in Little River

At first, the ice is paper-thin, fragile sheets that crumble in your hand. As winter’s cold progresses, the ice gets thicker and thicker as more ice is added from the bottom. As long as the pond or lake is deep enough, there should always be at least some liquid water underneath the ice. This is very helpful to the animals that live in the pond or lake. They can survive in the liquid water near the bottom until the spring thaw.

Now, think about a river or stream in which the water is constantly moving. All of that turbulence makes it difficult for a nice sheet of ice to form. On cold winter nights, the surface water of a river cools, crystals of ice form and start to grow. The constant water movement keeps the crystals from growing together into a solid sheet, instead you get a slushy mixture of water and ice called frazil ice. You can see this floating on the top of a river in early winter, or instead of floating on top, because the crystals are so small, they can easily be carried by the turbulence down to the bottom of the river.

Ice slab close-up with river behind it

As temperatures continue to drop, the frazil ice can start to join together at the surface and form round plates of ice with upturned edges (from the plates bumping together). This is called pancake ice. Or, what was more common on my river, ice will start to form along the edges of the river. Ice forms more easily along the edges because there is typically less water movement and the temperature of the shallow water on the edge cools faster. This is called border or shore ice. Border ice will generally enlarge toward the middle of the river until the ice from both sides meet.

Border ice forms along a small stream

Another interesting way a river can freeze is when the frazil ice that is transported to the bottom of the river attaches to the streambed and builds from the bottom up. This is called anchor ice. Anchor ice can grow very rapidly and block the flow of a river or stream causing local flooding. If there is particularly low flow of water along the bottom, an enormous amount of anchor ice can build up. This can be extremely harmful to aquatic life because the anchor ice can physically lift up parts of the streambed and move it downstream, movement akin to the action of a bulldozer, killing small fish and aquatic invertebrates (like dragonfly or caddisfly larvae) that live in the streambed, or freezing fish eggs that were waiting for spring to hatch.

I thought I first fell in love with ice in some dramatic location, perhaps when I crossed Lake Champlain on the ferry one cold winter’s night and watched the prow cut through the ice and listened to it grind against the hull of the boat, or when I was travelling as a National Geographic Grosvenor Teacher Fellow in the Arctic Ocean and witnessed firsthand the ethereal beauty of icebergs and the vast expanses of pack ice in the polar sea. But watching the beautiful, ever-mutable ice along my little river this winter has made me realize that I’ve loved ice since I was a kid watching icicles dangle from the gutters of my house, that no matter where you find it, ice is magic.

Nature News: New England forests will have to evolve with climate

published January 15 2020 in the York Weekly, Foster’s Daily and the Portsmouth Herald and on seacoastonline.com

Dryad emerging from an old dead tree. Dryads protect and die with their trees. I wonder what they are thinking as our forests succumb to climate change-who do they go after? All of us who use fossil fuels?

This past weekend was unseasonably warm. Record-breaking in fact, for New England, with temperatures a good 7 or 8 degrees warmer than past records.

It seemed like everyone was out taking advantage of the balmy weather to take a walk in the woods. I headed up a side trail on Blue Job Mountain and while working my way up a slushy streambank looked across a clearing and saw something I had never seen before. There, in an old broken-off tree stump was a figure, made of wood, that looked to be climbing out of the tree.

The tree must have been felled relatively recently because the wood was still a bright orange-brown, a splash of color surrounded by the snow-covered pines and oaks. It looked raw and newly exposed. Sunlight hadn’t gotten to it yet (ultraviolet rays break down the cellulose in wood, bleaching out the color, giving it a silvery gray sheen). This figure that I, rationally, knew was just a random carving of the wood into human form, looked back at me. I knew it was just wood, but it still was magical. I could see how people from many different backgrounds, from all over the world, have believed that there are spirits that inhabit trees, so for a moment I believed a wood spirit was looking back at me.

Trees have lives that follow vastly different time scales from ours. They usually live much longer than we do and don’t move as we do. They are root-bound. They only move by reproducing, by sending their seeds out ahead of them into new territory. This warm weather was a reminder to me of their vulnerability. How is the rapid warming of our Earth going to affect the forests of New England?

A little over ten thousand years ago, the glaciers were receding and trees were re-colonizing New England. Slowly their seeds were carried or blown north and slowly they colonized the newly formed earth. This is a process called succession. When there is no dirt (as when glaciers had scoured all the dirt from the land), first lichens and mosses colonize bare rock, break into it and build soil. Then grasses and small plants move in, followed by shrubs, followed by fast-growing, light-loving trees, followed finally by the trees of a mature forest – the beech and maple, pine and oak of our temperate, deciduous forests.

Now, as conditions shift, as it warms, many of these trees need to move north or die. According to Mass Audubon’s “Effects of Climate Change on Woods & Forests,” a general rule of thumb is that “most tree species can colonize habitat beyond their existing range at a rate of 100 km in a 100 years (about 62 miles per 100 years). Some species will be able to move that fast, but warming temperatures will likely require forests to shift by 400 to 600 km (about 250 to 370 miles) by 2100, a rate faster than most species can tolerate.”

One of my favorite types of tree spirits are the Dryads. I first read about these as a child in the classic Bullfinch’s “Mythology.” According to Bullfinch, Dryads are nymphs or spirits, bound to particular trees, caretakers of the trees.

“Dryads or Hamadryads, were believed to perish with the trees which had been their abode and with which they had come into existence. It was therefore an impious act wantonly to destroy a tree.” I guess the caretaking days of my Dryad were over. Her tree had been felled by age or a wind storm. Perhaps that is why she was stepping out of the tree?

Susan Pike, a researcher and an environmental sciences and biology teacher at St. Thomas Aquinas High School, welcomes your ideas for future column topics. She may be reached at spike3116@gmail.com. Read more of her Nature News columns online.