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.

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.

In winter’s cold, the subnivean zone is abuzz

Published January 21 2020 The York Weekly, Portsmouth Herald and Foster’s Daily and at seacoastonline.com Titled ‘Nature News’

The subnivean zone lies between the snow and the earth.

This winter has been troublesome; a few weeks ago it was so cold my pipes froze, then it we climbed to unseasonably warm temperatures, then some more snow, and now, very cold again-my pipes continue to freeze. One thing that makes me happy is that we have a nice layer of snow on the ground, insulation that is is vital to the survival of many of the plants and small mammals, even microscopic life forms, that are essential parts of our Northern ecosystem. So, for many, the recent snow was welcome relief from the cold.

While the surface seems empty, underneath, at the interface between ground and snow, a veritable city is rising. Old leaves and branches hold the snow up, creating an open space. The ground also radiates heat, warming the overlying snow, which instead of melting sublimates (when a solid turns into a gas without first becoming a liquid) directly into water vapor. Both of these processes leave a space between the snow and the ground, called the subnivean zone.

The word “subnivean” comes from the Latin for under (sub) the snow (nivean) and is a scientific term referring to the open passageways that form under deep snow.

Six or more inches of snow are all that are needed to trap the earth’s heat and allow a subnivean zone to form. This zone remains humid because of the transformation of snow into moist water vapor and is capped by a layer of ice that acts as an insulating roof. The temperature of the subnivean zone is generally a constant 32 degrees, protecting species that would otherwise freeze.

The most common inhabitants of the subnivean are mice and voles — they make tunnels under the snow connecting sleeping areas and sources of food. Red squirrels also burrow into the subnivean to stash food. Entrance holes to these networks allow carbon dioxide to escape. Carbon dioxide is released when these animals breathe and by the ground itself. Without the entrance holes to serve as ventilation shafts, carbon dioxide could build up to lethal levels.

While the subnivean zone provides protection for mice and voles, it is also the hunting ground for the short-tailed weasel (or ermine), a weasel that, except for its black-tipped tail, turns snowy white in the winter. This small weasel, just the right size to live and hunt in the tunnels under the snow, is a major predator upon small rodents.

All you need is about 6 inches of snow to allow the subnivean space to form

Recent research has unearthed a whole new category of inhabitants of the subnivean zone — microbes that are proving to be important players in the cycling of both nitrogen and carbon dioxide between the earth and the atmosphere. A deep snowpack with an active subnivean zone appears to encourage a healthy microbial population that, through respiration, releases significant amounts of carbon dioxide into the atmosphere. Studies suggest that as much as half of the carbon taken up by plants in the summer is released back into the atmosphere by microbes in winter (Paul Brooks, University of Colorado Boulder). At the same time these microbes, by processing and storing nitrogen, fertilize the soil as the snow melts.

Without a healthy snowpack, without these snowpack microbes, plants don’t do as well come spring. While these microbes may be releasing a lot of carbon into the atmosphere during the winter, they are also necessary for healthy plant growth — plants that will absorb carbon dioxide throughout the growing season.

For all these reasons, it seems to me, a nice deep snow, serving as an insulating blanket on the earth, is a welcome part of our northern winter.

Why do some trees get so tall?

published 12/31/2019 in the York Weekly, Foster’s Daily, the Portsmouth Herald and online on seacoastonline.com

I was just out visiting my son who lives on the coast of Northern California, the land of tall trees, the coast redwoods.  Coast redwoods (these are the state tree of California) are the tallest trees on Earth. I was thinking about our New England tall tree, the white pine (the state tree of Maine), and wondering whether they ever had a chance of growing as tall as the coast redwood.

Navarro River Redwood State Park near Mendocino California

There are a large number of factors that determine how and why a tree grows tall: genetics, environment, age.  The primary reason for a tree to grow as tall as it can is to beat surrounding trees to the sun. White pines and coast redwoods are great at this and will dominate a forest if they can get to the sun first.  White pines typically grow to about 150 feet tall (however pre-colonial white pines have been estimated to reach heights of at least 230 feet) while coast redwoods grow twice as tall-300 feet and taller (the tallest tree in the world is a 379 foot tall coast redwood named Hyperion).  How do they do it?

The two problems that have to be overcome to grow super tall are water and wind.  Coast redwoods tend to occupy sheltered valleys where they are protected from wind.  Like all trees they need to somehow distribute water to all parts of the tree. The long-held dogma of how this is accomplished is that groundwater enters the roots and is pulled upward through the tree by water evaporating from pores in the leaves.  Water is sticky, so as one water molecule evaporates from a pore in a leaf it pulls another water molecule up after it. The taller a tree grows the more difficult it is to get water up to the topmost leaves-gravity becomes a major drag. If those leaves can’t get enough water photosynthesis and growth start to slow.   

However this upward flow of water  isn’t the whole story. It turns out many trees can also absorb water into their leaves and move it downward towards the roots. There has to be water vapor in the atmosphere for this to be a useful adaptation.  Coast redwoods live in the fog belt, their needle-like leaves are almost constantly bathed in fog. Studies by the National Park Service found that some coast redwoods obtain 40% of their water from fog, not their roots!   And, according to a study on coast redwoods published in Functional Ecology (“Pushing the limits to tree height: could foliar water storage compensate for hydraulic constraints in Sequoia sempervirens?” published 2014 by H. Roaki et al) the pinnacle (topmost) leaves of the tallest growing coast redwoods stored water better than trees that didn’t grow as tall. So, tall-growing coast redwoods can take advantage of all that ambient water in the surrounding fog and both store and use it for growth.

Another factor in height is age-it takes time to acquire all of that biomass.  White pines easily live a couple hundred years-the oldest known specimens are over 400 years old.  Coast redwoods, on the other hand, are among the oldest living things on Earth-they can live for more than 2,000 years (the oldest living coast redwood is 2,200 years old).   Hyperion, the tallest tree on Earth, a baby by coast redwood standards at somewhere between 600 and 800 years old has still had a remarkably long life.

Redwood stumps provide nutrients for new growth. Here some sorrel grows at the base of a stump

So, while our East Coast white pines probably couldn’t ever grow as tall as coast redwoods, -conditions and adaptations aren’t quite right-one similarity between these two species is how it feels to walk into a white pine or a coast redwood forest.  There is a cathedral like quality to these forests, they are quiet and dark. The filtered sunlight adds to their majesty, illuminating the mist in much the same way that light falls through the stained glass of a human-made cathedral and illuminates the dust motes floating through the air.   These forests we walk through today are largely young trees. Just imagine the grandeur of a pre-colonial forest, fully mature white pines or coast redwoods reaching towards the stars.

Chickadee-dee-dees!

published Dec 25, 2019 the York Weekly, Portsmouth Herald, Foster’s Daily and seacoastonline.com

I think if you ask any New Englander to name the top three birds at their feeder, the chickadee would be on everyone’s list. I also think that of any of the common bird calls in our forest, the chickadee’s is the one most of us could easily identify. These tiny, round birds with a black cap and bib that contrasts with its white cheeks are found all over the northern parts of the United States and up into the middle of Canada.

black-capped chickadee

When not living in the suburbs you can find them in deciduous and mixed forest, almost any kind of open woodlands, as well as thickets. When we clear forests for agriculture or development, we are increasing the amount of forest edge – a habitat type that chickadees love (unlike something like an ovenbird that requires deep woods for nesting).

The black-capped chickadee (Poecile atricapillus) is one of seven species of chickadees found in the United States. They all have similar body shapes with sometimes subtle differences in color or streaking on their heads. For example, the boreal chickadee (the other New England chickadee) has a brown cap and cinnamon flanks and a more northerly range, preferring the boreal forests of Canada and the mountains of New England.

Chickadees probably do so well with humans due to their flexibility and curiosity. They are highly social birds that are quick to explore new environments and take advantage of resources (they will usually be the first bird to use a new feeder). According to the Cornell Lab of Ornithology, one study found that “every autumn black-capped chickadees allow brain neurons containing old information to die, replacing them with new neurons so they can adapt to changes in their social flocks and environment even with their tiny brains.” They really do have tiny brains, which makes their ability to memorize that much more remarkable. They often hide food for later use and can remember thousands of hiding places!

Try listening to their calls. They actually have a very complex language, much more than the obvious chickadee-dee-dee. They can communicate information about other flocks, predators and foraging information. For example, they add ”-dees” to their chickadee call to indicate higher threat levels.

From the number that show up at my feeder every day one, wouldn’t know that we are in the middle of a mass extinction of birds. A recent Science Magazine article recently reported that there has been a 29% decline in birds in the United States over the past 50 years (that’s almost 3 billion fewer birds on the North American continent today compared to 1970!). While chickadees aren’t considered endangered, or even threatened at this point, their distribution is expected to shift and their numbers decline due to ongoing climate change. A 2017 report by Massachusetts Audubon predicted that by 2050 the black-capped chickadee population is likely to disappear from coastal areas of Massachusetts and decline substantially throughout southern New England as rising temperatures push their range to the north.

For now, if you want to attract chickadees to your backyard, provide feeders (they are one of the easiest birds to attract to a feeder), black-oil sunflower seeds and suet will do the trick, and some standing dead trees for cavity nesting sites (they also like nest boxes).

While chickadees are around all year, I think of them as winter birds. Watching them at my feeder as snow lightly falls is a wonderful way to welcome winter in New England.

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.

Red Crossbills in New England

published Dec 17 2019 The Portsmouth Herald/seacoastmedia.com

I have been watching the “winter” birds return to my feeder – juncos and titmice, downy and hairy woodpeckers, cardinals and nuthatches. A birding friend who lives in Colorado just posted some gorgeous photos of red crossbills in his hometown of Estes Park. He said he is seeing them everywhere. I have never seen a crossbill (a type of large finch) even though we have both red and white-winged crossbills in New England, particularly in the winter. The North American range of the red crossbills that my friend Scott Rashid, founder of the Colorado Avian Research and Rehabilitation Institute, photographed extends down into the mountainous spruce and pine forests of Central America, while the white-winged crossbill range is mostly in the boreal coniferous forests of the north.

Both of these crossbills could, I think, be mistaken for a house or purple finch by a birder of my caliber (poor). I wonder whether I have seen crossbills in my backyard, but assumed they were house finches? Crossbills are larger than house and purple finches and both the white-winged and the red crossbill are rosy red all over with dark wings whereas the house and purple finches are reddish mostly in front. I’m describing male coloration – the females of all these species are drab, with the finch females being brownish and the crossbill females being yellowish-green.

Crossbills have a really wonderful adaptation to their lives in coniferous forests. Their bills cross at the tip so that when their bill is closed the tip of the bottom bill protrudes up and the tip of the top bill protrudes down forcing the upper and lower parts to cross each other. According to the Cornell Laboratory of Ornithology, crossbills employ a special technique using these unique bills to get to their favorite food, pine seeds. “A bird’s biting muscles are stronger than the muscles used to open the bill, so the Red Crossbill places the tips of its slightly open bill under a cone scale and bites down. The crossed tips of the bill push the scale up, exposing the seed inside.” They then extract the seed using their tongue and bill together.

One fascinating fact about red crossbills that Scott shared with me was the wide variety in overall size and particularly in bill size among what is now considered the one species of red crossbill (Loxia curvirostra). For example, there are types of red crossbills that are smaller in size with smaller bills who specialize in the smaller pine cones of hemlock trees while larger billed types will specialize in larger pine cones. There are currently 11 different types of red crossbill recognized in North America.

Another cool fact about both red and white-winged crossbills is that they are opportunistic breeders. Because their diet is largely composed of pine seeds (white-winged crossbills can eat up to 3,000 conifer seeds in one day!), because they feed pine seeds to their young, and because pine trees produce cones at different times of the year, these birds can breed whenever the seed crop is largest. This might mean nesting in the depths of winter – something I wouldn’t expect to see, a nest with young or some fledglings hanging out on a snowy afternoon.

The best time to find crossbills around is in the winter as they wander about in search of food. According to the Cornell Lab, “Crossbills are nomadic, especially in winter, and in some years irrupt far south of their normal range. At these times, they may show up in evergreen forests, planted evergreens, or at bird feeders.” Sometimes cone crops will fail in their breeding ground and migrants will show up further south in search of food. Making sure to include a variety of native conifers in your backyard can help attract them. Cemeteries and parks with ornamental spruce and pine plantings are also a good place to look as they often attract crossbills in winter.

Everyone I know who is a “real” birder has seen crossbills in New England in winter, so my personal challenge is to try to join the ranks. To that end I’ll be paying a little more attention to anything that looks like a house finch and to any reddish-pinkish birds hanging out in my conifers and feeding from the pine cones dangling from the upper branches.

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.