Saturday, April 1, 2017

Flashlight on a stick

Figure 1.  The truly amazing Flashlight on a stick
Yes folks, I have finally broken into the invention market.  After several minutes of research and development, I bring you, Flashlight on a stick (Figure 1).

Flashlight on a stick comes with two, count them, TWO revolutionary components: a shiny blue impact-resistant flashlight lovingly constructed from cheap flashlight-grade aluminum, and a high-quality, 100% organic, high-fiber stick.  Flashlight on a stick can be your third hand on those occasions when you are tempted to go against the advice of your dentist by holding a light in your teeth.  You can use it to illuminate specimens on a microscope (not provided), or as a handy door stop or paperweight.   

Flashlight on a stick has three settings, on, off, and out of batteries.  Because of it's unique single screw design, Flashlight on a stick can rotate through a full 360 degrees allowing you to deliver cool LED illumination wherever it is needed.  You can shine a light on impossible-to-reach-but-at-least-you-can-now-see-them items under your desk, or right up your nose.

You can have flashlight on a stick for 24 easy payments of $12.99....or you could just make your own.

Figure 2.  Light in use with microscope
But seriously folks, I needed a way to put light on specimens on a microscope (Figure 2) for a program in the woods far from electrical outlets.  Simple is sometimes best.  The flashlight cost $0.99 from an Ebay vendor; the mounting bracket cost $1.25....and I had some 2.5" by 1.5" lumber laying about the place.  The single screw mounting bracket really is convenient so you can direct the light anywhere.  I could see using this for camping.  I cranked out 8 of these in about half an hour and I'll probably use them until I retire.

Saturday, January 7, 2017

Cloudy with a chance of flies

Clouds of tiny insects, rising and falling hypnotically along lake shores, contribute to the ambiance of warm summer evenings. My recent bike ride was interrupted by a lungful of this ambiance.

If you find yourself in a similar predicament, you might wonder what these miniscule flies were doing before being swallowed, where they came from, whether they bite, and whether we need these interrupters of peaceful lakeside jaunts. We’ll get to these questions, but first, let me say that as an ecologist, I find these insects to be among the most fascinating and important freshwater invertebrates.

Non-biting midges, also called chironomids, are most conspicuous when they hover in swarms near water. Not to be confused with the no-see-ems or biting midges maligned by Thoreau, they constitute a diverse family found on every continent. Two midge species are the only known insects in Antarctica. One Antarctic species lacks wings entirely and is therefore, I suppose, at little risk of death by human inhalation.

Whether Earth-bound or in flight, mating is the reason for midge swarms. Newly emerged adults have a short time to find mates, and dense swarms function like singles bars.
My clumsy encounter with a nuptial swarm did not make much of a dent in local midge numbers. They are abundant. They’re also hyper-diverse, with more species in this one true fly family than in all the families of stoneflies combined. Entomologists have described more than 5,000 species and are regularly called upon to come up with scientific names for newly discovered species. Dicrotendipes thanatogratus, a midge named for the Grateful Dead (thanatos is Greek for “dead” and gratus is “grateful” in Latin), is one example.

With so many species, it’s not surprising that non-biting midges thrive in all sorts of habitats. Saint Michael’s College students and I have found them in every stream, pond, and lake we have sampled, and they often exceed 50 percent of the insects we capture. In ponds and deep river-silts, bright red midges called bloodworms use skin-bound hemoglobin to scavenge every trace of oxygen from their stagnant habitats. Dr. Richard Jacobsen studied a midge found only on the backs of mayflies; its life cycle synchronizes perfectly with that of its bigger host.

Non-biting midges are also diverse in their culinary predilections. They eat nearly every conceivable foodstuff; they can be scavengers, herbivores, predators, or parasites. One species, Metriocnemus knabi, feeds exclusively on insect parts in pitcher plants in northern bogs. There are abundant midges grazing algae in salt marshes, consuming leafy detritus in tree holes, and they may well be scavenging from the rain water in the gutters of your house. These insects are essential in the aquatic food webs that support fish populations, and anglers seek to replicate their delicate forms to lure their catch.

Like many insects, midges grow through a series of larval stages. Slim, legless, translucent larvae hatch from eggs laid in gelatinous masses. They grow quickly and become too big for their exoskeletons. These split, revealing softer exoskeletons that stretch and harden around their bodies. In streams, where I do much of my research, discarded exoskeletons accumulate behind rocks and logs. Sieving exoskeletons from stream froth is a little like panning for gold. Much information can be coaxed from these discarded shells. Cleaner streams host more midge species and certain species are never found in polluted streams.

After four rounds of growing and shedding, non-biting midges enter a pupal stage. They may appear somewhat static, but each pupa is a hive of cellular activity. Cells migrate and rearrange, forming compound eyes, six legs, and in most species, a pair of wings. After a few days, the pupae split and adults emerge. Some midges hatch only at certain times of day and the rhythm of a stream can be followed by sampling drifting pupal skins through the day.

The clouds of adult flies are a food source that moves from aquatic to terrestrial food webs, sustaining the swallows and bats that keep real pests in check.  Non-biting midge swarms will persist as long as the weather is warm enough for fly muscles to flap fly wings. Some species hatch early in the season, some later. There are species that hatch once per year; others can produce two or more generations in a season.

So when you find yourself in a swarm of insects this September, try to appreciate the romance. Perhaps the knowledge that fly love is in the air will make up for the occasional fly in your eye. Or in your mouth. Or snuffed right up your nose!

Declan McCabe teaches biology at Saint Michael’s College. His work with student researchers on insect communities in the Champlain Basin is funded by Vermont EPSCoR’s Grant NSF EPS Award #1556770 from the National Science Foundation.
This article was written for Northern Woodlands Magazine's Outside Story and first published on September 4th 2016
The photograph of an adult male midge was downloaded from Wikimedia Commons under a CC BY-SA 3.0 Creative Commons license.
Download the Article © by the author; this article may not be copied or reproduced without the author's consent.

Tuesday, April 26, 2016

Under the Water, December’s Peak Leaf Season

Pteronarcys.jpgBy December, foliage season is long over for us humans, but it’s peak season under the water. Last month, as the last bus of tourists departed for home, fallen leaves accumulated in our streams and rivers, starting a process that’s critical for the nourishment of everything from caddisflies on up the food chain to eagles and even people. In fact, most of a New England stream’s food supply originates in the form of fallen leaves.

The bright yellow and red piles that accumulate on river rocks and fallen branches are not nearly ready for consumption by discerning invertebrates. The witch’s brew of natural chemical compounds that discourages insects from eating green leaves on trees, can be just as repellent to creatures that scavenge freshly fallen leaves under water.  First, cold water must leach out those chemicals. Imagine the process as soaking and re-soaking a teabag. During this period, the leaves are also colonized by microscopic organisms. For a hungry invertebrate, the cleansed layered leaves, covered in fungi, bacteria, and algae, make a sandwich of which Dagwood Bumstead could be proud.

If all leaves were created equal, then the river food supply would consist of a brief crop polished off by whatever ravenous insect species got there first. But of course not all tree and shrub species lose their foliage at exactly the same time, and their leaves decompose at different rates. Some are tough, leathery, and laden with toxins. Certain laurel species can release so much cyanide that entomologists have used them to kill study specimens. Other species, such as linden, are comparatively soft and become an early underwater food source. Oaks and beech trees hold onto their tough leaves late into the season and when they finally fall, they are slow to reach an edible condition.

Variability in the timing of leaf fall, and in the rates at which leaves become palatable, means that edible leaves are available for most of winter. This is also the season when much aquatic invertebrate growth occurs.  A caddisfly species called Pycnopsyche gentilis acts like a chronicler of the leaf supply.  In fall and early winter, its larvae cut disks from leaves, and use silk to make and line pencil-diameter cases in which they live. In early spring, as leaves become scarce, and the larvae keep growing, they add to their cases using large sand grains.  This is why one can sometimes find cases with leaves at the back end and sand grains at the front.

Although fish aren’t typically leaf eaters, they nonetheless rely on the underwater foliage season. Cranefly larvae and stoneflies, fattened up on leaves, are protein-packed snacks for hungry trout, salmon, and bass.  Without invertebrates, fish would go hungry.  Without some knowledge of invertebrates, few anglers would know what to put on a hook to lure a spectacular brook trout.

Cleanest streams host most invertebrate species and simply counting the number of species can be the basis for an interesting study. For example, each fall, I visit forested and urban streams with Saint Michael's College biology students.  This year we found more than 20 species in Browns River, downstream from Mount Mansfield State Forest.  Centennial Brook drains South Burlington neighborhoods and parking lots, and hosts fewer than half that many invertebrate species. Browns River macroinvertebrates include clean-water loving giant stoneflies, and an assortment of mayflies. I have yet to meet a Centennial Brook stonefly because the community is dominated by midges, craneflies, and a particularly tough caddisfly that makes its living by filtering particles from the water.

A view into the world of submerged invertebrates is just a bunch of leaves away.  You can easily lift an intact chunk of leafy habitat from a streambed for study.  Equipment can be as simple as a basin of stream water. Drop a handful of streambed leaves into the basin and observations can begin. Rinse and remove the leaves one at a time to reveal the small creatures living among them.

Declan McCabe teaches biology at Saint Michael’s College. His work with student researchers on insect communities in the Champlain Basin is funded by Vermont EPSCoR’s Grant EPS-1101317 from the National Science Foundation.
This article was written for Northern Woodlands Magazine's Outside Story and first published on December 14th 2015
The photograph of a stonefly was downloaded from Wikimedia Commons under a CC BY-SA 3.0 Creative Commons license.  Download the Article

Saturday, January 30, 2016

Zebra Mussels

Invasive species have earned their bad reputations. English sparrows compete with native birds from Newfoundland to South America. Australian brown tree snakes are well on their way to exterminating every last bird from the forests of Guam. And I don’t think anyone can fully predict how Columbia’s rivers will change in response to drug lord Pablo Escobar’s escaped hippopotamus population.

While our climate protects us from rampaging hippos, the Northeast has plenty of exotic species in its waterways, including some that cause serious damage. Zebra mussels are possibly the most familiar of these. They were first discovered in Lake Champlain in 1993 by a precocious 14 year old, Matthew Toomey, who recognized one based on an identification card he’d received at school. Since then, the mussels have spread throughout the lake and their effects have been well chronicled. They kill native mussels; coat surfaces with razor-sharp shells; foul anchor chains; block water intake pipes; and steal plankton and other food from native fish.

With all of the negative press regarding the species, you might find it jarring to read anything positive about zebra mussels, particularly anything written by a biologist. Discussing positive effects of invaders is practically taboo. We don’t speak ill of the dead; we never praise invasive species. I’m certainly not advocating zebra mussel propagation, but like them or not, they are here to stay. These mussels are an important part of European ecosystems, and it’s interesting to consider what native organisms benefit from their presence.

Zebra mussels are voracious filter feeders. A single mussel can suck a liter of water through its body daily. All of this filtration removes plankton and particles from lake waters, but these particles don’t just disappear. The phrase immortalized in Minna Unchi’s children’s book Everyone Poops applies. Along with excrement, unpalatable particles rejected by zebra mussels are mixed with mucus and dropped on the lake floor. Mussel excrement and mucus might not sound appetizing, but it’s a smorgasbord for lake floor invertebrates and fish.

In addition to covering rocky surfaces, zebra mussels often carpet lake floor sand and silt. Formerly soft sediments that provided foraging grounds for sturgeon and other fish can become a tangled mess of living and dead mussels several inches thick. Not surprisingly, fish such as log perch, bullhead, and sculpins have difficulty finding their insect prey amongst the clutter of shells layered over their sandy habitats. When given the choice, juvenile sturgeon avoid zebra mussels and spend their time on sandy or rocky areas.

What’s bad for these predators may be good for their prey. To figure out just how good or bad zebra mussels could be for Lake Champlain invertebrates, we ran experiments under 30 feet of water in sandy areas of Appletree Bay. When my colleagues Ellen Marsden, Mark Beekey, and I fenced off lake floor patches with and without zebra mussels, twice as many invertebrates colonized areas with zebra mussels. More species also moved in. After a month, the number of species in experiments with added mussels doubled and included some species more typical of rocky lake floors. Nooks and crannies between zebra mussel shells seem to act like very small, natural shark cages that protect tiny insects from hungry fish. And when we placed insects and fish in aquariums, far more invertebrates survived with zebra mussels than without.

On balance, I would rather have a lake without zebra mussels than with them. But unless ways are found to eliminate them, it will remain important to understand how they affect native species. In Lake Champlain, the zebra mussel population grew rapidly and has since fallen below peak numbers, as often happens with this species in a new location. This month, for the first time in recent years, we pulled up a lake floor sample in Burlington Bay that entirely lacked zebra mussels. Perhaps we are reaching a new equilibrium?

Declan McCabe teaches biology at Saint Michael’s College. His work with student researchers on insect communities in the Champlain Basin is funded by Vermont EPSCoR’s Grant EPS-1101317 from the National Science Foundation.
This article was written for Northern Woodlands Magazine's Outside Story and first published on October 5 2015
The photograph of zebra mussels was downloaded from Wikimedia Commons under a CC BY-SA 3.0 Creative Commons license.
Download the Article

Thursday, December 17, 2015

Keeping it clean downstream

Agnetina.jpgIn peaceful streams, aquatic macroinvertebrates such as crayfish, stoneflies, and caddisflies travel over and under submerged rocks, foraging for other invertebrates, leaves, and algae. When rain falls, their world turns upside down.  At first only the surface is disturbed, but before long, runoff reaches the stream and increases its flow many fold. Silt and sand blast every exposed rock surface. At peak flow, boulders are propelled downstream by powerful currents.

How do small creatures survive such crushing chaos? They hunker down. Water-filled nooks and crannies extend deep below streambeds and far beyond river banks. These deep interstices provide a safe haven even while turbulent water pulverizes the riverbed, comparable to a storm cellar in a tornado.

Wednesday, October 14, 2015

Flat Stanley and the Centipede

Biologists sometimes field questions about a “huge scary bug” that appeared in someone’s home or worse yet on their person. Most turn out to be benign organisms that ended up in the wrong place. For me, the most common questions come in July, when male dobsonflies emerge from the Winooski River and often end up crashing into windows on the Saint Michael’s College campus where I teach. The males have impressive mandibles that look scary but are harmless to people.
Recently however, one of these questions did actually involve something dangerous. One morning I received a call from a friend and grade school teacher, who explained that she had managed to corral a very large and intimidating centipede in a plastic container at her school. I immediately emailed her a photograph of a house centipede, fully expecting that to be the end of the discussion. House centipedes commonly attract the attention of teachers and home owners. They frequently get trapped in the sink at my children’s school, and I discreetly liberate them so that they can eat real pests. However, in this case, “house centipede” was not the correct answer. I asked if the arthropod was slow moving and dark, thinking that perhaps she had found a stranded hellgrammite. No, she said, it was fast. This was getting interesting!

My friend described a centipede that was black and orange at the front, with a forked “tail” and yellow legs. Its most surprising feature was its size, a full six inches long. At this point, I asked for a photograph because the insect sounded like nothing I had encountered in Vermont. From the photograph, I determined that it was most likely a giant desert centipede (Scolopendra heros). That settled the first question, but left still many others unanswered. The school principal wanted to know if the centipede was dangerous. Were there likely to be more lurking about? Should he shut down the classroom? How does a desert centipede end up in Vermont?

I reassured them that it was unlikely to find even one such centipede in Vermont (and then less reassuringly suggested that, because one was found, they keep their eyes open). I informed the state entomologist and sent him photographs. I learned that desert centipedes give particularly nasty bites. In some cases, they can cause renal failure and even death. While death by centipede isn’t a common way to go, even in the desert, this species was certainly due some respect.

I guessed that the centipede may have come up from the desert southwest in packaging material, or perhaps through the pet trade. The truth was more surprising.  The school in question, like many Vermont schools, uses a children’s book called Flat Stanley to combine reading skills with art, geography, and just plain fun. Because Stanley is flat, he can be mailed in an envelope, and many children in schools across the world make their own Flat Stanleys and send them to friends in other places. Their friends photograph Stanley in interesting locations and return him along with local souvenirs. When my son did this, we sent Stanley to Ireland, Cyprus, and Australia.

Stanley was sent by my friend’s student to an aunt in Texas, and she mailed him back with Texas souvenirs.  The package included a map of Texas, a length of rope representing the horn span of a Texas longhorn, a piece of prickly pear cactus, and a Ziploc® bag with a hole chewed in the corner labeled, “DO NOT TOUCH – CENTIPEDE.”  Why one sends a dangerous centipede (or any centipede) through the mail is a mystery, but it certainly happened. While I can’t imagine that this centipede would establish in Vermont even if dozens were sent, it underscores the continuing need to educate the public about the dangers of moving species to new locations.

On a positive note, the school has added the now dead, preserved centipede to its invertebrate collection for classroom use. I think that speaks very well for the school that the students will learn valuable lessons from Flat Stanley’s travel companion. Perhaps it will inspire some budding entomologists?

Declan McCabe teaches biology at Saint Michael’s College. His work with student researchers on insect communities in the Champlain Basin is funded by Vermont EPSCoR’s Grant EPS-1101317 from the National Science Foundation. This article was adapted from the Newsletter of the Vermont Entomological Society and most recently circulated by Northern Woodlands Magazine's outside story.

Sunday, September 20, 2015

New semester; snorkeling; insect identification; and statistics!

A new semester; new students; and an 85 F temperature forecast for lab.  It seemed like a perfect opportunity to really experience Lake Champlain.  I bought out all of the remaining masks and snorkels from a certain local store and we were ready to go.

My customary first lab in Community Ecology has been to test the species area relationship.  It seems like a simple enough concept: bigger area - more species, but the concept underlies important conservation biology topics such as reserve design.  The lab also provides an ideal entry point to community ecology.  Bigger areas do tend to have more species, but also a mathematical inconvenience: there are also more individual organisms.  Imagine any community with some finite number of species.  We sample 1 individual and we automatically have sampled 1 species.  As we sample more individuals we also sample more species.  Therein lies the mathematical problem: do larger areas have more species for some biological reason.....or is it just because we sampled more individuals?

On cool September days we typically wade into Lake Champlain in chest waders.  But the warm weather this year was perfect for snorkeling.  So in we went!  Snorkeling or wading, the procedure is simple enough: Find submerged rocks of diverse sizes, net them, measure them, and identify all of the attached invertebrates.

The lab has all of the ingredients necessary for an excellent learning experience: field work; sampling real communities; insect identification; data generation; analysis; writing; and the opportunity to get wet in Lake Champlain on the second day of a new semester was icing on the cake.  This year yielded a bumper crop of very tiny zebra mussels along with 24 other invertebrate species.  

By now there are 22 students writing lab reports based on the data set.  They have learned how to deal with the mathematical sampling issue using rarefaction, how and why to log transform their data set, and how to use linear regression to measure the strength of the relationship between rock area and the number of species sampled.

I'm looking forward to reading the lab reports and moving on to another successful semester in Community Ecology!