The following is a series called “Critter of the Week,” dedicated to the 1000s of species living on St. Andrews University campus.
2 April 2021 (Installment 1)
Did you know we have tigers on campus? Well, maybe not tigers exactly--these tigers are actually beetles less than 1 inch long. They are called tiger beetles because they run along the ground to catch the prey insects they eat. Although their eyesight is great, they run so quickly that their eyes can't adjust to the movement, so they hold their antennae out in front of them to keep from running into things (https://www.sciencedaily.com/releases/2014/02/140211113704.htm). The species in the photo is called the oblique-lined tiger beetle (Cicindela tranquebarica), and it's one I hadn't seen on campus until a week ago. I got a decent photo this week, of a mating pair--males (on top) guard mates to prevent her from mating with other males (https://entomology.unl.edu/tigerbeetle/tiger_biology.htm#:~:text=To%20prevent%20immediate%20re%2Dmating,mating%20to%20discourage%20other%20suitors.). Larvae spend their time in deep burrows in the soil, like the sarlacc in Star Wars, eating any prey that happens to fall in. Many species tend to like sandy soils, hanging out on open sandy soil, on stream/river banks, or ocean beaches. If you encounter them, they will stop running and fly away from you, then will often land facing you--so it is hard to sneak up on them.
9 April 2021 (Installment 2)
Roses are red, violets are blue,
except if they’re yellow or green or white…
If this plant can’t find love, it won’t stew
it’ll make its own seeds by itself tonight!
Viola lanceolata, called Bog white violet or lance-leaved violet, is one of two species of white violets found on or near campus, and it is blooming now. This species is found in wet places. On our campus, it is found only in a strange wetland called the Carolina Bay. Carolina Bays (named for the bay trees that grow in some of them) are clay-lined oval-shaped depressions in the ground that fill with rainwater for at least part of each year. They are rare habitats, because many have been developed, drained, cut, or destroyed through other human activities like herbicides or mudding. Our Carolina Bay has many amazing critters in it, including some rare plants found in only a few places in the state. This violet is not rare, but it does have some interesting habits. For one thing, it makes two kinds of flowers—one that blooms out in the open (shown in the photos below), and another that has no petals and blooms close to the ground. Why would a plant do that? It turns out, it’s for insurance. Pollinators are often unreliable, so if pollinators are not around, any way that ensures seed production is beneficial to the plants. The regular flowers even have purple stripes called “nectar guides”, guiding pollinators to the place with the nectar reward (and the pollen), but even that does not guarantee pollinators will visit. So the tiny green flowers at the base of the plants fertilize themselves and then make seeds—no need for pesky bees or other plants. Who needs them? I guess you could say this violet is good at social distancing?
16 April 2021 (Installment 3)
Dedicated to the thousands of non-human neighbors who share our campus with us.
Could you imagine, in an average 79-year human lifespan, if you had only 2 years of childhood, followed by 75 years of sleeping (95% of your life), followed by 2 years of adulthood? No? This week’s critter of the week does that kind of thing, but all in one year—It is a tiny fly that starts out as an egg near the tip of a Japanese Wisteria (Wisteria floribunda) leaf. Once it hatches, it burrows into the leaf, feeding inside it—as if the top surface of the leaf was the ceiling and the bottom was the floor of a house, and it eats its way through the “rooms”—this is called leaf mining. It takes less than two weeks to eat and grow (the mine gets wider as it grows), then it gets ready go into the next phase of its life, the puparium (like a chrysalis), in which it slowly transforms into an adult. Once it pupates, it mostly sits there in the leaf litter for almost a year. Then the following March-April, the adult emerges and has only a little time to mate and lay eggs--kind of a grind of an existence. This fly is also a bit of a mystery. It is only known to eat Japanese Wisteria, but no one has found it in Japan. In fact, so far, the only place it has ever been found is here on the St. Andrews campus. It is quite probably a new species—we’ll find out hopefully within the year for sure—it was discovered here. Because of its weird life cycle, and because it is not so common, it has taken a while (5 years) to raise an adult successfully. So what did it eat before Japanese Wisteria was introduced from Japan? Many plant-eating insects are pretty picky eaters, because different plants have different poisons. It does not seem to feed on the native Wisteria growing on campus. Did it come from Japan? The plant this fly eats is all over the place here—Japanese Wisteria is an invasive species, meaning that it takes over places where it grows and grows out of control, keeping native plants around it from growing successfully. Japanese Wisteria has been introduced throughout the eastern US, and its leaves are available from April to October—so is this fly really only found here? Why is it active only in early spring, for such a short time? Perhaps I’ll be able to let you know in a future installment… for now, time to get some sleep!
23 April 2021 (Installment 4)
Dedicated to the thousands of non-human neighbors who share our campus with us. Brought to you by Science at St. Andrews and two students from my Biology 101 class.
Today’s critter of the week is actually about three critters and three small themes. First the critters: three different species of moths (see below). Although people often think butterflies fly during the day and moths fly during the night, there are lots of exceptions. Many moth species (like the ones below) fly during the day, and a few butterfly species (like the cave skipper in Central America) fly at night*. If you look at the ones in the photos closely, you’ll see they all look a little bit like bees, with yellowish contrasting with dark brown or black—those could be “warning colors,” which either advertise poisons within (so predators stay away) or mimic other critters that have those poisons (again, so predators stay away). There are many such mimics out there—a theme I will revisit. None of these three bee-mimic moth species had been documented on campus before (and more could be out there). All were seen feeding on azalea nectar that was extremely abundant here this past week. Which brings me to my next themes…
These moths are here because their food is here—a deceptively simple statement. In the photos, it looks like all they need is a few hundred azalea flowers to be happy. Yet these insects live a “double life”—their earlier life stages are caterpillars that chew on leaves of plants—totally different from the adults that suck nectar through straw-like mouths. And caterpillars are picky about what they eat. Thus, their host plants (plants caterpillars eat) must be here too—plants like native honeysuckle (Lonicera sempervirens) for the hummingbird clearwing (or blueberries, Vaccinium fuscatum and other species, for the slender clearwing), native honeysuckle (Lonicera sempervirens) for the snowberry clearwing, and Grapes (Vitis sp.), Peppervine (Ampelopsis areborea), and Virginia creeper (Parthenocissus quinquefolia) for the Nessus sphinx. Maintaining diverse plants here will support a large diversity of organisms that depend on them (theme 2).
Also (theme 3), the science of biodiversity depends on scientists and non-scientists alike, looking around and documenting what they see. It takes a village to figure out how many species we’ve got out there. In this case, Biology 101 students, including Matthew Williamson and Ivo Sperone, saw insects visiting azalea flowers and started taking photos. The result was that all together, we documented at least 8 species of bees, moths, and butterflies visiting azalea flowers.
If you want to document biodiversity too, iNaturalist (https://www.inaturalist.org/users/sign_in) is the perfect app to do it—all you need is a decent photo (cropped so the organism shows well), along with where and when you saw it. You can help document biodiversity here and elsewhere.
*If you want to tell a butterfly from a moth, look at their antennae—butterflies have bulbs at the end of their antennae, and moths do not.
30 April 2021 (Installment 5)
In this episode, we face carnivorous plants… The lake is full of carnivorous plants ready to swallow you whole… but only if you are about as small or smaller than the head of a pin… So you are safe--you can breathe a sigh of relief as you go for a swim in the lake…
Why would plants be carnivorous? You might notice in the close-up of the leaves below that the leaves are green. That means they conduct photosynthesis, the process of capturing light energy and using that energy to build sugars from carbon dioxide in the air (yes, plants are made of thin air!). If they make their own food, why would they need to be carnivores? The answer is that plants need more than sugar. This might not be a surprise—you would not do well if you lived only on sugar, as tempting as it may be for those of us with a sweet tooth. Plants are like us in that they also need nutrients like nitrogen (common in proteins we eat) and phosphorus, to function. In fact, the green stuff that helps capture energy from light (chlorophyll) is partly built out of nitrogen. Unfortunately, nitrogen is often hard to get—and when it is particularly hard to get, plants that end up with ways of getting more nitrogen do better than those that suffer with less. One way of getting more nitrogen is to team up with fungi (for a later post). Another way is to trap animals and get protein from their bodies.
Different groups of carnivorous plants have different ways of trapping insects. The carnivore pictured below is Utricularia inflata, or the inflated bladderwort. “Wort” means “plant”—so it is the bladder plant. There are two species of bladderwort on campus—one that blooms in spring and one that blooms in fall—those are the only carnivorous plant species on campus, although the Southeastern Coastal plain is the most diverse place in the world for carnivorous plant groups—even the Venus Fly Trap is found only in North and South Carolina. So what do these carnivores trap, and how do they trap them? The little bladders on the bladderwort’s leaves are bubbles of air under water, with doors that open inward. When a tiny crustacean (crab and lobster relatives) like water fleas swim by and trigger the door, the door opens inward. The tiny animal is swept into the bladder with the rush of water that enters, and the door closes—because the door only opens inward, the animal is trapped, and later digested. Now you can be amazed—or terrified—as you gaze at the beautiful, feathery, deadly underwater leaves of the bladderwort growing on the edges of our lake.
7 May 2021 (Installment 6)
I hate goodbyes… this is a time for goodbyes, to graduates and to others (for the summer at least)… During these past few weeks, a related event is occurring in the bird world. A river of birds has been passing through—a river of migrants moving north, seeking less competition for food than they had in the Caribbean or in the tropics, and seeking open breeding grounds. Some birds also overwinter here. Many birds (like white-throated sparrows and slate-colored juncos) that have been with us since the fall are taking their leave and moving back up to the northern US or Canada. Many of those will be gone from campus in a few weeks, if they haven’t gone already. Of the 153 bird species recorded from campus, at least 83 of those migrate (they are winter or summer residents)—at least 23 were just passing through on their way to somewhere else.
Some of the most spectacularly colored migrants are the wood warblers. They migrate on clear nights, finding their way by the stars. Other birds use the sun as a compass, or landmarks, or even the Earth’s magnetic field. To detect the magnetic field they must have magnetized materials in their bodies or charged chemicals that can respond to the magnetic field.
But our migrants are threatened. Migrants can be threatened in more ways than residents—residents can lose their homes, but migrants can lose their breeding grounds OR their overwintering grounds OR important stopovers. Habitat losses are one big reason for these threats. Another reason is pesticides—we are pouring poisons into our environment on homes, yards, and crops. This means our insects are disappearing, which means less food for birds. Another is herbicides—getting rid of plants that give cover for birds (protection from predators), or that serve as food for the insects they eat. Climate change may be another reason, as birds are migrating at different times (earlier), and may sometimes migrate too early or too late to intersect with food sources they depend upon to fuel their journey or to feed their babies on nesting grounds. Another is urbanization—buildings account for many bird deaths, as they see reflections of sky in them and ram into them at high speed (see below). In 1962, Rachel Carson wrote “Silent Spring”, warning us that we would lose our birds if we continued using some pesticides. Some like DDT were banned in the US soon after. Yet birds are still in decline, and studies suggest that in North America we have lost 30% of our birds since 1970.
The positive side is that when we see migrants, we can appreciate that they’ve survived a lot to get here—hundreds of miles, exhaustion, obstacles, predators—and a trip that is harder than it used to be. Another possible positive side is that many of the threats to migrants are things we humans can do something about—if only we could see the value in our non-human neighbors… On campus in late April this year, I heard or saw only 7 warbler species—in past years I have seen or heard 10 or 11 species. I hope this year is just a fluke.
I do hate goodbyes… (I could say the photos below are blurred with sentimental tears…but in reality I just don’t have the photographic equipment for good bird photography unless the bird is dead or right in front of me—forgive the blurs that are supposed to be birds). At this season, all I can do is hope that graduates stay in touch, and come back through periodically… All I can do is hope we humans change the practices that are making our birds and many other living things go extinct… that I can still continue to say “see you next year.”