Wild Side

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Bembix americana

Few things look less auspicious than a patch of bare sand. With no plants or animal visible to the casual observer, it’s easy to assume that bare ground scores an ecological zero. But in nature, nothing is useless, and barren soil is a crucial element in the lives of a surprising number of species.

How a patch of bare ground became empty in the first place has a big effect on what will use it, and over what time frame the spot will become inhabited. An empty patch in our front yard, for example, must surely have resulted from a spill of something toxic, maybe oil or antifreeze, in an area once used as a driveway: the spot remained utterly barren and compacted for years, and only now, after years of rain have leached away whatever was dumped here, has a crust of lichen and moss finally gotten established.

Elsewhere, a sufficiently hot wildfire can burn off all the organic material, leaving empty mineral soil behind. Or repeated disturbance can produce a similar effect: think of a heavily worn footpath, or the tire ruts on a regularly traveled dirt road. When the fire is past, or if the pattern of disturbance is interrupted, these spots embark on a trajectory of regrowth. Simple plants like mosses colonize the site by means of airborne spores, or lichens (amazing amalgams of algae and fungi) may appear. Over time, the organic remains of these colonizers form the beginnings of soil; other plants arrive, adding more organic matter and sending down roots through sand grains to loosen the substrate. Wait long enough and you’ll have a forest.

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Cicindela punctulata

But before all that happens, the very barrenness of the spot is a resource that wildlife can use. The punctured tiger-beetle, for example, Cicindela punctulata, spends most of its time hunting on the emptiest, flattest, and most compacted ground it can find. A visual hunter that relies on speed to run down its prey, this half-inch-long beetle eats ants and other smaller insects that venture across the bare soil. With no vegetation to obstruct its view, the tiger-beetle readily spots a target, and like a tiny, six-legged cheetah, it sprints so quickly after its victim that the eye can barely follow it. For this insect, bare ground furnishes the ideal place to hunt.

Many bee and wasp species use open ground not for hunting but for building their nests. Kicking sand through their legs like a terrier digging up daffodil bulbs, these ground-nesting insects move impressive amounts of soil as they dig the tunnels where they will lay their eggs. These nest burrows may be surprisingly long and elaborate, descending inches or even feet beneath the surface and sometimes branching into networks of side-tunnels and chambers. Each chamber will hold one or more eggs, and it will be stocked by the adult insect with either pollen or a paralyzed prey item for the young wasp or bee to feed on as it grows.

It’s not clear why such bees and wasps prefer bare ground. It may be as simple as making it easier to relocate the nest when they return from a foraging trip. Or perhaps bare ground signals a site where you can burrow with no interference from roots. But whatever the reason, the soil must be bare, and moreover, each species of burrowing wasp or bee has a strict preference for the type of soil it will nest in: sand or clay, coarse or fine, wet or dry, loose or compacted. So maintaining populations of all these beneficial insects requires not just the odd patch of bare ground, but many such patches, in different places and with different characteristics.

For some of the species that use bare ground, it seems like a very limited expanse will suffice. Some insects will dig their burrows in the space between clumps of grass or weeds. For other ground-nesters, it seems like a large bare area is required, or at least an area with many small bare spots in a small area. For instance, a bee called Bembix americana (it has no common name, though it is a common and widespread bee) prefers to nest in loose colonies of dozens or even hundreds of individual burrows. In an abandoned construction site near my home, such a colony covers an area of bare soil about 30 feet in diameter.

You probably already have some insects in your yard using snippets of bare ground. I’ve actually encouraged some bare spots to get larger and stay bare, and the result has been rewarding: new insects turn up, ones with interesting lives, beneficial habits, and, in some cases, exquisitely beautiful appearance. In nature, no niche goes unoccupied for long: even nothing is something, for the right creature.

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Widow or no?

Is this a black widow? It’s living in a bat house just outside our barn door in Chilmark! Are they common on the Vineyard?

The Pelikan Brief:

Wow. Yes, it appears to be a southern black widow, Latrodectus mactans. I’ve never heard a reliable report of one occurring naturally on M.V., though some sources say the range of the species extends as far north as Mass. A close relative, the northern black widow, L. variolus, is a lot more likely in our region and probably occurs here, though I’ve never found one on M.V.

The rest of the answer:

Yes, indeed it is a black widow, and a very interesting find! The small size, shiny black body, round abdomen, and especially the red “hourglass” mark this as a female black widow. Interestingly, though, there are several species of black widow, and this is not the one that is normally expected on the Vineyard. The complete hourglass marking, with the two lobes clearly connected, marks this as a southern black widow, which is generally believed to be rare at best in our region. Much more likely is the northern black widow, which is quite similar but features an “hourglass” that is broken into two parts. The northern black widow seems to be sparsely distributed but reasonably common in the Cape and Islands Region. The only ones I’ve ever seen have been in natural settings, not in human-made structures.

I’m afraid I can’t say just what is going on: southern black widows may be extending their range northward and colonizing our region. (Like many spiders, I imagine they can disperse as baby spiders by “ballooning” on the wind on strands of silk). They may have been here all along, but were overlooked. Or this individual arrived from elsewhere on a load of vegetables or landscaping material. Hopefully, a pattern of sightings (or an absence of sightings) in the near future will clarify the picture.

Black widows generally are famous as the most venomous spiders in North America, one of very few arthropods on the continent that is capable of killing a human being. (I set aside the special case of fatal allergic reactions to wasp or bee stings.) Being small spiders, they can inject only a tiny quantity of venom. But the venom is incredibly potent, acting on the victim’s nervous system to cause cramping, paralysis, and on rare occasions death when the muscles necessary for breathing shut down. There is an effective antivenin, and the thing to do if you think you’ve been bitten by a black widow is seek medical care immediate and, if possible, bring the spider with you so its identity can be determined.

But don’t panic! Black widows are timid spiders that rarely bite humans. The main use for their jaws and venom is to subdue small insects that blunder into the widow’s untidy web system. Given the chance when disturbed, a black widow, like other spiders, will hide rather than bite, and it is only when a black widow is faced with squishing that it bites in self-defense. Moreover, fatalities are very rare: one source reports that only about one percent of black widow bites are fatal, and that fatalities almost always involve children or elderly victims who are frail and have a small body size.

Black widows like dark, shady, enclosed spots (a classic black-widow bite scenario, back in the old days, involved spiders getting sat on in outhouses). Pay attention when you’re working or reaching into such places, and you will have little reason to fear this spider, which is (in my opinion) best thought of as an interesting and generally beneficial part of our ecosystem.

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a spotted-wing grasshopper.

In observing nature, one goal is to see what’s truly there, and not impose your own wishes or expectations on the world. The classic example of what to avoid is the sort of wishful thinking to which birders can be subject. It’s easy to see field marks that don’t exist if you’re burning to find a rarity, and equally easy to miss a rarity because you’re expecting just the common stuff.

A pasture grasshopper.

Photo by Matt Pelikan

A pasture grasshopper.

But even when you have no personal stake in what you see, it’s still possible for benign assumptions or inaccurate knowledge to distort what you see. Though I’ve had more than 40 years of practice in trying to be an impartial observer of nature, I can’t say I’m never guilty of making errors of this sort. I like finding a rarity every bit as much as the next guy, and I’m just as prone to ignorance. So it doesn’t surprise me too much when I find I’ve botched things. And so it was with me and the Gomphocerinae.

“Gomphocerinae” is a mouthful, but it’s shorter than the usual common name for this family of grasshoppers, “stridulating slant-faced grasshoppers.” They stridulate, or produce sound, by rubbing body parts together, and species within this family tend to have faces that slant sharply down and back from an overshadowing forehead.

In beginning my ongoing survey of Vineyard grasshoppers, I had drawn up a list of species I felt were possible here, based on range maps in field guides. And I now realize that, even as I drew up that list, I began forming misconceptions about the grasshopper species that I would find. Some that were familiar to me from my mainland days I thought of as common, and I assumed, without any real basis in fact, that I’d find them here, too. Certain other species, such odd-looking ones or ones that have unusual life histories, I now realize I classed as “exotic” — rare or specialized species that I couldn’t imagine occurring here.

To some extent, I now see, these assumptions affected how I spent my time in the field — where, when, and in what habitats I looked. And one group that I had unconsciously decided wasn’t worth sinking much time into was the Gomphocerinae, those grasshoppers of the stridulation and the slanting faces. But it wasn’t just a time allocation error: when trying to identify grasshoppers, I tended to start with the assumption that what I was looking at belonged to one of the families I expected.

Thus it was that my grasshopper list, closing in on a dozen species as this season began, lacked any representative of Gomphocerinae. But about a month ago, while tidying up my office at work, I came across a box of insect specimens labeled “Orthoptera.” These turned out to be the result of field work done 20 years ago; the specimens were meticulously mounted and labeled with date and location information but had not yet been identified.

The first thing I noticed was, you guessed it, a prime example of a stridulating slant-faced grasshopper — an “exotic” species I had offhandedly tossed in the “impossible” bin. It was a short-winged toothpick grasshopper, a bizarre, elongated insect with sword-like antennae and ludicrous stumpy wings. I had never imagined I’d find it here, even though its habitat is one that is easy to find on the Vineyard: dry, sparse, “bunch grass” habitat dominated by little bluestem. Bunch grass just hadn’t looked like good grasshopper habitat to me, and accordingly, I hadn’t explored it much.

I may have made some wrong assumptions, but you may be sure that at this point I was realizing that I had made them. I altered my strategy based on what I had learned and deliberately targeted a number of Gomphocerinae associated with bunch grass. First, I quickly located another location that had that most excellent toothpick grasshopper; here weren’t a lot and they were not yet mature, but this is a bug you can’t mistake.

I also found and photographed a second member of the family, a spotted-wing grasshopper, a nondescript bug that in years past I may well have written off repeatedly as a dully marked member of a different family. (They turn out to be common, common!) Finally, I went back through my file of unidentified grasshopper photographs and quickly picked out another member of Gomphocerinae, a lovely green species called the pasture grasshopper.

Better still, I began to get a sense for the entire family: what conditions its members like, what characteristics mark the family itself or help you sort out its members. In short, I learned something! I find this fun.

There are, presumably, other biases and misconceptions lurking in my understanding of grasshoppers (not to mention the other types of wildlife I observe). I haven’t discovered them yet, but with luck I will eventually. There’s always a moment of dismay when you realize what a bonehead you’ve been. But having realized it, at least you can get things right in the end.

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Ladybug larvae

The great outdoors can produce baffling mysteries. MV Times Wild Side columnist Matt Pelikan tries his best to solve them. Got a question for the Wild Side? Send it to onisland@mvtimes.com.

What is this creature? It was on plants outside my office… I’m not sure what the bush is so I took a picture of its growing berries in case that helps… Beach plums?

The Pelikan Brief:

That is a seven-spotted Ladybug on beach plum!

The rest of the answer:

Ladybugs love beach plums.

Photo by Danielle Zerbonne

Ladybugs love beach plums.

These colorful but homely creatures are the larvae, or immature stage, of a ladybug. As most gardeners are aware, ladybugs are highly beneficial insects (at least from the human perspective) because both adults and larvae eat a wide range of insects that are harmful to plants. They specialize in preying on soft-bodied insects such as aphids, scale insects, and mites, which suck vital juices from plants and can also carry disease. Most ladybugs pass through four distinct larval stages as they develop, before morphing into an adult, and the energy source that powers all that growing and molting is the caloric content of a ladybug’s prey.

There are somewhere around 500 species of ladybugs in North America and, to make a rough guess, perhaps 20 species on Martha’s Vineyard. These particular larvae appear to be those of the seven-spotted ladybug, which is a Eurasian species that has been introduced widely in the U.S. to help control agricultural pests. It is now widely established — so widely, in fact, that it may be out-competing many of our native ladybugs, such as the two-spotted ladybug that is the official state insect of Massachusetts. (I bet you didn’t even know we had a state insect!)

Many, perhaps most, ladybug species are mildly toxic, producing chemicals that give them a foul smell and taste. The bold, distinctive patterns these beetles show — black spots on a red or orange background, or in some cases red spots on black — serve to warn away would-be predators that have had first-hand experience trying to eat a ladybug.

The plant the larvae are on happens to be a beach plum, and this is not just coincidence. Beach plum, like its close relatives the shadbushes and wild cherries, is notorious for attracting sucking and leaf-eating insects of a wide variety. The plants of this family, in other words, furnish a prey-rich environment for ladybugs, and as a result are good places to look for these most excellent beetles.

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A plant pushing its way up through sand.

The great outdoors can produce baffling mysteries. MV Times Wild Side columnist Matt Pelikan tries his best to solve them. Got a question for the Wild Side? Send it to onisland@mvtimes.com.

I don’t get this: plants that grow in seemingly inhospitable places… saltwater, sand, sidewalk cracks…

How does this happen? How do they survive?

The whole answer:

Plants have evolved a huge arsenal of methods to allow to them to inhabit inhospitable spots. But the first question is, why do they want to live in inhospitable spots in the first place? The answer to that one is, simply put, to avoid competition. If you can grow under conditions that would kill most other plants, then you don’t have to worry so much about being shaded out by a taller plant, or having one with a bigger root system suck up all the water and nutrients.

I could go on for weeks about the various approaches plants take to make adversity less adverse. Here are just a few examples to illustrate how creative evolution has been.

Taproots. A long, thick central root plunging deep into the ground takes a lot of resources to grow. But once you’ve got one, you can reach moisture in the soil that is too deep for other plants to reach. You’re resistant to being pulled out by an animal that wants to eat you. And if a grazing animal does bite off your leaves, you have enough energy stored in your tap root to begin resprouting instantly. The ubiquitous dandelion is a great example, so successful largely because it produces a hefty tap root.

Thick skin. Many plants that grow in harsh environments have developed a thick skin, called a cuticle, on their leaves and stems. This tissue, usually waxy and impermeable, helps prevent unnecessary water loss that could kill the plant. In addition to keeping water in, a thick cuticle can help keep harmful substances out. Many plants adapted for life by the sea, for example, are resistant to the toxic effects of salt spray by virtue of a thick skin. And a thick cuticle can also help protect more delicate internal cells from damage from relentless sunlight.

Seasonality. In most places, conditions vary widely during the course of the year. And it’s not just the physical surroundings — the weather, amount of wind, or day length — that change: the amount of vegetation varies, too. So many plants have simply evolved a life cycle centered early or late in the season, when temperatures are moderate and when few other plants are active competitors. A great example would be the wood anemone, a little white wildflower of our woodlands that puts up leaves and blooms early in spring, before the trees have leafed out. In this way, the anemone gets the energy-intensive part of its life cycle over with before trees start hogging all the incoming sunlight.

You get the point: in the natural world, adversity represents opportunity for organisms that can find a way deal with the situation better than most competitors do. It isn’t that the well-adapted plants don’t suffer in inhospitable settings. It’s just that they suffer less than their competitors do, and that works out to be an advantage.

Seven-spotted Ladybug on beach plum.

These colorful but homely creatures are the larvae, or immature stage, of a ladybug. As most gardeners are aware, ladybugs are highly beneficial insects (at least from the human perspective) because both adults and larvae eat a wide range of insects that are harmful to plants. They specialize in preying on soft-bodied insects such as aphids, scale insects, and mites, which suck vital juices from plants and can also carry disease. Most ladybugs pass through four distinct larval stages as they develop, before morphing into an adult, and the energy source that powers all that growing and molting is the caloric content of a ladybug’s prey.

There are somewhere around 500 species of ladybugs in North America and, to make a rough guess, perhaps 20 species on Martha’s Vineyard. These particular larvae appear to be those of the seven-spotted ladybug, which is a Eurasian species that has been introduced widely in the U.S. to help control agricultural pests. It is now widely established — so widely, in fact, that it may be out-competing many of our native ladybugs, such as the two-spotted ladybug that is the official state insect of Massachusetts. (I bet you didn’t even know we had a state insect!) Many, perhaps most ladybug species are mildly toxic, producing chemicals that give them a foul smell and taste. The bold, distinctive patterns these beetles show — black spots on a red or orange background, or in some cases black spots on red — serve to warn away would-be predators that have had first-hand experience trying to eat a ladybug.

The plant the larvae are on happens to be a beach plum, but this is not just coincidence. Beach plum, like its close relatives the shadbushes and wild cherries, is notorious for attracting sucking and leaf-eating insects of a wide variety. The plants of this family, in other words, furnish a prey-rich environment for ladybugs, and as a result are good places to look for these most excellent beetles.

Luna moth attracted by light.

You think a porch light is attractive to moths? Try putting out an ultraviolet “black light” sometime! Many kinds of moths just can’t resist black light; in fact, biologists studying moths routinely use ultraviolet light sources to attract moths for collection or observation. But while the tendency of moths to fly toward light, and toward ultraviolet light in particular, is well known, nobody has come up with a fully satisfactory explanation. Most likely several factors play a role, and it’s also probably that different moth species respond to light for different reasons. And it’s worth keeping in mind that, for most of the evolutionary history of moths, all or most of the light at night came from the moon, stars, or the sky glow before sunrise and after sunset. So today’s situation, with artificial light sources popping up everywhere in moth habitat, is not what moths evolved to experience.

Moths are simple animals, and their needs in life boil to the usual basics. They need food, they need a mate, and it’s helpful to have some way of finding their way around. Explanations have been offered that relate to all three of these needs. For example, many adult moths feed on nectar from flowers. And many flowers glow under the ultraviolet let that makes up part of incoming sunlight (it’s the flower’s way of advertising for pollinators to come visit). So there may be some primitive tendency in moths to fly toward ultraviolet light in expectation of a meal. This tendency, then, would bring moths in to human light sources, at least ones that emit part of their energy in the ultraviolet range.

Many kinds of moths may also patrol large areas to find mates, and in order to be efficient about it, they would want to avoid going over the same area repeatedly. One way to do this is simply to fly in a straight line, and some moths may use the moon or bright starts to help this. If you head towards the moon, or keep it on, say, your starboard beam, you’ll keep moving in a roughly straight direction. But if you try this with a light source that is much closer than the moon, you either arrive there and then don’t know what to do next, or you end up circling the light in an effort to keep it at the same angle. Both mechanisms could bring moths to light.

Finally — and I get in over my head on this one — some biologists noted a similarity between the frequency of ultraviolet light and the resonant frequency of some of the chemicals, called pheromones, that moths produce to lure in potential mates. In other words, ultraviolet light somehow reminds moths of the irresistible smell of a mate, even though one stimulus is a visual one and the other is a scent.

So take your pick: any, or all, or none of the above. Many kinds of moths are attracted to light, and that’s really all anybody knows for sure. But there is also agreement that in today’s environment, moths are paying a price for their fondness for light. The moths around your porch light are essentially wasting their time, hanging around in a sterile habitat that is unsuitable for them to live or reproduce in. Disruption of moth life cycles by artificial lighting is a real problem, and it’s one you can help with by turning outside lights off unless you are actively using them.

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An unidentified bee, on coneflower, well covered with pollen.

Midsummer is peak season for most types of insects, but especially evident right now are the panoply of bees and wasps that live here. While it’s usually clear if an insect is a bee or a wasp, the distinction actually seems somewhat arbitrary to my inexpert eyes. Bees, in general, are plump and fuzzy; wasps are lanky and while they may have spines or hairs, they generally don’t look furry. In any case, one peculiarity marks this entire group of insects: while they have two wings on each side, the hind wing is much smaller than the front wing, and the two are locked together into a single unit, which looks and functions like a single wing, by a row of special anatomical hooks.

One of our less common bumblebees, probably Bombus perplexus, on lavender.

Photo by Matt Pelikan

One of our less common bumblebees, probably Bombus perplexus, on lavender.

As a group, the bees and wasps are unfairly maligned. With the current concern over declines in pollinator populations, pretty much everyone understands that bees and wasps of beneficial because of their role in transporting pollen from plant to plant. But these insects are still stigmatized as aggressive and feared because they can sting.

To be sure, there are a few species of each that are irritable enough to make awkward neighbors. The so-called social bees and wasps, that is, the species that live in large colonies and build elaborate nests, certainly will sting in defense of their homes. (Wouldn’t you?) Honeybees, yellow-jackets, and paper wasps all fall into this class. But the vast majority of our bees and wasps nest alone or in small groups and invest relatively little effort in their nests (which may be underground or in dead vegetation). While capable of stinging, most of these species are docile, and some, quite literally, won’t sting even if you try to make them (yes, people have experimented!). And even the social bees and wasps are generally quite amiable when they are out foraging, away from their nests.

The self-defense capability of bees and wasps does give these insects a degree of immunity from attack. Accordingly, they’ve evolved striking color schemes, usually involving black and yellow stripes, as a warning to would-be predators. It doesn’t always work; many species of birds, for example, snag wasps with impunity, often rubbing the stingers off on a branch before swallowing them. But the cautionary markings are effective enough so that other insects have evolved patterns that mimic those of bees and wasps: some hover-flies and bee-flies, for instance, look enough like bees that it takes a careful look and a knowledgeable eye to spot the difference. (Handy short-cut: flies almost invariably have short, stubby antennae, while antennae on bees and wasps are longer and often sharply bent.)

Solitary bees and wasps share a fondness for visiting flowers, and they are equipped with long tongues with which they extract pollen or nectar from blossoms. A great way, therefore, to get acquainted with these insects is to keep an eye on the same flowers that butterflies like to visit: milkweed, goldenrod, or garden plants like blazing star, butterfly-bush, or lavender, for instance. In good habitat, it’s not uncommon to find five or six species of bees and wasps feeding on the same cluster of flowers.

A wasp called Sanborn's bee-wolf absconding with a bumblebee.

Photo by Matt Pelikan

A wasp called Sanborn’s bee-wolf absconding with a bumblebee.

The dietary preferences of bees and wasps diverge, though, when it comes to the provisions they make for their offspring. Bees typically stock their nests with pollen, which they gather industriously and transport to their nests in specially designed sacks on their legs. Pollen grains stuck to the insect’s body get transported to other flowers, and it is the very hairy bodies of bees that make them such effective pollinators. Solitary wasps, in contrast, transport pollen less effectively and generally lay in a supply of arthropod meat for their young.

The process is a bit grisly, though it works out well from the human perspective: solitary wasps are important players in controlling populations of insects that eat plants, including crops and ornamentals. Here is where solitary wasps put their stingers to use: finding a suitable prey item (and most wasps are quite specific about the kind of arthropods they prefer), the adult wasp stings its victim, paralyzing it, and then hauls it back to the nest it has prepared.

Wasp eggs are laid on or next to the immobilized prey, and upon hatching, the wasp larvae feeds on the victim. It’s a fascinating bit of biology. Species taken as prey range from spiders to cicadas to grasshoppers; there are even wasps that capture bees. Some wasps subdue and carry prey considerably larger than themselves: I’ve seen a wasp carrying a bush-katydid that must have weighed twice as much as its captor.

Major players in our ecosystem, bees and wasps are highly evolved, highly diverse, and endlessly interesting to watch (as long as you give wide berth to the nests of social species). Give them some of your attention this summer.

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Luna moth.

The great outdoors can produce baffling mysteries. MVTimes Wild Side columnist Matt Pelikan tries his best to solve them. Got a question for the Wild Side? Send it to onisland@mvtimes.com

Here’s a good one –  a picture of a luna who battled his way inside my house and thrashed around until he finally settled on a jar of capers in my pantry. He was attracted to our porch light. Why is that? At one point I used to leave the porch light on overnight so I could go out in the morning and see what had gathered. But then I felt guilty watching the chickadees pick them off one by one from the screen in the morning.

The Pelikan brief:

You think a porch light is attractive to moths? Try putting out an ultraviolet “black light” sometime! Many kinds of moths just can’t resist black light; in fact, biologists studying moths routinely use ultraviolet light sources to attract moths for collection or observation. But while the tendency of moths to fly toward light, and toward ultraviolet light in particular, is well known, nobody has come up with a fully satisfactory explanation.

The rest of the answer:

Most likely several factors play a role, and it’s also probably that different moth species respond to light for different reasons. And it’s worth keeping in mind that, for most of the evolutionary history of moths, all or most of the light at night came from the moon, stars, or the sky glow before sunrise and after sunset. So today’s situation, with artificial light sources popping up everywhere in moth habitat, is not what moths evolved to experience.

Moths are simple animals, and their needs in life boil to the usual basics. They need food, they need a mate, and it’s helpful to have some way of finding their way around. Explanations have been offered that relate to all three of these needs. For example, many adult moths feed on nectar from flowers. And many flowers glow under the ultraviolet lightt that makes up part of incoming sunlight (it’s the flower’s way of advertising for pollinators to come visit). So there may be some primitive tendency in moths to fly toward ultraviolet light in expectation of a meal. This tendency, then, would bring moths in to human light sources, at least ones that emit part of their energy in the ultraviolet range.

Many kinds of moths may also patrol large areas to find mates, and in order to be efficient about it, would want to avoid going over the same area repeatedly. One way to do this is simply to fly in a straight line, and some moths may use the moon or bright starts to help this. If you head toward the moon, or keep it on, say, your starboard beam, you’ll keep moving in a roughly straight direction. But if you try this with a light source that is much closer than the moon, you either arrive there and then don’t know what to do next, or you end up circling the light in an effort to keep it at the same angle. Both mechanisms could bring moths to light.

Finally — and I get in over my head on this one — some biologists noted a similarity between the frequency of ultraviolet light and the resonant frequency of some of the chemicals, called pheromones, that moths produce to lure potential mates. In other words, ultraviolet light somehow remind moths of the irresistible smell of a mate, even though one stimulus is a visual one and the other is a scent.

So take your pick: any, or all, or none of the above. Many kinds of moths are attracted to light, and that’s really all anybody knows for sure. But there is also agreement that in today’s environment, moths are paying a price for their fondness for light. The moths around your porch light are essentially wasting their time, hanging around in a sterile habitat that is unsuitable for them to live or reproduce in. Disruption of moth life cycles by artificial lighting is a real problem, and it’s one you can help with by turning outside lights off unless you are actively using them.

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On the Vineyard, bog copper butterflies are only found in sphagnum bogs with thriving wild cranberry, and they rarely venture far from their specific bog.

“The fox has many tricks,” goes the saying. “The hedgehog has only one — but it’s a good one.” And so it is in nature: some species thrive by being flexible, while others evolve to be perfectly adapted to a very specific niche.

Consider, for example, the bog copper butterfly. Of all the Vineyard butterflies, this is the one most closely tied to a particular setting: sphagnum bogs rich in wild cranberry. You won’t find this tiny, delicate insect on the Vineyard outside a bog, and its life cycle is intimately tied to both that habitat and the wild cranberry that is the only plant the butterfly’s caterpillars will eat.

The bog copper, with a geographical range encompassing the northeastern United States and much of eastern Canada, is a close relative of the American copper, a versatile butterfly which you likely have in your yard. But somewhere along the evolutionary road, the bog copper opted for hyper-specialization, a life cycle centered on the challenging but predictable conditions of a bog.

Perhaps the biggest challenge a bog-dwelling insect faces comes from changing water levels. With limited mobility or none at all, the eggs and caterpillars of the bog copper need to be able to survive by exposure to air and prolonged submersion. Indeed, bog coppers are so well adapted to a wet environment that drying out is the real risk they face. A detailed study by entomologist David Wright, published in 1983, describes the fascinating adaptations of this butterfly.

cranberry-blossom.JPG

Photo by Matt Pelikan

The cranberry blossom.

Female bog coppers lay their eggs in late spring, one at a time, near the base of wild cranberry plants. In dry times, dew or any rain that falls beads up on the cranberry’s waxy leaves and is funneled down the stem to wet the butterfly eggs. And when water levels rise with fall or spring rains, the egg turns out to have a layer of air under its outer skin, allowing the egg to develop even under water.

The caterpillar begins its development inside the protective envelope of the egg, and then goes nearly dormant through the summer, fall, and winter, hidden from predators and buffered by the egg from changes in moisture. Come early spring, the caterpillar leaves its egg, begins feeding on cranberry leaves, and starts to mature. Again, it’s adapted to submersion: a tight layer of hairs on its body traps a layer of air that allows the exchange of gasses (specifically dissolved oxygen) from the water to the caterpillar’s tissues.

When mature, the caterpillar briefly pupates to change into an adult. Even here, the butterfly has a special talent: the pupa is equipped with a rasp-like structure that can make noise when the pupa twitches. It’s a tenuous last line of defense, but the noise might deter ants or other predators that attack the pupa.

Emergence of the mature butterflies is closely timed to the flowering period of the wild cranberry, tracking that bloom period through its year-to-year variation. The adult butterflies take nectar mainly from cranberry blossoms, and are likely an important pollinator of the cranberry plant. From time to time, adult bog coppers engage in brief, swirling mating flights or territorial disputes. But mostly, they sit — on cranberry plants, naturally — waiting for a member of the opposite sex to pass by.

Bog coppers are weak flyers with little inclination to leave their bog and their cranberry plants. I’ve never found this species outside a bog, and unless two bogs are very close together, there is little or no intermingling of the bog coppers that reside there. Ordinarily, you’d expect that inbreeding would weaken the gene pool of each of these little populations, resulting in its eventual extinction. But this butterfly is so well adapted that inbreeding actually strengthens its survival: the unique adaptations for survival in a particular bog are reliably passed down to the next generation, with little variation.

Bogs suitable for this butterfly are not numerous on the Vineyard. Small bogs can’t support enough butterflies for the population to persist for very long — though they may serve as “stepping stones,” helping the odd individual make it from one large bog to another nearby, if there is one. And commercially worked bogs usually don’t support the butterfly because of insecticide use or simply the physical disturbance of working the bog — a form of disruption evolution didn’t anticipate. But of the large and cranberry-rich bogs that we do have, a high percentage seem to support bog coppers. In some cases, the butterfly populations in those bogs may have been isolated from immigration for decades, even centuries.

The risk the bog copper takes, of course, is that conditions in its bogs will change, or that bogs will be destroyed. If the population in a bog winks out, recolonization of that bog depends on the rare arrival of a wanderer from another bog. And if no suitable bog is nearby, recolonization approaches impossibility. For now, several large bogs and bog complexes on the Vineyard support good numbers of this unique butterfly. But the bog copper’s survival here depends on keeping those bogs in a healthy, natural condition.

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If your oak tree is sporting bright green orbs, read on.

The great outdoors can produce baffling mysteries. MVTimes Wild Side columnist Matt Pelikan tries his best to solve them. Got a question for the Wild Side? Send it to onisland@mvtimes.com

What’s this…thing growing on young oaks in the woods behind my house?

The Pelikan Brief:

Galls — actually pretty interesting — occur when an insect (generally a wasp) hijacks the tissues of a plant to produce a little wasp nursery. In effect, the wasp induces a tumor and then the wasp larvae mature inside the “tumor.”

The rest of the answer:

Galls are a catch-all term for abnormal growths on plants that are induced by insects. Generally, galls serve as nurseries in which insect larvae can mature. The structure of the gall protects the larva or larvae while it grows, and the maturing insect draws its nourishment from the tissues of the plant. To put it bluntly, galls are tumors that insects deliberately cause in plants to meet their own needs.

While they can be dramatic and (depending on your perspective) unattractive, galls rarely do any serious harm to the plant they’re on. The insect that forms the gall, clearly, has an interest in keeping the affected plant healthy, because the plant is nurturing the insect’s offspring. One exception to the “do no harm” rule, though, has been very much on the radar of Vineyard horticulturalists: a wasp named Bassettia ceropteroides apparently colonized the Island recently, and the lumpy little galls it forms on oak twigs block the flow of fluids through the oak’s transport system. The leaves and growing tips of the oak die, and without the ability to produce leaves, entire oaks die as well if they are heavily infested. In my Oak Bluffs neighborhood, several oaks about three feet in diameter, which must be hundreds of years old, succumbed after just two years of infestation by this tiny pest.

Beyond the basic commonalities of gall formation, this is an incredibly complex phenomenon. Many thousands of insect species are capable of forming galls; in most cases, each type of insect requires a specific plant species in order to form galls successfully. Often the plant needs to be at a specific stage of growth in order for a gall to form. Galls can form on roots, leaves, or stems. What triggers a gall to form varies depending on the insect: chemicals in adult insects, eggs, larval insects, or insect secretions or saliva can all be the active agent in triggering gall formation.

Gall formation is an especially common strategy among a wasp family called Cynipidae, which has many hundreds of species in North America alone (the villainous Bassettia ceropteroides is a Cynipid). You might say that this family evolved with gall-formation as its central reproductive strategy. But thousands of insect species across six different insect orders — from mites to moths — have been shown to make galls. Gall formation is a common ability in insects, and the ability to do it must have arisen multiple times during the course of insect evolution.

Which is pretty remarkable when you think about it: to form a gall, an insect species must develop the ability to hijack the biochemical processes that govern tissue production in a plant, producing a structure that perfectly suits the insect’s needs. Galls are a great example of the highly specialized interactions that govern the lives of many types of insects.

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The Juniper Hairstreak butterfly.

I don’t know whether it’s a source of frustration or of ever-expanding interest. But the natural world never stands still, and most of the time, once you’ve answered a question about a wild species, it’s time to start answering it again. Your knowledge is always, always obsolete.

This principle is much on my mind right now as it applies to one of my favorite butterflies, the juniper hairstreak. Fifteen years ago, I felt I had a good read on this distinctive insect on the Vineyard: it was rapidly expanding from a beach-head in Oak Bluffs and Edgartown, and would soon occupy suitable habitat across the Island. But the expansion of the species on the Vineyard seems to have stalled, and I can’t quite tell if its numbers are plummeting, or if I’m not looking for it enough, or in the wrong places.

If you look where it occurs, the juniper hairstreak is fairly easy to find, and very much worth the effort. Like other hairstreaks, it’s a small butterfly, about the size of a dime when it perches with its wings folded over its back. Also, like other hairstreaks, its underside bears an elaborate pattern of stripes. But this species is distinctive because the basic ground color of its wings is olive — it is the Island’s only predominantly green butterfly, and fresh ones, especially, are stunningly beautiful.

The juniper hairstreak associates very closely with red cedar, though it uses relatives of this plant elsewhere across the butterfly’s continent-spanning range. Males spend most of their day perched on the tip of a twig, usually in the upper branches of a cedar. Females lay their eggs — tiny, ridged, pale green spheres — on twig tips as well, and the larvae, or caterpillars, spend their entire period of development eating cedar leaves. The species goes through two full generations each year on the Vineyard, with adults from the first one, which overwintered as pupae, active mostly in late April and May and adults from the second one flying in late July and early August.

Sometimes you can spot the profile of a juniper hairstreak perched on a twig-tip. During the appropriate season, I habitually scan cedar trees with my binoculars, looking for exactly this. But the best way to find this butterfly is to grab the highest branches you can reach on cedar trees and give a few hearty tugs. The main thing that happens is that a shower of prickly cedar leaves rains down on you, with much of the debris making its way scratchily down inside your shirt. But if you happen to be tugging on a cedar with hairstreaks on it, you’ll see them jolted into brief, swirling flight. Track them, wait for them to land, and enjoy binocular views of, arguably, our prettiest insect.

The juniper hairstreak’s history here is easy to recite since it’s quite short. Though looked for, this butterfly was unknown on the Vineyard until the mid-1990s, when a visiting naturalist named Paul Miliotis found some in a large stand of cedars on East Beach, Chappaquiddick. That alone was a bit of a puzzle: how long had they been there, and if they were recently arrived, why on earth did they arrive there instead of East or West Chop, both of which have plenty of cedars and both of which are closer to the mainland?

By 1998, my first spring on the Island, juniper hairstreaks proved to be all over Oak Bluffs; on some occasions, I found as many as 25 at a single location. I began shaking cedars elsewhere on the Vineyard, eventually finding this species as far south as Katama and as far west as West Tisbury. The pattern was one of expansion: where they were absent one year, they were present the next. But somewhere along the line, this pattern seems to have reversed. The cedars remain common, but it has been years since I’ve found the species outside of Oak Bluffs. Even there, it seems to be scarce at locations that formerly supported it in large numbers.

I found a juniper hairstreak this past weekend, probably an adult from the first generation, running late because of our protracted winter. I’ll check the area where I found it later in the season, hoping to find a solid population. But I’m wondering: was the abundance of this species circa 2000 a temporary thing? If so, how many times has the species expanded and contracted — possibly even disappeared and reappeared — on Martha’s Vineyard, and what prompts that pattern? How much of its current scarcity reflects a real decline in numbers, and how much reflects a shift of the population from places where I can find it to places where I can’t? This is a volatile butterfly, playing by its own rules, and I just can’t figure it out.