Authors Posts by Matt Pelikan

Matt Pelikan

Matt Pelikan
131 POSTS 0 COMMENTS

by -
0
Sonograms of about a half-second of two insect calls, one unknown from my yard and the other a known Carolina ground cricket from the Singing Insects of North America website. —Photo by Matt Pelikan

For many kinds of animals, hearing may be more important than vision, especially for governing social interactions. Birds, for example, have excellent eyesight, generally much better than ours, but the social world of many birds is more a world of sound than of vision. Their call notes maintain contact with associates, convey alarm, or express levels of arousal; their songs attract mates and mark the limits of territory.

Birders long ago realized that knowing the sounds made by different species was a powerful identification method, and accomplished birders can reliably identify hundreds of species by their songs and call. After all, it’s how the birds sort themselves out!

A basic insect recording rig. —Photo by Matt Pelikan
A basic insect recording rig. —Photo by Matt Pelikan

In the insect world, likewise, vision may be crucial for avoiding danger, locating food, or dodging obstacles while in flight. But some groups of insects have evolved complex anatomical structures aimed at producing sound for social purposes. The cricket calling in your yard is a male, advertising his presence to rivals and potential mates alike. If the weather is warm enough, the cricket may call nearly continuously for days on end, investing a high percentage of his energy into making noise.

The structures involved in insect sound production vary from group to group, but for crickets and katydids, the mechanism is a simple one. These insects rub rough areas at the bases of their wings together. The resulting scratches resonate across the leathery forewings of the insect, gaining volume, and some species also position themselves on leaves (sometimes dry, dead ones) so as to broadcast still more loudly.

But unlike the sound-producing mechanisms of a songbird or human, the so-called stridulatory apparatus of a cricket allows for very little variation. These insects have about as much flexibility in their sound-making as you do when you run your fingers along the teeth of comb. You can move your finger faster or slower, but you have almost no control over the pitch or tone of the teeth as you pluck them. The noise an insect produces, in other words, is largely determined by the configuration of its stridulatory structure. And since those structures vary from species to species, the sound you hear is in a sense a representation of certain details of the insect’s anatomy.

As a birder who has branched out into insect observation, I inevitably began trying to learn the songs of bugs. Some calls I’ve learned the hard way, tracing them to their source and then visually identifying the singer. But it’s also possible to learn songs from recordings, which are available on websites such as Singing Insects of North America (entnemdept.ufl.edu/walker/buzz) and Cornell University’s Macaulay Library (macaulaylibrary.org/), or on CDs that accompany some insect field guides.

Simply listening to recordings of known identity is one good way to learn insect calls; the human ear, as any musician will tell you, is a sensitive and discriminating instrument. But I’m also interested in using recording insect songs to produce physical documentation of the presence of different species. Moreover, because the production of sound is so central to the biology of crickets and katydids, I believe that analysis of their calls can help us understand the relationships among insect populations. Differences in the anatomy of insects will translate to differences in the sounds they produce, and careful enough examination of enough songs may lead to discoveries that other methods of observation have overlooked.

I’m currently experimenting with a field recording rig consisting of a basic “shotgun” microphone (designed to focus on sound coming from a very small area), a small digital audio recorder, and a set of cheap headphones to monitor the recording process. Good results are not easy to achieve: even with the shotgun mic, you need quiet, windless conditions and a close-range “listen” to get good recordings. But with care and patience, you can generally capture a few seconds of clean sound.

I use a free program called Audacity, a basic sound file editor, to snip out the best five or six seconds of a recording. Then I process the resulting file in another program, Raven Lite, to produce a graphical representation, called a sonogram, of the sound. (Raven Lite is available for free from the above-mentioned Macaulay Library website.) Sonograms have been used for years to visually portray bird songs, and more recently to illustrate the calls of bats. But the advent of digital sound formats, approachable processing software, and inexpensive recording equipment has made sonogram analysis available to amateur observers like me.

With the graphical representation of a song in front of you, you can see the timing of individual pulses of sound, examine their shape, determine what the primary frequency of the song is, and discern whether there are overtones or undertones. By comparing an unknown song to sonograms made from identified songs, you can find a good match and put a name to your anonymous singer. In effect, this technology allows you to eavesdrop on insects, capturing their conversations in a form that makes sense to a human mind.

by -
0

Even when they’re out of sight and out of mind, ants carry on with their important work.

Solenopsis molesta, a tiny, common species sometimes called the thief ant, magnified 30 times, shot through a microscope ocular. —Photo by Matt Pelikan

Suddenly, swarms of mysterious flying insects! First, I received a report of robust swarm of airborne bugs in Chilmark. Then another report came from an Aquinnah beach, and finally ace bird photographer Lanny McDowell posted a photo in a Vineyard birding Facebook group of a mockingbird inundated in a small but dense swarm of insects. Though that’s only three such reports, that’s three more than I’ve ever received in one season, and I surmise that this has been a good fall for this phenomenon. Perhaps the recent weather pattern — an extended dry spell followed by several heavy rains — prompted a burst of this activity.

First, it should be noted that lots of types of insects congregate into flying swarms, and they do it for several reasons. In particular, many types of midges (a group within the very large order of flies) often emerge from their larval state at once, in massive hatches. Such swarms are essentially insect singles bars — aggregations of individuals seeking to mate. Or sometimes, intent on feeding rather than flirtation, you may find a swarm of hundreds of dragonflies, convened where air currents concentrate prey.

The recent reports, though, didn’t sound to me like midges, nor yet like dragonflies. Happily, the observer in Chilmark managed to snag a few individuals out of the swarm she observed, and ran them by my office for examination under a dissecting microscope. And Lanny’s photograph showed enough detail of the insects for me to recognize them, in a general kind of way. In both cases, the flying insects were ants.

The idea of ants airborne on their own wings — especially in vast numbers — seems to surprise people, and reasonably so. We think of ants as being in or on the ground, or maybe inside a rotting log. We may admire their numbers or their industrious behavior, but there is nothing about routine ant behavior that would make one expect to see them take flight. And yet period swarming flights are a central part of the biology of most ants.

Here’s the deal. Virtually all of the ants you notice — the ones building ant-hills, scuttling across the pavement, or hauling food back to their colony — are females, though they lack a full set of reproductive apparatus. Inside an ant colony, often deep underground, there will be one or more special females (the number varies depending on species). These are queens, larger than their sister workers and basically optimized for laying eggs to populate the colony. You might say that the whole point of being an ant is to protect your queen, bring her food, tend her offspring, and allow her to reproduce.

But nothing lives for ever, and any species needs to have a way to disperse to new locations. Ants address these challenges by means of mass flights. First, seasonal cues prompt the queen (or queens) to begin producing different kinds of eggs, some hatching into winged males (the only time males are produced), others into queens, large-bodied like their mother but not yet quite ready to begin laying their own eggs.

These new queens also start their lives with wings, and in conjunction with the winged males, launch from the colony into a mass courtship flight. Each queen will mate with one or more lucky male (again, different ant species follow their own rules). The males, created to do nothing more than fly briefly and try to mate, die quickly. The now-fertile queens disperse, find a site for a new colony, and produce their own work force of sterile female workers. Voila! The species is perpetuated.

With a specimen queen from Chilmark adequately magnified, I was able to identify the ant species in that swarm as Solenopsis molesta, a tiny, common, and widespread species sometimes called the thief ant. Typical workers are only a couple of millimeters long; the queen, which I photographed, was about four millimeters long. The species is capable of colonizing a wide range of sites, from in the ground to inside the walls of a house. While Solensopsis often scavenges in natural settings, it can also turn up in homes and kitchens as a “grease ant.”

I have no idea what type of ants were involved in the other swarms; they could have been Solenopsis, too, but about 75 species of ant have been found on the Vineyard, with at least a few more surely not yet detected. Like ants most anywhere, ours are abundant and diverse, and mating swarms are a widespread habit among ants.

The sheer ant-power of their highly cooperative colonies makes them major players as scavengers, predators, and prey. But the main importance of ants may be their engineering prowess — the sheer volume of food they can collect and soil they can move.

Ants are agents for dispersing plant seeds; they break down debris and recycle nutrients; they aerate soil; their colonies host a wide range of parasites or partners, ranging from other ant species to beetles and bees. Mating swarms are an especially obvious sign of these humble insects. But even when they’re out of sight and out of mind, ants carry on with their important work.

by -
0

What’s this snake?

The garter snake that Laura Bamford found was a darker, less fancy version than this off-Island fellow. Garters on Martha's Vineyard, Matt Pelikan proposes, may have evolved so that their markings help them hide among plentiful oak leaves. – Photo by Matt Pelikan

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.

Dear Matt,

We spotted this snake near the Farm Neck golf course in Hart Haven. Do you know what it is? We pushed it off the road so it would not get run over.

Laura Bamford

Laura Bamford spotted this snake near the Farm Neck Golf Club in Harthaven.
Laura Bamford spotted this snake near the Farm Neck Golf Club in Harthaven.

The snake Laura photographed is a garter snake, the most common (or at least the most commonly encountered) snake on Martha’s Vineyard. (Garter snake taxonomy is a frightful mess, and depending on what biologist you’re talking to, our garter snakes can be called either Eastern garter snakes common garter snakes. There are a variety of other garter snakes found across North America, with the relationships among them not well understood.) A medium-sized snake, rarely exceeding three feet in length in my experience, this species is widespread on the Vineyard; in particular, it seems to tolerate human activity fairly well, and as far as I know is the only one of our snakes likely to turn up in densely settled residential areas.

Garter snakes have a preference for damp habitats, but are quite flexible in their ecological requirements; likewise, they are versatile hunters, taking anything from earthworms to frogs to mice. Like all of the Island’s snakes, they are considered non-venomous, thought their saliva contains chemicals that may be toxic to some of their prey species and, according to some accounts, slows the clotting of blood. Given their role in regulating small rodent populations, the garter snake is a beneficial animal that should be welcomed wherever you find it. Like all of our snakes, garter snakes have suffered from road kill and predation by skunks, raccoons, and cats.

This is generally a docile species which often doesn’t try to bite even when you handle it (though they do have teeth — and a large one, if sufficiently annoyed, is capable of giving a pretty good nip). A more likely response when garter snakes are disturbed is release of a burst of foul-smelling musk from glands near the anus, and/or defecation on whoever is disturbing them.

Garter snakes may live for a decade or more if they escape being eating or getting mashed by an automobile. They overwinter, often in groups, by hibernating in dens, which are generally rocky sites such as old foundation, stone piles, or pits of debris. In warm weather, this snake is active day and night, and it is generally not hard to find one on the Vineyard.

The one Laura photographed, largely brown with a sort of checkerboard pattern, is typical of the garter snakes one finds on the Vineyard. But over its wide geographic range, our garter snake (whether one calls it Eastern or common) is a surprisingly variable animal. In some populations, these snakes are marked with yellow and black bands, resembling the closely related ribbon snake, which is also quite common on the Vineyard. This striped pattern is evident on typical Vineyard examples like Laura’s, if you look carefully, but the yellow strips are muted almost to invisibility by brown markings.

The distinctive appearance of our garter snakes may reflect the geographic isolation of our population during the five thousand years or so that the Vineyard has been an island. My own hypothesis, which is probably all wrong, is that the dominance on the Vineyard of oak trees, which shed brown leaves which are very slow to decay, may have led our garter snakes to evolve markings that help the snakes hide among fallen oak leaves.

by -
0
A handsome trig or red-headed bush cricket. It is commonly heard but rarely seen.

You may think you know what a cricket is. But “cricket” is a generic term, referring to a large and varied group of species. With grasshoppers and katydids, crickets make up the insect order Orthoptera; crickets are distinguished by having long antennae (unlike grasshoppers) and being generally less grasshopper-like than katydids. It’s a fascinating group, and a musical one: Crickets (along with katydids and some grasshoppers) produce “songs” by rubbing specially modified body parts together — a process known as stridulation. In the case of crickets, it’s generally roughened veins along a tough, leathery forewing that rub, and because the vibration resonates across the entire wing, cricket songs can be impressively loud for the work of such small animals.

The most accessible example of cricket stridulation comes from field crickets, of which the Vineyard has two, possibly three species. These are the large black crickets you find in your yard (and in your basement); their bodies are close to an inch long, and on females, a long, needle-like organ called an ovipositor protrudes from the tip of the abdomen. It looks dangerous but isn’t – its sole function is laying eggs in soil or leaf litter.

The two field cricket species I’m sure occur here are almost impossible to tell apart by appearance. But happily, the timing of their life cycles differs reliably. The spring field cricket hatches in the late summer, passes the winter as a hibernating nymph, and resumes growth when the weather warms in spring. By about early June, this species is fully grown and singing away in yards, meadows, and pastures. Spending the winter as an egg, the fall field cricket lags behind its cousin in developing, not reaching maturity until late summer. There is a brief period from late July to mid-August when I think both species can be heard; but by September, only the fall field cricket is active, and the difference in seasonality helps keeps these two closely related species from interbreeding.

The field crickets give the quintessential cricket song: a loud, relentless, but rather musical “crick, crick, crick …” The song is so familiar that many people barely notice it. But although these insects are easy to detect, they probably are not the most numerous crickets on the Island. That honor, I’m persuaded, goes to one of the field crickets’ smaller relatives, the so-called ground crickets. These insects resemble their heftier cousins, but as a group, ground crickets top out at about a half-inch in length. Some species barely break the quarter-inch mark.

Ground crickets, which mature and begin singing in mid-summer, produce sound in the same manner as their larger cousins, and the nature of the sound is therefore similar. But being smaller, ground crickets stridulate much faster, producing something more like a twitter than a series of well-spaced “cricks.” (Imagine a quickly rotating pulley with a squeaky pivot.) If you have ears and have ever been outside in the summer, you’ve surely heard several species of ground crickets without knowing it; while they occupy many types of habitat, ground crickets call day and night, and some species thrive in lawns and gardens.

But hearing one and seeing one are two different things. Ground crickets spend most of their lives concealed in leaf litter on the ground. Being both small and the same color as the debris they hide among, ground crickets are very, very hard to get a look at. By tracing the sound of a singing one, I can often narrow the search to a patch of ground a few inches square. But start poking around to find the singer, and your quarry shuts up and scuttles away. If you get a glimpse, you’re lucky, and if you can consistently get good looks at these creatures, well, you’re a better naturalist than I am!

The ground cricket species do differ in appearance, though, and even more so in how they sound; each species has a typical rate of chirping and distinctive tone quality. I’m gradually learning to distinguish them on this basis (at least three species occur widely on the Vineyard). And our other groups of crickets, which are no easier to see than the ground crickets, can similarly be recognized by sound: the tree crickets (a group of odd, ethereal, greenish bugs that sing sustained, musical trills), bush crickets or “trigs” (singers of scratchy songs from the ground and undergrowth), and even the mole cricket (never heard one myself, but I’m told they live here).

Masters of concealment, crickets are part of a vast community of insects that most people never see. But they’re out there, reproducing, eating, and being eaten, part of the huge web of life that surrounds us. And above all, they’re stridulating, millions of individual plucking sounds adding up to the soundtrack that characterizes a summer night. Abundant now, their numbers wane as the autumn progresses. Enjoy them while you can.

by -
0
Black racers (Coluber constrictor) are important predators in grasslands, shrublands, and forest edges, which are all part of the Vineyard landscape. —Photo by Patrick Coin

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.

Dear Matt,

This, from our Tisbury columnist:

“By the way, have you seen a large black snake recently? Black racers (Coluber constrictor) are important predators in grasslands, shrublands, and forest edges, all part of the Vineyard landscape. They are harmless to humans but control rodent populations, including the white-footed mice that host deer ticks (and Lyme disease). The Vineyard Conservation Society is helping to collect data on these snakes.”

So, the question is, do you know any more than this? Should we be rooting for these snakes?

Yes, we should be rooting for them, and it’s been quite a while since I’ve seen a black racer. I wrote a column on what I perceive to be the steady decline in snake numbers about a year ago. I think racers are especially challenged because they move around a great deal, which makes them vulnerable to getting road-killed.

The Vineyard Conservation Society web site asks: If you have a black racer sighting to share, please contact BiodiversityWorks via email with any information, such as the location of the sighting, the date (or month and year), the number of times you saw it in that area, and any photos you may have of the snake. Email biodiversityworksLiz@gmail.com with any info.

Dear Matt,

stinkbug-eggs.jpgFound this on my grill cover last month.  It’s disappeared since, so I wasn’t able to observe it for long. It reminded me of something you’d find under the sea. This is a close-up; the entire thing was about a half-inch long. Do you know what deposited this interesting cluster?

It’s a cluster of insect eggs, likely something in the stinkbug branch of the business, but that’s the best I can do.

by -
0

Why choose venomous victuals when you could sup on a butterfly?

For this robber fly, supper will be a bumblebee. Sort of a mixed blessing, if one is not careful. (Photo by Matt Pelikan).

Predation of one insect by another is not surprising: entire orders of insects, like the dragonflies, are predatory; and among flies, beetles, and many other orders, some families have turned their back on eating plants and evolved into hunters. What surprises me is that, amid the vast variety available to an insect that eats other insects, some predators court danger by specializing in prey that fights back.

A robber fly preys on an ichneumon wasp. (Matt Pelikan)
A robber fly preys on an ichneumon wasp. (Matt Pelikan)

An example that I’ve been fascinated by lately is a dark gray robber fly called Proctacanthus (like most insects, it isn’t well enough known to have a common name). About an inch and a quarter long, Proctacanthus ranks among the largest robber flies found on the Vineyard, and although it seems to be rather solitary and territorial, it also seems to be fairly common and widespread. And, as far as I can tell, all it eats are bees and wasps.

Like all robber flies, Proctacanthus is harmless to people but bad news for other insects. Robber flies specialize in aerial ambush, picking flying insects out of the air, piercing their bodies with a sharp beak, and injecting the prey with chemicals that paralyze it and break down its tissues. The robber fly then, quite literally, drinks its dinner, using its pointed mouthparts like a straw to slurp up its liquefied prey. When the fly has drawn as much nourishment as it can from its victim’s body, it drops the empty husk and resumes hunting.

Suitable for their predatory habits, robber flies are powerful fliers, and their legs are equipped with long spines that help them capture and hold their victims. While many robber flies are generalists in terms of diet, others specialize. One species of robber fly is a notorious slayer of butterflies; another eats spiders right out of their webs. But none seem quite as wedded to taking dangerous prey as Proctacanthus.

The first Proctacanthus I ever found was clutching a bumblebee. A while later, I found one eating a black-and-white ichneumon wasp in a woodland clearing. Passing the same spot two hours later, I found what I feel sure was the same robber fly eating a different ichneumon wasp, this one bright orange. Almost every Proctacanthus I see is eating something when I find it; and every Proctacanthus I’ve seen with food has been consuming something that stings. When you’re not much larger than a wasp yourself, the possibility of death or serious injury from a sting is very real. So I found myself wondering how and why this fly evolved to live so dangerously.

The “why” is easy. Bees and wasps are a fine choice to specialize in, if you can avoid getting stung. Few other insects are looking to tangle with a wasp, so there is not much competition for prey. Because bees and wasps are abundant and diverse, they represent a plentiful, season-long source of food. And the fondness of bees and wasps for taking pollen or nectar from flowers makes them easy to find: a typical tactic for Proctacanthus seems to be to stake out a flower-rich area, wait for a bee to come close, and nail it.

Surely the size of Proctacanthus helps it successfully vanquish stinging insects. The wealth of spines lining its powerful legs undoubtedly help it keep a firm grip on its prey, and a fine layer of dense hair that covers parts of the fly’s body may offer a little protection against stings. But it was not until I saw Proctacanthus actually hit a prey item that I figured out its secret.

A female Proctacanthus had been hanging around my yard for a day or two; I had disturbed it several times and had seen it eating a tiny, iridescent green bee. Then as I was watching a yellow-jacket taking pollen from a flower, the wasp was suddenly swept out of my field of view by a swooping robber fly. Holding its prey, the fly landed briefly on a twig, quickly adjusted its grip on the yellow-jacket, and flew to another perch in a lilac bush.

I approached carefully, so as not to disturb the fly, but even so, I was enjoying close looks within about 15 seconds of its initial attack on the wasp. And at that point, the wasp already appeared to be totally paralyzed by the fly’s venom! Wrapped in the fly’s spiny arms, the yellow-jacket was utterly inert; the fly, with its beak embedded in the back of the wasp’s thorax, already appeared to be eating.

Perhaps all robber flies are equipped with venom that effective. But for Procatcanthus especially, the ability to quickly paralyze its prey is vital. Tackling wasps may sound dangerous. But with the right tactics and a fast-acting venom, Proctacanthus makes it look safe and easy, paralyzing its victims before they realize they’ve been attacked.

by -
0

The focus of the natural world shifts, on balance, from exploiting this year to preparing for next.

A female Carolina grasshopper, working her abdomen into the ground in order to lay eggs. (Photo by Matt Pelikan).

The standard division of a year into four seasons is a mighty coarse approximation. Shifts of light, air, and growth as the earth’s orbit progresses call for a much more nuanced taxonomy. This past week, for example, clearly registers in my mind as something like “early late summer” — a period of a week or two, around the third week of August, when you suddenly realize that the show is ending. The focus of the natural world shifts, on balance, from exploiting this year to preparing for next.

As with other subtle seasonal shifts, the onset of this brief moment is evident everywhere I look: hints of color in the trees, the ascension of goldenrod’s yellow on the landscape, the occasional call note of a migrating songbird overhead if you happen to be outside at night. The natural world poises to dive toward the shortest days.

Perhaps because every organism, in its own way, must respond to the approach of winter, this time is of particular interest to the naturalist. Certain of our butterflies, for example, have run their course for the year, at least as adults: they’re still out there, of course, as eggs, caterpillars, or dormant pupae, but the adults have died or, or if they’re still here, it’s only as worn individuals bereft of much of their color. But the biology of the life stages left behind is as elegant, if harder to observe, than the activity of the adults.

Each type of butterfly has its preferred form for overwintering. For some, it’s a simple egg, laid, in a wonderful tribute to optimism, near where the proper food plant for the caterpillar grew this year and might, with luck, appear again next spring when the egg hatches. For other species, partly grown larvae overwinter; in a few cases, like the Orange Sulphur, the caterpillars might even wake up to take advantage of warm days in the winter to feed and grow a little. Still other species overwinter as chrysalids, homely lumps unrecognizable as butterflies, buried in the leaf litter or stuck to senescing stems. When the right time comes next year, an adult butterfly will emerge, unfurl its wings, and seek to pass on its genes.

The complexity of this process of “winterization” is astounding. For many insects, each summer sees just a single generation, and their developing progeny are programmed to cease activity at the right time, hunker down, and wait for spring. But what triggers this response, and what happens, physiologically, inside the young insect to prepare its body for freezing weather? And for butterflies with more than one generation per year, how does the final generation know to shut down rather than mature?

Sure, there are a few general principles at work here. Day length, for example, is a reliable factor, and many plants and animals use it to time their life cycles. Likewise common in the insect world is the production of chemicals that protect cells against damage from freezing. But each species has its own rules, and it seems to me that to fully understand the life of just a single insect species would be the work of more than one human lifetime.

For some insects, late summer is the season for adults. Some of these species eat seeds, and need to wait until plants have done their part by maturing. Other late-season insects probably evolved their life schedule to avoid certain predators or parasites that are more prevalent earlier in the season. Others, like many of our grasshoppers and katydids, simply have large, complex adults that need a full growing season to make it to maturity. But these later-season insects have much to do and not long to live.

I make a sweep through the quasi-meadow in our front yard for insects. Numbers and diversity have dropped precipitously from even just a week ago; many flowers have finished blooming, fading to brownish stems and seeds. Yet bees are still working the flowers that remain in bloom, loading their pollen sacks with yellow powder to provision their young.

One grasshopper, my old friend Chortophaga viridifasciata, is present again in numbers. Adults of this species, which spent last winter half-grown and matured by May, have long since petered out. But the young produced by this year’s generation have just hatched. Tiny nymphs smaller than rice grains are already prodigious jumpers. Some of these same individual insects will likely furnish my first insects of 2015, miniature grasshoppers cavorting in the yard on a warm February day.

And in the state forest I find a Carolina grasshopper, laboriously waggling her abdomen into the ground to lay eggs. It’s hard work; with only her body weight to work against as she digs, she hoists her hind feet off the ground to muster all possible leverage. I watch for 20 minutes, my patience expiring before her job is done. But I’m grateful to her for her efforts, because she’s making provision for the year to come.

by -
0
Pelidnota punctata, also called a grapevine beetle. — Photo by Matt Pelikan

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.

Hi Matt: lived here all my life and don’t recall ever seeing one of these before. What is it? Thanks, Angie Waldron

Hi Angie.

This impressive beetle is Pelidnota punctata, sometimes known as the grape or grapevine beetle. It seems to be reasonably common and quite widely distributed around Martha’s Vineyard. But like a the vast majority of our beetles, its habits and life history mean that it isn’t often seen.

Adults, which can exceed an inch in length, are unmistakable with their yellowish color and array of six black spots. They eat grape leaves (as the beetle’s common name suggests) but are largely nocturnal; they roost for most of the day on the underside of leaves, where you’re unlikely to spot them unless you’re specifically looking. This beetle, though, is active at night, feeding and searching for a mate, and it is attracted to artificial lights. So most of the time when humans encounter it, Pelidnota is hanging from a shingle or window-screen near someone’s porch light. Despite their daunting size, these beetles are harmless, rather sluggish, and quite easy to handle.

The grub-like larvae of this beetle are even harder to find than the adults. They hatch from eggs laid on rotten logs and stumps and spend most of their youth feeding either on the decaying wood or on roots and detritus underground. As is not unusual for very large beetles, it takes a long time for a Pelidnota larva to mature: two full years may elapse between when an egg is laid and when the adult beetle finally emerges.

The grapevine beetle is a scarab beetle, belonging to the same family as the scarab that was sacred to the ancient Egyptians as well as more familiar species such as the Japanese beetle. There are many thousands of scarab species worldwide, but the members of this very large group can be recognized by their characteristic stocky shape, often glossy or colorful exterior, and short, bent antennae, tipped with a little group of finger-like tabs. These tabs are actually organs that are exquisitely sensitive to chemical signatures — in other words, scarab beetles smell with their antennae, and they do it very well. Scent helps these insects find others of their species and locate suitable food plants or sites to lay their eggs.

Pelidnota punctata has a broad geographical range, occurring across the eastern and central United States and in most of southeastern Canada. Across this vast area, this species shows a good deal of variation in features such as leg coloration and the size and placement of the six black spots. In fact, at one point entomologists have treated this beetle as multiple species — as many as 10 at one point! But current thinking is that only a single species is involved.

In theory the grapevine beetle might be undesirable because it feeds on grape leaves, and under the right circumstances this insect can get common enough to cause commercially significant damage in vineyards. But it’s rare for Pelidnota to occur in numbers large enough to amount to any harm, and this beetle plays useful roles breaking down old wood as a larva and serving as a prey item for birds as an adult (one of these beetles makes a significant snack for a bird like a blue jay or catbird). So on balance the grapevine beetle is a positive addition to our world, and given its striking looks, imposing size, and docile manner, it’s a beetle you should be happy to find visiting your porch light.

by -
0
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.

P1070387
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.

by -
0
Widow or no? — Sarah Andresen

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.