The scariest job in America?

Just in time for the “scare season”, the job search site has come out with its list of the Top 10 Scariest Jobs in North America. Coming in at #1 is forensic entomologist. This career, and the others selected for the list, were ranked according to the phobias associated with it and their particular levels of hideousness.

Forensic entomologist Zachary Venable
removes a fly puparium from something dead.

Forensic entomology, with origins from over 750 years ago, is associated with three phobias, according to the creators of the list. People with necrophobia (dead bodies), entomophobia (insects) and hemophobia (blood) are not recommended to enter this particular field as each day at the “office” is sure to include at least one of these subjects (if not all three). While the subject matter may not be “sexy” to most, the profession has been growing and developing in the last 30 years – enough so that it’s been represented in multiple films and TV shows like Silence of the Lambs, CSI and Bones. In real life, forensic entomologists have helped solve countless cases of murder and poaching, as well as some other cases that have relied on insect-derived evidence.

Dr. Jerry Butler, forensic entomology professor with the University of Florida, examining hairy maggot blow fly larvae (Chrysomya rufifacies).
(photo by Thomas Wright)

Many people mistakenly believe that forensic specialists work only on cases involving death. However, “forensics” refers to any form of science applicable to legal proceedings. So while murder and dead bodies are often part of a forensic entomologist’s job, they also contribute to other cases where no one has died, such as drug smuggling (last paragraph) and liability cases. But of course that may not be quite as scary.

On the scariest job list, forensic entomologist beat out some other jobs I find far more fear-inspiring, including miner, pharmaceutical trial subject and comedian.

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New invader discovered in NC

Annother exotic, crop-damaging insect was discovered in North Carolina last month. The insect Drosophila suzukii was detected in insect traps at both ends of the state by extension specialist Dr. Hannah Burrack. The fly, a close relative of the “fruit flies” used in genetic research (Drosophila melanogaster), was first detected in the United States in 2008 among the fruit orchards and vineyards of California. Last year D. suzukii (also called the spotted-wing drosophila or SRD) was detected in Florida where it became an issue in fruiting strawberry fields and on farms of the state’s fledgling blueberry industry.

A female spotted-wing drosophila (Drosophila suzukii) preparing to lay her eggs on a raspberry. The males are the only sex to bear spots on their wings. (photo by Hannah Burrack)

At the end of last month, Dr. Burrack found high numbers of SRD on strawberry, blackberry and raspberry fruit at The Upper Mountain Research Station of Ashe County in the northwest corner of NC. The damage to fruit was significant. However, the situation at the Sandhills Research Station in the eastern part of the state – about 60 miles west of Fayetteville – was less dire. The assumption is that SWD does not survive and reproduce well at high temperatures, which previous studies bear out. However, in all likelihood the SWD numbers will pickup with the cool temperatures of autumn and the maturation of fruit. Agricultural entomologists also predict that SWD will hit crops hard next summer.

Larvae of the spotted-wing drosophila (Drosophila suzukii) on a strawberry. (photo by Hannah Burrack)

In California, Oregon and Washington the SWD has infested most soft fruit crops including cherries, apples, blueberries, grapes, nectarines, pears, plums, pluots, peaches, raspberries, and strawberries. In NC it’s expected to have an impact on those fruits that are grown here. Dr. Burrack offers some hope that sanitation of growing areas (i.e. cleaning up dropped fruit and disposing of infested fruit) will have a big impact on limiting this pest. Likewise, pesticides seem to be fairly effective in knocking down SWD numbers. Of course preventing invaders like SWD from moving to new locations in the first place is the best strategy. But in all honesty its difficult to do that without impinging on interstate and international commerce.

More information can be found on Dr. Burrack’s blog.

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When nature pretends

Nature is full of impostors. Pretending to be something you are not is a strategy that works well for many species. Classic examples of this in the insect world are the numerous files and moths that impersonate stinging bees. This type of trickery is called Batesian mimicry (after Henry Walter Bates, the English naturalist that came up with the concept). Many predators (along with kids and non-entomologist adults) are generally fooled by this display. It’s natural that, after being stung by a bee, people generally want to avoid being tagged again. Sometimes this reaction is extreme and the mere sight of a wasp-shaped, black and yellow-colored insect can send someone into a panic – even if the insect is unable to sting.

Four non-stinging insects that are Batesian mimics of bees. From top to bottom: Hemaris diffinis (the snowberry clearwing moth, photo by Lynn), Laphrina divisor (a robber fly, photo by Steve Collins), Temnostoma alternans (a hover fly, photo by Darrin O'Brien) and Megacyllene robiniae (the locust borer, photo by M.F. O'Brien).

A couple of months ago we were visiting my wife’s grandmother who has a sprawling farm down near Fayetteville. The area right around her house is filled with beautiful, well-developed flower beds that were buzzing with pollinators at the height of summer. I noticed that one of the species that was fluttering around the flowers was a moth (probably Hemaris diffinis) which put on a very convincing impersonation of a bumble bee. It was so convincing that the kids were not willing to get close enough to verify that it was indeed a moth. We also saw a couple of flies that were also successful bee mimics. In fact there are numerous species of flies, non-stinging bees and at least one beetle that have evolved this same trick of looking like a stinging bee or wasp.

Aggressive mimicry is essentially the opposite of Batesian mimicry and a tactic whereby some plant or animal appears to be something harmless or attractive in order to get close to their prey. One of my favorite examples of this from the insect world are the femme fatale fireflies (Photuris spp.) discovered by Dr. Jim Lloyd from the University of Florida. The flashes of light from all species of fireflies that fill a field at dusk are the signals they use to defend territory and find mates. The pattern and duration of the signals are unique for each species of firefly and only the right timing and pattern of blinks will do. Signals that don’t conform to these specifications fail to “turn on” the right mates. But the females of some Photuris species have evolved the ability to mimic the signals of females from a different genus (Photinus). This trick lures in male Photinus fireflies that have the impression they are about to get lucky. Much to their chagrin, the femmes fatales then capture the unsuspecting males and turn them into a meal.

Aggressive mimicry: A female Photuris versicolor firefly that has captured and is feeding on a male Photinus tanytoxus firefly by mimicking female P. tanytoxus flash signals.
photo by Jim Lloyd

Recently I’ve been working on an ant-tended aphid system wherein an aggressive mimic resides. The ants tend and protect the aphids from predators and parasites in return for honeydew (a carbohydrate rich substance exuded by the aphids that the ants eat). It’s akin to the relationship between humans and dairy cows where cattle are cared for in exchange for producing milk. However, in some of the aphid colonies I’ve found hover fly larvae (Syrphidae) that the ants treat in much the same way they do the aphids. These hover fly larvae are voracious predators of aphids and will consume several of them a day. But the ants don’t recognize it as a threat to their aphid herd and will protect and relocate hover fly larvae the same way they do the aphids. In all likelihood the fly larvae have acquired the same “scent” as the aphids through evolution or by feeding on them. In either case, it’s the proverbial wolf in sheep’s clothing.

Last week, a paper was published that describes a new type of mimicry that is used by an orchid to attract pollinators. Blossoms of the orchid Epipactis veratrifolia produce odors that mimic the alarm pheromone of several aphid species. Females of several species of hover fly use aphid alarm pheromones to find and select locations for laying their eggs. The larvae can then hatch out and just start feeding. While larval hover flies are highly-adept at preying on aphids, fast and far-flying adult hover flies are well-designed for pollination. By luring in these female flies that are looking for a place to lay their eggs, the orchids get the flies to pull double duty. The adult flies will collect pollen on their bodies as they search the interior of the orchid blossom before carrying this pollen to the next flower they visit. The female hover flies also leave behind their eggs which hatch into hungry larvae that patrol the orchid and feed on aphids and other small, soft-bodies insects that attack the plant. It’s a brilliant adaptation.

The orchid Epipactis veratrifolia which uses scents that mimic aphid alarm pheromones in order to attract aphid-eating hover flies for pollination.

Orchids, many of which don’t produce nectar, are notorious for luring in pollinators using other tactics, like deception and mimicry. Some species (like those in the genus Ophrys) have flower structures and odors that mimic sexual cues. They have evolved to trick male insects into having sex with a fake “partner” while it gets covered in pollen. There are others, like Bulbophyllum phalaenopsis, that look and smell like decomposing flesh in order to bring in flies that are attracted to carrion. These plants have trap-like mechanisms that force the flies to get covered in the plant’s pollen before being released to carry it on to the next flower. However, the case of Epipactis veratrifolia, this orchid appears to be the first known example of a flowering plant attracting pollinators using the scent of live prey.

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Leigh Van Valen (1935-2010)

If you spend time in a museum, aquarium, zoo or similar type of place you’ll notice that the visitors get really excited (I mean really excited) about one thing in particular: feeding time. I’ve volunteered and worked in several places like this and the story is always the same. Kids will go nuts and crawl over one another to see snakes chase down and eat mice; they’ll push each other out of the way when tarantulas stalk and feed on cockroaches; and everyone is completely awestruck watching praying mantises hunt down crickets before snatching and eating them alive. It’s at times like these when people consider animals to be at their most exciting: the pursuit and the capture. Some people find it horrible, but wonderfully so.

The universal fascination with predation means that it comes as no surprise to others when I tell them that predator-prey interactions are one of my favorite things about nature and something I choose to pursue in my research. Everything thing about animals eating other creatures is fascinating. Considering all of this, one of my favorite concepts in predator-prey interactions will always be the “Red Queen’s Hypothesis.” The father of the Red Queen’s Hypothesis, Dr. Leigh Van Valen, died yesterday from leukemia at the age of 75.

... "said the Queen. 'Now, here, you see, it takes all the running you can do, to keep in the same place. If you want to get somewhere else, you must run at least twice as fast as that!' "
~ Alice: Through the Looking Glass

The theory behind Van Valen’s Red Queen’s Hypothesis is that plants and animals are locked in a life or death struggle with other plants and animals over evolutionary time. To distill this down into a single example, I’ll use that of bats and moths, on which I wrote a recent post. In this example, bats began navigating the night sky using echolocation to avoid obstacles and find prey (moths). In response to bats’ use of sonar for hunting, moths evolved (through natural selection) behaviors to avoid or avert echolocating bats (like erratic flying and dropping to the ground). As a response to this, some bats evolved calls that were quieter so they could “sneak up” on the moths. Essentially, the RQH describes an ever-escalating, evolutionary arms race between two sides that are forced to develop of strategies and counterstrategies in order to survive. It’s an idea that’s as vivid and elegant in its conception as its title.

Van Valen came up with the name for the Red Queen’s Hypothesis from a verse uttered by the Red Queen in Lewis Carroll’s work Alice: Through the Looking Glass.

“It takes all the running you can do, to keep in the same place.”

Alice finds that in the world she’s entered, one must run hard just to retain his or her position in space. In terms of bats and moths, it means that when one side develops an ecological adaptation that gives them an advantage, the other has to then develop a counter adaptation to survive or face extinction. Each player must actively evolve in order to maintain their relative effectiveness against the other species. It makes sense and seems intuitive and most biologists can rattle off a dozen or more examples of the RQH in action. Yet it wasn’t really established until Van Valen laid it out in 1973.

The RQH was only one of his many fundamental contributions to biology. Van Valen also gave us the Ecological Species Concept, which is one of the dozen-or-so definitions of what a species is. While the average person may not give a flip, the definition subscribed to makes all the difference in terms of species conservation laws and their enforcement. For instance, there are between 1 and 12 different species of brown bear (Ursus arctos), depending on whom you ask and which species concept they subscribe to.

Dr. Leigh Van Valen

Dr. Van Valen, a member of the Ecology & Evolution faulty at The University of Chicago, was also a talented mathematician and conceptualized “fuzzy sets” which are used to quantify qualitative criteria. The formulae help to assign a “degree of membership” to any number of things making it possible to draw mathematical conclusions from non-mathematical concepts. He was also a force in the fields of thermodynamics, logic, epistemology and probability theory. His life was prolific and his death is a great loss to science.

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The vertical gardeners

Autumn is here and that means it’s time to harvest the last of the veggies in the garden and start putting the soil to bed for the winter. I find that gardening is a wonderful activity to stimulate thinking and is when a lot of “ah ha!” moments seem to blossom. Recently I got to thinking again about some very interesting and novel research going on here in Raleigh that focuses on some different gardening fanatics.

A sample of some of the morphological diversity in Xyleborini ambrosia beetles (photo by Jiri Hulcr)

Now most people know about leaf cutter ants and how they cultivate huge gardens of fungus to support their colony. But they are not the only insects to do this. Another group of miniature mycoculturalists are the ambrosia beetles. This is a somewhat-obscure group of insects that live just under the bark of trees, in a layer called the xylem (the layer in which water moves upwards in a plant from roots to leaves). The ambrosia beetles are a polyphyletic grouping of weevils, meaning that the lifestyle they share (living under bark and cultivating fungus) has evolved multiple times (in fact, at least 11 times) in individual species groups. This indicates that the inner tree-dwelling, fungus-gardening gig is a pretty successful one and was adopted anew several times. It’s also withstood the test of time. While human agriculture has been going on in some form or another for about 12,000 years, the association between ambrosia beetles and their cultivation of fungal gardens began over 60 million years ago. So you’d expect them to be “master gardeners”… which they are.

One of the tricks of the ambrosia beetle trade is morphological. Successful human gardeners are said to have a “green thumb”, but the ambrosia beetles have something better. They are outfitted with structures called mycangia that they use to transport the seeds of their fungus gardens (spores, actually). As I mentioned already, the fungus gardening lifestyle evolved multiple times in these beetles, so as a result there is some diversity in the construction and location of ambrosia beetle mycangia. Some some beetles have these spore-holding pockets next to their mandibles, some under their wings, and some with grooves on their backs to collect and carry fungus to their next home. In all cases, when the beetles leave a tree they carry with them an instant garden.

Left: A cross-section image of fungus-bearing mycangia of Xyleborus affinis which reside in their heads and sit at the base of their mandibles. Right: A dissected Xylosandrus germanus with the mycangial structure removed from the inside of the thorax. (photos by Jiri Hulcr)

The relationship between beetle and fungus is a mutualism and neither organism would survive without the other. But the exact species involved are less critical. In general, the beetles are able to cultivate and feed on different types of fungus and 95% of the beetle species tested show no preference for one fungal foodstuff over another. The common thread is the fact that all of these fungi decompose wood. So the same colony of beetle can cultivate multiple types of fungus just like we grow tomatoes, potatoes, peas and corn in our little garden at home. Other ambrosia beetles that lack mycangial structures and the ability to grow their own food will engage in raids on established gardens. Beetles that engage in mycocleptism (fungus theft) will bore into the galleries of another species and chow down on that colony’s crops.

In their native ranges, ambrosia beetles usually stick to attacking downed trees that are already dead or dying. The fact they feed on wood-decomposing fungi makes it possible for them to feed on several different species of dead trees. The beetles rely on olfactory cues (scents) to find and identify downed trees that they then use as nesting and gardening sites. Their role in spreading fungi from place to place and cultivating its growth is important to the process of wood decomposition in forests. However this neat little system appears to come undone when beetles are introduced to new habitats that have unfamiliar tree species and strange chemical cues (or a lack thereof). And this is where the story of ambrosia beetles takes a sour turn.

A native redbay tree (Persea borbonia) being attached by the exotic ambrosia beetle, (Xyleborus glabratus) near Savannah, Georgia. Note the pin-like extrusions of sawdust as a result of beetle boring activity. (photo by Bud Mayfield)

In 2002, the an exotic ambrosia beetle from Asia, Xyleborus glabratus, was found attacking redbay trees (Persea borbonia) near Savannah, Georgia. Redbay is native species that is common in maritime habitats along the southern Atlantic and Gulf Coasts. It’s a close relative of the plant that is the source of the cooking spice called “bay leaf” (P. nobilis) and can be used as its substitute in recipes. In its home range X. glabratus attacks only already-doomed trees, but all of the redbay that has been hit by this beetle in the South are live and otherwise healthy. That is until the beetles and fungi move in. Once they are attacked 100% of the trees die.

The range of tree species in the U.S. that are attacked by X. glabratus extends beyond redbay to include other members of the Laurel family (Lauraceae). The other trees that have been confirmed as vulnerable are some notable and iconic species like sassafras (Sassafras spp.), camphor (Cinnamomum camphora), pondspice (Litsea aestivalis, which is Federally endangered) and avocado (Persea americana). The avocado industry in Florida has gone into panic mode in an attempt to fend off the invasive beetles and ease the damage that is certain to come. In the meantime, the beetles are still spreading southward towards the avocado growing areas of South Florida, using the redbay trees and other Lauraceae as a bridge.

The range map of the invasive redbay ambrosia beetles (Xyleborus glabratus) and a malady that it vectors, laurel wilt disease, in the S.E. United States. Color codes of counties reporting the disease corresponds to the year reported.

One of the alarming statistics is that X. glabratus is only one of about 260 species of ambrosia beetle that is recorded as exotic in the U.S. Another startling figure is that invasive ambrosia beetles are very abundant and account for 10% of insect species and 45% of the overall number of beetles here. The characteristic of attacking healthy, native trees is much the same for many of these other invasive ambrosia beetles that we know of and this has damaging impacts to native biodiversity. The Palamedes swallowtail butterfly (Papilio palamedes) is common in the South and highly dependent on redbay, swampbay and sassafras as host plants (all three of which are attacked by the beetles). While no comprehensive studies have yet been undertaken to determine the effects of beetle damage on their populations, redbay has completely disappeared from areas infested by Xyleborus glabratus leading to speculation that numbers of the Palamedes swallowtail in these areas will soon follow.

Invasive ambrosia beetles are damaging to economies as well, although (and coincidentally so) it is via commerce and international trade that most of them have been able to move around and become established in North America. For example, a large portion of the railroad ties used in the western United States once came from oak trees in Georgia and the Carolinas. However with the detection of a new ambrosia beetle species in Oregon, (Xylosandrus crassiusculus), orders for this Southern forestry product has completely stopped. On top of this, hundreds of thousands of dollars and tens of thousands of gallons of pesticides have been spent on eradicating this single species of beetle from the area around Portland, OR. Yet another species, the walnut twig beetle (Pityophthorus juglandis) vectors the ominous-sounding “thousand cankers disease” in native black walnut (Juglands nigra) and cultivated walnut species. This disease is often deadly to adult trees and impedes the growth of saplings.

The three beetles mentioned in this post are just a few of the invasive ambrosia beetles present in the U.S. Estimates are that on top of the species confirmed to be within our borders, more than 2,000 more exist in the Asian tropics and could pose just as great a risk. To use some gardening metaphors that I came up with while digging and thinking about all of this, these examples have been cherry-picked but represent an issue that is no small potatoes. In preventing further invasions we have a tough row to hoe and if we don’t nip future incursions in the bud we’re certain to face the grapes of wrath.

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Insects fight back (against bats)

Two weeks ago we were treated to a presentation by Dr. William Conner from Wake Forest University in which he discussed his research on the evolutionary arms race between tiger moths and one of their primary predators, bats.  As most people are aware, nocturnal bats use echolocation for navigating the darkness, as well as for locating and targeting their prey. The science behind echolocation in bats is considerably more complex than most people realize. But the same can be said for the strategies that some insects use to evade hungry bats.

A big brown bat prepares to make a meal out of a tethered moth. photo by Aaron Corcoran

Bats have had to evolve strategies to successfully use sonar for navigation. More specifically they need to sort through the echoes from multiple screeches and determine what they mean. Consider a cave in which reside dozens or hundreds of flying and screeching bats all using sonar at once. Then you can begin to imagine how confusing it all could get. With so many signals overlapping one another it would be difficult to figure out what is an echo of your own call and what is your roost mate’s call or echo. Likewise, bats have very sensitive ears which they need for capturing faint echoes coming from very small objects that are moving around quickly in 3 dimensions. Also, the small ultrasonic screeches emitted by hunting bats, while too high pitched for human ears, are very loud – on the order of being near the stage at a heavy metal concert (between 120 and 140 decibels). So bats have developed physiological adaptations that prevent damage to their ears from the high intensity signals that they produce.  Interestingly, the solution to these obstacles are some of the same technological breakthroughs humans have developed in the evolution of electronic sonar and radar technology. Of course, bats appear to employ them millions of years earlier.

The sensitivity of bat echolocation allows bats to pinpoint the location and direction of movement of their insect prey.

Another problem, at least for creatures the size of bats, is the issue of energy use and conservation. Bats have among the highest metabolic rates for animals. Insectivorous bats have to eat about half their body weight in insects each night or they can risk starving. Most of vast majority of food that becomes part of a bat’s energy budget is used for flight and heat production. The remainder of the energy budget that is leftover is comparably small which makes it something that should be closely controlled. Generating the powerful, ultrasonic pulses that bats use in echolocation also requires a lot of energy, but are also highly useful to the bats. So over time bats have evolved energy conservation strategies are designed to help them last a little longer on the energy they have.

When they are just flying around, probing the night sky for possible obstacles or flying prey, bats send out occasional ultrasonic pulses – just enough to get an idea of what’s out there.  But there is a trade-off in the resolution of the picture. You can think of the bat calls as a strobe light and the bat chirps as the individual flashes. Less energy is used if the strobe light pulses infrequently (say every 2 seconds), but its hard to track moving objects and it’s nearly impossible to play catch in this condition (I tested this hypothesis when I was about 11 years old). But if the light is cranked up to blink 10 times a second its easier to follow moving targets and to catch balls that are tossed to me. The trade off, however, is that this also requires 20x the amount of energy per minute. This is irrelevant in terms of the current cost of kilowatt hours, but a little energy can mean life or death to a bat. So one solution by bats is to strengthen the sonar resolution when it counts most. They do this by increasing the number of pulses they send out only when they are near moving prey or obstacles.  You can hear this happening in the video below of a bat closing in on its moth prey.

Pretty cool, right? But it appears that this dance in the night sky is an old one and that some insects have developed countermeasures to this strategy. The basis for the “stop and drop” response by these moths is an evolved behavior in which they stop flying, retract their wings and fall to the ground. By falling out of the sky and into vegetation the threat posed by airborne, echolocating bats is neutralized.

But the stop and drop response to increasing bat echolocation pulses is not exclusive to moths and is known about in beetles too. It appears to be a convergent behavior that’s part of a shared, anti-predator, defense repertoire used by many nocturnal, flying insects. These insects shift through a series of defense responses depending on how loud the sound is (intensity) and how fast the strobe light-like flashes of sound are being made by the bats (frequency).

Two photos of a bat tracking a moth. Top: a moth (bright streak) takes successful evasive action from approaching bat (broad streak across the photo). Bottom: the two streaks intersect as a result of the moth failing to elude the bat. photo by Frederic A. Webster

The response of a flying moth or beetle prey that senses bat echolocation is threefold and changes with the intensity and frequency of the bat’s signal. The first step is that the flying insect will change its course at the earliest signs of bat sounds in an attempt to avoid detection. If this doesn’t work and the moth determines that the bat is now tracking it, the second step is to start moving erratically and try to throw the bat off a successful trajectory (as did the moth in the picture above, top). If the echolocation pulses grow still louder and more frequent (which generally means that the bat is really close) then the moth or beetle stops flying and drops to the ground.

Of course, dropping into the darkness comes with its own dangers, particularly in the tropics. For a moth that falls to earth, death can just as easily come from falling into a pond and drowning or contact with soilborne diseases or dropping onto a predator’s dinner table (like ants, rodents, amphibians, etc.). To avoid this and to gain another layer of protection, some moths have developed another strategy for defense in the final stage of attack. Dr. Conner refers to this brief period of time as “the moment of truth,” which includes a second or two of rapid chirps from the bat and ends with a strike. Or a miss. But what could cause these warm-blooded, sonar-guided, finely-honed hunting machines to miss their mark?

ear mites in the genus Dicrocheles shown inside a moth ear. from Barber and Conner 2007

As it turns out, its jamming technology. The moth are basically interrupting the bat’s ultra-sensitive sonar. Some of the tiger moths studied in the Conner lab possess sound producing structures called tymbals. The tymbals, like the rest of the moth’s exoskeleton, are made from chitin, a light and durable material. It’s also flexible like plastic. In fact, if you’ve ever played with an empty, plastic soda bottle you have probably mimicked the way tymbals make sound. By pressing in a side of a soda bottle you can make a popping sound by changing its shape. Then by letting the bottle pop back into place you make another pop. This principle is true for the tymbals on a moth, which are attached to muscle groups that contract and relax in rapid succession and popping the tymbals in and out of place. This creates a series of snapping sounds that resembles a “buzz”… at least to animals with ultrasonic hearing. The moths use sound from these, in conjunction with pheromones, to inform potential mates of their species and suitability as a mate.  They also use these high-pitched buzzers to jam bat sonar signals.

Recall the first video in this post and how as the bat swooped in it ramped up its sonar signal and captured the tethered moth. Now compare that to the video above which shows “the moment of truth” and the bat coming in for the kill. You can hear the bat’s chirping becoming more rapid the closer it gets, and then loud buzzing sound which is created by the moth. This sound throws off the bat’s orientation, causing it to miss the target. It’s the bat equivalent of a left fielder loosing a pop fly ball in the sun. It’s pretty effective too with most attacks on buzzing moths failing to result in a capture. Dr. Conner discussed how one female big brown bat that was tested had failed in its attempts to capture a buzzing moth 38 consecutive times. For the 39th attempt the moth’s tymbals were silenced and the bat captured the moth straightaway.

Of course this is an evolutionary arms race. So when one adaptation is developed by moths, a counter-adaptation is evolved by bats. So it stands to reason that there is, somewhere, some behavior in bats that overcomes the “sonar jamming” and “stop and drop” behaviors of moths. And there is. Whispering bats (Barbastella barbastellus) have evolved echolocation pulses that are quieter allowing a bat to get closer to flying prey. This quieter call fails to trigger the defensive behaviors in moths that are in response to loud bat pulses.

Ear mites in the genus Dicrocheles hanging out and doing their thing inside a moth's ear.

Not to be left out, parasites of moths are also involved in this arms race. Obviously, if you live on a moth it’s important that your host survives, making your fates intertwined. It’s also fairly obvious that if you’re intent on having your moth live through nightly bat attacks where the only warnings are sounds, you need make sure your moth’s ears are in good, working order. This is no easy task if you’re a moth ear mite. Back in 1957, the acarologist Asher E. Treat published a paper on his observations of moth ear mites, with a surprising finding. Treat found that these mites only lived in one of the moth’s two ears. It was true for every single moth he sampled. Each case was the same. Female mites need to break through the ear drum to lay eggs inside, which causes complete deafness in that ear. However, any ear mites on a moth would sooner move to another moth than damage the second ear. Treat and others surmised that this was an adaption to prevent complete deafness in the host moths, which would render them prone to bat attack and decrease their chances of mating. Apparently the costs of riding on a deaf moth outweigh the benefits and behavior of using the second, perfectly good eardrum as a nursery.

Continuing study of this evolutionary arms race is fascinating in itself. It’s also fascinating to consider the convergent examples in human sonar and radar technology. In much the same way, this research is predictive of what likely exists in other biological systems that incorporate sonar. For example, less is known about echolocation in marine mammals and what countermeasures have evolved in their prey. In all likelihood they will be very similar to the behaviors in the bat and insect system.

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Back from the dead

Today I read an account of a fly, which was thought to be extinct, being found in Spain last year.  The fly, Thyreophora cynophila, was snapped by a nature photographer who posted an image of the fly on-line in the hopes of an identification.  No guesses came in for a long time as to the identity of the critter – which is odd for Europe with its profusion of professional and amateur entomologists.  But eventually someone identified the distinctive dipteran as a species not seen for over a century and a half.  Even back then it was so rare that only 16 curated specimens exist in the world.

The formerly-extinct bone-skipper fly (Thyreophora cynophila); female (top) and male (bottom).

The rediscovered fly, known as the “bone-skipper”, is a insect that is a specialist on the exposed bone marrow of dead mammals in the stages of late decay.  A prominent feature is its orange head which is glows at night.  A scientific paper out this month documents the success of trapping more of these flies, along with the authors’ theory as to why this species has disappeared for so long, citing three main reasons.  The first is that the predatory mammals, such as wolves and bears that can break open the large bones of mammalian prey, have all but disappeared in Europe. This is thought of as a limiting factor on the overall amount of exposed marrow in which the flies deposit their eggs.  A second reason is that sanitation practices in Europe have changed significantly in the last couple of centuries and any exposed bone marrow from livestock butchering is soon contained and disposed of for reasons of public health.  Perhaps the biggest reason that no one in recent history has seen this fly is that it appears to be active only in the coolest months of the year – when entomologists are rarely out collecting.  By far, most insects only forage and mate at times of the year when the ambient temperatures allow their “cold blooded” physiologies to be active. So aside from the severe shortage of very old, ungulate bone marrow, it turns out that people just weren’t looking at the right time.

While we may not notice the extinction of an insect as much as we do some larger species, such as birds and mammals, there have been a few notable insect species that have been lost to extinction.  Among them are the Antioch Katydid (Neduba extincta, which used to be found among the sand dunes of California), the Rocky Mountain Grasshopper (Melanoplus spretus, which used to blacken the skies of the western U.S. in great plagues), and the Xerces Blue butterfly (Glaucopsyche xerces, which also inhabited the sand dunes in California and was last seen fluttering around in the vicinity of Golden Gate Park).  All of these species are extinct as a result of habitat loss to development and modification, as well as pressure from invasive species.  The extinction of the afore-mentioned Xerces Blue became the inspiration for an biological conservation organization, the Xerces Society, which currently works to save endangered invertebrates and their critical habitat from succumbing to the same fate as its namesake.

The extinct Xerces blue butterfly (Glaucopsyche xerces) and namesake of the invertebrate conservation organization, Xerces Society.

Like the recently-rediscovered bone-skipper fly that has revealed itself as more alive than previously thought, there have been other exciting revelations in the last decade where living populations of insect species, that were previously declared extinct, have been found clinging to a less-defunct classification.  Plants and animals that perform this miracle of coming back from the dead are collectively referred to as “Lazarus species”.  One such insect that managed to come back to life is the Lord Howe Island stick insect (Dryococelus australis) which was declared extinct in 1930.  Much like the British Admiral for whom the Lord Howe Island Group was named, the stick insect bearing his name survived several brushes with extinction.  A population of 30 stick insects was discovered by entomologists in 2001 on a hellish, isolated, rock feature in the Lord Howe Island Group known as Ball’s Pyramid.  The overall population of the stick insects has since increased to about 450 individuals through a government conservation breeding program and some of those individuals have since been released on Lord Howe Island (following an island-wide rat eradication program).

The formerly-extinct Canterbury knobbed weevil (Karocolens tuberculatus), last seen in 1922 but rediscovered in 2004.

Several insects that have also managed to disappear for decades or centuries and, ostensibly, from the face of the Earth. For example, several of the moths in the diverse genus Omiodes are endemic to Hawai’i, a number of which have been declared extinct.  Some of the species that hang on are still being hammered by exotic predators and parasitoids that have been intentionally introduced to control crop pests, as well as from contact with agricultural insecticides.  However, some of the Omiodes species that were declared extinct have recently been rediscovered by researchers at the University of Hawai’i.  Tentative plans for conservation programs to help save these species are in the works.  The short-necked oil beetle (Meloe brevicollis) was also declared extinct long before being discovered again.  The larvae of this beetle are parasitic on solitary bees and feed on their eggs.  It was last seen in the 1940s and its numbers were likely curtailed as a result of farming activity, but a small population was rediscovered in 2007 on the island of Devon. Another beetle, the Canterbury knobbed weevil (Karocolens tuberculatus) was last seen in 1922 near Christchurch, New Zealand… that is until it was discovered by a graduate student studying its food plant in 2004. Four specimens of this nocturnal critter were collected at a light trap and submitted to the Canterbury Museum where it was determined to be the AWOL weevil.

New Zealand was also an important refuge for another insect that went extinct in its home range of the UK. Short-haired bumblebees (Bombus subterraneus) were last seen in Great Britain in 1988. The reason for this is likely due to the disappearance of wildflower fields that once dominated much of the countryside. With the loss of this vital nectar source and in conjunction with all of the other stresses brought on by development and a modern world (pesticides, pollution, parasites, etc.) carving out a living in the UK just got too difficult for this bee and it disappeared. However, the same insect was introduced to New Zealand over a century ago when it was still a British colony. Once released it proceeded to pollinate crops and continued to survive. The return to its homeland was complete this summer when several bees collected in New Zealand were released at restored wildflower fields in Kent, in southern England. Over the past several years a number of farms and other rural properties have gone through intense rehabilitation efforts to restore them to traditional wildflower fields by removing invasive weeds and instituting conservation measures to encourage growth and proliferation of native, nectar-producing plants. The silver lining to this story is that the effort to create a welcoming habitat for the short-haired bumblebees has resulted in the rebound of populations of five other rare, native bee species that also pollinate wildflowers and crops.

The gladiator Austrophasma rawsonvillensis (Notoptera: Mantophasmatidae), representative of a group that was once thought only to be found in the fossil record. photo by Mike Picker

Its rare to recover or rediscover a species that’s been declared extinct, but it’s even more unlikely to find an entire suborder of insects that’s disappeared.  However that’s exactly what happened in 2002.  It was an exciting time to be an entomologist when the Mantophasmatodea were found, alive and well, on the Brandberg Massif in Namibia (a virtual island in the sky).  These carnivorous insects superficially resemble grasshoppers and stick insects, but are most closely related to the obscure insect family Grylloblattaria. They are a stout little creatures that live in a landscape with the most diverse and abundant scorpion fauna in the world, for which they definitely earn the title of gladiators.

More recently, I’ve had the privilege of working in the lab of Dr. Rob Dunn during the reemergence of a couple ant species that are were declared extinct. Simopelta minima is a Brazilian species of ant that was named from four ant workers that were found in soil samples in on a cocoa plantation in the 1980s. The plantation has since been converted to farmland and the ant was considered extinct by the Brazilian government. However, more workers of the same species were discovered over 1,000 km away from the original collection site. The authors of the paper documenting this rediscovery suggest that the reason this species went undetected for so long is due to the paucity of sampling being carried out. People just weren’t looking hard enough.

An adult Pachycondyla chinensis attacking a termite, its main prey. photo by Benoit Guénard

One other person in Rob’s lab that is looking hard is Benoit Guénard, a PhD student in the lab. He’s a virtual Sherlock Holmes of ants and has made several interesting discoveries in his short time at NC State University. In 2006, during his effort to become more familiar with the ant fauna of North Carolina, Benoit found an ant that he was unable to identify. He found this same species in multiple areas of Piedmont and Coastal NC and in greater numbers than the other ant species. After trawling through numerous identification keys he determined that the ant was not native to NC, but rather it was native to Asia.  He also discovered that it was virtually unknown and unstudied in NC, despite its ubiquity and dominance here. The invasive ant, Pachycondyla chinensis is not new to the state.  It has been living – mostly undetected – among the forests, fields and streets of NC for nearly a century. Despite being a virtual unknown to North Carolinians, particularly compared to the other invasive ant that people here know (the fire ant, Solenopsis invicta), Benoit’s ant has a sting that poses a greater health concern to those that enjoy the outdoors. The sting of P. chinensis is painful and can cause severe swelling and anaphylaxis.  Largely through Benoit’s discovery, this species is now confirmed to be throughout much of the Eastern US and has been spotted in locations from Connecticut to Florida and as far east as Tennessee and Alabama. Yet three or four years ago, hardly anyone was even aware of it.

The rarest ant in North America, Amblyopone trigonignatha. photo by Benoit Guénard

Benoit was also the first person to find another ant that was discovered in 1948 and hasn’t been seen since.  The ants in the genus Amblyopone are primitive (for ants) and commonly referred to as “Dracula ants” in reference to the behavior exhibited by workers of feeding on the hemolymph of their colony’s larvae. After 61 years of no contact, Amblyopone trigonignatha was found in Benoit’s backyard (literally).  On one particularly sunny day in Raleigh during this past January, Benoit decided to take some photos of ants at his home and found what he thought was another, more common species of Amblyopone in the backyard.  He snapped a few good photos before… [gasp]… letting it go. There is a good, first-person account the story in the Myrmecos Blog, but the punchline is that another myrmecologist saw the photos months later and contacted Benoit with his thought that it might be the ant that is often considered the “rarest ant in North America.”

So naturalists are still out there, hunting elusive creatures that are waiting to be discovered and rediscovered. The likelihood that we’ll find another extinct suborder or family is low, but the resurrection of the bone-skippers, gladiators and Dracula ants from the annals of history is an exciting reminder of what may still be out there and waiting for us to find it… again.

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