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Bog killers

Sphagnum ground cricket (Neonemobius palustris) from Ponakpoag Bog, MA.

Sphagnum ground cricket (Neonemobius palustris) from Ponakpoag Bog, MA.

The one thing about plants that we take for granted is that they cannot really hurt you. Sure, some are full of toxic compounds and can be deadly poisonous if ingested. Others are covered with nasty spines or irritating hairs, and a tree  can fall on your head during windy weather and crack your skull. But we feel pretty secure in the fact that no plant can hunt and eat you. Things would be very different, however, if we weren’t some of the largest animals on the planet.

The call of the Sphagnum ground cricket is a soft, high-pitched trill, which is easy to miss unless your are looking for it. Click here to hear the recording of the call at the natural speed, followed by a fragment slowed down 5 times.

The call of the Sphagnum ground cricket is a soft, high-pitched trill, which is easy to miss unless your are looking for it. Click here to hear the recording of the call at the natural speed, followed by a fragment slowed down 5 times.

I was having these thoughts last Sunday when I went looking for another singing insect, the minute Sphagnum ground cricket (Neonemobius palustris), one of a few species of New England acoustic orthopterans that I had never managed to get a recording of. I decided to try looking for it at Ponkapoag Bog in the Blue Hills Reservation, about 10 miles S of Boston. Almost immediately after stepping on the wooden planks that run through the soggy Sphagnum bog I started hearing the characteristic, high-pitched tinkling of those small crickets. But it took me a while to find one, and I only managed to do so after a considerable amount of crawling on all fours, waving a shotgun microphone to pinpoint the source of the sound. Eventually I located one individual in a sunny spot, deep in a clump of red and green moss. As I was recording his song, I also marveled at the idyllic setting of this species’ home. “What a great place to live for an insect”, I thought, “no predaceous ground beetles, no centipedes, water and food plentiful.” But then I heard behind me somebody say “Look honey, bladderworts! They catch and eat aquatic insects.” Right, I forgot about the killer plants.

Looking like a hungry snake, the gaping mouth of the pitcher plant (Sarracenia purpurea) invites unsuspecting insects to their death.

Looking like a hungry snake, the gaping mouth of the pitcher plant (Sarracenia purpurea) invites unsuspecting insects to their death.

Bogs are strange communities, not quite aquatic, not quite solid ground. The constant presence of low levels of water leaches nutrients from the soil, making the habitat extremely poor in minerals, particularly nitrogen. Some plants can fix atmospheric nitrogen thanks to a symbiotic relationship with cyanobacteria in their root system, but most need to find another way, and some do so by becoming carnivorous. I looked around and just a couple of feet from where my cricket was happily singing sat a gaping mouth of the pitcher plant (Sarracenia purpurea). The plant was half hidden in the moss, the lower lip of its pitcher conveniently at  ground level, its entrance inviting to any cricket looking for a hiding place or something to eat. The bottom of the pitcher was dark with half-digested bodies of insects, a few still floating on the surface. The lip’s surface was covered with backward-pointing spines, making it easy for an insect to walk in, but virtually impossible to leave. It was as if you walked into your local grocery store, only to realize that you are in the Little Shop of Horrors.

Unlucky insects and arachnids being digested in the pitcher.

Unlucky insects and arachnids being digested in the pitcher.

In addition to bladderworts and pitcher plants, Ponkapoag Bog is a great place to see honeydews (Drosera rotundifolia). Unlike pitcher plants, which lure and drown insects, sundews actively grab them with their sticky, glandular tentacles that cover their modified leaves. They mostly catch small midges and gnats, but I saw one plant successfully capture a pretty big damselfly using two of its leaves at once. Of course the insect must first touch the plant, but once it does, it is pretty much doomed as the leaves curl and immediately start digesting the prey. I often complain that our huge body size prevents humans from appreciating most of the richness and beauty of the natural world, but carnivorous plants are another reason to think that maybe it is not such a bad thing after all.

Purple pitcher plant (Sarracenia purpurea) from Ponkapoag Bog, MA. The color of the plant is an indirect indication of the availability of nitrogen – the greener the plant, the more nitrogen is present in its environment. A recent study demonstrated that pollution by synthetic fertilizer makes carnivorous plants less interested in insects and more reliant on nitrogen dissolved in the water.

Purple pitcher plant (Sarracenia purpurea) from Ponkapoag Bog, MA. The color of the plant is an indirect indication of the availability of nitrogen – the greener the plant, the more nitrogen is present in its environment. A recent study demonstrates that pollution by synthetic fertilizer makes carnivorous plants less interested in insects and more reliant on nitrogen dissolved in the water.

The pitchers of S. purpurea are its modified leaves, not flowers. Its true and remarkably beautiful flowers appear in the late spring and, unlike the pitchers, are insect-friendly.

The pitchers of S. purpurea are its modified leaves, not flowers. Its true and remarkably beautiful flowers appear in the late spring and, unlike the pitchers, are insect-friendly.

Sundew (Drosera rotundifolia) from Ponkapoag Bog, MA with two half-digested midges.

Sundew (Drosera rotundifolia) from Ponkapoag Bog, MA with two half-digested midges.

Even an insect as big as a damselfly can fall victim to a sundew.

Even an insect as big as a damselfly can fall victim to a sundew.

The chorus grows

A singing male Handsome trig (Phyllopalpus pulchellus)

A singing male Handsome trig (Phyllopalpus pulchellus)

On this sunny Columbus Day I stayed at home, which allowed me to discover another beautiful musician in my garden’s chorus, the Handsome Trig (Phyllopalpus pulchellus) (also known as the Red-headed Bush Cricket). I already wrote about this species, but I never suspected that I would find one of my favorite North American orthopterans in my very own garden. Around noon I noticed a cricket song that I had never heard around my house before. Armed with a directional microphone and a net I followed the twitter, and found him singing from the upper surface of a large leaf, about 6 feet above the ground. This finding brings the number of crickets found around my house to 11:

Handsome trig (Phyllopalpus pulchellus)
Say’s trig (Anaxipha exigua)
Carolina ground cricket (Eunemobius carolinus)
Allard’s ground cricket (Allonemobius allardi)
Striped ground cricket (Allonemobius fasciatus)
Two-spotted tree cricket (Neoxabea bipunctata)
Snowy tree cricket (Oecanthus fultoni)
Spring field cricket (Gryllus veletis)
Fall field cricket (Gryllus pennsylvanicus)
Eastern ant cricket (Myrmecophilus pergandei)
House cricket (Acheta domesticus) (introduced)

Sonogram of the Handsome trig (Phyllopalpus pulchellus); click here to listen to the recording.

Sonogram of the Handsome trig (Phyllopalpus pulchellus); click here to listen to the recording.

A male Handsome trig (Phyllopalpus pulchellus)

A male Handsome trig (Phyllopalpus pulchellus)

Music in my head

Male Carolina ground crickets (Eunemobius carolinus) are the hardiest of all my garden's musicians, and may continue to woo females with their song well into late November.

Male Carolina ground crickets (Eunemobius carolinus) are the hardiest of all my garden’s musicians, and may continue to woo females with their song well into late November.

I have always wanted to be a musician. Not that I have any particular musical talents (and never learned to read music), but my fascination with sound was definitely one of the reasons for becoming an expert in the taxonomy of orthopteroid insects, nature’s preeminent musicians. Few things are more pleasant to me than sitting on the deck of our house near Boston on a warm summer evening – a high frequency sound recorder in one hand, a glass of gin & tonic in the other – and getting lost in the hypnotic chorus of about a dozen species of katydids and crickets that share our garden with us. (The best part of this activity is that I can call it “data collecting”.) Now that the summer is sadly over, all I have is the memory of beautiful garden soundscapes, and a bunch of recordings. There are still some strugglers out there – just the other night I found a Sword-bearing conehead (Neoconcephalus ensiger) singing on the lawn in front of our house – but let’s face it, it will be very quiet very soon. And thus I thought that this might be a good time to put all of this year’s recordings together into one composite soundscape, and relive the aural painting that I am privileged to experience every summer.

Some of the cricket species I recorded in or near my garden. The number under each name represents the sequence of joining the musical performance in the composite recording below.

Some of the cricket species I recorded in or near my garden. The number under each name represents the sequence of joining the musical performance in the composite recording below.

Some species, such as the ubiquitous Carolina ground cricket (Eunemobius carolinus), produce calls that are not especially musical, but rather reminiscent of a buzz made by overtaxed power lines. Others, like the Treetop bush katydid (Scudderia fasciata), make irregular, high frequency clicks that show no discernible rhythm. But, as I listen to the evening’s ambience, a repeating pattern begins to emerge. Snowy tree crickets (Oecanthus fultoni) stridulate in a way that is both highly rhythmical and melodious (Joni Mitchell fans will recognize this species in the song “Night Ride Home”), while the frequency-modulated chirps of Field crickets (Gryllus veletis) add a nice, if somewhat irregular, punctuation.

Some of katydid neighbors. Just like with the crickets, the number under each name represents the sequence of joining the musical performance in the composite recording below.

Some of katydid neighbors. Just like with the crickets, the number under each name represents the sequence of joining the musical performance in the composite recording below.

As the night falls more and more species join in. A Two-spotted tree cricket (Neoxabea bipunctata) utters short, piercing cries, usually in sonic pairs, sometimes in series of threes or fours. And although I cannot hear it, I know that the Drumming katydid (Meconema thalassinum), a relatively recent arrival to North America from Europe, is banging one of his hind legs against the bark of the large oak in our garden, creating a percussive line for the rest of the ensemble. Why this species has lost its ability to stridulate and instead evolved a drumming behavior is a mystery, but it is likely that the shift was driven by either a predator or a parasite the had used its (originally) airborne calls to find the singing males and do unspeakable things to them.

And finally, later at night (and later in the season), the True katydid (Pterophylla camellifolia) adds its voice to the chorus. This spectacular insect, whose song is recognizable to anybody who’s ever lived on the East Coast of the US, is the northernmost member of a largely tropical lineage of katydids, the Pseudophyllinae. Despite them being very large and remarkably common insects (you can hear true katydids in the middle of Boston and other large cities), few people ever get the chance to see one – they spend their entire lives high in the canopies of the tallest trees, and are encountered only occasionally, for example when a gust of strong wind knocks them down onto the ground. I have lived surrounded by True katydids for the last 20 years, but can count all my encounters with them on the fingers of one hand. Incidentally, if you ever wondered where the word “katydid” came from, listen to this species’ call. The more northern populations (and thus the ones that the Pilgrims first heard, and apparently were afraid of) have a call consisting of 2-4 syllables that can be interpreted as the sound “ka-ty-did” (or, as the legend goes, “katy-she-did-it”, thus betraying the identity of some murderous lady).

My foot has been tapping since the tree crickets started calling, and now, with the strong beat of the True katydid, I can’t help but imagine melodic lines filling the spaces in between the pulses. I sip my drink and let the mind wander.

A sonogram of a composite recording of most of the orthopteran species singing in my garden. On a good night I can hear them all, but here I decided to add them one by one to the recording to make each species' song stand out. Click here to listen to this soundscape. Please note that some species (esp. Scudderia and Microcentrum) may not be audible to a certain group of listeners (I am talking about you, men 35 or older; I count myself incredibly lucky for still being able to hear all my local species – but who knows for how long). It will help if you listen to this recording through headphones or external speakers; most built-in computer speakers may not be able to reproduce all frequencies (esp. the low frequency drumming of Meconema). (If you would like to see an animated sonogram with species names appearing as they join the chorus, click here; it is a large file, suitable only for a fast connection.)

A sonogram of a composite recording of most of the orthopteran species singing in my garden. On a good night I can hear them all, but here I decided to add them one by one to the recording to make each species’ song stand out. Click here to listen to this soundscape. Please note that some species (esp. Scudderia and Microcentrum) may not be audible to a certain group of listeners (I am talking about you, men 35 or older; I count myself incredibly lucky for still being able to hear all my local species – but who knows for how long). It will help if you listen to this recording through headphones or external speakers; most built-in computer speakers may not be able to reproduce all frequencies (esp. the low frequency drumming of Meconema). (If you would like to see an animated sonogram with species names appearing as they join the chorus, click here; it is a large file, suitable only for fast internet connections.)

A song of ancient Earth

The Greater Grig (Cyphoderris monstrosa) from the Pacific Northwest.

The Greater Grig (Cyphoderris monstrosa) from the Pacific Northwest.

Those who have been reading this blog with some regularity may have noticed that I find virtually all organisms equally fascinating. But some are more equal than others, and few animals and plants excite me more than phylogenetic relics. These are the last remaining members of lineages that were once dominant, or at least species-rich, but are now represented by only one or a few surviving species, species that still carry the old (plesiomorphic) versions of many of the organism’s characters. Such relics are often relegated to living in places that are inhospitable to their evolutionarily younger relatives, but are able to thrive thanks to their ability to handle extreme conditions (albeit this ability is often a relatively recent development). And though I am now in Gorongosa National Park, a place bursting with all kinds of fantastic African wildlife, before I resume my Mozambique Diary I first must recount an interesting encounter with a Mesozoic singing relic that I had only a few days before leaving for Africa.

Tall Mountain hemlock (Tsuga mertensiana) are the preferred singing perches of C. monstrosa.

Tall Mountain hemlocks (Tsuga mertensiana) are the preferred singing perches of C. monstrosa.

Nobody really knows who the first animal singers were. Chances are that the first acoustically active animals were aquatic — grunting placoderm fish, stridulating trilobites, or perhaps pincer-snapping eurypterid sea scorpions — they all have modern equivalents that produce sound underwater. But on land the first organisms that broke the silence were almost certainly small arthropods, whose bodies, encased in rigid plates and tubes of the chitinous exoskeleton, were perfectly suited to become percussive instruments. It is quite likely that a defensive sound production was the initial reason for the evolution of animals’ acoustic behavior, but it did not take long for them to start using sound as an effective attractant during courtship. The unquestionable leading voices of invertebrate love chorus are, and probably have always been, the orthopteroid insects – katydids, crickets, and grasshoppers. Their Permian and Triassic ancestors already had quite sophisticated sound-producing organs on their wings and must have dominated the soundscapes of the Pangean supercontinent. Wings of these fossil insects are often preserved with exquisite detail, allowing us to speculate about the kind of sound they made, and who their modern successors might be. In fact, thanks to a recent study by Jun-Jie Gu you can now listen to a Jurasic song of a katydid ancestor. A handful of direct descendants of these ancient singing insects, members of the largely extinct Mesozoic family Prophalangopsidae, or grigs, are still alive today, and their songs are quite similar to those of their long-gone forbearers.

Male Greater grigs usually call while sitting upside down directly on the tree trunk, which makes it easier for females to find them. Males are highly territorial and will defend their singing perches from other males.

Male Greater grigs usually call while sitting upside down directly on a tree trunk, which makes it easier for females to find them. They are highly territorial and will defend their singing perches from other males.

A few species of grigs can be found in cold, mountainous habitats of eastern Siberia and central China, and three additional ones live in the mountains of western US and Canada. Virtually nothing is known about the Asian species, but the North American ones have inspired research for decades, and we now know more about their behavior than about that of almost any other singing insect on the planet. And what fascinating behavior it is — these innocent-looking insects combine the love of freezing weather and cannibalism with a lust for virgins.

Last week I was in Seattle and decided to try my luck at finding the largest North American grig, Cyphoderris monstrosa. I had precious little time to do this and thus my only option was to look for it in the Cascades, about 70 miles E of the city. Alas, all I had to go by was a single record from 1909, with a vague description of the locality called Stampede, and I figured that it had to be the same place as what is now known as the Stampede Pass, an area covered with thick forest of hemlocks and pines on steep mountain slopes – just the right place for grigs. I got there in the early afternoon but the place did not look particularly inviting – every single road sign was pockmarked with shotgun blasts, what I took for colorful flowers on a meadow turned out to be piles of shotgun and handgun shells, and nearly all roads leading to what looked like a promising grig habitat had a “No trespassing” sign. Hoping that I will make a difficult target in a rainy night I decided to wait until dark and then search for the insects.

The Sagebrush grig (Cyphoderris strepitans) from Wyoming is found low to the ground in sagebrush meadows of the Rockies.

A closely related species, the Sagebrush grig (Cyphoderris strepitans) from Wyoming, is found low to the ground in sagebrush meadows of the Rockies.

The first grig started calling around 10 pm. His call was a high-pitched but rather pleasant warble, somewhat akin to the ring of an old-fashioned telephone. It was coming from a tall hemlock, and I had no other option but to start climbing. Thankfully, grigs are not particularly skittish, and once I located the male I had no troubles getting close to him. I recorded his call and then quickly grabbed him.

In the majority of the animal kingdom the male provides little more than reproductive cells that inseminate the female’s eggs, and hence the profusion of elaborate displays of masculine virility designed to convince the female of the male’s good genes, rather than his suitability for lasting partnership or shared investment in offspring. Usually, all the gullible female gets is a brief, entertaining show and the knowledge that she will never see the guy again. Not so in grigs. The females in these animals want to take home more than just a memory of a good time; they also demand a decent meal, something that will significantly contribute to the production of eggs. Because grigs literally live in their food, a male offering a piece of hemlock or pine, no matter how fresh and tasty, would certainly be given a cold shoulder. Having nothing else to give, the males are forced to make the ultimate sacrifice — they offer females parts of their own bodies to dine on. Like most insects, male grigs have two pairs of wings. The first pair, slightly hardened and modified into sound organs, is used to produce a song that guides the female to him. The second pair, however, is somewhat dispensable, and it has evolved into a pair of big, fleshy organs filled with the male’s blood (hemolymph), and this is what the female grigs lust for.

During mating the male locks the female in place on his back with an insidious trap on the tip of his abdomen. Female grigs are completely wingless.

During mating the male grig locks the female in place on his back with an insidious trap on the tip of his abdomen. Female grigs are completely wingless.

Once a female locates an interested male, she climbs on his back and immediately starts devouring his wings. While she is busy with her cannibalistic hors d’oeuvre, the male attaches his reproductive organs to those of the female and transfers a packet of sperm. He also leaves with the female a package of nutritious carbohydrates and proteins, known as the spermatophylax, which the female consumes after the mating. It seems that the role of these nuptial gifts is to ensure that the sperm he delivered has enough time to get where it needs to, and it also precludes her from mating again with another male, at least until she is done eating. More importantly, his edible wings and the spermatophylax provide the female with nutrients that she will be able to use to produce her eggs, making the male an active and invested participant in parenthood.

This singing Sagebrush grig male has already lost his virgin hind wings, and must count on the females' inability to distinguish his call from that of a virgin male.

This singing Sagebrush grig male has already lost his virgin hind wings and must count on the females’ inability to distinguish his call from that of a virgin male.

Although both the male and the female will soon be ready to mate again, the male now has a problem — he is not ready to retire quite yet, but he no longer has the tasty wings that attracted his first partner. Luckily for him females are not very good at distinguishing the song of an unmated male from that of one who has already lost his virgin wings (but there is evidence that the females preferentially mate with virgins). And once she climbs the back of a male and realizes that he no longer carries the tasty snack, it is too late. Male grigs have evolved an ingenious, if somewhat insidious, device on their abdomen, appropriately called the gin trap, which effectively locks the female in place and gives him extra time to transfer his reproductive cells. It takes a female a considerable amount of effort to disengage from the male, and there is plenty of time for him to pass on his genes.

I stayed in the forest until midnight, tracking, recording, and photographing grigs. By that time the temperature had dropped significantly and a freezing rain was pouring, which made for very compelling arguments to get back into the car and drive back to Seattle. But I was giddy with excitement of having found the grigs and, an unexpected bonus, not having been shot at.

A portrait of the Greater grig (Cyphoderris monstrosa).

A portrait of the Greater grig (Cyphoderris monstrosa).

Two males of C. monstrosa calling. Click here to listen to the recording.

Two males of C. monstrosa calling. Click here to listen to the recording.

Say’s trig

A male and a female of the Say's trig (Anaxipha exigua) from Woburn, MA.

A male and a female of the Say’s trig (Anaxipha exigua) from Woburn, MA.

Yesterday my wife called me – “You need to come to Mahoney’s [our local garden center], there are tree crickets on every Holly bush.” I promptly grabbed a few containers and was there in a matter of minutes. And indeed, the place was resonating with soft, bell-like calls of dozens of crickets, but I did not recognize the species. I spent about 20 minutes looking for them, eliciting confused stares from the staff and customers, but could not locate any singing males. In desperation I shook a few bushes, and eventually a female tree cricket (Oecanthus) flew out of one. But I was not convinced that this was the genus that was singing there; the call was just not very tree cricket-like.

I returned the following evening, armed with a shotgun microphone and headphones, intent on locating the callers. The staff of the center was apparently on the verge of kicking me out after watching me waving the long microphone around the shrubs like some deranged Dumbledore wannabe, but Kristin managed to placate them and so they left me alone. But even with the ability to pinpoint each caller, finding the crickets was very tricky, and it took me almost an hour to finally catch a couple.

The call of the Say's trig (click here to hear it).

The call of the Say’s trig (click here to hear it)

The mystery insects turned out to be not tree crickets but much smaller, and orders of magnitude more agile, Say’s trigs (Anaxipha exigua), named after Thomas Say, the prolific 19th century entomologist and malacologist, and the discoverer of this species. I had never seen a Say’s trig before, and was happy to add both the recording and photos to my database of local orthopterans. Anaxipha is a large genus of the cricket subfamily Trigonidiinae, with 135 described and a bunch of yet undescribed species, found mostly in the tropical and subtropical parts of the globe. The Say’s trig, along with the Handsome trig (Phyllopalpus pulchellus), is one of the few species of the group reaching as far North as Massachusetts. The call of the Say’s trig is an almost pure tune trill, with the loud portion at exactly 7 kHz, and a softer harmonic at 14 kHz (click here to listen to the recording).

Helmeted katydids

Helmeted katydid (Phyllophora boschami) from Pogera gold mining camp in the Enga Province of Papua New Guinea.

Helmeted katydid (Phyllophora boschami) from Pogera gold mining camp in the Enga Province of Papua New Guinea.

Porgera, a gold mine in the highlands of Papua New Guinea, is not a pleasant place for a biologist, especially if you are aware of the massive environmental damage of its operations, or the frequent human right violations that this mining camp is known for. But we had no choice but to sleep with the enemy, and ask for the mine’s help in helicoptering us into the remote highlands of PNG where our team was surveying animals and plants. Luckily, the heavily guarded fortress of Porgera had one redeeming quality – at night I was allowed to wander around our sleeping quarters and look for insects. This, being New Guinea, guaranteed that even a place as dismal as a mining camp was bound to reward me with something interesting. And I was not disappointed – not only did I find a lot of insects, but one of them turned out to be new to science. (Yes, I am aware of the irony of a mining camp being the type locality and the site of the only known population of Pandangraecia porgera Naskrecki and Rentz, 2010.) But the insect that really stood out in the crowd was a katydid Phyllophora boschmai, a member of a remarkable lineage of my favorite insects.

The body of helmeted katydid nymphs, like in this Phyllophora sp. from Eastern Highlands Province of PNG, is almost entirely covered by the helmet-like pronotum.

The body of helmeted katydid nymphs, like in this Phyllophora sp. from the Eastern Highlands Province of PNG, is almost entirely covered by the helmet-like pronotum.

The Phyllophorinae, known as the helmeted katydids (the names hooded katydids or box katydids are also used) are found primarily on New Guinea and nearby islands, although a handful of species venture into northeastern Australia, and a few places in the Philippines, Sri Lanka, and Taiwan. What immediately sets them apart is their size – many species are massive, and one, Siliquofera grandis, is the largest living katydid, with the wingspan of over 8 inches (20 cm)! Their morphology is also unusual – the pronotum, the part of the thorax immediately behind the head, is greatly expanded into a huge, helmet-like structure that covers the thorax and parts of the wings; in nymphs the pronotum may cover the entire body. This type of the pronotum usually indicates that the katydid is an exceptionally loud singer since the pronotum can act as a resonator and an amplifier of the call produced by the sound-producing apparatus at the base of the wings. But this is where things get interesting. If you were to peek under the huge pronotum of a helmeted katydid, you would find nothing. No sound-producing organs, no stridulatory file, nothing. These katydids cannot sing.

Some helmeted katydids, such as this Sasima versteegi from the Western Province of PNG, are huge.

Some helmeted katydids, such as this Sasima versteegi from the Western Province of PNG, are huge.

It appears that the huge pronotum is there solely as a defensive mechanism, protecting the softer, more vulnerable parts of the body. Why helmeted katydids have lost the ability to sing is still a mystery, especially considering the fact that they are a highly derived group, closely related to some of the loudest singers in the family, the Mecopodinae. But the real question is, how do males and females find each other?

In katydids, the acoustic communication – attracting each other with a song produced by rubbing their wings – is the only way (that we know of) for the two sexes to get together as these insects lack pheromonal communication or any other way to send long distance signals (some katydids use substrate vibrations to communicate, but this only works over short distances). But helmeted katydids are not entirely silent, either. They have evolved unique stridulatory structures at the base of their legs that allow them to produce loud, rustling noises, which both males and females use as a defense mechanism if they happen to be assaulted by a predator (click here to listen to the defensive stridulation of a helmeted katydid). These structures, however, cannot be used to attract the opposite sex in the dense vegetation of the New Guinea rainforest, and the mechanism by which the sexes locate each other is completely unknown.

The sternocoxal stridulatory apparatus of a helmeted katydid. The first segment (coxa) of the last pair of legs is covered with dense, parallel ridges that rub agains a series of pegs on the surface of mesosternal lobes on the ventral side of the thorax. The sound produced in this way is noise-like, typical of a defensive stridulation.

The sternocoxal stridulatory apparatus of a helmeted katydid. The first segment (coxa) of the last pair of legs is covered with dense, parallel ridges that rub agains a series of pegs on the surface of mesosternal lobes on the ventral side of the thorax. The sound produced in this way is noise-like, typical of a defensive stridulation.

But it wouldn’t be, if only I had the presence of mind to watch them more closely. While in Papua New Guinea I captured a male and a female of Phyllophora sp., and placed them in a large mesh cage. I kept looking at the pair, waiting for something to happen, but then it was dinner time and I was hungry and, long story short, when I came back the two were already relaxing with a cigarette in hand – I missed the whole thing! And it probably was quite a spectacle – I knew that they had successfully mated because the female now carried what looked like a pair of white testicles, a nuptial gift from the male. In many katydid species the male produces a similar gift, known as the spermatophylax, that the female later consumes. Why they do it is another story, but in an essence this is to prevent her from mating with another partner, and to ensure that the male’s sperm has time to enter her body. In this way the edible spermatophylax, which encapsulates a pair of small vesicles containing sperm, is indeed, from the functional point of view, a pair of autonomous testicles that the male attaches to the female.

What looks like a pair of testicles at the base of a female's ovipositor is the spermatophylax, a nuptial gift produced by the male during mating. It consists mostly of nutritious carbohydrates and proteins, and is subsequently consumed by the female. Its presence ensures that the male's sperm has enough time to enter the females genital opening, and effectively prevents her from mating with another partner, at least for some time. The nutrients in the spermatophylax also contribute to the fitness of his and her offspring.

What looks like a pair of testicles at the base of a female’s ovipositor is the spermatophylax, a nuptial gift produced by the male during mating. It consists mostly of nutritious carbohydrates and proteins, and is subsequently consumed by the female. Its presence ensures that the male’s sperm has enough time to enter the females genital opening, and effectively prevents her from mating with another partner, at least for some time. The nutrients in the spermatophylax also contribute to the fitness of his and her offspring.

And so the mechanism of the helmeted katydids’ long range communication remains a mystery. I never had a chance to watch these insects again, but hope to be able to return to New Guinea at some point, and finally document their courtship ritual, dinner be damned.

P.S. David Rentz, who also participated in the PNG katydid survey, has revised Australian Phyllophorinae, and wrote a post about these insects on his excellent blog BunyipCo.

Although mostly nocturnal, some species, such as this Phyllophora sp. from New Britain, can be found during the day on understory vegetation.

Although mostly diurnal, some species, such as this Phyllophora sp. from New Britain, can be found during the day on the understory vegetation.

A molting female of Phyllophorella woodfordi from the Solomon Islands.

A molting female of Phyllophorella woodfordi from the Solomon Islands.

A nymph of Sasima versteegi is a perfect mimic of mossy vegetation of the humid, lowland rainforest on New Guinea.

A nymph of Sasima versteegi is a perfect mimic of mossy vegetation of the humid, lowland rainforest of New Guinea.

Mozambique Diary: A talking grasshopper

A male Cataloipus cognatus munching on grass. [Canon 6D, Canon 100mm macro, 3 x Canon 580EXII]

A male Cataloipus cognatus munching on grass. [Canon 6D, Canon 100mm macro, 3 x Canon 580EXII]

One of the most endearing characteristics of grasshoppers is their ability to produce sound. Some of the most wonderful memories of my childhood include sitting in a meadow bursting with sounds of insects and watching grasshoppers use their hind legs to produce soft, rhythmical songs, and not realizing that a seed that would eventually blossom into a full-blown career in entomology is sprouting in my brain.

Despite the strangely persistent misconception, the sound of grasshoppers is not produced by rubbing their legs together (in fact, no insect makes sound in this way), but rather by dragging the inner side of the hind femur against a thick vein on the front wing (depending on the group, either the femur or the vein is armed with a row of stridulatory pegs). But this ability to produce loud songs is far less common among grasshoppers than it may appear to somebody who grew up in Europe, one of the few places in the world where members of the vociferous subfamily Gomphocerinae dominate the grasshopper fauna. I was surprised how few grasshoppers sing in North American or Australian meadows, and tropical grasshoppers of South America and Africa are almost all silent.

Females of C. cognatus are much larger than the males; they are also completely silent, whereas males produce a loud mandibular stridulation. [Canon 6D, Canon 100mm macro, 3 x Canon 580EXII]

Females of C. cognatus are much larger than the males; they are also completely silent, whereas males produce a loud mandibular stridulation. [Canon 6D, Canon 100mm macro, 3 x Canon 580EXII]

I was therefore quite startled when I caught yesterday in Gorongosa a beautiful grasshopper Cataloipus cognatus, and the insect responded to this violation of its freedom by producing loud and persistent squeaks. It took me a while to discover how the sound was produced. At first I thought that it was using its hind legs to make the sound, but this lineage of grasshoppers (Eyprepocnemidinae) lacks stridulatory pegs on their legs, and besides, I was holding it by the legs and thus it couldn’t use them even if it wanted to. Looking closely I realized that the grasshopper’s sound was coming from its mouth. I knew of a katydid species that was capable of stridulating with its mandibles, but had no idea that some grasshoppers could also do it.

Just to be sure I caught a few more individuals, and some made the sound while others didn’t. Then I noticed that the silent ones were all females, while all males were producing the sound. Since I don’t have a microscope here in the Chitengo camp (yet, one is coming soon, fingers crossed), I could not look at the structure of the sound-producing apparatus. But I recorded the sound and looked at its oscillogram, which revealed a clean, evenly spaced pattern of pulses, which is indicative of the presence of a distinct stridulatory file. This, combined with the fact that only males produce sound, seems to suggest that the sound might be used not only as a defensive signal, but rather that it may play a role in courtship. If this true, and I will try to confirm it by watching the courtship behavior of this species, it would make a very interesting case of independent evolution of courtship stridulation in eyprepocnemidine grasshoppers.

An oscillogram of the mandibular stridulation of C. cognatus; click here to listen to the sound.

An oscillogram of the mandibular stridulation of C. cognatus; click here to listen to the sound.