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Mozambique Diary: Sylvan katydids of Gorongosa

Apr8
Male Elegant sylvan katydid (Acauloplax exigua) in his typical resting position.

Male Elegant sylvan katydid (Acauloplax exigua) in his typical resting position.

A few nights ago, as I was walking towards my cabin along the edge of the Chitengo Camp, I heard a call of a cricket that I did not quite recognize. Cricket calls are unmistakable for their clean, almost melodious quality, very different from the call of a cicada or a katydid, which tend to be more “noisy.” But his call was very pure, almost bird-like, and it was coming from high in a tree. I expected to find a black, wide-winged Homoeogryllus cricket among the leaves, but to my delight the mystery caller turned out to be a gorgeous Blue-legged sylvan katydid (Zabalius ophthalmicus). This and a few related species produce some of the most pure tone, almost whistle-like calls, a rarity among katydids.

Sylvan katydids (Pseudophyllinae) are uncommon in this part of the continent. The greatest diversity of these insects is found in the rainforests of Central and West Africa, where most live high in the canopy. In Mozambique I expected to find only four species, and indeed found them all in Gorongosa (which of course is not to say that more are not to be discovered.) Virtually all sylvan katydids, true to their common name, are associated with forests and other woody habitats, and few are found in the open savanna.

Southern African sylvan katydids display two very distinct types of mimesis (camouflage). Species found in the canopy of broad-leaved trees (e.g., Ficus) are superb mimics of foliage, complete with leaf-like venation of their wings and fake fungal spots or other “damage.” During the day they rest with their wings spread flat against the lower surface of the leaf, and are absolutely impossible to find. (Interestingly, this type of behavior does not occur in any katydid species found in the New World – all North and South American katydids hold their wings in a vertical position, and during the day rest on twigs with their wings facing up in an imitation of a small leaf.)

Greater bark katydid (Cymatomerella spilophora)

Greater bark katydid (Cymatomerella spilophora) in the woodland of Gorongosa

The second group of species of Mozambican sylvan katydids are bark mimics. These species are associated with more open habitats, mostly miombo or mopane woodland, and spend the day resting on trunks of small-leaved trees, such as Acacia or Brachystegia. Their wings are held similarly flat against the bark, and their coloration is mottled, resembling the surface of the trunk. In addition, their legs are strongly flattened and covered with dense hairs, which helps them eliminate the shadow cast by their bodies.

One of the Mozambican species, The Common bark katydid (Cymatomera denticollis), is unusual among katydids in its ability to produce chemical defenses. Production of repellant chemicals has been documented in a few Neotropical species, but this is the first example of such a behavior in an African species. These insects, when threatened by a predator, fan their wings and reveal a brightly colored, red, orange, and black abdomen. At the same time a gland on their abdomen sprays a strongly smelling liquid. I have had no chance to look into the chemical composition of this substance, but its smell is very much reminiscent of that produced by their (unrelated) South American counterparts. In those katydids the repellant substances were identified as methylpyrazines, and I would not be surprised if the African species produced related compounds.

A song of the Blue-legged sylvan katydid (Zabalius ophthalmicus). Click here to listen to the recording: first played at the normal speed, followed by a fragment slowed down by a factor of 10 (for the katydid-challenged listeners, i.e., most males over 35).

A song of the Blue-legged sylvan katydid (Zabalius ophthalmicus). Click here to listen to the recording: first played at the normal speed, followed by a fragment slowed down by a factor of 10 (for the katydid-challenged listeners, i.e., most males over 35).

Female Elegant sylvan katydid, showing fake leaf damage and leaf-like venation on her wings.

Female Elegant sylvan katydid, showing fake leaf damage and leaf-like venation on her wings.

Sylvan katydids of Gorongosa in their typical daily resting poses: Blue-legged sylvan katydid (Zabalius ophthalmicus), Elegant sylvan katydid (Acauloplax exigua), Common bark katydid (Cymatomera denticollis) and Greater bark katydid (Cymatomerella spilophora).

Sylvan katydids of Gorongosa in their typical daily resting poses: Blue-legged sylvan katydid (Zabalius ophthalmicus), Elegant sylvan katydid (Acauloplax exigua), Common bark katydid (Cymatomera denticollis) and Greater bark katydid (Cymatomerella spilophora).

Mozambique Diary: Back in Gorongosa

Mar18

One of the first katydids I spotted was Horatosphaga serrifera, and elusive species, knwon only from a small handful of specimens. This group is highly sexually dimorphic and males look nothing like this chunky, flightless female. [Canon 14mm, Canon MT 24EX twin light]

One of the first katydids I spotted was a female of Horatosphaga serrifera, an elusive species, known only from a small handful of specimens. This group of katydids is highly sexually dimorphic and males look nothing like this chunky, flightless female. [Canon 14mm, Canon MT 24EX twin light]

Yesterday I arrived in the spectacular Gorongosa National Park in Mozambique. Last time when I was here the place was dry and dusty, but now, at the end of the rainy season the luxuriant vegetation is vibrantly green and after the misery of Boston’s winter the air feels throat-soothingly humid. During the day Gorongosa’s woodlands vibrate with calls of cicadas and grasshoppers, while nights are thick with crickets and frogs, randomly punctuated with blood-curling screams of a bushbaby. On my first stroll after dark I counted eleven species of praying mantids, and immediately ran into three species of katydids that I had not seen during my previous visit. Sandy paths around the main camp of the park are Roman arenas full of carnage indiscriminately dispensed by solifugids and giant Anthia beetles. Every lightbulb along the camp’s roads is dimmed with clouds of moths, dung beetles, and ants, and under each one sits a fat toad, gorging on the seasonal manna. It is heaven.

The purpose of my visit to Gorongosa is to lead a month-long survey of plants and animals of the Cheringoma Plateau, the poorly explored eastern rim of the Great African Rift Valley, of which Gorongosa is the southernmost tip. In a few weeks a large group of biologists will descend on the park, and trap, record, photograph, sample, measure, weigh, track, trace, and triangulate every plant, mammal, bird, reptile, frog, dung beetle, ant, katydid, and praying mantis living here. We will leave no stone unturned, no twig unchecked for ants, and no pile of dung uninspected for beetles. I will not be surprised if, once all the collected material is processed and identified, we might be able to double the number of species recorded from Gorongosa, which currently stands at 1,790 confirmed animals and plants. But before this happens there is still a lot of work to do and tomorrow Marc Stalmans, Gorongosa’s chief scientist and I are leaving on a reconnaissance trip to select the survey’s camp sites.

As a scientist I am absolutely giddy with excitement about what we will find and document, and as a nature photographer I am itching to point my lens at everybody and everything that crosses our path on the Cheringoma Plateau. In preparation for this unique opportunity I had packed my brand spanking new Canon 400mm; a cool new gizmo called NeroTrigger to remotely capture elusive nocturnal animals; a battery of flashes and macro lenses; and a waterproof housing for my camera to get some shots of the underwater life. All in all, really great gear. It is thus rather unfortunate that all of it was lost on my way to Mozambique. South African Airlines gladly took my luggage and a big wad of cash for the extra piece, but somehow forgot about the delivery part of the deal. There is a big Pelican case with $12,000 worth of gear floating somewhere in the nether regions of the aviation industry, and I can only hope that at some point it will resurface and I am reunited with my beloved gear. In the meantime I will make do with what I have, perhaps the limitations of my current gear will spur me to be more creative. Watch this space.

Below my feet, carnage. A big Anthia ground beetle killed another individual and is now gorging on it favorite soft part – the ripped off genitalia. [Canon 180mm, Canon MT 24EX twin light]

Below my feet, carnage. A big Anthia ground beetle killed another individual and is now gorging on it favorite soft part – the ripped off genitalia. [Canon 180mm, Canon MT 24EX twin light]

Coneheads

Mar1

A portrait of Brown-faced Spearbearer (Copiphora hastata) [Nikon D1x, Sigma 180mm]

A portrait of Brown-faced Spearbearer (Copiphora hastata) [Nikon D1x, Sigma 180mm]

A fact that entomologists are well aware of, but one that usually comes as a surprise to everybody else, is that most insect species are still unknown to science, and only a relatively small portion of them have been formally named and described. According to recent estimates only about a quarter of currently living species have the distinction of being assigned official, scientific names, and millions (millions!) of species, most of them insects, remain unnamed and unseen. I kind of knew that, but I still did not expect that the very first, very common conehead katydid that I saw during my first visit to Costa Rica, unquestionably the best biologically explored Neotropical country, would turn out to be new to science. And yet it was. I subsequently named it Copiphora hastata, or the Brown-faced Spearbearer, on account of the enormous, spear-like ovipositor, which the females of this species use to lay eggs underneath thick layers of accumulated leaves on the rainforest floor.

Central American Pit Bull katydid (Liromoetopum coronatum) lacks the large defensive cone on its head, but makes up for it with sharp, powerful jaws. [Canon 1Ds MkII, Canon 180mm macro]

Central American Pit Bull katydid (Liromoetopum coronatum) lacks the large defensive cone on its head, but makes up for it with sharp, powerful jaws. [Canon 1Ds MkII, Canon 180mm macro]

Conehead katydids (Tettigoniidae: Copiphorini) are some of the most spectacular insects that one is likely to encounter in a tropical rainforest. They are easily recognizable by the presence of a hypertrophied fastigium of vertex or, in other words, a giant cone on the head. The function of the cone varies from species to species. In forms that live in grasslands, the elongated process on the head helps the animal blend in amongst blades of grass, and such species are some of the best plant mimics among katydids. But in arboreal species, especially those that are found high in the trees of the Central and South American rainforest, the cone is a defensive weapon, quite effectively protecting them from aerial attacks by foliage-gleaning bats (Phyllostomatidae). Thanks to this protection, coneheads are some of the few Neotropical katydids that can afford to produce long, continuous calls, which other katydids tend not to do because of the risk of being detected by hunting bats. The situation is rather different in the rainforests of Asia or Africa – those places lack the foliage-gleaning bats, and most katydids serenade to their hearts’ content, and coneheads there usually exhibit rather reduced cephalic armature.

Rhinoceros Spearbearer (Copiphora rhinoceros) is an efficient predator, capable of catching and devouring other katydids and even small lizards [Canon 10D, Nikkor 17-35mm, Canon 580EX]

Rhinoceros Spearbearer (Copiphora rhinoceros) is an efficient predator, capable of catching and devouring other katydids and even small lizards [Canon 10D, Nikkor 17-35mm, Canon 580EX]

The diet of coneheads is quite varied – it often includes seeds, fruits, caterpillars, snails, other katydids, and even small lizards. Their mandibles are usually very sharp and powerful, and coneheads don’t hesitate to use them on potential predators, such as the fingers of an entomologist foolish enough to try to catch one. In fact, Costa Rican Rhinoceros Spearbearer (Copiphora rhinoceros) is one the few insect species that I am a little afraid to handle with my bare hands. Regardless, coneheads are still some of my favorite organisms. In Costa Rica, where I have been studying the katydid fauna for many years, I recorded nearly 60 species of coneheads, over a third of them new to science. Later this year I will be visiting Belize, and there is no doubt in my mind that the place will be teaming with spectacular coneheads. I simply can’t wait to see them.

Vargas' conehead (Podacanthophorus vargasi) is a small canopy katydid, found at middle elevations in Costa Rica [Canon 7D, Canon 100mm macro, 3 speedlights Canon 580EXII]

Vargas’ conehead (Podacanthophorus vargasi) is a small canopy katydid, found at middle elevations in Costa Rica [Canon 7D, Canon 100mm macro, 3 speedlights Canon 580EXI

Brown-faced Spearbearer (Copiphora hastata), a large rainforest species that I discovered on my first visit to Costa Rica [Canon 7D, Canon 100mm macro, 3 speedlights Canon 580EXII]

Brown-faced Spearbearer (Copiphora hastata), a large rainforest species that I discovered on my first visit to Costa Rica [Canon 7D, Canon 100mm macro, 3 speedlights Canon 580EXII]