Remarkable mimicry

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Spider that mimics a frog in our Rio Zunac Reserve. Photo: Lou Jost/EcoMinga.

I’ve been away again, this time gone for almost three weeks with a great group of students from Stanford University led by Dr Margaret (Minx) Fuller. We spent most of our time in the Amazonian lowland rainforest, but I also took them to EcoMinga’s Rio Zunac and Rio Anzu Reserves. Throughout the trip we found amazing examples of mimicry. The most unusual mimic was this spider, which was found by students Dylan Moore and Natalia Espinoza on our Rio Zunac trip. At first they thought it was a frog. It holds its forelegs in a position reminiscent of the hind legs of a frog, and its abdomen mimics a frog head, complete with eyes. I imagine that small birds or insects that would catch a spider might not want to waste energy or risk their lives trying to catch a frog.This spider seems to be related to the famous “bird poop spiders” but I don’t really know. If an arachnologist reads this, perhaps he or she could add some information about this?

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Above and below: Spider that mimics a frog in our Rio Zunac Reserve. Click to enlarge. Photo: Lou Jost/EcoMinga.

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Note added July 26 2017: Andreas Kay in nearby Puyo reports that he has also found this spider twice, and thinks it is in the genus Stephanopis; see his picture here:

https://www.flickr.com/photos/andreaskay/31583234000/in/photolist-Q7UkjN-Q7Uk8f-HpMphQ-HpRUzt-JkQCzc-JkQCbr-HBPABf-HEcfA6-eXy7XX-eXy7Ta-eXKv1S-egc5ed-dmufYw-dmucGX-bVDV1V-bPbYgn-bPbYeX

It is always a pleasure to browse his site, Ecuador Megadiverso.

I found another exquisite mimic in our Rio Anzu Reserve the next day. This leaf-mimic katydid would have passed unnoticed except that when we walked past, it went into its hiding pose and moved its two antennae together so that they appeared as one. That motion caught my attention, but it still took me a minute to see the katydid.

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A leaf-mimic katydid in our Rio Anzu Reserve. Click to enlarge. Photo: Lou Jost/EcoMinga.

The best way to see exotic katydids, grasshoppers, and crickets is to walk in the forest at night. Here are some others we found in the eastern lowlands on this trip.

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Dead-leaf katydid in the Amazon. Click to enlarge. Photo: Lou Jost/EcoMnga.

 

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Grasshopper in the Amazon. Click to enlarge. Photo: Lou Jost/EcoMinga.

 

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Amazonian nymph katydid. Click to enlarge. Photo: Lou Jost/EcoMimnga.

Mimicry is not limited to insects and arachnids, though. Birds can can also disguise themselves. The hardest birds to spot in these forests are the potoos, which look like dead stubs on tree branches. When some species of potoo sense danger, they even lift their heads to point straight up, enhancing the illusion. They sit all day on their chosen perch, and only hunt at night, sallying for large flying insects. The females lay their single egg carefully balanced on the broken-off tip of a branch, and the baby grows up looking just like an extension of the branch.

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Great Potoo. Click to enlarge. Photo: Lou Jost/EcoMinga.

 

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Common Potoo. Click to enlarge. Photo: Lou Jost/EcoMinga.

Thanks for looking,

Lou Jost, EcoMinga Foundation.

Closer videos of sticky chrysomelid beetle feet in action

Here are some more video segments (as GIFs) of the sticky hairy pads of the chrysomelid beetle feet in action. It looks like the beetle can control their stickiness very rapidly. I don’t really understand how. The stickiness is caused by microdroplets of lipids on the tips of the flattened hairs of the pads on each side of the claws. But surely this liquid can’t be emitted and re-absorbed quickly enough to allow the beetle to change from walking to defensive sticking and then back to walking again in the space of a few seconds.

Front foot:

Middle foot:

Hind foot:

Lou Jost
EcoMinga Foundation

Second trip to our Rio Machay Reserve: Orchids, magnolias, tortoise beetles, and toxic trees

Chrysomelid beetle feet in action.  Video: Lou Jost

Chrysomelid beetle feet in action. Video: Lou Jost

A few weeks ago I visited the east ridge of our new Rio Machay Reserve, and found lots of interesting things. I also seemed to get through the visit without touching any Toxicondendron trees (same genus as poison ivy but more virulent), which had caused grave problems to my students and I a decade ago. Encouraged by this, I visited again last week, to search for new Magnolia species and interesting, biogeographically-informative orchids.

I picked a perfect almost-rainless day. The forest was beautiful in the sun, with lots of butterflies and other insects. Right at the start, at about 1600m, I found another beautiful chrysomelid beetle from the tribe Cassidini, a “tortoise beetle” similar to the fancy species I wrote about recently (“An insect that uses its own feces to build a statue of an insect or spider on its back”). This one had a more colorful pattern, which had no obvious function.

The beetle's back pattern. Note the transparent sections of its shell. Photo: Lou Jost/EcoMinga.

The beetle’s back pattern. Note the transparent sections of its shell. Photo: Lou Jost/EcoMinga.

The feet of these Cassidinae beetles are very unusual, with mop-like pads of long oily flattened hairs that stick tightly to even the smoothest surface. When the beetle feels threatened, it sticks tightly to its leaf with these fancy feet, and pulls its shell tight against the leaf surface. The shell extends beyond the feet so there is no place to get a grip on this slippery dome. It can hang on against a force 100 times greater than its body weight.

I’ve been wondering how the beetle detaches the sticky feet from the surface when it wants to walk. From looking at the feet of the previous species, I inferred that the two long claws between the pads could act as a lever to separate the pads from the leaf surface. However, I made that inference based on microscopic observations of the dead beetle’s claws. This new beetle gave me the chance to observe the feet in action.

First I made some microphotos of the feet. The beetle sometimes stood still long enough to take the several hundred photos required to make each final image, though this required a lot of luck and patience. These feet had bigger secondary pads than those of the other species. Then I made a couple of videos of the feet in action. They are too big to include here, but I include a small reduced gif above, and I may put an additional one in a separate post, to keep this post from getting too heavy.

The full-sized video clearly shows that my earlier inference was wrong. The claws aren’t being used as a lever, at least not in the way that I imagined. The feet also pivot freely at times, as if the pads are not always sticky, though sliding might be easy since the surface tension isn’t broken (it is easy to slide a wet piece of glass over another piece of glass, but hard to pull them apart). Some articles had suggested that the beetle can produce the sticky liquid quickly when needed, and that the pads were normally not so sticky. Other people were skeptical of this, and the permanently-wet pads of the other species I photographed suggested that they were always sticky. I still don’t really know.

A miniature woodpecker, Lafresnaye's Piculet, just 9 cm long, smaller than some cigarettes! Photo: Lou Jost/EcoMinga.

A miniature woodpecker, Lafresnaye’s Piculet, just 9 cm long, smaller than some cigarettes! Photo: Lou Jost/EcoMinga.

Also early in my climb I saw a pair of adorable Lafresnaye’s Piculets, tiny little woodpeckers that specialize in pecking the thin terminal twigs of branches where bigger woodpeckers can’t go.

This orchid, Sphyrastylis dalstromii, has unusual leaves and flowers. Photo: Lou Jost/EcoMinga.

This orchid, Sphyrastylis dalstromii, has unusual leaves and flowers. Photo: Lou Jost/EcoMinga.

An unusual orchid, Sphyrostylis dalstromii, first discovered by my friend Stig Dalstrom, hung down from a trunk on the side of the trail. These plants have iris-like dagger-shaped leaves and the stem grows continuously from its tip, unlike most New World orchids which make successive short growths from a rhizome.

Later in my climb to the magnolia trees we’d recently discovered, I found one of the most spectacular Pleurothallis orchids in the world, P. (Elongatia) excelsa. I’d only seen this once before in my life. Most species in this artificial genus have tiny, dull flowers. John Jearrard writes this about the genus: “There is a strange fascination to Pleurothallis which are some of the dullest flowering plants imaginable. There are hundreds of them, actually more than 1000 at present but the number varies as more are found. The number reduces every time a botanist decides that a group aren’t really dull enough to belong, and shunts them off into a new genus. They are confusing, they are dull and they are fascinating.”

This species breaks all the rules of this group of orchids. It is huge, imposing, and spectacular. The plant is several feet tall and the pendant flower stalk is also several feet long. The flowers are enormous compared to the usual species. This plant was apparently not known from Ecuador until I found it here in the 1990’s. It was a real pleasure to see it again. (In a future post I might talk about its proper generic classification, which turns out to be very complicated. I think it is best placed in Elongatia, not Stelis, and certainly not Pleurothallis in any sense of that genus. See my article here for an introduction to problems of the old genus Pleurothallis, and see Wilson et al and Karremans for more technical discussion on the position of this species and its close relatives like “P.” restrepiodes.)

Click here to enlarge.  The mysterious Magnolia tree I found here. I cleared out some of the bamboo which was beginning to overtake it. Some day we may see it flower so we can figure out what it is. Meanwhile we will include it in the laboratory Magnolia propagation project we are doing in collaboration with the Jardin Botanico de Quito and the Universidad Estatal Amazonica, financed by a grant from Botanical Gardens Conservation International. Photo: Lou Jost/EcoMinga.

Click here to enlarge. The mysterious Magnolia tree I found here. I cleared out some of the bamboo which was beginning to overtake it. Some day we may see it flower so we can figure out what it is. Meanwhile we will include it in the laboratory Magnolia propagation project we are doing in collaboration with the Jardin Botanico de Quito and the Universidad Estatal Amazonica, financed by a grant from Botanical Gardens Conservation International. Photo: Lou Jost/EcoMinga.

Above that, at 2200m, I found a couple more of the giant-leaved mystery Magnolia trees I had come for. These have much bigger and more tapering leaves than the adult plants of our two new species of Magnolias from our nearby Rio Zunac Reserve. I strongly suspect they are different species, and hence probably new to science. [Note added April 30: Dr Antonio Vazquez, magnolia expert, and Eduardo Calderon, who has grown many Colombian magnolia species from seed, both say that juvenile magnolia trees often have much bigger leaves than adults, so I now think these forms are probably juveniles of the smaller-leaved species that Juan Pablo Reyes and our caretakers found on their visit here a few weeks ago. That may or may not be M. vargasiana, one of the new species from the Rio Zunac Reserve.] However w We do not know the juveniles of the new Magnolia species from the Rio Zunac, so we cannot rule out the possibility that one of those species has giant leaves when the tree is young. I could find no flowers, which would have settled the issue.


On my way down I was accosted by two Black-billed Mountain-Toucans (Andigena nigrirostris). These big toucans are always brave and curious in wild areas where nobody goes. These two came very close at eye level, rattling their beaks at me. But they were moving around too fast for good pictures. I got a few shots of one of them behind a tree. I include a better picture recently taken by Fausto Recalde in one of our other reserves. The Andigena toucans are among the most beautiful of the world’s toucans; besides this species, we are lucky to have two others in our reserves.

It was a wonderful day, but the next day I felt sick. The day after, I felt worse, and saw why. My right arm and the right side of my face was covered with a red rash. By the third day my right eye was swelling shut. I knew immediately what was wrong…

This time the toxic tree Toxicodendron, whose local name is "alubillo", got me again. This is the earliest stage. If left untreated my whole body would be covered with bursting yellow pustules in a week or two....Photo: Lou Jost/EcoMinga.

This time the toxic tree Toxicodendron, whose local name is “alubillo”, got me again. This is the earliest stage. If left untreated my whole body would be covered with bursting yellow pustules in a week or two….Photo: Lou Jost/EcoMinga.

In my post from last week about this trail, I wrote “From 1996 to about 2004 I spent a lot of time exploring the western arm of the horseshoe, but only visited the eastern arm once or twice. A poisonous tree called Toxicodendron (same genus as American poison ivy) is common near the beginning of the trail up the eastern arm, and I developed a nasty allergy to it. A week after my last trip there (2004?), my eyes were swollen shut and yellow liquid dripped from my earlobes, and I nearly clawed my skin off from itching…. Since then I thought it best to avoid that ridge.”

I did not have problems after my trip two weeks ago. but this time, in spite of my care, I had apparently brushed against the dreaded Toxicodendron tree known here as Alubillo, which I had worried about in my earlier post. I knew that by next week, my whole body would be covered with this rash, and by the week after that, my eyes would be swollen shut and yellow liquid would be dripping from my ears. I don’t know what would happen after that— by the fourth week I had found a doctor who knew the cure (after many stupid doctors who prescribed nonsense). So I have now begun taking that cure, prednisone, and already I am better. (Added note: My friends who are reading this, please don’t worry about me, this is a common routine for me…)

[AApril 30: Photos of the Toxicodendron added below. Note to self: Learn to avoid!!]

Lou Jost
EcoMinga Foundation

An insect that uses its own feces to build a statue of another insect or spider on its back

The membracid treehopper I posted recently is weird enough, but it is not the strangest insect I’ve seen this year. Those treehoppers evolved complex structures on their backs, sometimes imitating ants, showing that under some conditions this kind of imitation gives the treehopper a fitness advantage. Now I’ve found another insect with a fake insect on its back, but this time the insect itself builds the fake insect, out of its own droppings, and without being able to see what it is doing!

Evolution works with what’s available in small steps, and not all groups of insects have complex structures growing out of their backs that can later be molded by natural selection into the shape of a nasty insect. Herbivorous beetle larvae, for example, lack such structures. They’re just shaped like boring caterpillars (and often mistaken for them, though they have no extra “prolegs”, just the regular six legs of most insects) without much fancy ornamentation. Even if models of scary insects would be useful for these larvae, there is not enough random structural variation to get the evolutionary process started in that direction.

However, several groups of these beetle larvae have evolved an unusual defense that might provide material for further natural selection: they build a shield on their backs, made out of their own droppings, often mixed with their own shed skins. The poop-shield, usually called a “fecal shield” in the literature, is not only a physical protection but also a chemical one, which has been shown to repel some predatory insects. It can have considerable structural complexity, and lots of variability.

Some of the most elaborate fecal shields are made by the chrysomelid beetle larvae which turn into “tortoise beetles”. Some species make coils of rope-like structures made of poop, while others make flat solid shields. These insect sculptors use a prehensile anus called the “anal turret” to accurately place each piece of poop on the ever-growing structure. The structure is connected to their bodies by some mobile hooks that the insect can move, deploying the shield as needed, though the range of movement is limited.

These complex yet variable structures, like the pronotum of a treehopper, provide natural selection with raw material for more elaborate constructions. Some of these structures, by accident, might vaguely resemble scary insects. If there is a selective advantage for structures that resemble scary insects (in other words, if the benefits outweigh the cost, so that bearers of such structures leave more offspring than larvae whose structures do not resemble scary insects) then eventually the members of a species may all end up building models of scary insects on their backs, and the accuracy of such models will increase over time in the population.

I recently found the chrysomelid beetle species shown here, whose larvae appears to be following this route, building a crude statue of a scary insect or spider on its back. [Note added April 22: expert Caroline Chaboo, U of Kansas, confirms this belongs to the tribe Cassidini.] I found two of these larvae on a small cloud forest tree called “morochillo” (in the tomato family, Solanaceae). When the larvae were young, they made fairly boring “legless” shields not much different from the kinds that many other chrysomelid larvae construct. They would use their anal turret, which is a flexible sort of hose, to place their feces carefully on the shield. When they shed their skins, as all insects do, the head capsule and hollow spines and other skin debris would be added to the shield. I have no idea how they knew where to put the droppings and skin pieces, since their eyes can’t see the top of the shield, where all the interesting stuff is.

As the larvae got older, they began to build long artificial “legs” on their shields. The shields were not both equally convincing; one larva had more realistic “legs” than the other. Eventually one of them disappeared, while the other made a pupa on its leaf, with the shield still attached.

I took the pupa into my house so I could see the beetle that would emerge. Eventually it did emerge, and I was surprised to see that the adult beetle ALSO had a fake insect on its back! But this one was just a flat silhouette of a big fly, in black, on a transparent carapace.

The beetle was fascinating not only for its fake fly but also for its strange feet. Under a microscope they looked like janitors’ mops, with divided, flattened hairs dripping a clear liquid from their ends. This clear liquid stuck the flat hairs to any smooth surface. My beetle easily held tight to perfectly smooth glass with these feet. Its two long claws between the flattened hairs probably act as levers to unstick the hairs when the beetle wants to leave. This group of beetles is famous for its ability to stick to leaves; they can hold on to a leaf even against a force 60-100 times their own weight. For more detailed analyses of the remarkable mechanisms involved, see here and here.

A magnified view of the flattened, divided hairs with their liquid droplets. Photo: Lou Jost/EcoMinga.

A magnified view of the flattened, divided hairs with their liquid droplets. Photo: Lou Jost/EcoMinga.

A note on the photos: The photos of the live larvae were made using normal macro techniques. The photos of the live adult were stacked composites of a few photos in the case of the views from the top. The live adult on the camera filter, however, was made from a stack of several hundred photos. It didn’t sit perfectly still and I had to manually edit out the wandering antennae.

The high-magnification images of the feet were made immediately after the beetle died, and each consist of about seven hundred photos. I probably shot 5000 photos in total. It was hard!!! I used a 10x Mitutoyo microscope objective attached to various long-focal-length lenses on an old Nikon D90, moving on a StackShot rail. I get roughly similar results mounting the microscope objective directly on a Panasonic bridge camera, the FZ300, or on a Sony HX400V, and these can be managed by wireless smartphones with no need for a moving rail (the lens changes focus internally to image the different planes of the subject). In some cases, cross-polarized light was used to limit reflections. Small stacks were processed in Photoshop while those with hundreds of images were stacked with Zerene.

Lou Jost

Weird treehopper!

For years I’ve wanted to see one of the strange Membracid treehoppers, which biologists often write about but rarely find. At last I found some of them, feeding on one of our rarest tree species, Zapoteca aculeata. These bugs are only about 6-7mm long but are very complex for their size. They are related to cicadas, true bugs (like the assassin bug), and leafhoppers. The weird ones are in the family Membracidae. The species I found is in the genus Cyphonia, maybe C. trifida, though the pictures of C. trifida on the internet all show a single large yellow patch on the side of the head (see here, here, here, and here for examples) where mine have two small yellow patches.

These guys suck sap from trees, and are often social, occurring in loose or dense colonies. Mine are living on a single tree of Zapoteca aculeata. This species of tree was thought to be extinct, but was recently rediscovered here in Banos by my friend Nigel Pitman. It grows in several of our Banos-area reserves (our new Rio Machay Reserve, Cerro Candelaria Reserve,Naturetrek Reserve, Rio Zunac Reserve, and perhaps others) and we use it as one of our reforestation species when reforesting old pastures. I have a few in my yard and that is where I found these bugs. I’ve never seen them on any other tree. However such small bugs could easily escape my attention, so that doesn’t mean much.

Why do these bugs have what looks like a home-made TV antenna coming out of their backs?? Some species have even crazier horns than these, with hanging spheres and extra horns going in all directions. In one group of species, the back horns are clearly imitating big ants, which would frighten many predators. The videos below show some of those species:

In other species, the horns may imitate a common insect-eating fungus. Predators wouldn’t want to eat dead prey, so this might make sense. Some other species have elaborate horns whose functions are complete mysteries.

It has recently been discovered that these bugs “sing” to each other by transmitting vibrations through the tree stem and leaves. The vibrations don’t go into the air, just through the tree stem, so we can’t hear the sounds unless a device (like an old phonograph needle) converts the vibrations into aerial sounds. Both males and females make these songs, and a given species may have several different “songs”. Some are mating songs, some are aggressive songs, and some are warning calls. Males may even try to “jam” the songs of other males by singing a counter-song.

Listen to this NPR radio story with recordings of some songs (click on “Listen” in the NPR story page).

Here is a video made in Ecuador about these insects and their calls — I recommend you start at the 2:00 mark, the beginning dialogue is insufferable (I wish the narrator had been David Attenborough…):

And here is a whole library of calls of many different treehopper species; download any of them and listen with Windows Media Player or equivalent.

Might these vibrations be part of the reason for the weird horns on these bugs’ backs? Maybe they are resonators tuned to sense specific vibrations. The whole casque and horn assembly forms a big helmet, and itis hollow, an empty dry shell like an eggshell, with a huge airspace inside, suggesting that it might play some acoustic role. But I don’t think anyone really knows. Here is a diagram of the helmet (technically called the “pronotum”) from a recent scientific paper. The only connection of the helmet to the body is through the front legs and the neck.

Some of my pictures of these bugs are composites of many hundreds of images, each taken at a slightly different distance from the subject. These images have tiny depths of field, but the sharp parts of each image can be combined using software (Zerene Stacker). The insects are dead specimens in those pictures. I’ll add a post about this method one of these days if I can find the time.

Click here for more amazing treehopper images from Ecuador, taken by my friend Andreas Kay. Also see these amazing treehopper images from Piotr Naskrecki. And more here.

Lou Jost