Category: News

The surreal treehoppers

November 26, 2010 • 8:00 am

Last week’s Nature highlighted the sculptures of Alfred Keller (1902-1955), and the example, a model of the Brazilian treehopper Bocydium globulare, struck me as one of the weirdest animals I’ve ever seen:

Martin Kemp describes Keller’s work:

Keller was trained as a kunstschmied, an ‘art blacksmith’. From 1930 until his early death he was employed by the Berlin Museum für Naturkunde (Museum of Natural History), painstakingly labouring over his recreations of insects and their larvae. Each took a year to complete. Keller worked first in plasticine, from which he cast a model in plaster. This plaster reference model he then recast in papier maché. Some details he added, cast in wax, with wings and bristles in celluloid and galalith (an early plastic material used in jewellery). Finally he coloured the surfaces, sometimes with additional gilding. The levels of patience and manual control Keller exercised were incredible. His fly, for example, boasts 2,653 bristles.

. . . Keller was a sculptor of monumental one-off portraits. Each model is a masterpiece, with no effort spared. It is difficult to see how such a skilled artisan could survive in today’s museums, with their emphasis on cost analysis. Keller’s exacting models may be things of the past, yet they are far from obsolete. Like the great habitat dioramas, they exercise a magnetic attraction.

The first thing a biologist does on seeing a model like this is think, “This can’t be real,” and resorts to some Googling. Sure enough, it’s a real insect.  Here are two photos by Patrick Landmann (check out his other terrific nature photos):

The second thing one asks is, “What the bloody hell is all that ornamentation on the thorax?” (Note that the “balls” on the antenna-like structure aren’t eyes, but simply spheres of chitin.)  A first guess is that it’s a sexually-selected trait, but those are often limited to males, and these creatures (and the ones below) show the ornaments in both sexes.  Kemp hypothesizes—and this seems quite reasonable—that “the hollow globes, like the remarkable excrescences exhibited by other treehoppers, probably deter predators.”  It would be hard to grab, much less chow down on, a beast with all those spines and excrescences.

Note, though, that the ornament sports many bristles.  If these are sensory bristles, and not just deterrents to predation or irritating spines, then the ornament may have an unknown tactile function.

Membracids, related to cicadas, are in the class Insecta (insects, of course), the order Hemiptera (“true bugs”) and the family Membracidae.  Like aphids, which are also “true bugs,” adult and immature treehoppers feed on plant sap.

For a wonderful panoply of membracid photos, download this pdf file. Here are some of the images, showing that, as Kipling said, “The wildest dreams of Kew are the facts of Khatmandu.” If Dali invented insects, they’d look like these (all photos by Patrick Landmann):

The color and shape of this last one makes me suspect that it’s mimicking a wasp:

h/t: Matthew Cobb

Wasps: artists or robots?

November 15, 2010 • 5:13 am

by Matthew Cobb

[Continuing my lazy practice of re-posting material from elsewhere in the blogosphere and bringing it to the attention of WEIT readers, here’s one I posted last week over at Pestival (the insect arts festival – yes, honest!  Go look!)]

In case you weren’t listening to BBC Radio 4 at 06:15 am the other Sunday morning, I thought I would present to you the case of one of nature’s artists, the potter wasp. This small solitary wasp was the subject of the excellent Radio 4 programme The Living World. Anyone, anywhere in the world, can listen to it again here:

The female wasp makes a little clay pot about 1cm across, with a small hole in the end. She lays an egg in the pot, and then crams it full of living, semi-paralysed caterpillars which her offspring can eat. You can see quite how small the pot is in this photo from the BBC website, by Andrew Dawes. The “pot” is the tiny white thing underneath the middle finger!

[EDIT: The following (clearer) picture was taken by WEIT reader TrineBM (see comment 2 below)]:

According to Wikipedia (so it must be true, no?) the great entomologist Karl von Frisch, who was the first to study the honey bee’s waggle dance, claimed that the shape of the potter wasps’s pot inspired native American pottery designs. Quite how one could know that was true (or not) is hard to say – and what about other pots from round the world that look pretty much the same?

But is the wasp really an artist? Does it know what the pot should look like? John Walters, who’s been studying the potter wasps on this Devon heath for the last four years, says that he thinks each wasp has a different style – some pots are symmetrical, others have distinct twists. That doesn’t mean to say they know what they’re doing. Indeed, it seems certain they do not.

One of my favourite studies of animal behaviour was carried out on a potter wasp in 1978 by Andrew P. Smith, then of the University of Sydney. On the other hand, I seem to be one of very few people who rate this work – it has only been cited 13 times in the last 32 years. I feel your pain Dr Smith!

Andrew’s wasp – Paralastor – makes a rather more elaborate nest than the Devon potter wasp, a kind of odd umbrella shape, made up of a mud column and a bell-shaped entrance, leading to an underground chamber where the larva can munch its way through its living lunch, as seen here:

This picture shows the female wasp in action:

So how does she know what to build? Construction takes place in stages:

But does she have an image of what the final nest should look like? Or does she simply know that she’s carried out a series of behaviours and simply do them in sequence? The answer to both these questions is “No”.

Through a series of experiments involving changing the ground level, or altering the angle of the column, or making holes at various points, Smith was able to show that the wasp in fact proceeds by a series of steps, each of which is induced by a particular stimulus. If she sees a hole, she makes a column – even if this ends up with a bizarre double-umbrella nest:

The conclusion of the paper – apart from a lot of very tired and confused wasps – is this rather neat flow diagram, showing how the wasp decides what to do next:

So the wasp is not an artist, it’s more like a simple robot, carrying out a task when the appropriate conditions are provided. Less romantic, but still amazing!

Andrew P. Smith (1978) An investigation of the mechanisms underlying nest construction in the mud wasp Paralastor sp. (Hymenoptera: Eumenidae). Animal Behaviour 26:232-240.

The evolution of cat coat patterns

October 27, 2010 • 8:35 am

Why are some species of kittehs plain, while others have spots, stripes, or more elaborate patterns? A provisional answer comes from a new paper by William Allen et al., “Why the leopard got his spots: relating pattern development to ecology in felids”, in the Proceedings of the Royal Society.  The paper’s title, of course, comes from Rudyard Kipling’s Just So Stories.  And the short answer is this: the coats of wild cats help camouflage them, and what pattern evolves depends on where the species lives.

The simple answer comes from a rather elaborate analysis.  The authors set up the paper with what I think is a good specimen of clear scientific writing.  It’s not Joyce, of course, but these guys know how to write. I love the alliteration of “flanks of felids” and the breeziness of “pounce or quick rush.”

The patterns displayed on the flanks of felids are intriguing in their variety. Previous studies of the adaptive function of cat coat patterns have indicated that they are likely to be for camouflage rather than communication or physiological reasons [1,2]. The primary hunting strategy of felids is to stalk prey until they are close enough to capture them with a pounce or quick rush [3,4]. As hunts are more successful when an attack is initiated from shorter distances [5,6], cats benefit from remaining undetected for as long as possible and camouflage helps achieve this. Many smaller cats are also likely to be camouflaged for protection from predation [7].

The authors first note that others before them have suggested—and supported with some data—the idea that spotted or stripey cats live in forested habitats, and plain cats in open habitats.  But they quantify this “complexity” by doing a developmental analysis of coat patterns on pictures taken from the internet.  I won’t go into the details, but they match the photographs with patterns generated from a mathematical model in which pattern results from the interaction of two diffusible chemicals along gradients of the body.  Given a model that matches an existing pattern (they used 35 species of felids), they could then encompass “pattern” in the mathematical constants involved in generating it.  They could then correlate these constants with various aspect of cat ecology: where they live, preferred times of activity, how big they are, what they eat, and how social they are.

Here’s an example of a cat that came out “plain” in their analysis: the caracal (Caracal caracal), from Africa and the Middle East:

Nine of the 35 species were considered “plain.” Here’s a cat considered “patterned and complex”: the gorgeous clouded leopard (Neofelis nebulosa), from southeast Asia:

Sixteen species were considered patterned, with four of these, including the clouded leopard, as “always complex.”  The other ten were considered “variable”,” since there was polymorphism: individuals within a species can look quite different.

The results?

  • Pattern itself, whether complex or not, was significantly associated with habitat, with more patterned cats in more “closed” habitats (forest, jungle, etc.).  Plain cats are found in open habitats like grasslands, deserts, and mountains.
  • More irregular patterns, like the cloud leopard, are significantly associated with tropical forests and other “closed” environments.
  • “The more time cats spent in trees, the more likely they were to be patterned.”
  • Pattern polymorphism, as in the melanism of “black panthers,” was significantly associated with living in temperate forests that vary seasonally and also with habitat generalism. This supports the idea that “disruptive selection,” that is, selection for different patterns in different places, maintains the intra-specific variation in coat color.
  • There were a few “outliers,” or exceptions—cats that had patterns not fitting into the habitat correlations given above.  One is the very rare bay cat (Catopuma badia; I’ve posted on it before), which is plain though it lives in tropical rainforest:

And another outlier is the black footed cat of Africa (Felis nigripes), which is patterned though it lives in open habitat (savannah, grassland, and semi-desert):

The authors note that the tiger is the only wild cat with vertical stripes, and the common notion that this camouflages them in grassland is unfounded: tigers don’t live in grasslands.

The conclusion, then, is that the patterns of cat coats reflect, in large degree, selection for camouflage in their natural habitats. This camouflage almost certainly evolved to hide them from prey, and, in smaller cats, predators as well.

I love the inclusion of a Kipling quote in their conclusion (reference “45” is to the Just So Stories):

These findings support the hypothesis that felid flank patterns function as background matching camouflage. Evolution has generally paired plain cats with relatively uniformly coloured, textured and illuminated environments, and patterned cats with environments ‘full of trees and bushes and stripy, speckly, patchy-blatchy shadows’ [45].

Now the sample size—35 species—is not large, and some of the associations were barely significant from a statistical standpoint.  This could reflect the low power of tests in small samples. Nevertheless, the study offers a good working hypothesis for the evolution of pattern not just in cats, but other species that “need” to be cryptic.  What remains to understand are those outliers like the bay cat, and also the existence of developmental change of pattern, in which some species are patterned when young and lose the patterns when they get older.  Lions, which are spotted as cubs, are a good example of this:

This change might not be adaptive per se, but simply be an atavism: a holdover from an ancestral spotted pattern that still persists in the young.

_________

Allen, W. L., I. C. Cuthill, N. E. Scott-Samuel and R. Baddeley. 2010.  Why the leopard got his spots: relating pattern development to ecology in felids.  Proc. Roy. Soc. B online: doi: 10.1098/rspb.2010.1734

Shark jaws

October 23, 2010 • 5:50 am

Here are two more photos from my immensely edifying visit to Jim Krupa’s lab at The University of Kentucky.  They show the extreme diversity of morphology that evolution can produce in a single group.

The first shows the jaw of what I remember as a tiger shark, Galeocerdo cuvier.  National Geographic notes that “They have sharp, highly serrated teeth and powerful jaws that allow them to crack the shells of sea turtles and clams. The stomach contents of captured tiger sharks have included stingrays, sea snakes, seals, birds, squids, and even license plates and old tires.”

The rows of teeth are lined up, waiting in the wings, to be replaced after one on duty is lost. The teeth aren’t embedded in the jaw, but merely in the gum tissue.  Wikipedia has a good article on them.

Sharks are in the class Chondrichthyes:  they have cartilage rather than bone.  The subclass Elasmobranchii includes sharks, skates and rays.  And the tiger shark is in the largest order of elasmobranchs, the Carcharhiniformes.

And here’s one of the weirdest elasmobranchs—the jaw of the Port Jackson shark (Heterodontus portusjacksoni), endemic to Australian waters.  It’s in the order Heterodontiformes (“bull sharks”), distinguished, among other things, by having the mouth completely in front of the eyes. The “Heterodontus” part of the genus name means “different teeth,” and that’s indeed what you see, spectacularly, in the jaw.  Having differentiated teeth in the jaw is very rare in sharks:

The small teeth in front are for grabbing and piercing, the ones at the rear for grinding up stuff, especially molluscs.  The Florida Museum of Natural History site notes:

This species feeds primarily on echinoderms, crustaceans, molluscs, and some small fish. Sea urchins and large gastropod molluscs are noted in almost every study on the diets of Port Jackson sharks. Stomach contents are typically ground up too small for full identification, thus leading researchers to believe Port Jackson sharks grind their food thoroughly before swallowing. This is also supported with juvenile diets, since it has been noted that juveniles eat more soft-bodied animals, and contain less molar-like teeth.

Here’s what the jaws look like in situ:

For $750 you can actually buy a Port Jackson shark for your aquarium, but I’m not sure why anyone would do that, as they grow over five feet long.

You can see the variety of sharks’ teeth here, and if you’re into buying recent or fossil teeth, here’s a place to start,

Secular ethics classes a success in Oz

October 22, 2010 • 5:59 am

I reported a while back that ten public schools in New South Wales, a state where by law the students have a weekly hour of “special religious education” (SRE), were trying out classes in secular ethics as an opt-in alternative. I noted, many Christians didn’t like this at all—they claimed the classes drew people away from Jesus.  Too bad, because the government has just deemed the experiment a success.  You can download the 101-page government-commissioned report at the site (check out Appendix 2).

Reading the report, the education minister concluded that “The independent evaluation found high levels of engagement among students when discussing ethical issues and that it enabled them to discuss and understand the principles of ethical decision-making.  It also found that the course met the aim of introducing students to the language and nature of ethics and ethical issues.”

In response to “criticisms from religious groups” (p. 14), the report notes dryly:

In evaluating the course materials an effort has been made to consider the philosophical background and the pedagogical approach on which the course is based. The field of Moral Philosophy has a two and a half thousand- year history and a logically rigorous methodology; the ethical inquiry approach has been employed widely for three decades by philosophers concerned to introduce philosophy (including ethics and logic) to the broader community. These are philosophers who decry relativism.

The report concludes:

The call for a secular ethics-based complement to SRE in NSW schools is not without precedent, and there is evidence here that secular ethics and SRE can exist respectfully side by side. In this evaluation an attempt has been made to assess the extent to which the ten week ethics pilot provides an appropriate model for an ethics-based complement to Scripture, and to do so on the basis of rational argument and empirical evidence. Further decisions rest with the Minister.

Go Minister!  One small step for Australia, one great leap for mankind.

h/t: Russell Blackford at Metamagician

Ten needless deaths

October 17, 2010 • 9:04 am

That’s ten needless human deaths on top of 30,000 needless goat deaths.  NPR reports today that ten Indians were killed in a bizarre religious episode:

An argument over sacrificing goats during a Hindu festival triggered a stampede that killed 10 people Sunday in a packed temple in northern India, officials said.

More than 40,000 people, many inebriated, had taken their goats to the Tildiha village temple in Bihar state to offer sacrifice and prayers to the goddess Durga on the last day of the Navratri festival.

As the worshippers lined up before the butcher, a scuffle broke out and some people were trampled, Banka district spokesman Gupdeshwar Kumar said.

“People were vying with each other to get their goats sacrificed first, and they had a verbal duel with the butcher,” Kumar said.

Four women and six men died in the stampede, and another 11 were injured, three of them critically, Banka district police director Neelmani said. The injured were being treated in hospitals.

Villager Umesh Kumar, 35, said the temple was so full, “people didn’t have any place to walk around … and there was a commotion when people tried to have their goats sacrificed.”

The district spokesman said some 30,000 goats were sacrificed at the temple on Saturday.

The 10-day Navratri festival honors Durga, the Mother Goddess in the Hindu religion.

The village in Banka district is about 120 miles (200 kilometers) southeast of Bihar’s state capital, Patna.

It’s hard to impute this tragedy to anything other than religion.  People like Robert Wright and Robert Pape can claim (wrongly, I think) that foreign occupation is the overwhelming cause of suicide bombings in the Middle East, implying that maybe those deaths would still occur without religion.  Others claim that the troubles in Northern Ireland resulted from historical/political and not religious divisions.  But it’s hard to see how any of these deaths—human or goat—would have occurred had there not been a need to propitiate gods.

L. A. Times report on the Secular Humanism conference

October 10, 2010 • 11:10 am

Today’s L. A. Times reports on the big humanism meetings, and the opening doesn’t augur well for objective journalism:

As the largest organization of American atheists, agnostics and other religious skeptics gathered in Los Angeles this weekend, there was a predictable amount of scorn heaped on Christians, Jews and Muslims.

Religion was dismissed as “nonsense” and “superstition”; those who believe were described variously as “ignorant” and “stupid.”

Things get better, though, and the article cites these as “good days, generally speaking, for the nonreligious.”  All the big guns get a mention, and they cite my favorite moment of everything I watched:

When Mooney, a leading voice for accommodation, said there was nothing to stop a nonreligious person from being spiritual, Myers’ reaction was nearly physical. “Whenever we start talking about spirituality,” he said, “I just want to puke.”

Agreed!  How can Mooney, The Great Communicator, think that if atheist accommodationists and atheist non-accommodationists both emphasize their common spirituality, everything will magically improve and the faithful will suddenly come to Darwinism? Once again I must pull out my favorite Orwell quote: “One has to belong to the intelligentsia to believe things like that: no ordinary man could be such a fool.”