Not a fly: the dobsonfly

September 17, 2013 • 5:44 am

by Matthew Cobb

The class Insecta contains many weird animals, although the weirdness lays mainly in the eye of the human beholder. Readers from the Americas who spent their childhood messing about by rivers will probably be no stranger to the dobsonfly, but to us effete types from elsewhere in the world, it is a bizarre beast:

(I don’t know where this image originally came from, and a Google image search didn’t help.)

Dobsonflies are not flies (order Diptera) – according to timetree.org they separated about 300 million years ago, not very long (in geological terms) after those crazy crustaceans came out of the sea and turned into what we now call insects. Dobsonflies are members of the order Megaloptera. This group used to be part of the Neuroptera along with lacewings, owlflies and antlions, but the order has now been split into the Megaloptera (dobsonflies, fishflies and alderflies) and the Neuropterida (lacewings etc). There are about 220 species of dobsonfly and about 300 species of megalopteran.

The larvae – known in the US hellgrammites and often used as bait by anglers – live in freshwater and take several years to develop. The dramatic and scary-looking adults emerge, mate and then die. Here’s some pictures of dobsonfly courtship and mating (quite SFW). They won’t hurt you, no matter how intimidating those mandibles look.

(Note the three occeli on the top of the head, just behind the roots of the antennae – these simple eyes are used for navigation (they detect polarised light) and also for rapid detection of movement overhead, and are shared by most flying insects – they are one feature that distinguishes queen ants (which have to fly) from their sisters, which do not.)

The dobsonfly in the picture above is an adult male; there is a sexual dimorphism, which strongly suggests either the males use those mandibles to tussle with each other for access to mates (like the mandibles of a stag beetle) or the females directly choose males with bigger/stronger mandibles. The antennae are also dimorphic, suggesting the males may track female pheromones:

Male and female eastern dobsonflies, Corydalus cornutus (Linnaeus), showing differences in mandibles and antennae.

Male (left) and female eastern dobsonfly Corydalus cornutus (photo by Lyle J Buss, University of Florida).

Here’s a nice video of a male crawling all over someone’s hand – the male tries to fly and you can see his two pairs of wings quite clearly:

The male also ‘pees’ on the man in the video – whether this is some kind of defence mechanism I’m not sure.

Females lay eggs on leaves above water, as a white mass. Females will often lay eggs on adjacent leaves, suggesting their may be some kind of oviposition pheromones. The larvae hatch and then drop into the water where they are ferocious predators, growing up to 9 cm in length and living under stones:

Hellgrammite from here. The name was even used as a supervillian in DC comics!

When the larva is ready to pupate (this can take five years), it migrates out of the water and its cuticle hardens to form a pupal case. The male’s long antennae are bent back, as this dissection shows (photo by Atilano Contreras-Ramos):

The adults then mate, and the whole cycle begins again.

Like mayflies and many other river-dwelling insects, dobsonflies are very sensitive to pollution. If you have dobsonflies in your local stream, be pleased! It’s a good sign.

One thing I haven’t found out – why are they called dobsonflies?

To find out more:

http://www.tolweb.org/Corydalus

http://entnemdept.ufl.edu/creatures/misc/eastern_dobsonfly.htm

Hili dialogue: Tuesday

September 16, 2013 • 11:17 pm

Hili has her noms:

Hili: After unsuccessful hunting a full bowl gives you a great spiritual experience.

A: Welfare state has its positive side.

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In Polish:

Hili: Po nieudanym polowaniu taka pełna miseczka dostarcza wspaniałych przeżyć duchowych.
Ja: Państwo dobrobytu ma swoje zalety.

Only if you’re Polish. . .

September 16, 2013 • 12:48 pm

. . . will you be able to understand my interview on Polish television this morning. I’m told the translation is good, and you can sort of make out the English words below the simultaneous translation, but I advise you not to try.  If you understand Polish, go here to see the seven-minute archived interview.

It’s in the main square of Cracow, which is gorgeous.  Here’s the banner:

Screen shot 2013-09-16 at 9.29.34 PM

a translation by my friend Malgorzata:

translation

and a screenshot:


Interview

Some Reading for Wallace Year

September 16, 2013 • 12:44 pm

by Greg Mayer

I should probably have posted something like this earlier, but here are a few recommended books about and by Wallace. It’s an idiosyncratic list, reflecting what was interesting and available to me, but might still be useful as a starting point. Wallace is of course mentioned in many books on the general history of evolution and Darwinism, but the following are works devoted primarily or exclusively to Wallace. I’ll start with a few biographies of Wallace, then a collection of essays, and finally some things written by Wallace himself.

The frontispiece of Island Life, 1880.
The frontispiece of Island Life, 1880.

Raby, P. 2001. Alfred Russel Wallace: A Life. Princeton University Press, Princeton, N.J. A well-received biography by a Victorianist interested in scientific travellers, covering the whole of Wallace’s life.

Shermer, M. 2001. In Darwin’s Shadow: The Life and Science of Alfred Russel Wallace: A Biographical Study on the Psychology of History. Oxford University Press, Oxford. Another biography, by an author probably more familiar to WEIT readers as the editor of Skeptic magazine and for his efforts in combating pseudoscience. Shermer’s academic credentials are in the history of science, and this book is based on his doctoral dissertation. Although Shermer might not appreciate the comment, I found the book refreshingly free of the sort of semi-quantitative psycho-history that the subtitle threatens.

Wyhe, J. van. 2013. Dispelling the Darkness: Voyage in the Malay Archipelago and the Discovery of Evolution by Wallace and Darwin. World Scientific, Singapore. I’m reading this now, having recently gotten my copy, and hope to say more later. Although briefly covering the whole of Wallace’s life, it concentrates on his time in the Malay Archipelago, which was the most scientifically creative part of his life. Van Wyhe is of course the editor of both Darwin Online and Wallace Online.

Smith, C.H. and G. Beccaloni, eds. 2008. Natural Selection and Beyond: The Intellectual Legacy of Alfred Russel Wallace. Oxford University Press, New York. This is a collection of essays edited by Charles Smith, editor of the essential Alfred Russel Wallace Page, and George Beccaloni, who has led the Natural History Museum‘s celebrations of Wallace Year. The essays, by scientists and historians, cover a broad range of historical and scientific issues, everything from a tour of Wallace’s many homes, to his studies of animal coloration, to his fight against vaccination.

For the works of Wallace himself, we can always view the online versions at Wallace Online and the Alfred Russel Wallace Page, or go to a good library, but a number of Wallace’s works are still in print. Here’s a sampling of some of my favorites.

Wallace, A. R. 2002. Infinite Tropics: an Alfred Russel Wallace Anthology. A. Berry, ed. Verso, London. Edited by Wallaceophile Andrew Berry, this is a collection of excerpts from throughout Wallace’s writings on a broad range of topics. If you are going to have only one book of Wallace’s writings, and you want to see what he thought about (almost) everything, this is the one.

The new issue of Island Life by University of Chicago Press, with commentary by Larry Heaney.
The new issue of Island Life by Univ. of Chicago Press, with commentary by Larry Heaney.

Wallace, A.R. 1880. Island Life. Macmillan, London.  Just reissued by the University of Chicago Press, with commentary by my friend and colleague Larry Heaney of the Field Museum. Larry, well known for his work on Philippine Island mammal faunas, provides an extensive introduction that explicates and puts Wallace’s work in modern context. Being very interested in islands, it was the first of Wallace’s major works that I obtained a copy of for myself (I got the 1892 second edition).

Wallace, Alfred R. 1870. Contributions to the Theory of Natural Selection. MacMillan, London. My second Wallace book, obtained in exchange for a six-pack of beer, this is a collection of some of Wallace’s most important papers, including both the “Sarawak paper” and the “Ternate paper“. It was reissued in 2009 by Cambridge University Press.

Wallace, A.R. 1869. The Malay Archipelago: the Land of the Orang-utan, and the Bird of Paradise. Macmillan, London. There are many reissues of this book concerning Wallace’s travel and discoveries in the East Indies. The Dover reprint was long available, but is now out of print; here’s a recent in print edition.

Wallace is just starting to have his letters and notebooks get the same detailed attention that Darwin’s have. Here’s a recent issue of his letters written during his eastern expedition.

Wyhe, J. van, and K. Rookmaaker, eds. 2013.  Alfred Russel Wallace: Letters from the Malay Archipelago. Oxford University Press, Oxford. This is either just out or will be out soon; I haven’t seen a copy yet.

And finally, one of my favorite individual papers by Wallace, which I give as an assigned reading to my evolutionary biology classes.

Wallace, A. R. 1860. On the zoological geography of the Malay Archipelago. Journal of the Proceedings of the Linnean Society: Zoology 4: 172-184.  pdf

Is it a beetle? Is it a fly? No, it’s a beetle fly!

September 16, 2013 • 5:02 am

by Matthew Cobb

Take a look at this beautiful insect, photographed by the amazing macro photographer Melvyn Yeo:

If you said it’s been photoshopped, you’re wrong. If you said ‘it looks like a beetle-fly thing’ you’d be right. It is called a beetle fly, and it shows a stunning example of convergent evolution. In beetles, the front pair of wings have evolved to form the beetle’s ‘shell’, and they flip up and separate during flight.

In the Celyphidae, a group of flies found in tropical Africa and in the far East, the scutellum, which is a structure at the rear of the insect’s abdomen  THORAX [EMBARRASSING INSECT ANATOMY FAIL] has stretched out to form a hard ‘shell’, just like in a beetle, except that it is solid and does not divide into two. You can see it’s a fly because it still has a fly’s usual front pair of wings, and, just above the ‘knee’ of the middle leg, the reduced rear wing or haltere, which we have discussed three times in the last two weeks!.

Now I said ‘convergent evolution’, but it’s possible they are mimicking beetles (why?). Mind you, if it’s convergent evolution, what solution have the two groups converged on? Are there common selection pressures, and if so what? And if those pressures are so important, why haven’t other groups of flies taken the same route?

Whatever the case, one issue I haven’t been able to resolve is how the flies… fly. I presume the scutellum flips up, but that would create hellish aerodynamics, so maybe they just fly very badly. Any answers out there?

My colleague Richard Preziosi and I were looking at this and Richard hazarded that it’s a gravid female (i.e. she’s looking to lay eggs), and indeed it does almost seem like you can see eggs through the lower part of her abdomen. But a quick image search on Google reveals that lots of the pictured flies (not of the same species) are equally rotund. Here’s another one, from Wikipedia:

Photographer liewwk from Kuala Lumpur has a couple of nice photos including this one:

S/he says about the ecology of this species: ‘Very common in low land jungle with stream/river nearby, size ~3-5mm and very shy to human, not easy to get close normally”

Here’s another picture by Melvyn Yeo:

My favourite fly book, Stephen Marshall’s Flies, says on page 359:

“Known beetle fly larvae … feed on decaying grass or skeletonizing the upper surfaces of dead leaves. Beetle flies are usual found in wet areas, often among grasses near bodies of water. Most of the 120 or so species  in this small family are Oriental, several species occur in Africa, some range as far north as Afghanistan and nepal, and others are found southeast to new Guinea and the Solomon Islands. These attractive insects are relatively well known despite their mostly tropical range.’

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Two cartoons: Darwin & Wallace, and the truth about Tetris

September 16, 2013 • 3:08 am

by Matthew Cobb

I spotted both these on Tw*tter (as the microbl*gging site will henceforth be known on this bl*g).

The first is by Ainsley Seago and is from here on the wallacefund.info site.

The second will change your mind about everyone’s favourite Soviet shapes game:

BTfjG8zIcAAw67H.jpg-large
I spotted this here, but I’m not sure who actually made the image…

A rather personal interview with Dawkins

September 15, 2013 • 11:06 pm

The Sydney Morning Herald has published a rather revealing interview with Richard Dawkins: “An arch atheist reveals his poetic soul.” It includes a number of Dawkins’s statements that have elicited controversy—and will continue to do so. As I’m visiting Auschwitz today, I’ll let readers argue about these themselves, but, as always, be temperate and considerate of fellow commenters.

Excerpts from the interview:

He frowns: ”Hmmm, well, yes … I chose not to make this a misery memoir or talk about my feelings too much. I do go into bullying a bit; I wasn’t bullied but I am ashamed of having not stood up to bullies on behalf of others. I wasn’t beaten a great deal but when I was it damn well hurt.” He doesn’t blame the headmaster who inflicted the beatings and had two canes – one more painful for greater crimes. ”They all did it and it’s wrong to judge the past by the standards of today. For example, my childhood was thoroughly racist in a benign, paternalistic sort of way. The Africans were all ‘boys’ – nice and funny but you couldn’t actually trust them to do any sort of competent job.”

. . . Recently Dawkins has been attacked for claiming teaching a child about the fires of hell is worse than child sexual abuse. On Twitter people have said things such as, ”Oh Richard, I’m such a fan of yours but you really have gone too far …” He frowns: ”I just don’t get that. I think the reason is that when people think of sexual abuse they think of a horrendous experience like being raped or buggered violently. But I was talking about things like what happened to me – a master at school stuck his hand down my trousers and had a little fiddle and that was it. It was unpleasant but not the same thing.”

But what about a father persistently going into his daughter’s bedroom for years? ”Oh yes, awful. But there is a spectrum of awfulness and the horror of telling a child about hell is somewhere in the middle: you burn forever, your skin peels off and you grow another so it can burn off again. If you were a child who really believed that, wouldn’t it traumatise you more than having someone stick his hand up your skirt?”

. . .It is seven years since The God Delusion but Dawkins can’t stop writing, lecturing, blogging and tweeting about the iniquities of faith. He comes out at the sound of the bell every time; he rings the bell himself.

”I do, I do. But I get fed up with being treated as though I was a nasty, humourless, negative person. I feel that if people can’t argue with you, the best they can do is criticise you as a person.” But his own attacks are often ad hominem too – he is contemptuous of people who disagree with him. ”I’m contemptuous of their ridiculous beliefs, but not of them as individuals.”

I do think it would be best for Richard to lay off the Twitter. If there’s one thing I’ve learned after years of writing, both here and in popular magazines, it’s that you should not respond to criticism in all but the most severe cases.  In certain quarters even an apology is sufficient to damn you even more severely. And I still see no need to tw- – t except to note that I’ve published yet another piece on this site (this piece, BTW, is number 6003).

I have read Richard’s book, and I had the opposite reaction to that of the interviewer:

In his autobiography he writes entertainingly of family, school, friends and undergraduate days in Oxford; but once he starts postgraduate work, we are plunged into detailed descriptions of research, early forays into computer programming, complete with diagrams, and some fancy linguistics. I enjoyed the book, I tell him, up until he disappeared into the laboratory. It is, in a sense, a book of two halves.

I found the “life history” stories intriguing but not nearly as lively as when Richard writes about science. When he describes his Ph.D. experiments on animal decision-making, the book comes alive. It’s clear that what excites him much more than the recitations of his life story is the history of his scientific work.

I realize that the eyes of many readers will glaze over when they get to the parts about computer programming and chicken experiments, but for me, as a scientist, they show an engagement and joy with ideas that is far more intense than Dawkins’s engagement with other human beings.  The book ends with the writing and publication of The Selfish Gene.

h/t: P