Re: When Giants Had Wings and Six Legs

[Mark Hallett <marksabercat@yahoo.com>]

When I was living and working in San Diego as a
free-lancer artist/museum technician back in `73, I
would cast my bleary eyes from my kitchen drawing
board (I  routinely worked on my commissions till 2:30
or 3:00 in the morning)to the floor, where the
cockroaches would scuttle down from the attic of my
ancient rental to perform intricate, and entertaining,
mating dances. They were only 2" long, however.... 
--Mark  
--- Danvarner@aol.com wrote:
> Hey! The world of prehistoric insects has its own
> Jim Cunningham! This is 
> from today's New York Times. If you go to the link
> you can see a nice graphic of 
> a life-size dragonfly giant. I still think a larva
> of one of these would be a 
> nightmare! Kind of reminds me of my basement room
> when I was a kid. DV   
>     
> 
> When Giants Had Wings and 6 Legs
> 
> February 3, 2004
> By HENRY FOUNTAIN 
> 
> 
> 
> 
> 
> There was a time when giants roamed the Earth. 
> 
> No, not those giants, the dinosaurs that stomped and
> slogged their way through the Mesozoic Era. These
> giants
> crawled and crept, slithered and scurried, burrowed,
> slinked, skittered and, above all, flitted and
> fluttered
> millions of years before the dinosaurs arrived. 
> 
> They were the giant arthropods of the Carboniferous.
> 
> 
> There were extra-large mayflies, supersized
> scorpions and
> spiders the size of a healthy spider plant. There
> was an
> array of giant flightless insects, and a
> five-foot-long
> millipede-like creature, Arthropleura, that
> resembled a
> tire tread rolled out flat. 
> 
> But perhaps the most remarkable of all were the
> giant
> dragonflies, Meganeuropsis permiana and its cousins,
> with
> wingspans that reached two and a half feet. They
> were the
> largest insects that ever lived. 
> 
> These large species thrived about 300 million years
> ago,
> when much of the land was lush and tropical and
> there was
> an explosion of vascular plants (which later formed
> coal,
> which is why the period is called the
> Carboniferous). But
> the giant species were gone by the middle to late
> Permian,
> some 50 million years later. 
> 
> Scientists have long suspected that atmospheric
> oxygen
> played a central role in both the rise and fall of
> these
> organisms. Recent research on the ancient climate by
> Dr.
> Robert A. Berner, a Yale geologist, and others
> reinforces
> the idea of a rise in oxygen concentration - to
> about 35
> percent, compared with 21 percent now - during the
> Carboniferous. Because of the way many arthropods
> get their
> oxygen, directly through tiny air tubes that branch
> through
> their tissues rather than indirectly through blood,
> higher
> levels of the gas might have allowed bigger bugs to
> evolve.
> 
> 
> But there are other possibilities - a lack of
> predators,
> for example. Fundamentally, no one is certain why
> there
> were giants. 
> 
> "It's been out there in the literature for a long
> time
> without a causal mechanism," said Dr. Robert Dudley,
> a
> professor at the University of California at
> Berkeley who
> has studied the effects of elevated oxygen pressures
> on
> modern insects. "This is a very imperfect science.
> There's
> a very fragmented paleontological record." 
> 
> Dr. Jon F. Harrison, a professor at Arizona State
> who has
> performed similar studies, said, "It's still in the
> realm
> of speculation." 
> 
> While there has been much interesting research, he
> added,
> "it doesn't prove anything yet." 
> 
> Some scientists argue that these large species may
> have
> been nothing out of the ordinary, that, in effect,
> they may
> not have been giants at all. 
> 
> Dr. David Grimaldi, a curator in the division of
> invertebrate zoology at the American Museum of
> Natural
> History and co-author of a forthcoming book on the
> evolution of insects, noted that most Carboniferous
> insects
> were of very similar size to those found today. But
> the
> fossil record tends to be biased toward larger
> specimens
> for the simple reason that they are easier to find. 
> 
> Though about a million insect species now exist, Dr.
> Grimaldi added, over about 75 million years of the
> Carboniferous, as species came and went, there were
> bound
> to be many more. So the largest species may simply
> represent the upper range of a far more diverse
> population.
> 
> 
> "If you increase the sampling over millions of
> years, to
> some extent you are bound to encounter some giants,"
> Dr.
> Grimaldi said. 
> 
> Still, the idea that there were bugs larger than
> anything
> to be found today captures the imagination,
> particularly
> the idea of a dragonfly with wings as wide as some
> hawks'
> (though much less substantial), plucking smaller
> prey out
> of the air as modern dragonflies do. 
> 
> For a long time, scientists believed that an insect
> of that
> size must have been able only to glide, but most now
> believe that the giant dragonflies actually flew. 
> 
> "It's pretty obvious that they were active fliers,"
> said
> Dr. Roy J. Beckemeyer, a retired aeronautical
> engineer in
> Wichita, Kan., who has studied modern and fossil
> dragonflies for a decade. Dr. Beckemeyer says he is
> fortunate to live where he does because many of the
> best
> fossil insect specimens come from deposits along
> ancient
> bays in what are now Kansas and Oklahoma. 
> 
> One of his specialties in aeronautics was wing
> flutter, the
> relationship between bending and twisting that in
> the worst
> of circumstances can cause an airplane's wings to
> fall off.
> Modern dragonflies, he said, bend and twist their
> wings,
> giving them both loft and propulsion. 
> 
> There are similarities in the corrugated structure
> of
> ancient and modern dragonfly wings, Dr. Beckemeyer
> said,
> though in modern species the twisting occurs in the
> outer
> half of the wing. "In ancient dragonflies, it
> appears there
> was a more gradual twisting over the whole length,"
> he
> said. "It's likely that they didn't fly as fast." 
> 
> Even slow flight for an insect that big, however,
> requires
> much muscular activity, which creates heat. Dr.
> Michael L.
> May, an entomologist at Rutgers, was the first to
> show that
> the ancient dragonflies must have had some way to
> dissipate
> 
=== message truncated ===


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