Insect inspiration solves giant bug mystery
by David Catchpoole
Can you imagine a time when mayflies were over five times bigger than today, and
the ground was walked by giant ants—their queen bigger than a hummingbird?
What about if insects looking somewhat like gigantic flying cockroaches with 43–cm
(1½–ft) wingspans came into your kitchen? Would you have felt uneasy with
gargantuan dragonflies—wingspans as wide as a hawk’s—darting around
you?
Sound impossible? In fact, all of these examples are known from actual fossils—so
at some time in the past such creatures were living on this earth.1,2,3 The largest fossil insect
found so far, the dragonfly Meganeura, had a wingspan of 71 cm (nearly
2 ft 5 in).1,4 For years, scientists have puzzled over how
such giant insects could have existed at all, let alone fly.
The problem was lack of oxygen. Biology textbooks have long taught that insects
don’t breathe—at least, not like we do.5
Instead of lungs sucking in air via nostrils or mouth, insects have a network of
tiny air tubes (tracheae) which open to the outside air via a row of small holes
(spiracles) along each side of the body. It was understood that insects don’t
actively inhale or exhale; so it was taught that air only seeps in and
out of the insects’ air tubes passively. Obviously, such ‘passive
diffusion’ is a very slow process. And it only works over short distances.6,7,8
Photo by Robert Jensen, <www.bobjensenphotography.com>
How short?
Only about 0.5 cm (0.2 in)! So an insect could not be wider than about 1 cm (0.4
in)—about the size of the largest insects flying today.2
More than that and not enough oxygen would get to the insect’s innermost cells.
But the colossal fossil Meganeura dragonfly had a body (thorax) nearly
3 cm (1⅛ in) across! How to explain that?
Some scientists thought that atmospheric oxygen levels in the past were higher,
allowing insects to attain larger sizes.1,2,9
In theory, if the atmospheric oxygen were much more concentrated, then oxygen could
penetrate further into an insect’s air tubes, allowing insects to grow bigger.
But this idea has problems—and in any event does not explain why other giant
creatures of the past (e.g. giant marsupials, which everyone accepts were living
in an atmosphere the same as today’s) have also disappeared.
A recent amazing breakthrough seems to have given an answer, overturning the long–held
idea that insects don’t breathe. Researchers used new X–ray technology
to look inside live insects—which showed that insects pump their air tubes
much as humans expand and contract their lungs.10,11,12
It was taught that air only seeps in and out of the insects' air tubes passively
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‘Previously we all thought that most insect breathing tubes were fairly stiff,
but they are anything but stiff’, said Dr Mark Westneat, leader of the research
team.13 ‘We could watch
the tracheal tubes in the head and thorax, which are not squishy parts of the body,
really squeezing and releasing.’
Even while at rest, the insects exchanged up to half of the air in their main tubes
about every second.14 As Dr Westneat
observed, ‘They are really pumping some gas.’15
(This is comparable with birds and mammals—e.g. humans at rest have a lung
ventilation of about 10%, but this may reach 75% during exercise.10)
This remarkable discovery solves the mystery of how colossal insects could have
existed in the past, without the need for higher oxygen levels in the atmosphere.
X–ray photos of the beetle Platynus decentis show tracheal tubes
expanded at rest (A, arrowhead e); compression occurring (B); maximal compression
(C, arrowhead c) followed by rapid expansion (D)—the entire respiratory cycle
takes less than one second.
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Where did the giants go?
Given that the giant insects of the fossil record, with tracheal breathing, would
have been able to live in an atmosphere similar to today’s, why don’t
we see such megabugs today?
In addressing that question here, our starting point, from the Bible, is that insects
were created; they did not evolve. (Note that this view is not shared by
Dr Westneat, who kindly allowed us to publish these X–ray photographs (p.
46) on condition that we make it clear that he and his co–workers ‘are
studying the evolution of respiration and are not willing to mix religious belief
with science’.16 See box
on right.) Were giant dragonflies created as their own special kind? Probably not—it
is much more likely that they were descendants of the original created kind of dragonfly—just
as we see a large range of dog sizes that have been bred from the wolf kind.17 The fossilization of these giant insects
(and other creatures) can be readily understood as a legacy of the global Flood—which
happened not billions of years ago but only around 4,500 years ago.
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Insects pump their air tubes much as humans expand and contract their lungs
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So why did the colossal insects disappear? Perhaps the giant insect representatives
of each kind perished in the Flood, so the genetic information for large size was
lost. Or possibly the ensuing Ice Age and/or different post–Flood climate
took their toll on the larger insects, i.e. there was a climatic selection pressure
for smaller size. Alternatively, some may actually still exist today (see box on
right).
Perhaps the explanation, as for other giant animals which have since become extinct,18 involves post–Flood
man. Giant insects may well have been seen as a nuisance or menace and killed accordingly.
They may also have been a readily captured food source (Genesis
9:3) as humans spread out and repopulated the earth after the Flood.19 If the larger insects were more frequently/readily
killed, then eventually the genes for large size would have been eliminated.
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Created or evolved?
Recognizing the implications of their work for evolutionary theory, Dr Westneat
and his colleagues1 said: ‘[A]ctive tracheal breathing in the head
and thorax among insects may have played an important role in the evolution of terrestrial
locomotion and flight in insects, and be a prerequisite for oxygen delivery
to complex sensory [neurological] systems and the brain [emphasis added].’2
But Thomas Miller, an insect physiologist at the University of California, said
of insect breathing, ‘It looks like there’s a very complicated neurological
system to keep all this coordinated.’3 So if breathing had to evolve
to get a neurological system, which in turn is needed to coordinate the breathing,
this would be a classic case of irreducible complexity, where all the complex
features could not have arisen step–by–step but had to have appeared
at the same time.4
Certainly, in relation to how insect bodies work, there are levels of complexity
which are only just becoming apparent as researchers probe deeper. Indeed, ‘there’s
even emerging evidence that insect breathing is synchronized with the pulsing of
the creatures’ circulatory systems, a level of physiological sophistication
few had imagined.’3
Complicated, coordinated, sophisticated—all of which speak of insects having
been designed rather than being the result of some blind process of evolution. Commenting
on these latest findings, May Berenbaum, an entomologist at the University of Illinois,
said, ‘Insects never cease to amaze with their capacity to do a lot with the
little they have. We were clearly mistaken to underestimate the capacity of their
tracheal respiratory system.’
No wonder the Bible says that anyone who denies there is a Creator God is ‘without
excuse’ (Romans
1:20).
References
- Westneat, M.W., Betz, O., Blob, R.W., Fezzaa, K., Cooper, W.J. and Lee, W.–K.,
Tracheal respiration in insects visualized with synchrotron X–ray imaging,
Science 299(5606):558–560, 2003.
- Argonne National Laboratory, Field Museum, Argonne discover insect breathing
mechanism, <www.anl.gov/Media–Center/News/2003/news030124.htm>,19 June
2005.
- The Seattle Times, Aristotle erred; super X–ray proves insects do
breathe,
seattletimes.nwsource.com/html/healthscience/134621012_bugs24.html, 7 July
2003.
- Behe, M.J., Darwin’s Black Box—the biochemical challenge
to evolution, Simon & Schuster, New York, 1998.
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Are any giant insects still left?
While not quite matching some fossil giants, there certainly are large insects living
today. Indonesia’s atlas moth (Attacus atlas) and Papua New Guinea’s
Queen Alexandra birdwing butterfly (Ornithoptera alexandrae) both have
wingspans of 30 cm (12 in).1
Indonesia’s Atlas moth (above) and the massive beetle from South America known
as Titanus giganteus (left) are among the largest known insects living
today.
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Then there’s Australia’s Hercules moth (Coscinocera hercules),
with a wingspan up to 36 cm (1 ft 2⅜ in)!2 Malaysia’s giant
stick insect Pharnacia serratipes has an overall length (i.e. including
extended fore and rear legs) of 55.5 cm (nearly 22 in).3 The South American
longhorn beetle (Titanus giganteus) can be over 16 cm (6⅜ in) in
body length (not including antennae), as can another beetle, Dynastes hercules.
In terms of solid bulk, probably the champion insect would be the acteon beetle
(Megasoma acteon), the males of which can be 10 cm (3½ in) long, 5 cm (2
in) wide and 4 cm (1⅝ in) thick;4 while possibly the heaviest is
the goliath beetle (Goliathus goliath) of Africa, reputed to weigh up to
100 g (3.2 oz)—more than a small bird!5
It is remotely possible that some giant insects still exist. Entomologists estimate
there are still many unknown insect species living in inaccessible tropical forest
areas.
References
- The world’s largest butterfly and moth, <www.geocities.com/thesciencefiles/thelargest/butterflyandmoth.html>,
13 January 2004.
- Australian Insect Farm Quarterly News,
www.insectfarm.com.au/dec2001.htm, 13 January 2004.
- Branscome, D., University of Florida Book of Insect Records,
ufbir.ifas.ufl.edu/chap33.htm, 23 December 2003.
- Welcome to the wonderful world of insects,
www.earthlife.net/insects/six01.html, 22 December 2003.
- Insect information,
www.landcareresearch.co.nz/education/insects_spiders/insects, 22 December 2003.
References and notes
- Dudley, R., Atmospheric oxygen, giant Paleozoic
insects and the evolution of aerial locomotor performance, The Journal of Experimental
Biology 201:1043–1050, 1998. Return to Text
- Graham, J.B., Dudley, R., Aguilar, N.M. and
Gans, C., Implications of the late Palaeozoic oxygen pulse for physiology and evolution,
Nature 375(6527):117–120, 1995. Return to Text
- Painter, D.,
Big ideas about big bugs, ASU Research, 24 July 2003.
Return to Text
- Big Wings, <studentwebs.coloradocollege.edu/~in_ulbrick/page3.html>,
22 Dec. 2003. Return to Text
- ‘[I]nsects obviously require the exchange
of the same vital gases as ourselves, but they do not breathe since they lack lungs.’
University of Massachusetts Dept. of Entomology, Insect Misconception/Misinformation
#10: Insects ‘breathe’,
www.umass.edu/ent/BugNetMAP/mis_10.htm, 11 July 2003. Return
to Text
- Farb, P. and the Editors of Life,
The Insects, Time–Life International (Nederland) N.V., 1964.
Return to Text
- Curtis, H., Biology, 4th
edition, Worth Publishers Inc., New York, USA, pp. 529, 538, 690–691, 1983.
Return to Text
- ScienceNet—Biology & Medical Science
<www.sciencenet.org.uk/database/Biology/0109/b01008d.html>, 27 February 2003. Return to Text
- Harrison, J.F. and Lighton, J.R.B., Oxygen–sensitive
flight metabolism in the dragonfly Erythemis simplicicollis, The Journal
of Experimental Biology 201:1739–1744, 1998. Return
to Text
- Westneat, M.W., Betz, O., Blob, R.W., Fezzaa,
K., Cooper, W.J. and Lee, W.–K., Tracheal respiration in insects visualized
with synchrotron X–ray imaging, Science 299(5606):558–560,
2003. Return to Text
- Scientific American.com,
Ultrapowerful X–rays reveal how beetles really breathe, 14 July 2003. Return to Text
- The Seattle Times,
Aristotle erred; super X–ray proves insects do breathe, , 7 July 2003. Return to Text
- CNN.com, CNN talks with researcher
about bug breathing,
www.cnn.com/2003/TECH/science/01/24/coolsc.bug.interview/, 27 February 2003. Return to Text
- The total time of tracheal compression varied
between species, ranging from 0.7 seconds in ground beetles up to 1.6 seconds in
carpenter ants. Compression of the tracheae was often synchronous throughout the
head and thorax, but local tracheal compression also occurred. See ref. 10.
Return to Text
- SciTecLibrary—Scientific News, Breathing
without lungs: how do insects do it, <www.sciteclibrary.com/eng/catalog/pages/4561.html>,
16 July 2003. Return to Text
- For an analysis of such views making a false
distinction between religion and science, see: Wieland, C.,
A look at some myths about scientists, Creation 11(3):29,
1989. A leading anti–creationist philosopher Michael Ruse also wrote a stunning
article, How evolution became a religion: creationists correct? National Post,
pp. B1, B3, B7; 13 May 2000. Return to Text
- Batten, D.,
Ligers and wholphins? What next? Creation 22(3):28–33,2000.
Return to Text
- Such as the giant marsupial Diprotodon
and the six–metre–long [20 ft] goanna Megalania.
Return to Text
- For example, one commentator attributes the
apparent extinction of the large 10–15 cm (4–6 in) longhorns (Xixuthrus)
in Fiji to the (former ruling) British Government’s prohibition of cannibalism
on the islands: ‘To compensate, the native inhabitants took to eating the
20–cm–long [8 in] larvae of this beetle, literally ripping out all the
available habitat of rotten wood while searching for the tasty larvae.’ Coleoptera:
On insects, protection and conservation strategies, 13 October 2003.
Return to Text
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