Bug Non-Deadend Tracheal Tubes Evolution Possible - UFOs?

[Humblemunn]

Okay, no-one is going to like this speculation, I know, but it's a valid one imv. The title says it all.

X-Ray Images Help Explain Limits To Insect Body Size

 

Speculation on oxygen levels in the past is very varied, this paper Atmospheric oxygen level and the evolution of insect body size in Figure 1 even shows a potential peak in the middle of the Cretaceous. Evolution of dinosaurs on the Antarctic contintent are known to have been more primitive than their counterparts on the other continents due to the harsh and challenging environment. Could this combination of factors have given the giant insects a temporary advantage which then led to the evolution of super-oxygen-systems of non-deadend trachea tubes? Are the luminous fast flying objects seen reported in the skies of the modern era, something which is much more earthbound than ET?

Edited August 29, 2013 by Humblemunn

[Moontanman]

Are you suggesting that UFOs are giant glowing insects?

[CharonY]

I must admit that I have no clue what I just read. The words imply that they mean something obvious but they do not appear to make any kind of sense to me.

[Humblemunn]

Are you suggesting that UFOs are giant glowing insects?

Yes, at least the obvious cases of a sharp change in direction. I'm even speculating that these giant glowing bugs are responsible for cattle mutilations. It makes more sense than ET or a covert "government black helicopter" operation in my view.

I must admit that I have no clue what I just read. The words imply that they mean something obvious but they do not appear to make any kind of sense to me.

lol. You might a mental block with the concept of giant bugs actually existing as we speak. There's no real reason why there couldn't be. If they evolved a strategy of elusiveness as well as speed, it would fit all known UFO phenomena. Beetles and bugs can look very metallic, rounded and saucer-like if need be.

[arc]

And the lack of fossil evolutionary evidence pertaining to a gradual increase in size is due to?

[Humblemunn]

And the lack of fossil evolutionary evidence pertaining to a gradual increase in size is due to?

It's only bones which get fossilised as far as I know. I remember a case of an ancient insect being preserved in a drop of amber, but that only happens exremely rarely.

[John Cuthber]

It's only bones which get fossilised as far as I know.

Then learn more.

[Humblemunn]

Then learn more.

That's not very helpful. I can assume that giant insect bodies degrade too quickly in fossilizing environments such as shallow ponds to become fossilized unlike an Archaeopteryx for example.

 

Okay, I've done a google search and looked at the Brea Tar Pits which have the best fossilized animals that there is.

The first step was to identify the insect traces. Holden and colleagues determined that different larval beetles were responsible for the exceptionally preserved traces on the bones of ancient mammals. By identifying those traces and researching the biology of the trace-maker, the team was able to pinpoint the climatic conditions and the minimum number of days it took for some of the carcasses to become submerged in the entrapping asphalt. Even after 10,000-60,000 years, the traces provide clear evidence that submergence took at least 17-20 weeks and occurred during warm to hot weather.

 

It's only the traces of insects on the mammal bones that identifies them, not the insect fossils themselves.

 

Another source of information:

Compressions

Some fossil evidence formed when the insect (or part of the insect) was physically compressed in sedimentary rock. In a compression, the fossil contains organic matter from the insect. These organic residues in the rock retain their color, so the fossilized organism is conspicuous. Depending on how coarse or fine the mineral comprising the fossil is, an insect preserved by compression may appear in extraordinary detail.

Chitin, which makes up part of the insect's cuticle, is a very durable substance. When the rest of the insect body decays, the chitinous components often remain. These structures, such as the hard wing covers of beetles, comprise most of the fossil record of insects found as compressions. Like impressions, compression fossils date back as far as the Carboniferous period.

 

So, all we need is Antarctic giant bugs which have a very low Chitin content and when compressed, the organic residues of decay don't retain their color.

 

Edited August 30, 2013 by Humblemunn

[arc]

[Humblemunn]

The Encyclopaedia Britannica supports the possiblity of my speculation:

 

Insect fossil record

 

The insect fossil record has many gaps. Among the primitive apterygotes, only the collembolans (springtails) have been found as fossils in the Devonian Period (about 416 million to 359 million years ago). Ten insect orders are known as fossils, mostly of Late Carboniferous and Permian times (318 million to 251 million years ago). No fossils have yet been found from the Late Devonian (about 385 million to 359 million years ago) or Early Carboniferous (about 359 million to 318 million years ago) periods, when the key characters of present-day insects are believed to have evolved; thus, early evolution must be inferred from the morphology of extant insects.

 

It has become evident that insect evolution, like that of other animals, was far more active at some periods than at others. There have been geological epochs of “explosive” evolution during which many new forms have appeared. Those epochs may have followed some modification or innovation in body function, or new developments favoured by climatic changes or evolutionary advances of other animals and plants. During those periods of evolutionary change, new methods of feeding and living led to diversity of insect mouthparts and limbs, the origin of metamorphosis, and other changes.

Insect phylogeny

The simplified family tree shown here illustrates the presumed evolutionary history of winged insects (Pterygota) throughout the geological periods from the Devonian to the Recent. The apterygotes, which are regarded as survivors of primitive insect stock, are omitted from the family tree. Dark lines indicate the periods during which the various orders have been found as fossils. Some lines stop at the names of orders now extinct and known only as fossils. Light lines indicate the hypothetical origin of various orders. Many insect types, traces of which have not yet been discovered, must have been produced during the explosive periods of evolution in Carboniferous and Permian times.

The primitive wingless insects gave rise to a paleopterous stock. Descendants of this stock included ancient fossil types that flourished in Permian times, such as the giant dragonflies or Protodonata (some of which had a wing span of more than half a metre) and the dragonflies and damselflies (Odonata) and mayflies (Ephemeroptera), both of which have persisted with little change to the present. The primitive insect stock also gave rise to a neopterous stock, believed to include the progenitors of the remaining insect orders. The Orthoptera (grasshoppers) and the Plecoptera (stoneflies) have been found as fossils even in late Carboniferous times. The Isoptera (termites, sometimes placed in the order Blattodea), Embioptera (webspinners), and Dermaptera (earwigs), though doubtless of ancient origin, have not been found yet as fossils dated earlier than the Mesozoic Era (251 million to 65.5 million years ago).

The evolutionary radiation believed to have given rise to the orders listed above in the Middle Carboniferous Period is thought to have also produced a paraneopterous stock, which formed the base for a new evolutionary radiation during the Permian Period. Present-day derivatives of this stock evolved into the Psocoptera (psocids), Mallophaga (chewing lice), Anoplura or Siphunculata (sucking lice), Thysanoptera (thrips), Heteroptera (true bugs), and Homoptera (e.g., aphids).

Several phylogenetic lines are exopterygote—i.e., insects with simple metamorphosis, some of which, such as Mallophaga and Anoplura, are secondarily wingless. The remaining orders are endopterygote (insects with complete metamorphosis). They are derivatives of an oligoneopterous stock, which gave rise to Neuroptera (lacewings), Hymenoptera (ants, wasps, and bees), and Coleoptera (beetles) in the Early Permian Period (299 million to 271 million years ago); the early ancestry of these orders is obscure, however, and the earliest fossils closely resemble present-day forms. One line from the evolutionary radiation at the beginning of the Permian gave rise to a mecopteroid stock, and there is good evidence that a sub-radiation of these mecopteroid orders (sometimes called the panorpoid complex) provided the origin for the present Mecoptera (scorpionflies), Diptera (true flies), Siphonaptera (fleas), Trichoptera (caddisflies), and Lepidoptera (butterflies and moths).

Evolution Wings and flight

Insect wings develop as paired outgrowths from the thorax, stiffened by ribs, or veins, in which run tracheae. These tracheae follow a consistent pattern throughout the Pterygota, and their specific modifications (known as venation) are important in classification and in estimations of the degree of relationship between groups. The basic consistency of venation suggests that wings have been evolved only once among the insects; that is, all the Pterygota arose from a single stem in the family tree (see above). By the time fossil insects are found (toward the end of the Carboniferous), wings are developed fully. In the Paleoptera the wings are held aloft above the back, as in mayflies, or held extended permanently on each side of the body, as in dragonflies. Throughout the Neoptera there is a wing-flexing mechanism (secondarily lost in butterflies) that enables the wings to be folded back to rest on the surface of the abdomen.

Winged insects must have made their appearance very early in the Carboniferous, but there is no fossil evidence to show the way they evolved. One hypothesis is that wings arose as fixed planes extending sideways from the thorax and that these planes were used, perhaps in some large leaping insect, for gliding. Later muscles developed, first to control inclination and then to move the wings in flapping flight. Another hypothesis is that wings may have originated from large thoracic tracheal gills, similar to the movable tracheal gills along the abdomen of some mayfly larvae. Such outgrowths could have been useful to insects exposed by the drying up of a temporary aquatic habitat and might have carried them in rain-bearing winds to a new watery home. It is likely that the most primitive symphylan-like insects were terrestrial. Throughout insect evolution, however, independent adaptations to aquatic habitats have occurred. Usually the pattern is one in which the adults leave the water and disperse. Many pterygote insects have become secondarily wingless, sometimes as single species or groups of species within large orders and sometimes as entire orders (the parasitic lice, Mallophaga and Anoplura, and the fleas, Siphonaptera).

Metamorphosis

It generally is agreed that insect metamorphosis evolved as adult insects gradually adopted different modes of life from those of larvae. The characters of larva and adult became genetically independent; in response to natural selection, therefore, each was able to evolve independently of the other. Mouthparts, limbs, and other morphological features were modified in different directions and in higher groups. Where these differences were extreme, an intermediate pupal stage evolved to bridge the morphological gap between larva and adult. It seems quite probable that the development of metamorphosis occurred more than once during the evolution of insects.

Feeding methods

Insects did not evolve in a constant environment. Throughout geological time there were prodigious changes in climate; in addition, evolution was continuous among all other animals and plants. Geologically the selection pressures among insects were changing continuously. At the end of the Mesozoic Era the first flowering plants appeared. Insect evolution has paralleled that of the flowering plants; they have evolved together. As Lepidoptera (butterflies and moths), Hymenoptera (ants, bees, and wasps), Diptera (true flies), and Coleoptera (beetles) began to feed upon flowers, nectar, or pollen, flowering plants came to rely more and more upon insects—rather than upon the wind—for transferring their pollen. Flowers evolved nectaries, scents, and conspicuous colours as attractants for those insects that could effect cross-pollination. Insects likewise evolved appropriate mouthpart modifications for extracting nectar from flowers.

During the Mesozoic warm-blooded animals (mammals and birds) first appeared; by the dawn of the Paleogene Period, they had become predominant among the Earth’s large animals. The warm fermenting excrement and the decaying dead bodies of mammals furnished excellent nutrient media for many insect larvae, notably among the Diptera and Coleoptera. The adults in both groups found their nourishment in flowers. Some heteropterans (true bugs) and dipterans pierce the skin of birds and mammals and feed on their blood. The Anoplura (sucking lice) and the Siphonaptera (fleas) have become so specialized for this type of parasitic existence that their relationships to other insects are not yet known with certainty.

Continuing evolution

Evolution is occurring among present-day insects. They exhibit a balanced genetic polymorphism; in other words, in response to small environmental changes, one genetic form, more successful than another, will become more plentiful. Sometimes there is no visible difference between these forms, the advantage presumably lying in some physiological change. It is advantageous for a species to have a gene pool from which favourable characters can be selected so that the species can respond to environmental changes. Changes within a species may occur progressively over a large geographical area. Such a progressive genetic change is termed a cline; in some cases insects at the extremes of the cline are so unlike that they are taken as separate species and may be infertile when crossed.

One well-known example of evolution in action among insects is industrial melanism (accumulation of the black pigment melanin); many butterflies inhabiting industrial areas have become almost black during the past century, black forms being more tolerant of pollution and less conspicuous to predators. Another example of this cline type of evolution is the development of insect strains resistant to an insecticide that has been applied heavily in an area for several years. In many parts of the world houseflies became highly resistant to DDT.

Edited August 30, 2013 by Humblemunn

[Humblemunn]

Then learn more.

I have indeed. Here's my best guess as to the identity of these speculated giant bug UFOs:

 

Diaphanopterodea

 

The Diaphanopterodea or Paramegasecoptera are an extinct order of moderate to large-sized Palaeozoic insects. They are first known from the Middle Carboniferous (late Serpukhovian or early Bashkirian in age), and include some of the earliest known flying insects.

Overview

Despite their very early appearance in the insect fossil record, they represent a specialised group of Palaeodictyopteroidea (Palaeozoic beaked insects), unique among representatives of that group in having evolved the ability to fold their wings over their thorax and abdomen in a manner similar to, but not homologous with, the Neopteran insects. The nymphs also had an unusual appearance, being covered in numerous hairlike filaments.^[1]

Diaphanopterodea are distinguished by a number of other characteristics, and are generally considered to be a monophyletic group. About ten families are known. The group died out at the end of the Permian period, victims of the End-Permian mass-extinction, without leaving any descendants.

 

We have only assumed they died out, though, haven't we? Perhaps there were descendents which survived the mass extinction?

 

The wing-folding is a required feature to fit the UFO hypothesis. This paper might help in deciding other potential candidates: Wing folding in pterygote insects, and the oldest Diaphanopterodea from the early Late Carboniferous of West Germany

 

Edited August 30, 2013 by Humblemunn

[Arete]

Insects do not actively "breathe" the way that vertebrates do. They rely on natural gas dispersion through their rigid tracheal tubes to fuel cellular respiration. We know that gas dispersion decreases along the length of a tube. As such, there becomes a point where a tube is too long for natural gas dispersion to deliver enough oxygen for effective cellular respiration. This in turn means that there is an upper limit on the length of tracheal tubules in insects, and therefore their body size.

 

It therefore follows that, if in the past, the quotient of oxygen in the atmosphere was increased, the maximal length of a tubule effective for respiration would increase, thus allowing larger insects. This is used as a potential explanation of the larger insects seen in the fossil record.

 

Therefore, if the original evidence you're presenting is deemed correct, and I see no reason for it to not be, it actually provides a clear explanation as to why super sized insects are not extant in the present day.

[Humblemunn]

Insects do not actively "breathe" the way that vertebrates do. They rely on natural gas dispersion through their rigid tracheal tubes to fuel cellular respiration. We know that gas dispersion decreases along the length of a tube.

Without doing any searches, wouldn't a fast flying large insect be able to force air down long tracheal tubes? This also fits with eyewitness observations of entities which suddenly spring from the earth's surface into the air with tremendous speed.

 

Also, it could have evolved a mixture of short and long trachea tubes for a combination of fast flight and some slow speed flight, but not perhaps an inbetween speed. Just two possible speed settings would also fit with eyewitness observations.

Edited August 30, 2013 by Humblemunn

[Moontanman]

So we are talking about giant beetles that fly at hundreds if not thousands of miles an hour and glow in the dark? This is not even close enough to being right to be wrong.

 

How or why would a giant insect be able to make a right angle turn any better than a human pilot in a jet?

 

Cube square law... just saying...

Where do they breed, where are the giant insect larvae?

[Arete]

Without doing any searches, wouldn't a fast flying large insect be able to force air down long tracheal tubes?

 

Not really. Tracheal tubes are one-way tubes so blowing in the surface of them does little to increase dispersion. Even it it did, as soon as the insect came to rest it would begin suffocating.

 

To repeat, the initial link actually provides a plausible explanation of why giant insects DON'T currently exist, rather than provide a platform to speculate that they still do.

[Humblemunn]

So we are talking about giant beetles that fly at hundreds if not thousands of miles an hour and glow in the dark? This is not even close enough to being right to be wrong.

 

How or why would a giant insect be able to make a right angle turn any better than a human pilot in a jet?

 

Cube square law... just saying...

Where do they breed, where are the giant insect larvae?

(i) Not necessarily beetles no, especially due to their high chitin content which would have been fossilised and found potentially.

 

(ii) Hundreds of miles an hour with bioluminescence, yes

 

(iiI) Because they would have evolved to do so. Humans have a blood pressure issue I believe.

 

(iv) They breed in remote places we can't get to. Funnily enough, there is a case of bizarre giant insect larvae:

 

The Creature of the Dump

 

Paula's first reaction to seeing this "thing" was saying, "Oh, my God! What are you?"

Paula was familiar with the outdoors and was reasonably sure of what animals she might encounter in a junkyard. But this thing she could not identify. She stepped cautiously closer to it, thinking that the vibration of her digging maight have driven it from its burrow.

She stopped about four to five feet away from the creature. What she could see of it was poking out of the ground about five inches. "At this point, I wasn't sure what end of the animal I was looking at," Paula said. "It was about two inches in diameter, and the end of it was perfectly smooth and round - like a cue ball. It was light-brown in color, very much like the surrounding earth. It had a worm-like shape, but didn't taper down at the end as worms do, and was firmer around looking. It had no distinguishing or familiar features to indicate to me what it was."

Its size made it obvious that this was not a worm - at least not any kind of worm Paula had ever heard of. And she could not see its entire body, only what was poking out of the ground, so who knows what the rest of this thing really looked like.

STRANGE EYES

Paula looked at the creature closely, trying in vain to find anything familiar about it. She could not detect any eyes, mouth, nose or ears. It had no fur, scales or worm-like ripples on its skin. What it did have was patches of peach-like fuzz - very fine and spaced apart like the hair on a young human's arm - covering what looked like soft, dusty skin about the texture of a person's. It was not wet, slimy or tough looking.

By now, Paula was completely perplexed. This was like nothing she had ever seen in person, at a zoo, or on any nature program on television. And if this creature wasn't strange enough, it then gave Paula a remarkable surprise.

"All of a sudden," she said, "while I was examining it, two big beautiful crystal blue eyes popped open! Now I knew what end of the animal I was looking at."

All thoughts of this being some kind of giant worm were immediately dismissed. Worms don't have eyes - not like that! More curious than frightened of this remarkable animal, Paula began to wonder how big the body was and what its arms, legs, and tail looked like - or if it even had any such parts. "The white of the eye surrounding its blue iris was the whitest I'd ever seen - a pure virgin white. The size of the eyes were quite big in proportion to its body size. I wondered if it were a juvenile."

Paula was totally astounded when the eyes opened because while first looking at it she could not tell that it had eyes at all; there were no visible eyelids, eye lashes, bulges, indentations, holes or slits of any kind. The curiosity seemed to be mutual. "My presence didn't seem to bother it because it studied me for only a short period of time. Then it ignored me. It appeared content and relaxed while it exposed itself to the sun. Its slow motion movement and blinking reminded me of a turtle."

A CLOSER LOOK

Paula felt that the creature was harmless and stepped even closer to it for a better look. She looked for its mouth, nose, and ears, but couldn't find them. She wondered if they were camouflaged in the same way that its eyes had been. She also tried to determine where its head ended and neck began because it had no chin or indentations of any kind to separate the two. The body, neck, and head appeared as one - like a living, flexible tube with eyes.

Paula was startled when the creature began to move, and she instinctively stepped back. The animal slowly began to sway the top of its body back and forth as it stretched itself upward toward the sky, all the while slowly blinking.

"I tried to get it to look at me again by clapping my hands and yelling, but it continued to ignore me." Since it had no discernable ears, Paula wondered if perhaps it couldn't hear sound. So she tried waving her arms and hands about to draw its attention to her. But all it did was stare at the sky, continuing to sway its head back and forth, stretching upward while blinking slowly. It was as if it were hypnotized by the light of the sun.

BACK UNDERGROUND

After about five minutes, the creature decided to retreat into its lair. "I watched it until it finally pulled itself slowly back into its burrow. I looked into the hole after it, but it was so dark that I couldn't see anything."

Paula isn't quite sure what to make of this peculiar encounter, but it haunts her. "I haven't been able to erase it from my mind, and it's driving me crazy! I've asked many people about it and have spent countless hours searching the Internet for answers to any known or unknown animal fitting the description of the animal."

Paula returned to the dump site the following Spring in hopes of getting another glimpse of the mysterious creature. No such luck. Some of the hole openings were there, however. "I am convinced that this animal still exists and lives there. It's possible that it hibernates, so I will go back again in early to mid-summer and try and get another glimpse of it - and possibly capture it on film."

Hopefully, Paula will succeed in capturing the animal on film or video. It could be something well known to science, if unusual. For now, however, the creature of the dump remains unknown.

If any readers out there suspect they know what this mystery creature might be - some kind of weird eel, lungfish or whatever - write and let me know. Or if you have encountered anything like it - or any other kind of unexplained creature for that matter - tell me about that as well. For current reader ideas, see "The Dump Creature: What Was It?" - S.W.

Not really. Tracheal tubes are one-way tubes ...

You've missed the point entirely. I'm speculating that non-deadend trachea tubes have evolved in some insects. So my air-jet hypothesis does have some validity.

 

...........................................................................................

 

I searched on-line for more worm-like possible giant bug larvae and happened across this Look Out for the Tatzelwurm “Worm with Claws” and found this tentative connection with insescts:

 

 

Other Behaviors of the Tatzelwurm

The Tatzelwurm has been reported as a hibernating creature, which hibernates during the winter. They say it sleeps in crevices on mountainsides which has also given it the German name stollenwurm (worm that lives in holes). But on occasion farmers did find them sleeping in hay stacks and barns.

 

One certain farmer reported killing a hibernating Tatzelwurm at which point a green liquid drained out of it’s mouth. Then in 1924 two men discovered a five foot long skeleton resembling that of a lizard. So of course the legends continued, and I don’t know if there’s any truth to them, or maybe folks were creating stories from things that could be related to the mythical creature.

 

 

Why Is Insect Blood Green Or Yellow?

 

You’ve probably heard someone use the phrase “blood red,” but have you ever wondered if all blood really is red? For example, think about the bugs you’ve seen splatter against your car’s windshield, leaving behind a clear, yellowish, or greenish liquid. That liquid, is hemolymph, or insect blood.

Insect Blood

The blood of an insect functions differently than the blood of a human. In humans, blood gets its red color from hemoglobin, which travels through blood vessels carrying oxygen from the lungs to the rest of the body. Insect blood, however, does not carry gasses and has no hemoglobin. Instead, bugs have a system of tubes that transport gasses directly between their cells and the outside air.

In fact, insects don’t even have blood vessels. Instead there is a hollow space inside their external skeleton in which their blood oozes around. This cavity extends to the antennas, legs, and wing veins. The bug’s heart, a long tube that stretches the length of its body, pushes the blood from the rear end of the insect on forward. The bug may also have little hearts at the ends of its extremities to help move the blood along.

Pigment

Pumping blood is a slow process: it takes about eight minutes for an insect’s blood to circulate completely. Like human blood, bug blood carries nutrients and hormones to the insect’s cells.

Hemolymph itself, the insects' "blood" lends the yellowish color, while hemocyanin, the oxygen-transporting copper-based complex in the higher arthropods lends the greenish color.

 

 

 

This is an alleged photo of one:

 

Edited August 30, 2013 by Humblemunn

[Arete]

You've missed the point entirely. I'm speculating that non-deadend trachea tubes have evolved in some insects. So my air-jet hypothesis does have some validity.

 

The tracheal tubes of insects look similar to our circulatory systems, in that they start out as large tubes and branch until they deliver air to individual cells e.g.

 

 

As such a large tube straight through an insect's body would not function effectively to deliver air to cells. An open ended invertebrate tracheal system would have to function in an entirely different manner to those currently known. It's kind of like speculating that a population of elephants evolved their ears to enable them to fly, and that's what UFOs are.

[CharonY]

 

 

It's kind of like speculating that a population of elephants evolved their ears to enable them to fly, and that's what UFOs are.

 

Interestingly that is precisely what crossed my mind when I read OP. But I was sure that he could not really mean that UFOs could be giant insects, as the first part of the post (as has been noted) clearly describes the size limitation. But alas, I was proven wrong.

 

It should also be noted that flight is quite energy-demanding, requiring even higher respiratory rate which makes large flying insects even less likely.

[Moontanman]

(i) Not necessarily beetles no, especially due to their high chitin content which would have been fossilised and found potentially.

 

(ii) Hundreds of miles an hour with bioluminescence, yes

 

(iiI) Because they would have evolved to do so. Humans have a blood pressure issue I believe.

 

(iv) They breed in remote places we can't get to. Funnily enough, there is a case of bizarre giant insect larvae:

 

The Creature of the Dump

 

 

 

You've missed the point entirely. I'm speculating that non-deadend trachea tubes have evolved in some insects. So my air-jet hypothesis does have some validity.

 

...........................................................................................

 

I searched on-line for more worm-like possible giant bug larvae and happened across this Look Out for the Tatzelwurm “Worm with Claws” and found this tentative connection with insescts:

 

 

 

 

 

Why Is Insect Blood Green Or Yellow?

 

 

 

 

This is an alleged photo of one:

 

That picture is not the picture of any arthropod, larvae or adult...

[Endy0816]

Giant Glowing Beetles in the sky!

 

It is only a matter of time that some mutant GM bacteria causes them to hybridize with the Bombardier Beetle. The attack on humanity will soon commence!

[Humblemunn]

The tracheal tubes of insects look similar to our circulatory systems, in that they start out as large tubes and branch until they deliver air to individual cells e.g.

 

 

As such a large tube straight through an insect's body would not function effectively to deliver air to cells. An open ended invertebrate tracheal system would have to function in an entirely different manner to those currently known. It's kind of like speculating that a population of elephants evolved their ears to enable them to fly, and that's what UFOs are.

You're not giving evolution the respect it deserves. You're statement "As such a large tube straight through an insect's body would not function effectively to deliver air to cells" is unvalidated guesswork.

 

The true experts are willing to admit that the evidence is scant on the "oxygen-limitation" hypothesis:

 

What Keeps Bugs from Being Bigger?

 

This study is a first step toward understanding what controls body size in insects. It’s the legs that count in the beetles studied here, but what matters for the other hundreds of thousands of beetle species, and millions of insect species overall, is still an open question.

 

If the orifices to the legs limit beetle size, then why not just grow bigger openings? There may be genetic or developmental barriers that can't be overcome. Or, the issue may be mechanical. Insects wear their skeletons on the outside, and therefore many joints need to be narrow to work. Perhaps an oversized orifice would mean that the leg-body joint wouldn’t bend as well.

 

Is it too much to consider the possiblity of non-leg-segmented evolution in some flying insects? Reported bizarre flying entities are reported with thick legs and almost humanoid in appearance. This fits with the giant bug hypothesis and the respect for evolution and the fact that we don't know everything.

 

Strange but true?

It should also be noted that flight is quite energy-demanding, requiring even higher respiratory rate which makes large flying insects even less likely.

This seems slightly illogical imv. With the necessary oxygen intake, the energy-demand for flight isn't an issue. It would be highly advantageous for an insect species to be of giant size. No more fear from birds. It would be the other way round.

 

Edited August 31, 2013 by Humblemunn

[Humblemunn]

A unidirectional flow of air for a flying insect would be highly advantageous, analogous to the unique evolutionary system of the birds:

 

The air sacs permit a unidirectional flow of air through the lungs. Unidirectional flow means that air moving through bird lungs is largely 'fresh' air & has a higher oxygen content. In contrast, air flow is 'bidirectional' in mammals, moving back and forth into and out of the lungs. As a result, air coming into a mammal's lungs is mixed with 'old' air (air that has been in the lungs for a while) & this 'mixed air' has less oxygen. So, in bird lungs, more oxygen is available to diffuse into the blood (avian respiratory system).

 

 

 

[Arete]

You're not giving evolution the respect it deserves. You're statement "As such a large tube straight through an insect's body would not function effectively to deliver air to cells" is unvalidated guesswork.

 

 

Given it's my profession to study evolution I think I certainly give it the respect it deserves.

 

I think you're unwilling to consider basic insect physiology - the purpose of the tracheal network in an insect is to allow air to dissipate through the insect's body, so that air can reach cells - much in the same way that a vertebrate circulatory system's purpose is to allow oxygenated blood to reach the cells of the vertebrate's body. A large diameter tube though an insect's body will not achieve this function. As such in order to achieve your unidirectional airflow proposal, the suggested "giant" insects you're proposing would need a respiratory system substantially different from both the insects observed in the fossil record and the present day - i.e. substantially different from any insect respiratory system currently known.

 

Also, the quotes you're using to support the assertion that "admit that the evidence is scant on the "oxygen-limitation" hypothesis" don't actually suggest that at all, and come from a popular science article and not the primary research itself. I would also outright disagree with the first quote - studies on diffusion limitations on insect body size date back to the early 1900's: www.jstor.org/stable/2810299

 

and there's a plethora of studies supporting the hypothesis:

e.g.

http://www.pnas.org/content/104/32/13198.short

http://deepblue.lib.umich.edu/handle/2027.42/62968

http://rspb.royalsocietypublishing.org/content/277/1690/1937.short

 

So, the evidence you cite (and other work on the topic) provide a well supported explanation of why giant insects DON'T currently exist, rather than provide a platform to speculate that they still do. The irony of suggesting that rejection of your proposal is based on "unvalidated guesswork" is that what you're asking us to accept is that UFO sightings are explained by giant, luminescent beetles no one has ever actually observed, which have evolved completely novel respiratory systems also never observed in any insect, past or present.

Edited September 2, 2013 by Arete

[Ringer]

Insects do not actively "breathe" the way that vertebrates do. They rely on natural gas dispersion through their rigid tracheal tubes to fuel cellular respiration. We know that gas dispersion decreases along the length of a tube. As such, there becomes a point where a tube is too long for natural gas dispersion to deliver enough oxygen for effective cellular respiration. This in turn means that there is an upper limit on the length of tracheal tubules in insects, and therefore their body size.

Out of curiosity, was this tracheal tube system homologous to, say, a primitive chordate circulatory system or were they derived independently? Also, is it understood what the primitive character state was for this? I assume extremely primitive states relied solely on Brownian motion, but I've not seen how many primitive circulatory systems are assumed to have evolved independently.

[Arete]

I have no idea regarding common evolutionary history - but systems to deliver things or connect cells in multicellular organisms - such as the insect respiratory system, vertebrate circulatory/nervous/lymphatic systems, plant vascular systems all seem to have a degree of morphological homology - I'd hazard a guess at it being resultant of convergence due to similarity in function, rather than parallel evolution though.