I N S E C T F L I G H T
A. The accepted theory and its critique.
The accepted theory of the origin of insect flight is not usually
called more than the "most acceptable theory". On the other hand its
weak points are not often discussed either. But by clearly pointing
out these problems it is possible to list a number of requirements
that a theory of evolutionary process must meet to be convincing.
This essay presents an alternate theory in the form of a chain of
reasoning based on existing facts, and it will attempt to meet these
requirements. Like any in any logical exercise, the idea proposed
will be acceptable or unacceptable depending on whether the existing
facts are correct and whether the reasoning is acceptable.
A theory of the origin of insect flight must answer these questions:
What is the origin of the wings and of the flight mechanism?
What function did these have when first emerging which would be adaptive
and keep the from disappearing?
If these functions were not the same as presently, how did changes
in functions occur?
What is the sequence of events that offers the minimal gaps in the
continuity of the development?
What support for the theory can be drawn from existing facts?
Has any of these original elements survived in some form?
Before going into the new theory it will be useful to review the accepted
rewritten till here 10/7 Sunday night
ACCEPTED THEORY 1
<[>Origin of wings and flight: "The...widely accepted
paranotal theory postulates that wings arose from lateral tergal expansions,
or paranota, of the thorax. It is maintained that the prothoracic
lobes of some of the most ancient fossil insects are organs of this
kind which had persisted long after the paranotal of the other thoracic
segments had developed into o wings. Paranotal expansions occur in
positions characteristic of wings, not only in the thorax, but also
on the abdomen in various arthropods; among insects they are seen
in many larvae and also in Lepisma, where they contain tracheae recalling
those of a wing pad. It is suggested that they became sufficiently
large to function as gliding planes or to control landing in leaping
insects. Later they acquired basal articulations which, along with
the development of muscles, enabled them to become organs of independent
flight. It is not improbable that at an early stage in their evolution
wings were concerned more with sexual display or temperature regulation
than flight." R. G. Davies, Outlines of Entomology, 1988 p.
There is also a tracheal gill theory, which is not accepted, because
wings and gills do not share the same anatomical development and "do
not seem to be serially homologous with tracheal gills". It is also
based on assuming that winged insects had aquatic ancestors, and this
is not supported by the facts. (ibid.)
ILL - Protorthopteran fossil reconstruction!
ACCEPTED THEORY 2
"It is now widely, but not universally accepted that insect wings
arose from meso- and metathoracic paranotal lobes, homologous with
those which occur on the prothorax of members of the Paleozoic order
"In these ancestors it is supposed that the lobes later came to serve
for delaying descent, as parachutes and then as aerofoils, those on
the meso-and metathorax becoming enlarged and MODIFIED
UNTIL M WITH ASSOCIATED CHANGES IN THE SKELETON, MUSCULATURE
AND NERVOUS SUPPLY OF THE THORAX, TRUE FLAPPING FLIGHT WAS EVOLVED.
THE PROTHORACIC LOBES BECAME OBSOLETE and ULTIMATELY
DISAPPEARED, AFTER PERSISTING FOR A WHILE IN A FEW LINES."
(R. J. Wootton (chapter The fossil record and insect flight, p.
ACCEPTED THEORY 3
(Wigglesworth):
"At the present time there
is almost universal support for the paranotal theory. Most authors
suppose that the outgrowths were favoured in selection by their ability
to serve as planes utilized in gliding from high vegetation to the
ground. Hinton starts further back and considers the first step towards
flight to have been attitude control of legs and body to ensure that
the falling insect landed on its feet and could make a quick escape
from predators, namely spiders. Enlargement of lateral outgrowths
would be a later step in making true gliding possible. Flower, who
suggests that gliding could have begun in small insects of 1 cm length
even before lateral planes appeared, points out that diminutive paranotal
lobes at their earliest appearance could have played an important
role in attitude control.
"Then, as visualized also by Pringle, hinges to the planes and muscular
control of their inclination would enable large adult insects to exercise
control over the direction of gliding; and, finally, relatively slight
alterations in the muscular system would provide for slow flapping
flight. That is probably the most widely accepted conception of the
evolution of wings and flight. (V. B. Wigglesworth: The Evolution
of insect flight in Insect Flight, ed. R. C. Rainey,
Symposia of the Roy Entom Soc of London, 1976).
ACCEPTED THEORY 4 -- WOOTTON!!
The paleontological evidence, slender as it is, seems to favour the
existence in the Devonan a small -- c. 10mm? -- insects, whose initially
protective(!) thoracic paranota became enlarged in association
with their value first as parachutes, in delaying descent; next as
gliding surfaces; then as steering vanes, as they developed the ability
to slightly pronate, supinate, el;evate and depress the pads by action
of the pleural leg muscles."
This theory presents the following weak points:
NO OXYPRAGMA -- 1. did these flanges or vanes arise at a size and
shape useable for gliding? To say that they did so assumes that they
were immediately plane-like, two-dimensional, not round in cross section,
that they were of sufficient surface area and that they were angled
at more or less horizontal. Suppose the origin of these flanges was
apical, long, rod-shaped? Ill Could these survive selection
until they mutated, accidentally without any selective pressure into
flange shape? It seems there is a lack of continuity in the evolution
of wings.
DEPENDS ON JUMPING -- 2. The theory also assumes the existence of
a jumping function prior to the appearance of flanges/wings. But considering
that even in the order Orthoptera, where grasshoppers and crickets
belong taxonomically, other (genera), Blattidae, or cockroaches, Mantids,
most certainly in possession of wings, show no sign of jumping structures
and behavior, it is also an arbitrary assumption that jumping is the
basis of wing origin.
PROBLEMS WITH DEPENDENCE ON JUMPING -- 3. NEW TEXT: There are a number
of variables here. One is the location and position of plane of the
flange (or flap or vane), and the other is the attitude, or angular
position of the body at the instant of leaping. ILL
If the postion of the flange is correct for a jump that starts
from horizontal, it will be unsatisfactory for a jump starting on
a 60% plane ?? THINK ABOUT THIS! And even noregenerally, an immobile
vane is optimal only if it is in the correct plane, and only in certain
parts of the jump trajectory. A horizontal vane will not only impede
the vertical vector of the speed of descent, it will also similarly
impede the ascent. This poses the question why slow down an escape
HERE I AM ASSUMING THE THE TRAJECTORY IS SYMMETRICAL! IS IT WITH HOPERS?
PARACHUTING -- This action slows descent and so it does not seem to
be especially useful to an insct escaping. It is hard to see any advantage
to it in any other activity. As a mating display it appears contrary
to profit, because approach rather than distancing is the aaim. To
say that perhaps paarachuting was performed by a pair of the mating
insects, and they remained close to each other is a possibility, but
full of problems. The only possible way parachuting would work might
be as a mating swarm, where a large moving mass of insects create
a visual and perhaps auditory attraction for other individuals.
OLDER TEXT:For flaps or flanges to aid the aerodynamics of jumping
the position of the insect body in relation to the direction aimed
at poses certain requirements. The flanges lie horizontally only if
the long axis of the jumping insect is both longitudinally and cross-sectionally
horizontal ill. Obviously, if the flanges are at any angle
to the direction of flight, they impede the jump. Grasshoppers very
often (%?) jump from vertical position on a stem or branch and in
such position the pronotal vanes would not help them land upright
-- they would oppose motion forward, Ill . A minimum fitness
of design must be reached before the requirements of proper aerodynamic
performance. If the flaps were relatively large relating to the mass
of the main body, they would have slowed the jumpers speed both ascending
and descending. It would have been then better to have large mass
relative to smaller vanes surface,. But this would tend to defeat
the purpose. And as the insect imagined becomes smaller, so is the
possibility that vanes would make it practically float. Such narrowly
limited design is not what is usually found in a source of fast evolution,
such as the "invention" of the e wing and flying. This does not seem
like a source of explosive development
)By the way jumping and then flying could have been the way
HARDLY ANY PTERYGOTES JUMP -- 4. Here is a question: considering that
it is only the Orthopteran order that contains jumping insects, and
in this order of 5 suborders and 12 families, only 2 suborders and
7 families are jumpers, why should we think that flight is derived
based on jumping. We are talking about grasshoppers and crickets as
against walking sticks, timema(=?) mantids, cockroaches and rock crawlers.
It just does not seem likely that cockroaches or the mantids could
have once been jumpers but had later lost the ability. They would
have had to redesign a highly specialized jumping mechanisms built
into the hind leg and the general mass-force design required for sensible
projectile direction.
WHY IMPROVE ON JUMPING ANYWAY? -- The closely slected development
of a aerodynamic flap is certainly conceivable. A vane quite small
in relation to the insect's size could be sleected for maximizing
the occasion the insect lands right-side up. This can be effective
in escape. But it only matters in sparsely covered ground. In thick
vegetaion or a jumping insect disappears because its speed is not
successfully followed by the visual system of an observer, and as
long as it is no longer seenm the jump is positively selected. After
all, jumping is a rather good way of escaping for grasshoppers at
least from human attention. But if birds and mammalian carnivores
are better at it, they were not around into Carboniferous days of
jumpers, when on land only primitive vertebrates existed, and other
insects where with nothing better than insect vision. Why would it
be necessary to improve on jumping? The presence of the giant Negater,
with a 70 cm wingspan possibly indicates that there were no larger
faster predatory insects: it likely was so big because it was at the
top of the food chain. If these conditions of predation prevailed
in early times, then jumping by insects may have evolved in relation
to reptiles and mammals.
NO SIGN OR VESTIGE OF SALTATION IN OTHER PTERYGOTA!
6. As yet another objection to jumping as precursor of flight, it
can be asked that if such was the case, how is it that not the slightest
vestiges of jumping structure or behavior are present in any form
whatsoever in the great many kinds of flying insects? And even though
they have all acquired wings, it seems unlikely that these orders
and families at one time jumped. But as we shall later see in this
argument, traces of other functions, which could have been origins
of wings can be identified.
DID SALTATION arise from stridulation IN ORTHOPTERA AT LEAST?
7. Come to think of it, how did jumping originate? It requires an
initial starting action and properly designed apparatus. How could
it then start from scratch? Could an insect begin jumping by deciding
to do so, using legs that have never been able to jump? As discussed
above in the role of stabilizing vanes, if requirements dictate limited
tolerance how probable is the arising of a new function and structure?
It seems reasonable to suppose that an innovation that may not be
useable until further development has little chance of surviving,
and so the innovation should be brought up, so to speak, in a tolerant
nursery environment where it can freely change and experiment under
protection from disappearance. As seen later, this is exactly the
environment that logically gave a start and developmental possibilities
to flight in all phyla(?). And in this way even the origin of jumping
can be explained. (See later: jumping, that is the development
of an enlarged hind leg is easily derivable from stridulation!)
Or add it here?
WHERE DOES THIS GO??? TO STRIDUL origin of JUMP, where
it doesn't Support! Most acridoids make no sound! "Actually,
the majority acridoid world fauna is formed by the Catantopinae, Pyrgo
morphidae and Acridinae, which have no sound producing mechanism,
or only poorly defined ones. It is worthy of notice that an expansion
of the medial area of the hindwing, forming a tympanate area, occurs
not infrequently in some Acridinae in which no specialized sound-producing
organs are known, for example in Acrida, Amohicremna, Entryxalis and
others; Acrida, however, makes a distinct flight noise. B.
Uvarov, Grasshopper and Locust, Cambridge U Press, 1966 (I THINK
this is really supportivE!)
SUPPORT for STRIDULATION LEADING TO JUMP: There are femoro-tegminal
and tibio tegminal mechanisms for stridulation. Of tibial types, subfamily
Hemiacridinae has rubbing by "inner spines or spurs of the hind tibia."
( though direct observations on action are lacking. Uvarov Grasshoppers
and Locust p ?
But then this IS SUPPORT: "Several genera of African and Asian savannah
grasshoppers have sines on hind TIBIA, and they rub these against
the usual scrape vein of the tegmen, but they also have the usual
femoro-tegminal mechanism. "They also have well developed tympanate
areas of the tegmina" Uvarov p.180 . AND there is another common
mechanism: tegmino-femoral! Here roles are changed, femur has a simple
scraper ridge, "which rubs against a specialized intercalary vein..."
<<Uvarov, but THIS is not important!
Also: "Most (but not all) of acridoids have a pair of tympanal organs
on each side of the first abdominal tergite" Uvarov, p.189 (THIS GOES
TO CICADA TYMPANUM SUPPORT?)
JUMPING IN OTHER PTERYGOTA
8. Other winged jumpers are the tree and leafhopper Heteroptera. Her
the legs are not the agents of jump, but some mechanism inside the
thorax is. (LOOK UP!) But these insects also produce low-level sounds.
(Most likely the sounds are produced n the thorax, and this has lead
to jumping!-work this out !)
SUMMARY OF WEAKNESSES IN ACCEPTED THEORY
In summary, there are four things the established theory lacks:
i) accounting for the physiological source of flanges, the functionality
of its undid shape, size, function.
ii) It provides no immediate use for the structure in its earliest,
germinal form. (Oxydynamism.)
iii) It assumes that a flange can be used only for flight (no polydynamism)
iv) it does not provide a continuous account for the development
of wings from flanges. It only states that wings develop
from flanges. How exactly would stabilizing planes develop
moveability? (No continuity - synecheia),
only a coarse resolution of details.
LESSONS LEARNED AND A PROPOSAL: A NEW THEORY THAT AVOIDS THESE PROBLEMS
AND MEETS THE REQUIREMENTS: ontology, oxypragma, polypragma, synechia
and support
Keeping in mind these weak points we can establish a more convincing
theory that will account for
a) The immediate functional applicability of the original wing source/structure.
Since we shall refer to this quality often, it might be good to use
the term oxypragma. As an example of oxypragma we can cite
b) The physiological basis for its emergence, or its ontogeny.
The ontogeny of . . .
c) The way in which, if the proposed original or earlier function
was not the same as its later-evolved function, it could somewhere
in the sequence of its development immediately, or oxypragmatically
provide a basis for flight. The ability of a function to perform an
additional function or more can be called multifunctionality or
polypragma. An example of polypragma is - - -
d) An acceptably detailed and continuous account describing the stages
of an evolutionary sequence, This can be called continuity
or synechia. For example . . .
LOOKING FOR A NEW THEORY
QUESTION OF ONTOLOGY AND OXYPRAGMA
To start off let us look at the fundamental structure of the insect
wing. W have to start off with the paranotal lobes, since these are
these are the only physical evidences for anhting resembling a wing.
A paranotal lobe is anatomically an evagination of the integument,
or a folded plate of an insect's integument. This fact provides for
the original source of its existence, the emrgence of a lobe can be
seen as an accidental, trivial development of already existing material
and structure. The inherent tendency of insectan integument and indeed
of fundamental biological defvlopmetn to fold over is a solid basis
for such an assumtion. However, the action of folding has no connection
to muscluar structuring. Originally there is no basis or necessity
for the lobe appendage to be moveable. If immovebale, the lobe could
only help in gliding, but this idea has beeen shown to present complications.
Furthermore, what was the absolute size of the lobe when it first
became existent? How large did it have to be to be considered existenet?
Clearly there is a n undefiuned range of size wherein the lobe would
be present yet not of a size where it could be significant in magnitudes
related to physical actionm such as an aerodynakic role? How large
does to perform some function that could be significant in insect
behavior and adaptation? So far in the paleontological record we have
and may never have any clues to these questions. It is time to move
further back and take a broader view at insect behavior: some function
must be found that would enable the emergent lobes to perform an adaptive
function. Oxypragma must be found for the earliest emergent lobes.
PANORAMA OF INSECT BEAVIOR TO FIND POSSIBLE APPLICATION FOR OBSERVED
LOBES. Insect behavior typically consists of the following faculties:
Sensory perception
Basic responses and patterns of behvaior (Reflexes, learned and instinctual
Peridocity and clocks
Orientaion, navigatingm homing
Host selection and feeding
Parental care and presocial behavior
Population behavior
Behavior, genetics, evolution and speciation
Eusocial behavior
In all the above where could an insignificant, minute lobe, with no
moblity assume an adaptive function? We can select sensory reception,
communication as the only imaginable parts of behavior where such
structure could be adaptive. A small extension of the body wall could
act as a propriomechanical sensor, one detecting movements of the
body, or perhaps as an optical or tempoeratursensor, but there is
little trace of specialized neurological equipmtn associated with
present day wings, so this assumption seems semi-trivial.
But as for communication, we need not look to far, because we know
of many small structures in existing insects that can play a role
in sound production, namely minute appendages, serrated or otherwise
designed for stridulation. It therefore stands to reason that a proto-lobe,
a small extrusion of integument on the thorax can be rubbed by a leg
for making sound. For te sake of an argument we can say that we have
found an oxypragma, or immediate adaptive applicability for
paranotal lobes at an early stage of their exisztence.
Now we should examine how important sound production is for insects:
Sound production and associated behavior is widely extent among insects.
What functions does sonification offer? It can be a act of self-protection,
escape, since many insects emit sound when captured or disturbed.
With some insects territory is proclaimed by sound. But the most frequent
and most noticeable function played by sonification is in attracting
the opposite sex in courtship and mating.
IMPORTANCE OF SONIFICATION
The degree of significance attached to sonification is obvious when
noting how diverse a set of methods insects have for sound making.
WIDE SPREAD USE AND FUNCTIONAL ADAPTATION OF SONIFYING IN INSECTS
Which insect sonify? Most! Very much used. It is so important that
insects employ all available body parts to make sound. LIST HERE.
Why is sonification important for insects? Their vision is poor, it
is only sound (or odor) that can establish communication between physically
non-adjacent individuals. And they can be. Moths are triggered into
evasive action by ultrasonic bat sounds. They can be profoundly sensitive
to sound. Many insects can synchronize with other nearby individuals.
Was sonification present in early insects? Most likely. since it is
presently performed by almost all anatomical parts and it is used
for basic parts of behavior, such as survival and reproduction.
If making sounds is therefore as wide-spread, perhaps(?) more
so than flying, perhaps even more, if larvae and burrowing insects
(Tenebroids??) use it, then it is likely that sonification is very
ancient behavior and certainly PREDATE flying.
Stridulation, or making a scraping sound by rubbing
together a body part against another with serrated surface is the
commonest sonification method. It exists in a great many orders, and
practically all body parts are employed. Stridulatory organs can be
found on the head (Nitidulidae, Erotylidae). Some "tenebroids beetles
(wood-boring?) have striations on the underside of the head". mouthparts
often act as sonifiers: "Corixa americana rubs its front legs against
the proboscis", clicking mechanisms on the underside of thorax, file
under prothorax rubbed by leg (Siagona, a scarabid). Ridges on the
abdomen can be rubbed by the edge of the wing cover (in some Scarabidae),
or by the femur (Heteroceridae).
The legs are an important tool in stridulation. "Some log-horned
beetles (Prionus) rub hind legs along edges of the elytra. A few aquatic
insects rub legs against the head.
SEGMENT RUBS SEGMENT!" Many long-horned beetles" rub rear edge
of one segment of the thorax (usually the pronotum!) against another.(GT:
bring this up later!!) Some Hymenoptera (ants, mutillid wasps) rub
edges of adjacent abdominal segments against one another.
TYMBALS Cicadas create their loud buzzing by vibrating drumhead-like
membranes through a complicated mechanism.
TAPPING Termite soldiers thump their heads against the ground, death
watch beetle Anobium thumps its head on the side of its burrow. Certain
grasshoppers tap feet in the ground, and some cockroaches hit tap
the abdomen tip on the ground.
AIR PIPING The mammalian source of sound, the air is also
used by insects for the same purpose. The queen bee, May beetle and
the bowfly expel air through spiracles.
WING AS SONIFIER
VIBRATION And finally, wings. These organs create a humming or buzzing
sound, (frequencies?) just as they perform their flight function.
The Scarabidae, the Orthoptera, the Heteroptera, the Diptera and the
Hymenoptera almost always produce a tone audible to humans. Frost
p. 201) Whether the producers of these sound hear it is another matter.
Wing vibration is known to be a sexual identifier and caller in .(DO!)
I DIDN'T WRITE DOWN THESE EXAMPLES! (Curiously enough sometimes
the thorax is involved: a bumble bee with wings held will still emit
a buzz by means of some vibration inside the thorax. One can presume
the vibrating wing muscles to be the sources of this sound.)
On the other hand, the wings are also used in stridulation.
The well-known grasshopper noise, that of the short-horned grasshoppers,
comes from rubbing the row of pegs on the hind femora against the
front wings. Others scrape wings together while hovering. Long-horn
katydids make vibrations of an elastic membrane, the tympanum, part
??? the base of the right front wing. Crickets rub together the bases
of their front wings.
EVEN some larvae stridulate. Pasalus cornutus rubs together
the ridges of the mesothoracic legs. The metathoracic legs are tiny
and have developed into organs for rasping. (Frost/Dover p. 203)
{Mention this again as: an "extra leg" (a mutant freak...)
developed into wing?} ILL
APPEARANCE OF VISUAL ROLE OF LOBES through size increase as resonator
However, supposeing the lobes gained functional status by stridualting,
then if they would increase in size through selection, at one point
they would also bcome visual objects. This could happen if a small,
ridged structure develops additional contiguous platelike extensions
that would resonate under stridulation. ILL THis devlopmetn could
give rise to eovlution in size of lobes-like extensions, and
once the structure reaches a certain size, it wll automatically become
oxypragmatic as a visual object.
VISUAL COMMUNICATION COMPONENTS OF FLIGHT
Today wings fill important visual roles. First wings, in Lepidoptera,
or butterflies and moths, the optical designs of wings certainly play
a vital role in species recognition for the purposes of mating as
well as defensive. The defensive significance of this role is emphasized
by the existence of false mimicry. However, this function can be performed
by a secondary wing development, the elytra, as in beetles (Coleoptera),
so that perhaps it is not so much the wing, but any large area exposed
before or after flight that offers the visual information. Wings simply
act as large visual surfaces. Secondly, wings can give visual infornation
thourhg the flight pattern they enable an insect to use in mating
communication, but this activity exhibits a dynamic effect, not a
simple pasive visual one.
VISUAL communication by wings today
Insects use a variety of methods for visually communicating. Their
bodies, wings are often designed in shape and color and pattern to
intraspecific identification, and for defense. They use even the most
subtle ways: looking like an object or like another species. We are
only interested her with wings, so other visual structures are not
covered below.
a) The most primitive fliers, the Odonata show every indication of
being visual signalers. Let us consider how in bright sunlight the
large, shiny, with a lenticular structure reflect light like a mirror.!!
We read in Lanham, The Insects, Columbia U Press, 1964, p.185: "In
a spacious mountain canyon one may see the sun glinting on the wings
of hundreds of dragonflies, from half a mile away, as two or three
hundred feet high in the air, each patrols its bit of airspace." Their
positions at rest strongly support their visual use as well. <[>Mayflies
close the wings together over the body, pointing up.] Different dragonflies
hold the wings, at rest, straight in a horizontal position, or horizontally,
but curved, so the outer ends are lower then the inner part (Libellulidae-
ILL, or vertically damselflies (Zygoptera). Obviously, these positions
each are noticeable from different angles of observer position. Moreover,
the closing and opening of the wings is automatically a signal function
of visual pulsation. ILL
b) The wings are highly functional visual signallers in higher orders
of flight evolution. For example, Drosophila males exhibit a set of
mating displays which are composed of orientation, tapping, wing vibration,
wing flicking, wing waving, wing semaphoring, wing scissoring, leg
vibration, leg rubbing, circling, licking, and finally mounting. (H.
T. Spieth, Courtship behavior in Drosophila, Ann. Rev. Entomol.,
19: 385-405, 1974; quoted by M.D. Atkins in Introduction to Insect
Behavior, Macmillan, 1980, p.112 ) It is evident that
wings are performing a visual function and it is also reasonable to
imply that such wings, being reflective surfaces, whether moving or
not must have played an important visual role in insect behavior preceding
the era of flight. Both the functions of simply reflecting light,
or pulsating flashes, or dynamic visual exhibit of different wing
motions without reflection of light are subject to selection and thus
the wings will develops selectively for structural strength and size
of surface area. In a short time lift would come as an almost unavoidable
CONCLUSION SO FAR: wing as stridu/visu origin possuble, BUT NOT CLEAR-CUT,
ETC and still no explanation for wing MUSCULATurA. MORE EXAMINATI)ON
IS NEEDED.
THE FIRST ROUGH ONTOGENIC DERIVATION OF WINGS -- PARANOTAL LOBES10-5-90
If wings are sound-producers now could they have been sound producers
originally? Even if they were too small or too slow moving to produce
flight they could most certainly sonify. But what if they were not
moveable? Could they sonify then? By all means. They could have been
stridulatory apparatus. A leg could scrape them.
Physiological derivation of wings.
send this with illustrations!
1. Structure of wing, sacklike, ill. and its attachment
to and articulation by two different sclerites makes its up-and-down
movement possible. This motion is sufficient for sonification, and
as soon as the pre-wing surface area increases enough so that the
surface-to-mass ratio permits it, the sonic function of buzzing
becomes polypragmatic: vertical lift automatically becomes possible.
Lift necessitates another factor to be present -- through some asymmetry
of motion -- either in intensity, speed. It is not necessarily
THE SOURCES OF FLIGHT MECHANISM IN INSECT MUSCULATURE -- IN APPENDIX,
OR HERE? THERE are newer finds about wing origin to be incorporated
STILL from WOOTON FLIGHT p237 ff
However, it is not to be simply deduced that wings were originally
sound-making organs (something they still are this day -- also mention
later!) for wings may be derived from earlier forms, and from slightly
different uses. here: leg-wing, two sclerite rubbing,
etc. ills
NARRATION LEADING TO THE NEW THEORY -- 10 - 5 - 1990
With all the above having been considered, let us take some general,
panoramic looks at the topic in order to find some new observations
on which to base new propositions concerning the origin of wings and
What are wings? Flying structures. What else are they? They are also
visual signallers, based on color and slow movement. The evidence
has been supplied above. And they are also vibrating structures or
simply put. they buzz.
Now -- let us go back in time. Suppose the wings were unmoving, rigid,
small pronotal lobes. Could they still function in any capacity related
to their present actions? Without motion they could not buzz, without
sufficient size and motion they could not be visual signallers.
What could a paranotal extension, a relatively thin lobe as hard
as the integument do? There is one thing it is perfectly suited for:
stridulation. They could have formed one part of a stridulatory set
of organs: a leg with a file could have brushed against them. Evidence
for the widespread application of sonification to all body parts supports
this possibility.
(The ontogeny of lobes - did happen, so needs no excuse, but it is
also supported by the presence of lobes on the abdomen in some cases.
Anyway, lobe can be explained as originating as folds of the integument
occurring through natural variation or mutation.
For what purpose we still do not know, but the fact is at one time
they became mobile. At this time the lobes, if of satisfactory size,
could also sonify using each other, rubbing one another, or perhaps
if the angle of their growth in rubbing the dorsal or pleural integument.
Suppose the wings originally moved not in a simple up and down, vertical
direction but as they do today, partly back and forth, that is in
the horizontal plane. This idea implies that simple horizontal movement
thought to be primitive, as represented by the Odonata is actually
the original action, and the Odonata have lost the ability because
their wings for one needed no concealment because they live in open
areas over water, on the other hand because as visual signallers for
territorial and mating service, their wings are to be seen as much
as possible.
Also, if mobile, the lobes would possess immediate applicability,
or oxypragma. Any moving filed, if within range of an insects visual
sensation can act as a visual identifier, signaller. So flight could
reasoned this way could have arisen from either or both visual and
sonifying functions.
But we cannot be satisfied because the objections raised against the
gliding theory still are not satisfied. Assigning a stridulation function
to the earliest, mobile or immobile, paranotal lobes of minimal size
is rather an incomplete theory, because it still leaves gaps, namely
the development of muscular mobility is left without any basis.
And so we must go on. We must examine data for other possible clues!
1Let us go back to the sonifying abilities of flight. Suppose we kept
the musculature and neurology of flight, but reduced the size of the
wings gradually. The wings would get smaller and smaller, buzzing
away. The function of flight would gradually diminish as the size
went down, and it would reach a size where flight was excluded, however
the buzzing function could still be working away.
Would this not be a simple way to explain the origin wings and their
motion? Originally they were sonifiers, to be used in display, either
in territorial or mating service. Yes these is logical and simple.
The wings and flight still perform what they originally were created
for, but through simple development such as size and asymmetry of
movement they can also <[>provide for lift and flight. Again, the
visual function discussed before are still part of the possibilities.
The buzzing system, at different states or speeds could suddenly perform
another operation. (Nice case of oxypragma (and polypragma)
Again, we have here a somewhat convincing explanation for flight origin,
but alas, one gap still remains. We are still left with the question
from what source would wings and their musculature functionally develop
to be resonating organs?
Perhaps looking into the muscular mechanism of flight gives some clues.
Most sources, at popular and professional levels generally show a
pair of contrasting pictures that explain the two major modes of flight
mechanism. One is the indirect flight of the Odonata and Orthoptera,
the other is the indirect one seen in the Diptera. ... ? On fist examination
it seems that one depends on muscles, the other on a mechanism involving
sclerites, hard parts and muscles. Unfortunately these diagrams are
simplified, diagrammatically is a little but enough to occlude the
true state of affairs. They make it seem as if insets with slow wing-beat
simply move the wing up and down by pulling alternate sets of muscles,
whereas insects with rapid beats utilize a mechanism to keep wing
beat high without relying on muscles that would be too sow to perform
at such rates.
But both mechanisms rely on ...
The flight action in Sarcophaga (Diptera) (R. G. Davies. Outlines
of Entomology, Chapman and Hill, 7th ed. 1988, p.26) employs a click
mechanism whereby the wing goes into a lower position and stays there
until it is triggered into the high position. This action is clearly
describable as a bi-stable, or two-state vibrator. What enables an
insect to possess such a mechanism? The nature of the materials involved.
The substance of the insect integument is elastic to a point where
it can be flattened into thin, flexible sheets, and then can act like
springs. When this elastic material is bent and held, upon release
it will spring back to its natural position. Any number of tension
and escape mechanism are utilized by humans to achieve effects. The
bow and arrow(?) is one, the clock, with its escape mechanism, locks,
ball-point pen buttons are just three examples.
So an flying insect's thorax possesses a bistable click mechanism.
So what? Big deal. Their job is to work the wings, without wings there
is no flight. Wings had to be there first for a flying mechanism to
develop. This is very true -- however, stopping at this point would
be a great mistake:
Let us start in the present and go back in time and ask: what if we
keep the click mechanism but go back to the time when wings were just
lobes; could they function in flight? The answer is no. Small wings
are like no wings, someone would say.
But such a statement would remind us to complete our journey back
up to the point when there were no wings or lobes of any kind. What
would our clicking mechanism be useful for?
HERE: THE KEY TO THE MYSTERY: CLICK MECHANISM.
First just ILLDavie.26 or the German author p 63?ALSO
DRAW GT MODEL OF SAME
"The wing movements of most insects produce a humming or buzzing sound,
but in some insects the thorax is also involved in the production
of sound; a bumble bee held by the wings will still buzz (by vibrations
of the thorax.)" (Borror, Introduction to the Study of Insects,
THE ANSWER IS RIGHT BEFORE OUR EYES:
Silly question: for just exactly that -- clicking! And what would
a insect do with a clicking mechanism?
Exactly the same it does with leg rubbing, stridulating, segment
rubbing, taping the feet, or wing vibration -- it would make sounds.
Now, the widespread use of sonifying by insects is certainly accepted,
and it is reasonable to assume that insect sonification must have
been functional before the development of wings since it plays a basic,
vital role in insect communication and mating and so it can be concluded
that if sonyfying predates flight than sonifying could be the source
of flight once the continuity of functional evolution from one to
the other is laid out convincingly. the source of flight can be an
existing sound producing mechanism, to which lobes are added for modifying
and/or amplifying the sound.
BRIEF STATEMENT OF THE PROPOSED THEORY here, and chart of same. FULL
SUMMARY COMES AT END OF SECTION<< just before supporting facts
. . . Supposable shapes of lobe, and its oxypragma, etc.
Argument: Odonata have no click mechanism
But what if someone says: the so-called primitive fliers, The Odonata
and Orthoptera?? have no click mechanism. The answer is that they
do possess it in a less intense form: they have a stable and less
stable positions of wing. Their wing structure is "semi-bistable."
ILL We can quote J.W.S. Pringle (Chapter 7 Locomotion, p.
435 ...): "Partly because of ...<[>the] elastic cuticle at the hinges
and partly because of the general elasticity of the solid cuticle
and muscle, movement of the wings is influenced by elastic forces.
Sometimes, as in the mesothorax of Schistocerca, the wings
assume a fully down position when the main flight muscles are relaxed;
sometimes, as in Sphingidae and Anisoptera (Odonata), the stable position
is horizontal."
THE SOURCE OF THORACIC SONIFYING: -- still to be worked out in detail!
(To meet the requirement of relying only in documented substratum
(source) for a proposed sequence of events: ) The physical properties
of the cuticular materials and the presence of thoracic and leg musculature
only need a novel set of neurological stimuli to appear. There is
1. Wing muscles are partly identical or derivable with leg muscles
- used originally for audio or visual communications -- The legs themselves
may have been the signallers; lobes may have appeared to amplify this
visual leg action; this could have had audio side-products.
2. Indirect wing muscles are derived
3. derivation from breathing musculature
This may come here or as an appendix (or maybe
simpler here, more technical in Appendix.)
STUPID: Remember to learn terms properly: tegmina=, terga=,
In brief summary, let us state the proposed origin of
insect flight:
Use of sound in communicating is present
Emergence of sound producing structure in the thorax
Emergence of integumental lobes to modify, amplify the thoracic sound
Development of lobes in size and texture through further selection
Development of vibrating ability of lobe
Emergence of visual communicative potential of developing lobe
Emergence of flight from lobe and its vibration
Of course the evolution of the wing from whatever other source would
have developed the present system, but that point of view still places
the origin of wings back into the limited realm of the accepted
theory where it is not explained.
SUPPORTING FACTS
1. SURVIVAL OF ORGAN AND FUNCTION That the functions of visual and
audio communication are still present. The fact stares us in the eye!
And Has not been noticed!
2. EXISTENCE OF TWINGLESS THORACIC BUZZ Thoracic buzzing in bumble
bee -- mentioned again
3. THE VIBRATOR NATURE OF THE WINF MECHANISM "In other orders, a
click action may be produced by other parts of the wing articulation
and may also be effective, when the wings are folded, for the production
of sound or in preflight warming. Usually the amount of nonlinearity
in the elastic forces is controlled by the pleurosternal or tergopleural
muscles;" (Pringle, Chapter 7, p. 436) The audio production properties
of the wing-mover system in the thorax is clearly expressed by (ibid.,
p. 437): The existence of these elastic forces in the wing suspension,
considered together with the fact that the wings have appreciable
inertia, show that the system must behave as a resonant mechanical
R. J. Wooton says (p. 250 "(Equally) uncertain is the position of
the first wings, both in in flight and at rest. Apparent homologues
of the flexor muscle have been reported in both Ephermeroptera and
Odonata; ...but it is hard to believe that the Neopterous condition
was present from the first. Yet the resting position of the wings
found in Palaeodictyopteroids and Anisopterous Odonata renders these
latter insects so wholly dependent on aerial locomotion that it seems
very probable in early, weakly-flying insects. A more feasible alternative
is that adopted by Ephemeroptera, whose wings are held above the body
at rest, but partly remoted.
"The position of the wing pads of Paleozoic nymphs lends weight to
Sharov proposal that insect wings were at first posterolaterally directed;
but they may have been flexible enoiugh at the base to allow promotion
to the perpendicular position of flight.From this condition true Neopterous
foldinbg could readily have evolved by refinement of the axillary
sclerites and musculature. THIS MEANS FOR GT: maybe original location
of lobes was indeed not horizantal as lobe on "Palaeodictyopter? This
would be an indication that gliding or flight was not the original
purpose. But then we do not have enough evindence to be sure about
any ramifications of such a statement. STUDY THIS MORE!
4. CICADA TYMBALS: The presence and nature of the sonifying tymbal
mechanism of cicadas presents facts that support the general argument
in several ways. The resonating material is thin, membranous integumentary
material, where storable energy, introduced and released by muscles
creates sound is parallel or homologous in anatomy, in material and
in structure to the proposed function of the earliest wings: cutical
membrane used for sonification. The two systems have diverged only
in gross design, as anatomical placement and method of articulation.
This fact emphasizes the adaptability of the integument to sonic functions.
Indeed, the fact that the sound producing tymbals and the sound sensing
tympana are directly anatomically adjacent and both work on the basis
of the acoustic properties of cuticular membrane not only suggests
a shared ontogeny, butalso testify to the readiness with which the
insectan structure makes use of these properties of the cuticle. Moreover
these qualities of elasticity are also the foundation of detecting
tactile sensations.
5. MECHANICAL PROPERTIES OF INSECT CUTICLE "LIKE OAK" "Jensen and
Weis-Fogh 91962) give some figures for the mechanical properties of
the two types of cuticle found in the locust. The solid tanned cuticle
from the thorax, legs, and wings is similar in its mechanical properties,
with a coefficient of elasticity of 800-1000 kg mm-2, and
a tensile strength of 8-10 kg mm-2 for an elongation 2-3%;
these are comparable to the values for oak wood: WING MADE OF CUTICLE!
check once more!
6. THE EMPTY THORAX
The thorax was busy taking care of the legs, but obviously, there
was more potential in it. Compared with other segments/body parts,
the thorax, or more generally, the volume of space potentially available
to the thoracic mass was relatively empty -- even now the thorax is
generally still smaller than the abdomen. The thorax, therefore had
room for more musculature and integument to come into some use. By
self-definition today the thorax is capable of holding both the leg
and the wing musculature, then when it held only the leg musculature,
the thorax was utilizing only "50%" of its potentials. And the abdomen
was already specializing in other functions, so the thorax, already
possessing the leg-moving or breathing, neuro-muscular mechanism,
had a good chance of being put toother uses, such as sonification.
Put another way, Nature would have been exceptional if it had not
used every and any opportunity to construct. Also, because the hard
parts of the integument are bounded or bridged by softer materials,
like islands in the sea, there is possibility to fold or bend these
surfaces relative to each other. These contingencies create a potential
for the reflective and elastic properties of these materials, combined
with muscular action for being selected for a role in communication.
8. PRESENCE OF VISUAL CLUES -- the BODY ITSELF! The sight of the
general body of the insect is in itself visual datum, and so the superimposition
of added clues would be a matter of evolutionary course.
9. SUPPORT of FLIGHT MUSCULATURE DERIVATION FROM EXISTING MECHANISMS
But things are simpler than all that: the direct flight muscles, at
least, are more or less identical with leg muscles, (coxo-pleural
propmotors, remotores, and maybe abductor and adductors, too. THIS
IS TO BE DEVELOPED FURTHER. above and/or in Appendix.
10. SCLEROTIZATION as available basis for new structures and functions:
"...the development of refined interrelations between muscles and
sclerites has been the principal line of evolution in the arthropods.
(Snodgrass, Principals of Insect Morphology, p. 53)
11. WING MOVEMENT AND STRIDULATION THE SAME IN CRICKETS Cricket stridulation
muscles (Chapman, p.686): In gryllids and tettigoniids, where stridulation
involves movement of the wings, the same muscles are used in both
flight and stridulation. Wing closure during stridulation by a cricket
is produced by the indirect dorso-ventral muscles which produce the
upstroke in flight; wing opening, the equivalent of the downstroke,
involves the dorsal longitudib\nal muscles and the direct wing muscles..
At first the muscles are activated only via the slow axons, but as
excitation increases fast axons begin to fire, the muddles contract
more strongly and the intensity of the song is increased." GT: a clear
homolog or what???
12. LEG MUSCLES partially SAME AS STRIDULATORY MUSCLES IN ACRIDOIDS.
"In acridids, where stridulation is produced by movements of the femora,
muscles at the pleurocoxal and coxotrochanteral joints are involved.
Some of these muscles have a dual function, since they also move the
wings during flight. In all the grasshoppers species studied the order
of activation of the muscles is the same, with fast units becoming
active after slow units." (Chapman, p. 686) GT: This may be a record
of evolutionary development: the slower neural activity belongs to
visual and audio action, while the fast ones, secondary to the slow
ones, developed for added intensity and velocity needed for flight.
THE EQUALITY OF LEG AND FLIGHT MUSCLES is not new! Wooton,
p. 250: the thoracic paranota ..."developed the ability slightly to
pronate, supinate, elevate and depress the pads by action of the pleural
leg muscles; and ultimately. in the case of the meso and metathoracic
lobes, as flapping aerofoils, powered mainly by bifunctional leg muscles
including those operating in the Blattodea and perhaps supplemented
by others now retained only in Odonata.
LEG MUSCLES AND WING SCLERITES AS ORIGINAL MECHANISM: The original
use of the wing sclerites, small hard areas above the legs on the
side integument could theoretically fill the roles of movable surfaces
either for reflection of light or production of sound. ILL
THEORY OF EXACTLY HOW LEG MUSCLE COULD MOVE SIDEPLATES FOR SOUND OR
VISUAL SIGNALING: If the coxal motor muscle is activated while the
insect's leg is not free to move, asit quite commonly may be when
holding on to the substrate, like a plant stem, then, since the leg,
which is the insertion part cannot move, the part which is the origin
of the muscle will tend to move. If this part is a small structure,
such as the wing sclerites, the coxal muscles could quite possible
vibrate it.
13. ROLE OF MATING DISPLAY The idea that the original use of wings
was in mating display, as suggested by some authors, and the
present proposition mutually sopport each other. CAN ADD MORE HERE
The generality of the appearance of wings in the last instar is significant,
and has many corroborating facts: Ephermeroptera, termites, ants,
the holpometablous insects, the mating/species identifier function
of wings in Lepidoptera, etc. This could be all secondary development
but presently we have no way of checking the facts.
14. THORACIC BREATHING as source of indirect flight muscles: "The
changes in thoracic shape which accompany flight movements also help
to pump air through the air-sacs and tracheae.. "(Davies, p. 30) Of
course thoracic breathing while flying is necessitated most strongly
be the action of flight. The only thing to be said for thoracic breathing
when not in flight is mcsular respiration might be advantagous if
the insect is large. NOT SO SURE
15. LEG MUSCLES SAME AS WING MUSCLES --already covered above? (Wooton
p 248 and Davies ILL)
16. MORE SUPPORT FOR SOUND/VISUAL ORIGIN OF FLIGHT: WING ACTION AS
DISTORTING FUNCTION: The action of the indirect muscular activation
of the wings can be technically described as the deformation of a
plate or membrane. ILL. The principal in the action of sonic
transducers such as headphones, speakers, or eardrum are identical:
deformation or distortion of a membrane. Again there is a shared function
in the wing mechanism and audio functions. As a matter of fact, under
the right circumstances we could build a model of a flying insect
by designing a speaker with wings attached to the sounding membrane
and by electronically controlling the vibrations we could make it
fly. Light weight would be necessary, also to obtain forward flight
it would be helpful to have a composite speaker whose membrane would
be divided into several adjacent membranes each controlled by a different
audio line. ILL
It can be mentioned that the proprioreceptor systems of insects
are also based on deformation sensing. Unlike the vertebrates, where
body movement is detected by deformation of muscle, it is supposed
that in insects the same is mostly perceived by sensing the deformation
of the integument.
All this suggests that thoracic deformation for visual or auditory
purposes had a considerable likelihood to be the source of flight.
16A. A QUESTION?--- to GT: MUSCLE SPEED IN CICADA TYMBAL ACTIVATION
AND WING FREQUENCY IN FLIGHT. If "in the ciadas the tymbals vibrate
naturally at the frequency of about 4,500 cycles per second" (Wigglesworth,
Life of Insects, World, 1964, p. 205), then WHY is click mechanism
needed for smaller insects bees to beat wing at 190 beats per seciond,
Drosophila at 250, mosquito at up to 600 and when even at the high
limit of wing beat rate the Ceratogonid midge (Forcipomyid)
does over 1000 cps? (WHILE large insects beat far below at cicada
tymbal rate: butterflies at c. 8-12 beats per secind, locust at 18-20,
? ?) IS THERE A FREQUENCY MULTIPLIYNG MECHANISM
IN THE CICADA TYMBAL?(Besides the fact that each excusion
amd recursion of the membrane gives two clicks?) -- an answer to this
problem would clarify whether you need click mechanism for slow flight,
or would it??
(CICADA TYMBAL COVERED! -- supports possibility of interior sound
production. Natbe earliest thoracic sound producer had a membrane
and this later developed into the lobe. UNLIKELY !!)
SYNECHIA ?
A theoretical reconstruction of the development of flight: i n
s t e p s:
The material source of click mechanism is indisputably present: the
sclerotized plates (terga, sterna, ?pleura), sclerites, tissues of
various degrees of elasticity are
Its energy source is the muscle and its design is the snappiness of
a folded piece of elastic laminate
Work on illustrations showing possible vibrating/pulsating
mechanisms in just folding
and muscle, and folding arising from (purposeless) development
1. The origin of the indirect, tergosternal muscle mechanism of
flight. The problem is: W R I T E ! . . This can
be solved, see below, but then it is also only a supposition that
the pronotal, horizontally disposed lobe is the original form of the
precursor of wings. The lobes may have indeed first developed in other
positions. ILL Existing muscles and movements, such as the
oblique intersegmental muscle, or others providing for the movement
of segments in relation to each other, an ancient activity in arthropods
is full of potential for creating and activating visual or audio sound
producers, and in this case the lobes may have been located anywhere
on any segment joints, all around the body limited only by practical
selection. ILL here of different hypothetical views of insects
with lobes in different places. Perhaps lobe was not horizontal but
angled, and was on the side. We could argue that they evolved for
audio or visual system before becoming adapted to flight. It can
also be supposed that the flight functions of the wings developed
simultaneously with the emergence and development of the visual/audio
function, in which case there is no question of what came first.
*N.B. !!! Also remember: the quotation about Onychophora (Peripatus)...
larva having lobes on all segments. HEY! THIS OFFERS A "SUBTHEORY"
FOR source of wings as lobes used for swimming by aquatic larvae!!!!
folds are part of integumental structure the (tergo-sternal
border) ! quote !
2. As to the problem of the Odonata not having click mechanism
(and ...) Not having a clicking mechanism: may be lost in these
because large wings beating slowly do not need it. or else SUBALTERNATE
NEW THEORY: it all started with slow bending of side cuticle to pulsate
light w/o click mechanism. this is not good! Lacks ontogenic oxypragma.
OKAY saved: PRINGLE 455 - this idea is now placed above, after click
mechanism idea
PHILOSOPHICAL COMMENT
The accepted theory of lobes leading to parachuting, etc. is at first
glance the most direct route leading to flight, therefore it is obvious
why so far we had accepted it. . But the alternate theory proposed
here offers a more direct path, which at first glance seems indirect
in that it presents a totally unexpected origin for a function. However,
1) the existence or survival of the proposed original functions seems
to say: here is the original function still going on, the secondary
function is oxypragmatic, it automatically arises from the first when
conditions are right, and
2) Many biological structures functions were reasoned out to derive
from unexpected sources. Take for example the origin of the vertebrate
jaw and auditory organs derived from gill arches, take the ...
EVALUATION OF THE PROPOSED THEORY:
The proposed theory meets the requirements posed:
1. The ontology of the wing
2. The oxypragma of the earliest wing
3. Its polypragma, if any
4. The ontology of the flight mechanism. the oxypragma of the flying
5. Support by other facts
6. Survival or presence of proposed original functions.
1. Chart of evolution of flight (One or two different ones.
2. Stridulation leading to saltation