vignettes digger wasps and the evolution of instinct

8/9/2019 VIGNETTES Digger Wasps and the Evolution of Instinct

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Digger Wasps &

the Evolution of Instinct


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Digger Wasps and the Evolution of Instinct

Native to Australia is a digger wasp (a.k.a. mud wasp) that protects its progenyfrom parasitic wasps by erecting the mind-boggling mud sculpture shown above.

This incredible design is built by a single female wasp, and is nearly identical to thestructures built by all other females. Slight variations occur because the wasps usetheir own bodies to measure, and they vary in size.

The sculpture consists of a mud-lined tunnel (constructed first), an invertedexterior bell (comprising stem, curved neck, flange and cylindrical bell), and sealedbrood chambers (built last). When finished it looks like a showerhead about 1.5"high, projecting from the ground at a perpendicular. The wasps often build onslopes, as shown.

With its mandibles the wasp makes the inside of the bell so smooth andslippery that its very difficult for the parasitic wasp to land on, and too large for theparasite to reach the neck with its front legs while gripping the bottom of the bell with

its back legs. These dimensions are, of course, perfect for the digger wasp to accessits brood chamber.

The wasp starts by digging a tunnel about 3 inches (8 mm) long. Shell laterdivide this into brood chambers, but first she must build the device that will

A.P. Smith, Nest Construction in the Mud Wasp, Paralastor, Animal Behavior26 .


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protect those chambers. Starting at the open end of the tunnel she builds the stem,extending about 1.2 inches (3 cm) above ground and perpendicular to it. (How sheachieves a perpendicular is a mystery, but what follows is even more amazing.) Nowshe builds the neck, which must curve 20 degrees from the horizontal, however theground may be sloped. Thus a neck built on a vertical stem must curve through 160degrees, while a neck added to a stem extending from a vertical bank needs to curvethrough only 70 degrees. Observers have determined that the wasp uses the length ofher own body to fix the stem length at about 3 cm. The Gould & Gould article I referto, which is based on information collected by field observers, makes no mention ofhow the wasp may cope with the far more complex task of fixing the neck-angle.(The illustrations show the bell-angle to be more like 45 degrees than 20 degrees.Gould & Gould offer no explanation.) With the neck completed, the wasp fashionsthe flange and bell. (I know not where the bell starts and the flange stops, so I haveno idea why the flange is called out as a separate part of the construction.)

Scientists call this innate behavior. Despite the apparent ingenuity of thiscomplex defense system, experiments show that the wasp has no overall conception

Digger Wasp Collecting Liquid, Presumably Water, Showing Surface Tension

Credit: Wikipedia http://news.nationalgeographic.com/news/2002/10/1025_021025_GiantHornets.html


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of the finished product, and instead slavishly follows a set of innate instructions codedin her genes. She breaks down the complex task into a series of simpler tasks thatcorrespond basically to the structure's four components (stem, neck, flange andcylindrical bell). Each of these requires a cycle of repetitive behavior that continuesuntil some innately specified sub-goal is reached, then she goes on to the next step.

If thwarted at any stage (say by experimenters burying the stem), she just goes onbuilding that stage until it once again reaches the desired length. Science concludesthat this is pure instinct, unlearned (innate) behavior.

(The original article focused on proving, by tampering with the construct, thatwasps are incapable of conscious thought. My focus is on the marvels of instinct, so Iput the tampering illustrations in my notes at the end of this vignette.)

This amazing nest-building is carried out by a creature whose brain isinfinitesimal, yet there must be gigabytes of instinctive data stored in that brain orelsewhere in the wasps nervous system. There being no need to process instinctivedata, it could be stored here and there in various parts of the body where its mostneeded. This would leave the tiny brain free to handle non-innate matters.

Its thought by some that instinctive data may be stored in DNA, perhaps inunits called memes. (The termmeme was coined by Richard Dawkins, an Oxfordzoologist, and stands for a cultural or behavioral element passed on by imitation orother non-genetic means. The roots of the term are mime, mimesis, mimetic,memetic, the Frenchmeme forsame, etc.) It would seem that most adherents of thememe theory use the word to represent thought stored in DNA. That is, they believethat memes may be inherited and stored like genes.

The scientific establishment refuses to recognize memetic theory as validscience. Small wonder. It really strains the credulity to accept that abstract thingscan be transferrable like genes.

Merriam-Webster simply defines the meme as an idea, behavior, style, orusage that spreads from person to person within a culture. (All sources seem toignore that the word is, as best I can determine, pronounced as in meems. A nicething to know, if you plan to discuss it.)

Most scientists give short shrift to instinct, calling animals that manifest itautomata. But more and more cognitive scientists and comparative psychologists(Henri Bergson, Peter Carruthers, James and Carol Gould, and Donald R. Griffinamong them) accept that animals think consciously about what they do. Bergsonand Griffin hold that there is some consciousness in all instinct, and vice-versa.

But Im not here to engage in that conundrum. Id rather discuss instinct on itsown. Its marvelous -- every bit as fascinating as learned behavior, perhapsmore sobecause it's so mysterious. But exactly whatis instinct and where does it originate?

Instinct is probably evolution, arrested. This arrest may mark a species' limits,or it may be voluntary, a species-wide decision that its survival behavior needs nofurther improvement. How this might work is a mystery, but it couldn't depend solelyon circumstances or individuals. It must follow some mysterious theme that makes aspecies' instinctual evolution everywhere and simultaneously complete. This remainsunintelligible to us because, to paraphrase Bergson, instinct is not within the domain


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of intelligence. Evolution has occurred along divergent lines, and at the end of thetwo principal lines we find intelligence and instinct in forms equally pure but turnedin opposite directions -- intelligence toward inert matter, instinct toward life.

Until all four components of the digger wasp sculpture are complete, the device

doesn't keep out enough parasites to ensure survival of the diggers, so if the evolutionof this design had taken countless generations of digger wasps, each making minorimprovements, the parasites would have destroyed them long ago. This suggests thatthe instinctive behavior didnt evolve slowly. Perhaps, as is thought to occursometimes in evolution, the grand design originated fairly quickly, say within ageneration. In digger-wasp terms, this would be a year or less.

So, although it boggles the mind to consider the possibility, the amazingsculpture of this digger-wasp nest most likely evolved and was passed along, notthrough individuals but via species-wide behavioral changes. If it began with digger

wasps building just a stem, for whatever purpose, then it began with all diggers doingthe same. Then they added a neck, perhaps to keep out rain. Maybe not untilparasitic wasps began taking a heavy toll did the diggers devise the bell.

If consciousness, even intelligence, plays a part in evolution, it seems toslumber after a species opts for pure instinct. On the other hand, some species useboth instinct and intelligence. Even humans have residual instincts, though sciencetends to shrug them off, along with other extrasensory phenomena.

http://oddsbodkins.posterous.com

NOTES

A.P. Smith, Nest construction in the mud wa sp, Paralastor,Animal Behavior26, 232-240, 1978.

(Source of drawings)

The Animal Mindby James Gould and Carol Grant Gould, Scientific American Library, pp 236, $32.95 ... James

Gould, famed for his behavioural studies of honeybees, is professor of ecology and evolutionary biology at

Princeton University. Carol Grant Go uld is a talented science writer. ... 13 August 1994 by GAIL V INES...

The use of bells is also found among mud-nesting wasps (a.k.a. mason wasps) native to Queensland,

Australia. Their nests are usually attached to tree trunks or the sides of buildings, often in small groups.

The wasp s start with the bell shape. Females lay an egg inside each bell, then paralyze caterpillars for

the developing larvae to feed upon. Finally, the wasps seal the bells with mud. The larvae pupate inside

their bells and emerge as fully developed adults.
http://oddsbodkins.posterous.com/http://oddsbodkins.posterous.com/


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Bells apparently serve as brood

chambers. No mention of

defense against parasitic wasps. Why only 1 bell? Finished nest

A wasp is any insect of the order Hym enoptera and subo rder Apocrita that is not a bee, sawfly, or ant.

The less familiar suborder Symphyta includes the sawflies and wood wasps, which differ from the

Apocrita by having a broad connection between the thorax and abdomen, as opposed to the usual

threadlike connection. Also, Symphyta larvae are mostly herbivorous and caterpillar-like, whereas

those of Apocrita are largely preda tory or parasitic.

Most familiar wasps belong to the Ac uleata, a division of the Apocrita whose ovipositors (egg-layers) are

modified into venom ous stingers. This includes ants and bees. In this sense, the species called "velvet

ants" (Mutillidae) are actually wasps.

A narrower meaning of the term wasp is any member of the Aculeate family Vespidae. This includes the

yellowjackets (Vespula, Dolichovespula spp.) and hornets (Vespa spp.).

The following characteristics are present in most wasps:

Two pairs of wings (exception: female Mutillidae)

A stinger (present only in females because it derives from the ovipositor)

Few o r no hairs (in contrast to bees); exce ption: Mutillidae

Predators or parasitoids, mo stly on other insects; some species of Pom pilidae, such as the

tarantula hawk, specialize in using spiders as a host

Wasps are critically impo rtant in natural bio-control. Nearly every insect species considered a pest by

humans has a wasp species that is predatory or parasitic upon it, so more and more, wasps are used in

agricultural pest control.

Mud daubers are a commo n species of wasp.

USES IN PHILOSOPHY

Some writers in the philosophy of mind, most notably Daniel Dennett, have cited the behavior of wasps

for their arguments about human and animal free will.


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A typicalSphex wasp dro ps a paralyzed insect near the ope ning of the nest, then inspects the

nest, leaving the prey outside. During this time an exp erimenter can mo ve the prey a few inches aw ay

from the opening of the nest. When the Sphex emerges, it quickly locates the moved prey, but now its

behavioral "program" has been reset. After dragging the prey back to the opening of the nest, once again

the Sphex is comp elled to inspect the nest, while the prey is left outside. This can be repeated time and

again, with the Sphex never seem ing to notice whats going on, never able to escap e from its

programmed sequence of behaviors. Dennett's argument quotes an account of Sphex behavior fromWooldridge's Machinery of the Brain (1963). Douglas Hofstadter and Daniel Dennett have used this

mechanistic behavior as an example of how seemingly thoughtful behavior can actually be quite

mindless, the oppo site of free will (or, as Hofstadter described it, antisphexishness).

In addition to this seemingly instinctive and programmed behavior, the Sphex has been shown,

as in some Jean Henri Fabre studies, not to count how many crickets it collects for its nest. Although

the wasp instinctively searches for four crickets, it cannot take into acco unt a lost cricket, whether the

cricket has been lost to ants or flies or simply been misplaced . Sphex drags its cricket prey towards its

burrow by the antenn ae; if the antennae of the cricket are cut off, the wasp would not think to

improvise and p ull its prey by a leg.

The navigation abilities and other behavior of Sphex w ere studied by the ethologist Niko

Tinbergen, as explained and demonstrated by Richard Dawkins in the 1991 Royal Institution Christmas

Lectures, Growing Up in the Universe .

Wasp stinger, with droplet of venom

Credit Wikipedia


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Great Golden Digger Wasp credit: kniphofia100 > albums > Wildlife (Bugs)


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A.P. SMITHS FIGURES SHOWING DIRTY TRICKS PLAYED BY OBSERVORS

When observer pokes hole in neck, wasp sees hole as her tunnel & builds

another stem, neck & bell.

When observer buries stem, wasp goes right on building, though bell ends

up being on ground & useless as defense.

vignettes digger wasps and the evolution of instinct

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