Jan 12: Dance language: basic facts

The Basic Facts (not in dispute)• Forager honey bees, on returning to nest,

perform a "dance" which containsinformation about the distance anddirection of food they have found

• Bees in the nest pay attention to thedancers

• At least some of the dance followers endup at the food

The dance language of honey beesDescribed by Karl von Frisch in 1940s toexplain the ability of honey bee foragersto recruit nestmates to food

Dance communicates flight directionrelative to sun in orientation ofwaggling runs…….

Jan 12 -- Dance language --Basic description

…or relative to gravity.

…relative to the sun...

And it also communicates flight distance--in duration of waggling run

Jan 12: Dance -- von Frisch’s hypothesis

Von Frisch's Dance Language Hypothesis

• The dance followers extract the spatial informationfrom the dance, and use it to get to the generalvicinity of the food

• These prospective recruits use odors (learned whilefollowing the dancer) to narrow their search

Jan 10: Dance-- von Frisch’s evidence

Von Frisch's Evidence for Dance Language Hypothesis

• Observational evidence• correlation between the bee’s flight path (direction and

distance) and subsequent dance behavior• correlation between dance following and recruitment• problem: CORRELATION ≠ CAUSATION

• Experimental evidence• "fan" and "stepwise" experiments to test whether recruits

search preferentially end up near where the dancers aresignaling

• problem: other hypotheses might predict same results--this isexample of "weak inference"

Jan 12: Dance--fan & step exps

Fan and Stepwise Experiments: recruits appear predominately atbaits nearest the location foragers are indicating in dances

Bait stations

Labeled bee at forager station

[Control beestrained to allfeeders]

Jan 12: Dance -- Odor Search Hypothesis

The Hypothesis• Dance contains spatial information, but

the followers do not use it• Instead, bees get recruited to the food

solely through the use of odors learnedwhile following the dance

Wenner's Challenge: The Odor Search Hypothesis

Wenner's evidence• Von Frisch's results: all explained by odor

search hypothesis (claims Wenner)• Wenner's direct tests: recruits go to major

source of odor, not to location signaled bydancer

Dancers’ feeder

Jan 12: Dance-- von Frisch rebuttal

Attempts to resolve the controversy -- von Frisch• Argument from design: a complex trait like the dance

MUST have a function (and the one we hypothesize)

• Experiments showing that recruits searchrandomly when the dancers are disoriented

Dance on horizontal is scatteredwhen bee can’t see sun...

…and so are recruits

(this is a fallacious argument: to see the flaw,consider the moth spiralling into the flame)

Dance on horizontal is scatteredwhen bee can’t see sun...

…and so are recruits

Jan 12: Dance-- von Frisch rebuttal

Disoriented dances = Disoriented recruits (2002)

But, perhaps the procedure thatmakes the dance disoriented alsodisrupts the ability of dancefollowers to stay with the dancerand perceive odors she carries

Sherman & Visscher 2002

Jan 10: Dance-- Gould

Attempts to resolve the controversy --Gould's "misdirection"experiments, a "strong inference" approach

• Paint out ocelli of dancer, andshine bright light on dancefloor

• Ocelli: three single-lens eyeson top of insect head;involved in adjustingsensitivity of compound eyesto light.

Compound eyeOcelli

Jan 10: Dance--Gould predictions

Predictions of alternative hypotheses in Gould’smisdirection experiments

Recruits should flyhere if using odors

And here if usingspatial information

Dancer: orients to gravity (ocelli painted)Recruit: can measure dance relative to light

Jan 12: Dance--Gould results

Gould found that bees tend to go in direction dancerpoints

Wenner’s rebuttal: Wind direction could have changed; sample sizes small

Light 30o to left of vertical Light 75o to left of vertical

Jan 12: Dance -- Robot bee

Attempts to resolve the controversy --the “robot” bee• Mechanical bee signals direction of food

(Michelsen et al. 1992)

Jan 12: Dance -- Robot bee results

Robot Bee results

• Recruits go in direction indicated by“dancer”

• Effect is independent of direction ofwind

Wenner’s rebuttal: multiple approaches byrecruits may have been counted, henceinflating the effects

Jan 12: Dance -- New approach

Where Do We Stand Now?

• What about the evidence that recruit bees may sometimes useodors in preference to spatial information?

• Answer--von Frisch himself had argued that odors areimportant in the recruit process, and had already shownhimself that odors can override spatial information.

• Wenner sees this as weasling.

• On balance, evidence favors dance language hypothesis:by far the most parsimonious explanation of the data

(Wenner still denies this)

• Thus, the controversy continues. As a great physicist onceremarked, scientific progress occurs one funeral at a time.

Jan 12: Dance -- Deeper lessons

Deeper Lessons

• Necessity of persistent and creative experimentation instudy of behavior

• Wenner’s critique served useful function in inspiringadditional experimental approaches

• Good experiments must create situations thatdiscriminate between competing hypotheses (stronginference)

• Our conclusions are always subject to uncertainty (true ofany field of science)