[Paleopsych] SW: On Social Learning in Insects

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Sociobiology: On Social Learning in Insects
http://scienceweek.com/2005/sw051230-5.htm

    The following points are made by L. Chittka and E. Leadbeater (Current 
Biology
    2005 15:R869):
    1) The rapid expansion of the field of social learning in recent decades 
[1,2]
    has almost entirely bypassed the insects. But a close inspection of the
    literature reveals numerous cases where insects appear to learn by 
observation,
    eavesdrop on members of the same or different species, and even engage in
    teaching other members of a society. In fact, the first hint of observatory
    learning by animals dates back to Darwin's field notes published by Romanes
    [3,4]. Darwin suggested that honeybees learn the art of nectar robbing --
    extracting nectar from flowers via holes bitten into the tubes, without 
touching
    the flower's reproductive organs -- by observing bumblebees engaged in the
    activity. Experimental proof for this conjecture remains outstanding, but it 
is
    interesting to note that Darwin thought that observatory learning might 
occur
    across, rather than within, species
    2) Early in the 20th century, researchers became aware that many adult
    phytophagous insects prefer host species that they themselves had fed on 
when
    they were larvae -- even where the insect species, as a whole, was a 
generalist
    with multiple acceptable hosts [5]. In what has become known as "Hopkins' 
host
    selection principle", it was thought that the larvae become conditioned to 
the
    chemosensory cues associated with food provided by their parents. This is a
    non-trivial suggestion, as the nervous system of a holometabolous insect is
    extensively rearranged and rewired during metamorphosis; nevertheless, there 
have
    been convincing studies to show that such pre-imaginal conditioning indeed
    occurs. This shows that insect parents can pass on valuable information 
about
    suitable food types to their offspring, simply by placing eggs on suitable 
host
    plants, or by provisioning eggs with certain food types. In a similar vein,
    researchers have considered the possibility of "traditions" being 
established in
    honeybees colonies. Foragers can be trained to feed at a certain time of 
day, and
    it was shown that these learned temporal preferences are picked up by larvae 
via
    vibratory cues. The individuals so taught will display the same preferences 
when
    they themselves become foragers.
    3) One of the most spectacular examples of social learning occurs in the 
honeybee
    dances. Inside the darkness of the hive, successful foragers display a 
series of
    stereotypical motor behaviors which inform other foragers of the precise 
location
    of floral food, up to several kilometers away from the hive. Dancers 
essentially
    "teach" recruits by putting them through a symbolized version of the "real 
life"
    flight to the food source. Recruits memorize and decode the information 
delivered
    in the dances, and subsequently apply the information on the flight to the
    indicated food source. Note that this constitutes a form of observatory
    (unrewarded) learning: while dancers occasionally give food samples to 
recruits
    by regurgitating food, these food samples are not a prerequisite for 
successful
    information transmission. Such mouth-to-mouth contacts between bees, 
however,
    serve another function in the context of social learning: successful 
foragers can
    teach their nestmates the scent of the food they have located.
    4) With the exception of Darwin's suggestion that honeybees might copy bad 
habits
    from bumblebees, the examples above are all cases where the transmission of
    information is of mutual interest, for example between parents and 
offspring, or
    between members of a colony of related individuals. A recent focus in social
    influences on learning, however, concerns cases where individuals 
inadvertently
    leave cues that can be used as publicly available information by other
    individuals for adaptive behavior [2]. A relatively simple form is local
    enhancement, where animals are drawn to sites where conspecifics are present 
[1].
    The newcomers may then learn, on their own, that the site contains valuable 
food,
    for example in Vespid wasps. Bumblebees are attracted to members of the same
    species when they scout for a novel flower species, and can learn about 
suitable
    food sources by observatory learning from unrelated individuals, without the
    necessity of direct interaction with these individuals, and without the 
presence
    of rewards. This means that bees, by observing the activities of other 
foragers,
    can bypass the substantial costs of exploring multiple food sources by 
individual
    initiative.
    References (abridged):
    1. Galef, B.G. and Laland, K.N. (2005). Social learning in animals: 
Empirical
    studies and theoretical models. Bioscience 55, 489-499
    2. Danchin, E., Giraldeau, L.A., Valone, T.J., and Wagner, R.H. (2004). 
Public
    information: From nosy neighbors to cultural evolution. Science 305, 487-491
    3. Romanes, G.J. (1884). Mental evolution in animals. AMS Press, New York
    4. Galef, B.G. (1996). Introduction. In: Heynes, C.M., Galef, B.G. (Eds.), 
Social
    learning in animals. (1996). Academic Press, San Diego
    5. Hopkins, A.D. (1917). A discussion of C.G.Hewitt's paper on 'Insect 
Behavior'.
    J. Econ. Entomol. 10, 92-93
    Current Biology http://www.current-biology.com
    --------------------------------
    Related Material:
    ON ALTRUISM OF INDIVIDUALS IN INSECT SOCIETIES
    The following points are made by Edward O. Wilson (citation below):
    1) Altruism is self-destructive behavior performed for the benefit of 
others. The
    use of the word altruism in biology has been faulted by Williams and 
Williams
    (1957), who suggest that the alternative expression "social donorism" is
    preferable because it has less gratuitous emotional flavor. Even so, 
altruism has
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    advantage of being instantly familiar. The self-destruction can range in
    intensity all the way from total bodily sacrifice to a slight diminishment 
of
    reproductive powers. Altruistic behavior is of course commonplace in the
    responses of parents toward their young. It is far less frequent, and for 
our
    purposes much more interesting, when displayed by young toward their parents 
or
    by individuals toward siblings or other, more distantly related members of 
the
    same species. Altruism is a subject of importance in evolution theory 
because it
    implies the existence of group selection, and its extreme development in the
    social insects is therefore of more than ordinary interest. The great scope 
and
    variety of the phenomenon in the social insects is best indicated by citing 
a few
    concrete examples:
    a) The soldier caste of most species of termites and ants is virtually 
limited in
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that
    arouse the rest of the colony, but, when they do, they normally place 
themselves
    in the position of maximum danger. When nest walls of higher termites such 
as
    Nasutitermes are broken open, for example, the white, defenseless nymphs and
    workers rush inward toward the concealed depths of the nest, while the 
soldiers
    press outward and mill aggressively on the outside of the nest. Nutting 
(personal
    communication) witnessed soldiers of Amitermes emersoni in Arizona emerge 
from
    the nest well in advance of the nuptial flights, wander widely around the 
nest
    vicinity, and effectively tie up in combat all foraging ants that could have
    endangered the emerging winged reproductives.
    b) I have observed that injured workers of the fire ant Solenopsis 
saevissima
    leave the nest more readily and are more aggressive on the average than 
their
    uninjured sisters. Dying workers of the harvesting ant Pogonomyrmex badius 
tend
    to leave the nest altogether. Both effects may be no more than meaningless
    epiphenomena, but it is also likely that the responses are altruistic. To be
    specific, injured workers are useless for most functions other than defense,
    while dying workers pose a sanitary problem.
    c) Alarm communication, which is employed in one form or other throughout 
the
    higher social groups, has the effect of drawing workers toward sources of 
danger
    while protecting the queens, the brood, and the unmated sexual forms.
    d) Honeybee workers possess barbed stings that tend to remain embedded when 
the
    insects pull away from their victims, causing part of their viscera to be 
torn
    out and the bees to be fatally injured. A similar defensive maneuver occurs 
in
    many polybiine wasps, including Synoeca surinama and at least some species 
of
    Polybia and Stelopolybia and the ant Pogonomyrmex badius. The fearsome 
reputation
    of social bees and wasps in comparison with other insects is due to their 
general
    readiness to throw their lives away upon slight provocation.
    e) When fed exclusively on sugar water, honeybee workers can still raise 
larvae
    -- but only by metabolizing and donating their own tissue proteins. That 
this
    donation to their sisters actually shortens their own lives is indicated by 
the
    finding of de Groot (1953) that longevity in workers is a function of 
protein
    intake.
    f) Female workers of most social insects curtail their own egg laying in the
    presence of a queen, either through submissive behavior or through 
biochemical
    inhibition. The workers of many ant and stingless bee species lay special 
trophic
    eggs that are fed principally to the larvae and queen.
    g) The "communal stomach", or distensible crop, together with a specially
    modified proventriculus, forms a complex storage and pumping system that
    functions in the exchange of liquid food among members of the same colony in 
the
    higher ants. In both honeybees and ants, newly fed workers often press 
offerings
    of ingluvial food on nestmates without being begged, and they may go so far 
as to
    expend their supply to a level below the colony average.
    2) These diverse physiological and behavioral responses are difficult to
    interpret in any way except as altruistic adaptations that have evolved 
through
    the agency of natural selection operating at the colony level. The list by 
no
    means exhausts the phenomena that could be placed in the same category.
    Adapted from: Edward O. Wilson: The Insect Societies. Harvard University 
Press
    1971, p.321.
    --------------------------------
    Related Material:
    ON EVOLUTIONARY BIOLOGY AND THE STUDY OF INSECTS
    The following points are made by Nipam H. Patel (Proc. Nat. Acad. Sci. 2000
    97:4442):
    1) A great number of studies aimed at understanding the evolution of 
development
    have been carried out within insects. Without a doubt, this is largely 
because
    our detailed understanding of the genetic and molecular basis of pattern
    formation in the model insect, Drosophila melanogaster, provides an 
excellent
    starting point for a large number of comparative studies. In addition, 
insects
    are an evolutionary diverse group of animals; almost one million species of
    insects have been described, and estimates of insect diversity place the 
total
    number of undescribed insect species at over 20 million.
    2) More importantly, there is an enormous range of morphological and
    developmental diversity found within this group of animals, extending from
    spectacularly colored butterflies, to stick insects, to horned beetles, to
    wingless silverfish, to minuscule parasitic wasps. Over the last few years,
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    closely related species of Drosophila, to comparing gene expression patterns 
to
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    differently related members of this group.
    3) A number of investigations have also focused on the evolution of the
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of
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    formation... It is particularly important that researchers continue to take
    advantage of as many different groups of insects as possible; this is the 
only
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    Proc. Nat. Acad. Sci. http://www.pnas.org