ENY 6203  Techniques for Marking Insects
Many types of ecological and behavioral studies of insects  require the
 marking  and subsequent recognition of individuals.  In some studies each
individual must be given a distinctive mark; in other studies members of
each of a few groups must be recognizable; and in still others all that is
required is that previously marked individuals be distinguishable from
unmarked ones.
These are some examples of studies employing marked insects :
      * Estimates of population density by capture-release-recapture
         technique
      * Studies of dispersal and migration
      * Detection of the number of nymphal molts
      * Determinations of longevity and mortality
      * Determination of home range and territoriality
      * Studies of feeding specialization by individual predators or pollinators
      * Studies of dominance hierarchies, leks, and female choice

Criteria for judging  marking  techniques
The following criteria should be considered when selecting a  marking 
technique:
(1) Persistence.  Will the  marking  last as long as required?  Is it equally
      permanent for all individuals?  Will it survive molting?
(2) Recognition of individuals or groups.  Does the technique offer
      distinctive marks to discriminate as many individuals or groups as
      required?1
(3) Effect of  marking .  Does the  marking  process injure the individual?
      Does the marked individual have a different chance of survival than the
      unmarked?  Is the behavior or physiology of a marked individual
      different than an unmarked one?
(4) Ease of  marking .  Can the necessary numbers be marked in the time
      available and with reasonable expense for equipment and supplies?
(5) Ease of recognition.  Can marked individuals be easily and reliably
      separated from unmarked ones?  Can specially marked individuals or
      groups be easily and reliably distinguished from one another?
1For example, 100 butterflies per color can be marked distinctively by this system (one dot on each front wing):
(6) Transfer of mark to unmarked individuals.  Can unmarked
    individuals become marked by contact with marked individuals?  Are the
    eggs or progeny of marked individuals marked?  If such transfer does
    occur, can it be relied upon?

 Marking  techniques
 Marking  techniques that have proved useful in entomological studies are
listed below:
(1) notches or amputation.  Notches can be made in the pronotum or
    elytron and coded by position or number.  Portions of a leg or an elytron
    may be cut off.  Both notching and amputation will sometimes last from
    one instar to the next.
(2) scratches or brands.  Marks, numbers, or letters can be scratched or
    burned into the elytra or pronotum.
(3) paper labels.  F. A. Urquhart used this system to get returns of
    migrating monarch butterflies from more than 2000 km away.  Adhesion
    is the principle problem.  The return address is the greatest advantage
    over other systems.
(4) colored thread.  For instance, tied between the abdomen and thorax.
(5) spots of ink, paint, or dope.  Differences in shape, position, color, and
    number allow coding of many individuals.  Materials used include india
    ink,  marking  pen ink, acrylic paint, nail polish, stains , dyes, oil paints,
    fluorescent paints, and pigmented shellacs.  These may be applied to the
    wing, thorax, or elytra with pen, brush, single bristle, small wire,
    pointed stick, or syringe.
(6) colored dusts.  Dyes, colored chalk dust, metallic or fluorescent
    powders applied by shaking the insect with the dust, brushing, or
    dusting.
(7) colored sprays or dips.  Fluorescent paints, oil paints, aniline dyes, or
    colored inks applied with sprayers or atomizers or as a dip.
(8) stained or colored food.  Rearing larvae on dye-containing food may
    yield colored adults.  In some instances the adults lay colored eggs.
    Colored food may be seen within the digestive tract of transparent
    larvae.
(9) radioactive materials.  Applied externally as spray or dip.  Applied
    internally by incorporation into food or drink, by direct feeding of isotope
    solution, or by injection.  Radioactive wire or metal foil attached
    externally or implanted.  The principal advantage  of radioactive
     marking  is that marked individuals can be detected without visual
    examination (for instance in the soil or in the dark).  In some cases
    radioactive  marking  endures one or more molts and may be passed from
    males to females in the sperm and from females to eggs.  Other
    avantages are that the marked insect is no easier for predators to detect,
    the marked insect can be detected by a sensor that can activate a relay,
    the tag may pass from a prey insect to its predator, and very small
    insects  may be easily and persistently marked.  Disadvantages: Outdoor
    release of radioactively marked insects  is generally prohibited.  Use of
    radioactive materials requires costly equipment and special training and
    is strictly regulated.
(10) metal discs.  Glued to foraging honeybees and bearing identifying
    numbers.  The discs can be collected by powerful magnets as the bees
    pass through chutes at the hive entrance.
(11) mutant genes.  Mutant genes with easily recognized phenotypic effects
    are available for some insects  (e.g. Drosophila spp., Musca domestica,
    Aedes aegypti); however, individuals with such genes may be abnormal
    in their ecology and behavior.  Genetically marked colonies have been
    used to investigate mating ranges of honeybees.  Here no other type
    mark would work so well.
(12) natural marks.  Sometimes insects  from certain populations are
    recognized by natural marks.  For instance, butterflies of one subspecies
    are at least statistically distinguishable from those of another; aphids
    may be recognized as coming from a particular area by the virus they
    carry; syrphids may become marked with the pollen of flowers typical of
    a certain habitat or elevation.  Insects  from certain localities may have
    characteristic allozyme frequencies or they may contain or bear certain
    rare elements--see (13).
(13) rubidium and rare earth elements.  When a site is treated with
    compounds of unusual chemical elements, the insects  in the area pick up
    minute amounts that can be detected by sensitive techniques such as
    atomic absorption spectroscopy or neutron activation.

References
Southwood, T.R. E.  1978.  Methods of  marking  animals.  Pages 70-92 in
    Ecological methods with particular reference to the study of insect
    populations.  Chapman and Hall, London.
Walker, T.J., and S.A. Wineriter.  1981.   Marking  techniques for individual
    recognition of insects .  Fla. Entomol. 64(1): 19-29.
Wineriter, S.A., and T.J. Walker.  1984.  Insect  marking  techniques:
    durability of materials.  Entomol. News 95(3): 117-123.

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