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1629Do bowl traps with bees in them increase the probability of other bees being trapped?

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  • Sam Droege
    Jun 25, 2011
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      Quite a number of times I have heard people speculate that bowls with bees in them are likely to be more attractive to capturing additional bees than bowls that do not have any bee in them at all.
      I don't believe that this has been tested.

      So last week at had some young visiting researchers (Molly, Cece, and Jacob) who did some interesting tests that shed at least some light on the topic.

      Short Answer .... NO and the probability may be decreased.

      The longer answer is below

      Methodology
      • 3.25 ounce solo souffle bowls painted fluorescent blue were used.
      • Transects of bowls were deployed in lawns and weedy fields on the Beltsville Agriculture Research Center near Building 308 and one site (Site 3) in a northern Virginia suburban yard from June 22-24, 2011.
      • Pairs of bowls were placed so they touched one another with one bowl having a large bee (Apis or Bombus) place in it and the other bowl with nothing.
      • The large bees came from other studies and were preserved in ethyl alcohol.
      • Bowls were filled with a mixture of water with a small amount of Blue Dawn Dishwashing liquid in it.
      • At a site, A transect of 10 pairs of bowls was laid out with pairs of bowls 5m apart with treatment cups alternating from left to right in those pairs along the transect.
      • Five sites were established.
      • Bowls were emptied 24 hours after they were put out and the contents sorted to Genus.
      Results

              Table.  A table showing the number of large bees and small bees captured at each site (the large bees added to the "With Bee" bowls were excluded)
      With bee
      Without bee
      Site
      Big
      Small
      Total
      Big
      Small
      Total
      1
      2
      7
      9
      2
      15
      17
      2
      1
      12
      13
      3
      21
      24
      3
      2
      4
      6
      1
      8
      9
      4
      3
      10
      13
      1
      8
      9
      5
      0
      3
      3
      5
      16
      21
      Grand Total
      8
      36
      44
      12
      68
      80



      I will send an Excel file separately
      • Overall nearly twice as many bees were found in bowls that DID NOT originally have a large bee in them.
      • This pattern was repeated at each site with the exception of Site 4 where 4 fewer bees bees were found in the bowls that did not have bees.
      • The effect appeared to be greatest in small bees but relatively few large bees were captured in this study so this is not completely established.
      • The effect was the opposite of what was expected from conversations with people who used bee bowls, the expectation was that having a bee in a bowl would increase the likelihood of another bee going into a trap.
      • As was pointed out by Molly, Cece, and Jacob, it could be that the alcohol used to preserve the bees that were initially placed in the bowls had a negative effect, so another round of tests are planned for this summer using freshly frozen bees instead.
      • As usual, it is difficult to determine the universality of these results as each species and sex of bee would have its own proclivities and preferences for trap types and deployment, however, it does demonstrate that presence and types of bees in a trap could influence later capture probabilities which would alter assumptions regarding comparability of bee composition across locations, particularly if those locations had very different numbers of bees.
      • It should also be pointed out that this test looked at the probability that a bee makes a choice between two bowls as to which to die in, however, a different and more rigorous test would be to separate the treatment bowls to see if this pattern repeats when the choice is not which bowl to die in, but whether to die in a bowl at all.
      • Future tests will include looking at the impacts of the presence of small bees in a trap on the probability of additional bees being captured and looking at this same test when the bowls are not adjacent to one another but spaced out so there is no interaction between bowls with and without bees.
      A good student project to repeat in other geographic locations.

      sam

                                                     
      Sam Droege  sdroege@...                      
      w 301-497-5840 h 301-390-7759 fax 301-497-5624
      USGS Patuxent Wildlife Research Center
      BARC-EAST, BLDG 308, RM 124 10300 Balt. Ave., Beltsville, MD  20705
      Http://www.pwrc.usgs.gov

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