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Insect diversity in old field succession

Kelsey Nosek, Wesley Jones, Hannah Ramage

We hypothesized that the diversity of insects in the K2 loop trail will change based on the amount of woody plants present.  

We used pitfall traps to sample insects.  Pitfall traps were set 20 meters apart on transects A and B.  The dots on the map indicate where we placed the traps.  Pitfalls were only placed on transects A and B and not on transect C because we thought we would be covering all habitat types with these two transects.  Antifreeze was placed in the traps to kill and preserve the insects.  We used antifreeze that does not smell sweet to avoid attracting small mammals.  We sorted the insects into 14 categories and used a chi-square contingency table to analyze the data.

Our null and alternative hypotheses were
Ho:  Frequency of insect types are independent of habitat type
HA:  Frequency of insect types are not independent of habitat type

There were three habitat types:  
1.)  Young forest, high floodplain
2.)  Transition zone, medium floodplain
3.)  Prairie/meadow, low floodplain

We rejected the null hypothesis.  There were significant differences between the types of insects among the three habitat types.  

General trends

  • More ants, spiders/harvestmen, crickets, moths, butterflies, grasshoppers, and snails in prairie
  • More isopods, millipedes in young forest
  • Intermediate frequencies in transition zone
We unintentionally caught five small mammals (two least shrews, one short-tailed shrew, one prairie vole, and two white-footed mice). 
There is debate on which chemical concoction is best for pitfall traps.  Ethylene glycol and water is more hazardous to wildlife, but propylene glycol is less effective.