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Effects of insect abundance on spider distribution along the Rail Trail

Maggie Furtner, Erin Wiemels, John Sherers, and Josh Hanselman

Introduction

We conducted a research project to investigate the effects of insect abundance on the distribution of spider webs along the Rail Trail.  The trail is heavily populated by insects and orb-weaving spiders, including Micrathena mitrata and Micrathena gracilis.  The east side of the trail is adjacent to a patch of flooded forest, and the west side of the trail is close to Big Walnut Creek.  In September 2016, we observed a large number of spider webs on the east side of the trail, next to the flooded forest.  

hypothesis

We hypothesized that the uneven distribution of spider webs along the Rail Trail was due to a higher abundance of insects in the flooded forest on the east side of the trail.

methods

We counted the number of spider webs on both sides of the trail for 4 weeks.  We installed 9 insect traps (18 traps total) on each side of the trail; 5 traps were unbaited fly paper and 4 traps were plexiglass plates covered with a sticky glue (Tree Tanglefoot).  We counted the number of trapped insects by size class (small, medium, and large).  

results

There were significantly more spider webs on the east side than the west side of the Rail Trail.  Medium and large insects were significantly more abundant on the east side than the west side of the Rail Trail.  

discussion

Our results supported our hypothesis.  Both spiders and insects were more abundant on the east side of the Rail Trail near the flooded forest.  The flooded forest potentially provides breeding habitat for insects, thus contributing to the uneven distribution of spiders and insects.