314 
Psyche 
[Vol. 90 
Methods and Study SItes 
During 1980-1982, Gordon VanWoerkom (Hope College) and I 
observed the relationships between bracken fern and its associated 
arthropod community in Michigan. Our original intent was to 
determine to what extent seasonal patterns of insect species diversity 
are a reflection of quantitative or qualitative changes in the chemical 
composition of their host plant. We uncovered an arthropod com- 
munity associated with bracken that is much more complex than 
expected. These arthropods were identified to species whenever pos- 
sible, and their behavior was recorded by 16mm and 35mm cameras. 
The bracken-arthropod study was conducted on four lOO-m^ plots 
of bracken occupying different environments within the confines of 
the Hope College Field Station. This 80 acre field station is located 
in Allegan County, 2 miles south of Holland, Michigan. The mild 
climate of the preserve is due to the thermal moderating effect of 
Lake Michigan. Primary vegetation consists of virgin forest, mature 
(second generation) deciduous forest, as well as open fields punctu- 
ated with sand “blow-outs” in various stages of ecological suc- 
cession. 
In upland areas, where the bracken plots are located, the soil 
consists of a relatively thin layer of sandy-loam topsoil overlying 
what was formerly extensive sand dunes from Lake Nipissing. 
Bracken fern has established extensive stands in discrete patches 
throughout the preserve, some under forest canopy and others 
under open field conditions. 
Results 
Although predaceous ants and spiders are abundant during the 
spring, the diversity of herbivorous species is low, supporting Law- 
ton’s (1976) observation that, “The evidence strongly suggests that 
bracken in May and June may not be an easy resource for herbi- 
vores to exploit.” However, protein levels are highest in the spring 
(about 25 percent of the dry weight) and 40 percent lower by 
August-September (about 10 percent of the dry weight). Further- 
more, concentrations of lignins, tannins, and silicate are lowest in 
the early spring and tend to increase throughout most of the season, 
all of which might be expected to make the plants tougher and 
therefore less palatable. As Lawton (1976) further points out. 
