spiderfile.htm (spiders of Kentucky)
https://en.wikipedia.org/wiki/Spider (general background
https://spiderid.com (identification of spiders using pictures)
arachnids_cohen_weiner/ Intro.html (arachnid identification)
Field Sampling Techniques
To better illustrate how this exercise may unfold in your class, we played
the role of students and proposed our own hypothesis to investigate as
part of a pilot study. Here, we present our experimental design and
describe the methods utilized to collect data in the field. We used
simple descriptive statistics to analyze and interpret our findings, and
multiple evaluative strategies to assess the overall merits of our
particular project. Recognizing the limitations of our pilot study, we
recruited a small number of K–12 students to replicate our collection
efforts and identify problems in our sampling design. In addition, we
describe a number of other potential field projects that other
students might choose to explore as part of their own investigation.
The student learning outcomes (SLOs) for this inquiry-based exercise
were adapted from the Pacific Education Institute (2015):
• SLO 1: Develop information literacy; activities: search printed literature and Internet sources to summarize a broad topic of interest.
• SLO 2: Formulate investigative questions; activities: ask questions about abundance and differences between groups, conditions, or habitats.
• SLO 3: Demonstrate systems-level thinking; activities: identify
habitat types and associated structural and organismal differences between them.
• SLO 4: Identify variables of interest; activities: choose variables
to be measured in at least two different locations or measured
together to test for relationships.
• SLO 5: Formulate a hypothesis and collect data; activities: propose a hypothesis based on identified variables, design a sampling protocol, and collect data.
• SLO 6: Analyze and interpret data; activities: plot and statistically
analyze data to elucidate patterns for comparison to other systems.
Does Wolf Spider Density Differ between Habitats?
After addressing the review questions (Box 1), we chose to investi-
Methodology & Data Analysis
gate whether the density of wolf spiders varied between different
habitats. We hypothesized that they would be more prevalent in
an undeveloped field than in a typical urban backyard. We utilized
a comparative field investigation (Pacific Education Institute, 2015)
to study the differences. The following protocol was designed to
sample these habitats, and our data are presented and analyzed in
much the same way that students would use with their own
We used quadrat sampling to test our hypothesis regarding spider
density in two distinct habitats. This sampling technique is commonly used to determine a species’ presence or absence and to provide estimates of overall abundance and density (Jaeger & Inger,
1994). The protocol first involved dividing the habitat of interest
into a rectangular grid of equal-sized units (Jaeger & Inger,
1994). For our study, we used a meter wheel and surveyor flags
to divide a 0.10 hectare (0.25 acre) backyard habitat into four
square grids of equal size (length 30 m × width 30 m = 900 m2).
This habitat was largely comprised of a uniform turf of centipede
grass (Eremochloa ophiuroides). By comparison, the undeveloped
field was ~0.41 hectares (1.0 acre) characterized by sandy soil with
a mix of bahia grass (Paspalum notatum), southern wiregrass (
Aris-tida beyrichiana), and patches of dogfennel (Eupatorium capillifo-lium) among other invasive species. For consistency, we laid out
an identical grid consisting of four squares of equal size (900 m2)
centered in the interior of the larger field (see protocol references
in Box 2). We constructed a circular 1 m2 quadrat using ¾ inch
plastic tubing purchased at a home improvement center for under
$15. Students could also use a standard hula hoop as a quadrat
but would first need to calculate the internal area as follows: area =
π(d/2)2 = __ m2.
Prior to sampling, we recorded the time and temperature and
provided a basic description for each habitat in our field journal.
We sampled at night, entering each square of our rectangular grid
at a randomly chosen compass direction and walked 10 paces
before dropping the quadrat. Flashlights were held at the temple
with the beam pointed downward at a 45° angle to maximize eyeshine detected. The number of spiders visible from our original
position was recorded, and we proceeded to encircle the hoop to
identify any others that faced a different direction. Although the
spiders commonly shifted positions or partially retreated into their
burrows, few moved more than short distances when fully illuminated. Upon completion, we retrieved the hoop and walked
10 paces in a randomly chosen compass direction before dropping
the quadrat and repeating the process. For both field and backyard
habitats, we counted the number of spiders in 10 randomly
selected quadrats for each square of the grid. We sampled on only
one occasion, to highlight the extent of data that could be collected
by students in just one evening (total data collection time:
~30 minutes per habitat). For this field protocol, each quadrat represents an independent sample, and statistical inferences can be
drawn from the data, assuming that the sample size is sufficiently
large (Jaeger & Inger, 1994). Although our time in the field was
limited, we still collected data from a total of 40 quadrats in each
habitat and were able to make statistical comparisons. Using the
Analysis ToolPac feature available in Microsoft Excel, we compiled
our data and tested the following null and alternative hypotheses
using a two-sample t-test:
• Ho = The abundance of lycosid spiders does not differ between