This study investigated whether wolf spiders use their posterior eyes for night vision when catching prey. Spiders were collected and their eyes painted over: posterior eyes only, all eyes, or left untouched. They were then placed in containers with crickets in total darkness and the number of captures was recorded. Statistical analysis showed spiders with posterior eyes painted caught significantly fewer crickets, supporting the hypothesis that posterior eyes are important for night vision and prey capture. Further testing could examine the role of anterior eyes by blinding them instead. The study concluded the posterior eyes are important for wolf spiders to catch prey in the dark.

1. Studying
Posterior Eye Function
in Rabida Rabidosa
Courtney Dunn, Debbie Huynh, Kerry
Harrington, Nancy Huynh

2. Introduction
Question: Do wolf spiders use their posterior
eyes to catch their prey at night?
H0: There will be no difference in prey catching
ability between normal, partially, and
completely blind spiders.
H1: If the posterior eyes are used for night
vision, then the spiders should have
significantly reduced ability to capture prey in
the dark with posterior eyes painted.

3. There has been extensive work done on
jumping spiders and the functions of the
different sets of eyes, and how they are used to
hunt in varying light conditions.
In jumping spiders, the posterior eyes are
used for prey detection in low-light conditions
and the anterior eyes are used in brighter
conditions (Blest, et al)
Significance

4. Experimental methods
1. Collect spiders
2. Fast for at least
1 day

5. Methods
3. Cool spiders
thoroughly.
4. Paint eyes:
a. posterior eyes
only
b. all eyes
c. back

6. 5. Acclimations:
a. Allow
spider to warm
up for 15 min.
b. Allow
cricket to
acclimate in
container for 15
min.

7. Methods
6. Add spiders to
cricket container
7. Allow 15 min.
for trial in total
darkness
8. Repeat for all
treatments.

8. Result
Expected value= (Row total x column total) / grand total
X2= [(19-7.67) 2 /7.67] + [(1-7.67) 2 /7.67] + [(3-7.67) 2 /7.67]
X2= 25.38
α= 5.99 [for d.f=2]
Yes No Row totals
Normal vision 19 1 20
Expected 7.67 12.33
Partially Blind 1 19 20
Expected 7.67 12.33
Totally Blind 3 17 20
Expected 7.67 12.33
Column total 23 37 60 Grand total

9. Discussion
The blinding of the posterior eyes has
significant effect on wolf spiders' ability to
capture prey.
The fact that partially blinded spiders
captured fewer crickets than totally blinded
spiders was surprising, but I think it was a
chance occurrence that could be ruled out by
performing more trials.
However, the function of the posterior
eyes could be further tested by blinding the
anterior eyes and testing for prey- capture
ability in darkness.

10. Conclusion
Accept H1 - blinded eyes reduced their ability
to catch prey in the dark