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Student Number: 1006143718
Lab: Week 1- Thursday 6:00PM
TA Name: Casey Carlisle
Species Number: 4
Does the number of available perching sites affect the number of preys collected by
Libellula pulchella
?
Introduction
Libellula pulchella
are twelve-spotted dragonflies that live largely in North America near bodies
of water, i.e., ponds, streams, lakes, etc. These insects are extremely territorial, and aggressively defend
their breeding site – typically by males (Pezalla 1979). While defending their territory, they also hunt by
waiting for their prey to be vulnerable on water surfaces.
Libellula pulchella’s
hunting behaviour can be
described as hawking.
The insects patrol, pursuit, flight, and attack by forming their legs into a claw if threat or prey
arrives on their territory (Pezalla 1979). However, all this can only occur with the right perching sites.
Their choice of perching sites is dependent on various factors such as: sun exposure, and unobstructed
view of territory (Pezalla 1979). Their territorial and hunting behaviour – hawking, can be an adaptive
trait for their viability. It is unknown if limited availability of perching sites affects their survival in their
environment. Furthermore, the number of available perching sites affect the number of preys collected by
the
Libellula pulchella
, overall affecting their survival.
Methods
To explore the hypothesis, I will control the number of available perching sites (independent
variable) by setting a certain number of branch sites in each environment that is being created. Other
controlled variables include the following: gender, type of prey, temperature, no obstruction of view to
territory, and time. I will measure the number of preys captured or attacked (dependent variable) by
providing an equal number of preys in each environment and then physically counting what is left.
To conduct the experiment, I will create a controlled group in a laboratory with five available perching
sites (branches attached in various areas in one container) and place a single male
Libellula pulchella
with
4 mosquitoes and 4 spiders in an environmental temperature of 25
o
C (Duong et al 2017). I will place
cameras around the container and after 2 days count the number of preys captured or attacked. In an
