Elevated temperature does not affect growth of Vanessa cardui larvae.
By the Turbo Turtles
William Gardner, Mia Gomez, Rose Hoover, Djimon McLean,
Kaylin Nunez, Victoria Reis, Manuel Sanchez
Ms. Susna Attilus, Ms. Maria Licona, Ms. Carneasha Parks
Introduction
Increased temperature in the environment of different animals can change the
way the animals develop, produce fertile offspring, and adapt to their environment.
People can use this experiment in the real world to prevent extinction of the Painted
Lady species of butterfly. To prevent extinction of these butterflies, scientists could
observe what temperature the butterflies are able to live in. They could check and see
what other places have the right climate to have a backup place. The Vanessa cardui,
known as the Painted Lady Butterfly, will be the species of study in our scientific
caterpillar experiment.
Vanessa cardui, known as the Painted Lady Butterfly, is found in all continents
except for South America, Antarctica, and some areas of Australia. Vanessa cardui lives
in temperate climates, even the mountains in the tropics. It has a lifespan of about 2 –
4 weeks, in which it does a complete metamorphosis. The Painted Lady Butterfly
needs different environmental variables to survive its unique lifestyle. It needs
camouflage, temperate climates and nectar and plants for food.
The Turbo Turtles designed an experiment involving caterpillars. We used the
Painted Lady Butterfly for our experiment because they were easy to raise and work
on. Our problem statement for the experiment was “Does the temperature to which a
chrysalis is exposed affect the rate of caterpillar development?” Our overall hypothesis
is that temperature will affect growth rate, with warmer temperatures promoting faster
growth.
The null hypothesis is that there will be no difference in the rate of growth
development between the two groups. Our alternative hypothesis (two-tailed) is that
there will be a difference in the rate of caterpillar development between both groups.
We tested our hypothesis by making two groups of the caterpillars – a control and
treatment group. Our two groups have these scenarios – the treatment group is over a
heating pad that’s turned on and the control group is over a heating pad that’s turned
off.
Methods
For this experiment, we used 16 small caterpillar containers, two heating pads, 20
painted lady caterpillars, two large plastic bins (to contain the caterpillar cups), two
thermometers, caterpillar food, wax markers, and little paintbrushes. We used the 16
little containers, caterpillar food, wax markers, and little paintbrushes to prepare our
Painted Lady caterpillars. Our experiment was to test if warm temperature increased
the growth rate of the Painted Lady butterfly from the final stage of its life: chrysalis to
butterfly. We put 11 caterpillars in their own individual little containers inside each
big plastic bin used for the experiment. Each bin was placed on a heating pad. For
the control group, the heating pad was turned off, and for the treatment group, the
heating pad was turned on low. The treatment group was raised at 24oC, and the
control group was raised at 22oC (room temperature). All caterpillars got the same
amount of commercially prepared food, 9 grams per larva. We then watched all 22 of
them each day to see which ones had begun the process of chrysalis to butterfly.
Results
After about a week the caterpillars in the treatment group started to go into their
chrysalis stage. A few days later most of them were ready to become or were
butterflies. Full results can be found in Table 1.
The control group pupated on 6/30/15, 1 to 7 days after the treatment group. We
also discovered that the treatment group had pupation dates more spread apart from
each other, from 2 to 8 days apart, than the control group. We used the MannWhitney U Test to see if this difference between control and treatment was
significant. The control group had a mean of 11 days to pupation with a variance of
zero. The treatment group had a mean of 12.25 days to pupation with a variance of
13.1. Based on the statistical test that we recorded, we failed to reject our null
hypothesis. Temperature did not have a significant effect on the pupation rate of our
caterpillars.
Table 1. Days to pupation of Painted Lady caterpillars. There was no significant
difference in time to pupate between treatment and control groups.
Days of pupation for control group
Days of pupation for Treatment Group
C1
T1
11
10
C2
T2
11
C3
T3
11
C4
T4
11
C5
T5
11
C6
T6
11
C7
T7
11
C8
T8
11
C9
T9
11
T10
10
18
18
10
10-died
later
10
10
T11
12
Mean=11
Mean=12.25
Variance=0
Variance=13.1
Discussion
The null hypothesis of this experiment was that there would be no difference in the
rate of caterpillar development between two groups of caterpillars raised at two
different temperatures. Based on statistical analysis of the data, there was no
significant difference in development time between the control and treatment groups
(11 for control and 12 & 8.7 for treatment). (Table 1) Thus, we failed to reject our
null hypothesis. Caterpillar deaths in the early times of the experiment might have
interfered with the results, since we did not count these as pupated. For example we
had 10 caterpillar deaths in the treatment group. Another factor that may have
affected the results was that the temperature difference (2˚C) might have not been
significant enough to have an effect on the treatment group. Experimental conditions
were not always perfect. During the experiment, a few unexpected events occurred
that may have affected or altered the results. Some students had jostled the caterpillars
around, possibly causing other effects.
Our experiment could help in the real world because scientists might know where they
could raise butterflies if the species was in danger of going extinct. For example, they
could use the information obtained in this experiment to have a better understanding
of where Painted Lady butterflies have a better chance of surviving to become adult
butterflies from caterpillars because the temperature would be good for them.
On a larger scale, our findings tell us that global warming might not have a strong
effect on Painted Lady caterpillars, since they seem to grow at the same rate even if the
temperature varies a few degrees. Because of this, they might not be the best species to
use to find out if other types of animals would be sensitive to slight temperature
changes caused by global warming.