Saddleback Journal of Biology - Saddleback College

Fall 2009 Biology 3B Paper
Figure 3. The larval and cocoon stage incubated at 22.2C at Day 16. Larva have progressed through
metamorphosis by entering into the cocoon state. No present adult Vanessa cardui.
Figure 4. The larval and cocoon stage incubated at 27.7°C at Day 16. Majority of the cocoons have undergone
metamorphosis to adult stage.
Discussion
The mean length of days of V. cardui
incubated at 27.7°C to reach the cocoon state was
11.45 days, while that of those incubated at 22.2°C was
15.57 days. Upon performing a one-tailed t-test with
unequal variances, the p-value obtained was 1.49×10 -6 .
The null hypothesis can be rejected, as the p-value is
significantly smaller than 0.05. Thus, the temperature
of incubation during the larval to cocoon stage does
play a significant role in the rate of metamorphosis.
The hypothesis that a higher temperature will increase
the rate of metamorphosis in V. cardui was supported.
According to Kelley and Debinski (1999), the
temperature of incubation during the larval stage of the
species V. cardui was a significant factor in
development. The study indicated that larval stages of
V. cardui had the capability of extending the necessary
growth period to develop into the adult form, in
reference to the effects of food limitations (Kelley and
Debinski 1999). Upon incubating a total of 5 groups of
this particular species, the data depicts that the
temperature did indeed affect the growth period of the
V. cardui. The size of the caterpillars during the larval
stage was visibly smaller in the lower temperature
groups than that of the caterpillars incubating at 27.7°C
(Figure 3). Although Kelley and Debinski stated that V.
cardui had the ability to elongate their growth period
before maturing into a cocoon, the data clearly reflects
that this elongation process does not necessarily mean
the larval stages will reach the same lengths before
maturing into their chrysalis form. The cocoons of the
caterpillars incubated at 27.7°C also appeared larger in
comparison to those of the specimens held at 22.2°C
(Figure 4). The time to reach the smaller cocoon size,
however, was longer as the mean amount of days to
begin cocooning was 15.57 days. These results indicate
that Vanessa cardui do have the capability to elongate
their growth periods before reaching their adult stage.
This elongation, however, is not in reference to the
lengths of the caterpillars as the size of both the cocoon
and larval stages of the lower temperatures were
visibly smaller.
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Saddleback Journal of Biology
Spring 2010