How will the addition of specific nutrients affect the size and survivorship of
Monarch butterflies (Danaus plexippus)?
David Hill, Matt Redmon, Tiphanie
Copeland
Jordan Park School of Extended Learning
Minneapolis, MN
Introduction | Methods |
Results | Discussion | Acknowledgements
|Biographies
Introduction
Is it possible to make monarchs larger than usual by providing them with extra nutrients?
We decided to start this research to find out if there is a way to create monster
butterflies. While measuring butterflies during field research, we observed that
some monarchs were larger than others. Those observations raised some questions.
How do nutrients affect monarch growth? How do the effects of nutrients compare
to the effect of genetics? We thought it would be fun to see if we could alter monarch
growth by adding nutrients to their basic milkweed diet.
Hypotheses
- Ho: Adding nutrients will have no effect on monarch growth and development.
- Ha1: Adding nutrients will positively affect monarch growth and development.
- Ha2: Adding nutrients will negatively affect monarch growth and development.
Methods
We tested our hypotheses by rearing monarch larvae under three treatments. One group
was the control and received regular milkweed (Asclepias syriaca). The
second group received regular milkweed dusted with bee pollen. The third group received
regular milkweed misted with a 20% sugar solution. We kept all the larvae at school
during the week and took them home during the weekends.
We received 60 monarch eggs from the University of Minnesota Monarchs in the Classroom
program. Twenty eggs were introduced into each of three containers containing the
three milkweed treatments (control/untreated, sprayed with 20% sugar solution, and
dusted with bee pollen). We applied the treatments to all of the milkweed leaves
in the containers.
We began weighing the larvae three days after the eggs hatched. Each weekday we
weighed and measured the length of each larva in each group. We kept track of larval
survival. We cleaned the cages each day and provided the larvae with fresh, treated
milkweed. We continued feeding the larvae over weekends, but no data were collected
over the weekends. Our measurements ended after the larvae pupated.
Results
Mortality
Forty-four out of 60 larvae died before they reached the adult stage. In the control
and sugar groups, 7 larvae lived and 13 died. In the pollen group, 2 lived and 18
died. Using a Chi-Square test, we found that there was no difference in monarch
survival among the three groups (X2 = 4.26, df = 2, p = 0.1188).
|
Treatment Group |
Survived |
Died |
|
Control (plain milkweed) |
Observed |
7 |
13 |
|
Expected |
5.33 |
14.67 |
|
Milkweed + Bee Pollen |
Observed |
2 |
18 |
|
Expected |
5.33 |
14.67 |
|
Milkweed + Sugar |
Observed |
7 |
13 |
|
Expected |
5.33 |
14.67 |
Table 1. Observed and expected numbers of larvae surviving and dying in three treatments.
Size
We compared the mass of the larvae in the three groups using T tests. We compared
the mass and length of the larvae on the last day that we measured them. We could
not include the bee pollen treatment larvae in the comparison because only one larva
survived until this time. We compared the mass and length of the control group larvae
and the sugar larvae and found a significant different between the two groups. The
mean mass was 1.035 for the sugar group and 1.151 grams for the control group (Figure
1). The mean length was 37.5 mm for the sugar group and 45.25 mm for the control
group (Figure 2). There was not a significant difference in mass between the two
groups (t = 3.03, p = 0.203). We failed to reject our null hypothesis of no difference
in mass. However, monarchs in the control group were significantly longer than monarchs
in the sugar group (t = 2.45, p = 0.035). We rejected our null hypothesis of no
difference in length.
Figure 1. Average mass of larvae over time for three treatments.
Figure 2. Average length of larvae over time for three treatments.
Discussion
We ran into a few challenges while conducting our experiment. In the process of
learning about monarchs and their life cycle, we came to understand just how fragile
these creatures are. Initially we had wanted to see if the larvae could grow on
a diet of butter applied to the bottom surface of milkweed leaves. We discovered
that many of the larvae for this experiment died in the oily film. Those larvae
that did survive were severely emaciated. Because of the apparent cruel nature of
this experiment, we decided to just test the sugar solution and bee pollen. Also,
we were surprised to learn that monarch larvae will cannibalize other eggs. Some
of the eggs never hatched because the larvae that hatched first ate them. We found
that it was difficult to supply fresh milkweed each day. Weighing and measuring
the larvae was also very tedious work. Taking the larvae home did not always work,
due to parental reasons--especially when larvae pupated on the lamp shade!
We also had some additional observations. Most notably, we observed that the color
of the larvae was different among the three groups. Those in the control group had
what we considered a normal color. However, the larvae in the sugar solution group
had a dingy color and the larvae in the bee pollen group appeared to be even brighter
than the control larvae.
Acknowledgements
We wish to express our thanks to Karen Oberhauser and the staff of Monarchs in the
Classroom for making this opportunity available. We wish to thank our teacher Mr.
Hill for walking us through the process. Special thanks to Dr. Gupton, Principal
of Jordan Park School of Extended Learning. Thanks also to our understanding and
patient parents. We thank the students who supported and aided us: Chase Foote,
Erin Laxton, Dwayne Fisher and Mai Der Vang. Finally, we thank the National Science
Foundation, the Science Museum of Minnesota and the Bambergers for the use of their
wonderful ranch.
Biographies
David W. Hill is a seventh and eighth grade science teacher
at Jordan Park School of Extended Learning. He is a scientist in the field of limnology
and has been in the field of education for 27 years. He is married and has three
grown children and three grandchildren. He enjoys his research, cooking, and fishing.
Matt Redmon is an eight grader at Jordan Park SOEL. He
enjoys science projects like this one. He also enjoys meeting new people. He says
that if he ever had a chance to do another project like this one, he would!
Tiphanie A. M. Copeland goes to Jordan Park SOEL and will
be going to Washburn High. She likes to listen to the Backstreet Boys and loves
to do math. She hopes to be working with the government soon. She also hopes to
do another program like this one in the future.