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4A: Monarch/Viceroy Case:
Case Two—Monarch and Viceroy Butterflies
Task Description
Each group will receive a folder with information on species that exhibit a particularly
interesting biological phenomenon. The materials in the folders will include narrative
descriptions of the organisms and their natural history, pictures, and data tables or
graphs that should help you understand the biology of the characteristics under study.
For each of these cases, your group will develop a scientific argument that will attempt
to explain the evolution of the trait or phenomenon in question from a Darwinian
perspective. This means using the Darwinian model along with all the prior knowledge
and beliefs on which it is based. All the material in the folder should be considered data
that can be used to develop and then justify your Darwinian explanations.
Your group's task is to:
1. Develop a Darwinian explanation that fully accounts for the particular phenomenon in
question. In your explanation be sure to include all the elements of Darwin's model.
2. Next, describe what data or material from the case you could use to support the
explanation you developed. Be as specific as possible in identifying both data you used
and what specific statements in your explanation that data supports.
Each of the above components are to be written after group discussion on a separate
sheet of paper. As we have seen from our previous work in class, the use of precise
language is extremely important in developing proper evolutionary explanations. Please
be as clear and explicit as possible. Use complete sentences and proper grammar
throughout the activity.
Your work will be evaluated based on:
•
Consistent use of a Darwinian model and the prior knowledge and beliefs
•
Completeness and thoughtfulness of your answers
•
The presentation and coherence of your written statements
•
Use of complete sentences and proper grammar
Problem Statement
As you can see, the viceroy and monarch butterflies closely resemble each other. Both
have orange wings with black stripes and white spots that are easily seen against the
colors of the meadows in which they live.
Given the information provided in this folder, construct a Darwinian explanation for the
development of the similarity in coloration between the viceroy and monarch.
Materials available in the folder:
•
Problem statement (this page)
•
Pictures of monarchs
•
Monarch life history information
•
Pictures of viceroys
•
Viceroy life history information
•
Phylogenetic tree of butterflies
•
Range map and population density information
•
Blue jay feeding information
•
Graph of insects eaten by blue jays
Monarch Gallery
Monarch life history
Throughout the summer, female monarchs seek out milkweed plants in meadows
and abandoned fields in the northern U.S. and Canada. Females lay their eggs
exclusively on milkweed plants, and each female lays about 400 clear green oval
eggs. The monarch egg (no bigger than the head of a pin) is attached to the
underside of a milkweed leaf. Within a few days the egg hatches and a yellow,
black and white striped caterpillar emerges, beginning its life cycle.
As caterpillars, monarchs are totally dependent on milkweed plants. Milkweed
contains toxic substances called cardenolides that are poisonous or distasteful to
other animals, but harmless to the monarch. After eating the egg from which
they hatch, the tiny caterpillar begins eating milkweed leaves. The larva are
voracious eaters, growing rapidly. In the two weeks following hatching, the
caterpillar sheds its skin four times to accommodate its growth.
After two weeks, at five centimeters in length and 3,000 times its birth weight, the
caterpillar is ready for its transformation. It spins a cocoon and develops into a
butterfly using the reserves built up by the caterpillar. The monarch butterfly
emerges after approximately five days. The adult butterfly has no jaws and feeds
instead with its long tongue on nectar and sap.
Viceroy Gallery
Viceroy Life History
Throughout the summer, female viceroys seek out poplar and willow trees in
the northern United States and Canada and lay their eggs on the leaves. The
viceroy egg is attached to the underside of poplar and willow leaves. Within a
few days, the egg hatches and the caterpillar emerges.
As caterpillars, viceroys remain in the trees on which they were hatched and
the leaves provide their sole source of nutrition. The mature caterpillar looks
mildly fearsome with its hunched and horned foreparts. The chrysalis
(cocoon) bears a striking resemblance to bird droppings, giving it protection
from predators.
After a few days, the adult viceroy emerges from the chrysalis and spreads its
colorful monarch-like wings. The adult butterfly has no jaws and feeds instead
with its long tongue on nectar and sap.
Adult viceroys have few natural predators. Blue jays are known to be one of
the birds that prey upon them. Predation of viceroys by blue jays, however, is
rather low. On average these birds consume roughly 0.2 individuals per day.
Phylogenetic Tree of Select Butterfly Families and Subfamilies
Family HESPERIIDAE
Family PAPLIONIDAE
Family PIERIDAE
Family LYCAENIDAE
Brassolinae Viceroy Butterfly
Amathusiinae
Satyrinae
Morphinae
Calinaginae
Charaxinae
Nymphalinae
Family NYMPHALIDAE
Heliconiiae
Acraeinae
Danainae
Ithomiinae
Tellervinae
Libytheinae
Subfamilies
Monarch Butterfly
Range Map of Monarch and Viceroy Butterflies in the Meadow
0.5
km
Range of Monarch Butterfly
Range of Viceroy Butterfly
Population Density Table
Species
Monarch (Danaus plexippus)
Viceroy (Basilarchia archippus)
Individuals/m2
2.2
0.3
Blue Jay: Primary Insect Predator
Blue jays are widespread in eastern North America and can be easily identified
by their distinctive crest and blue striped wings. They are usually seen alone or in
pairs in woodlands with clearings. Males are responsible for feeding females who
are incubating eggs, and they also help the female feed nestlings. Young blue
jays stay with their parents for two or three months and the family can be seen
hunting together during this time.
Blue jays are very agile and lively and spend a large part of their day searching
for food. Although blue jays are chiefly vegetarian, they are opportunistic feeders
and will freely take a variety of food if it is readily available. To supplement their
diet of nuts and seeds they often eat human food waste and insects. When
hunting insects they are visual predators, relying on movement and coloration to
help them identify their prey. They have the ability to vomit up food that is
unpalatable (tastes bad) or poisonous and appear to learn from the experience
as they avoid those food items in the future.
They are the primary flying insect predator in this type of meadow. The insects
on which they normally feed are similar in coloration to one another. Most are dull
green or gray and do not stand out from the vegetation in the environment.
Dietary Components
Nuts
Seeds
Insects
Moths
Grasshoppers
Lacewings
Other Butterflies
Monarch Butterflies
Units Consumed/Day
21.0
57.3
15.4
11.0
22.4
10.5
0.5