Monarch Butterfly

Introduction

Flying through the sky with vibrant colors are the monarch butterflies, known for their vibrant orange color. They are also know for their seasonal migration just as birds do, leaving their summer breeding grounds for the warmer temperatures in Mexico and California. This migration is a long road for monarchs and they need stamina in order to complete the journey. In The Redder the Better: Wing Color Predicts Flight Performance in Monarch Butterflies they perform an experiment to determine if wing color determines flight performance in which they recorded the color of the butterflies wings and their sex. They then attached monarch butterflies to a flight mill to record how far they can fly and how long they can fly. From this they made conclusions that flight distance and wing color are connected to one another.

Taxonomy and Nomenclature

Kingdom: Animalia (multicellular, heterotrophs)


Phylum: Arthropoda (exoskeleton, segmented body)


Class: Insecta (ability to fly and use legs)


Order: Lepidoptera (wings covered in scales, body has tiny sensory hairs)


Family: Nymphalidae (brush footed meaning shortened front legs)


Genus: Danaus


Species: Danaus plexippus

Danaus plexippus translates to Monarch Butterfly

Get to Know Monarch Butterflies

Geographical Location

•North and South America

•Australia and New Zealand

•Islands in the pacific and Atlantic

•Western Europe


Migration

•Follow a pattern of seasonal migration like some birds

•In North America, the eastern population of butterflies overwinters in the volcanic mountains of central Mexico

•Western populations overwinter on the coast of California


Habitat

•Frost Intolerant

•Breeding habitat is dependent on milkweed

•Need dense tree coverage during winter months (CA has eucalyptus trees which provides great shelter)

Food

•Larva feeds on milkweed plants where they can get and store cardiac glycosides which makes them poisonous

•Adult Monarchs feed on flower nectar

Appearance

•Bright orange with black borders and black veins

•Females have thicker veins than males

•Males have a swollen pouch on the bottom of there back wings

•Poisonous to vertebrates because of the milkweed they eat

•Their color serves as a warning sign that they are poisonous but also allows them to camouflage from a distance


Does Wing Color Predict Flight Performance?

Experiment


Experiment: The Redder the Better: Wing Color Predicts Flight Performance in Monarch Butterflies

Written By: Andrew K. Davis, Jean Chi, Catherine Bradley, Sonia Alitzer

•121 individual monarch butterflies tested (3 trials)

•Observations taken before flight: wing area, length to width ratio, melanism, orange hue

•Use of a tethered flight mill apparatus in order to determine the butterflies speed, duration, and distance

Diagram of a tethered flight mill apparatus

Use of Tethered Flight Mill Apparatus

•Butterfly attached to rod using ultralight steel wire glued to thorax

•Photogate flag is used to interrupt the infrared light which indicated a full rotation of the carbon rod was there to

•Time of flight was measured until the wings of the butterfly were no longer moving


Results

•Average flight distance: 4.0 km (2.5ish miles)

•Female v. Male flight distance: 4.57 km v. 3.59km

•Average flight duration: 61.3 minutes

•Average flight speed: 3.9 km/hr (2.4 mph)

•Females flew further than males so sex effects flight distance

•Individuals with redder wings (lower hue scores) travelled farther for both males and females

•No significant effect of forewing area, width to length ratio, or relative body size on the distance of the flight


Graph Analysis

Both graphs show the distance each monarch butterfly flew in kilometers based on their wing hue with the higher numbers on the x-axis being lighter orange to yellow and the lower numbers on the x-axis being the deeper orange to red hue. The different shapes plotted on the graphs represent which trial the butterfly was a part of. Based on both graphs it is obvious that monarchs with deeper wing hues did fly further distances and as the wing hue gets lighter the distance gets shorter. Comparing the graphs to each other overall female monarchs flew farther than male monarchs. As a lot of females flew more than 6 km while almost all of the males flew less than 6 km. These graphs support the idea that females fly farther than males can and a deeper wing hue leads to improved flight performance.

Conclusion

•There is a correlation between wing hue and flight duration in Monarch Butterflies as Monarch Butterflies with deeper orange hues fly further distances for longer periods of time

•This claim is backed up by evidence in the experiment as butterflies with deeper hues of orange travelled farther than those with lighter hues of orange in all 3 trials of this experiment

•This connects to previous experiments that Monarch Butterflies who migrate in the fall have deeper orange hues than those Monarchs who were examined in the summer

•This experiment gives an improved understanding of monarch butterflies and their flight tendencies based on wing hue and sex


Looking Ahead

It is still unknown what mechanism causes a connection between wing hue and flight, although there are some hypothesis’ of how such as overlapping biochemical pathways or by metabolic constraints that affect both wing color and flight independently. There is still not enough data out to determine how these two variables are connected, this experiment only shows that there is a connection