MadSci Network: Zoology

Re: are there any other catipallirs that can eat milkweed?

Date: Mon Sep 3 16:50:56 2007
Posted By: Shireef Darwish, Grad student, Department of Plant Science, McGill University
Area of science: Zoology
ID: 1187885493.Zo

Hi Celeste,

Are there any caterpillars that feed on milkweeds other than monarchs?
Great question! There is actually a whole group of related Lepidoptera (the
Order containing butterflies and moths) known as milkweed butterflies (a
subfamily, Danainae, in the family Nymphalidae), which includes about 300
different species that feed on milkweeds! However, only four of these
species are found in North America, the most well known being the monarch
(Danaus plexipus). The other three North American species are known as the
Queen (Danaus gilippus), the Tropical Milkweed Butterfly (Lycorea
cleobaea), and the Soldier Butterfly (or "Tropic Queen"; Danaus eresimus).
The adult stage (the butterfly) of these species will lay their eggs on the
lower surface of milkweed leaves so that when they hatch the caterpillars
can immediately begin to munch on the leaf tissue. As they eat, the
caterpillars will also ingest the toxic, milky latex secreted from the
wounded leaves. However, milkweed butterflies are “immune” to these toxins,
and actually store them in their own body tissue to deter hungry birds from
eating them (monarchs really are what they eat!). Check out this webpage
about the role of milkweeds in the monarch lifecycle from

There is another species of caterpillar that is not part of the “milkweed
butterfly” group known as the milkweed tiger moth (Euchaetes egle). There
are also a bunch of butterflies, like the Eastern Black Swallowtail, that
will feed on the nectar of milkweed flowers (unlike the caterpillar stage,
adult butterflies do not eat leaves). However, the nectar of milkweed
flowers does not contain the same toxic chemicals that the leaves contain,
making the nectar safe for consumption by a wider variety of butterflies.
This is a common challenge faced by plants – plants want to defend their
leaves (food-producing organs carrying out photosynthesis), typically with
chemical defenses or physical ones like thorns or hairs, while encouraging
pollination of their flowers by insects. Milkweeds are a great example of
this. Remember, just as there are many species of milkweed butterflies,
there are also a number of different species of milkweeds (about 140
recognized species of Asclepias). Not all of them produce the same kinds or
amounts of toxins characteristic of the Asclepias eaten by monarch
caterpillars. Check out this great page from Duke University for pictures
of different Aclepias (

Hope this helps! Enjoy exploring the wonderful world of plant-insect


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