Milkweed bugs are now thriving
Milkweed bugs feeding on a common milkweed pod |
The milkweed bug (Oncopeltus fasciatus) is specialized for
feeding on milkweeds. The principal food of this bug is the milkweed seed,
although the nymphs will feed on the leaves and stems. Milkweed plants contain
a series of toxic chemicals called cardiac glycosides. Although these
glycosides are generally toxic to insects, the milkweed bugs are not affected. Further,
the toxins give the bug a bad taste, which helps keep them safe. It is thought
that the coloration of the milkweed bug is a signal to birds or other predators
to keep away.
The milkweed bug grows well on Asclepias seeds, but grows poorly
on seeds of other kinds of plants. In nature the bug is only found breeding on milkweeds
of a variety of species. Because of its preference for milkweed seeds, it
synchronizes its life cycle with milkweed pod formation. The female only lays eggs
at a site where the milkweed pod density is the highest.
Milkweed bugs on pods of whorled milkweed (A. verticillata) |
The insect is able to
insert its proboscis through the pod wall and suck out the nutrient-rich
materials from the seeds.
Because of its preferential attack on milkweed pods, the
milkweed bug is a potential threat to the milkweed population. However, rarely
does one find milkweed bugs in such large abundance that the milkweed
population may be seriously affected. However, I once saw a nice patch of the
Endangered purple milkweed destroyed by a milkweed bug infestation.
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