Tom's Blog

Friday, September 18, 2015

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.

See this link for further milkweed buginformation.


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