Monday, November 5, 2018

Yard Critter of the Week

False Milkweed Bug


There has been confusion as to the identity of this insect. The BugGuide page linked above discusses this confusion, between the similar in appearance Small Milkweed Bug.

Even one of my field guides seems to get it wrong (and I in turn misidentified it at first).

There are many insects that mimic the appearance of others in what is known as Mรผllerian Mimicry. As milkweed has chemicals which are toxic to vertebrates, some insects have evolved to use these chemicals as defense against predation. The Monarch Butterfly is a famous example. Its appearance is a signal to predators to leave it alone. Other butterflies, such as the Viceroy, have evolved a similar appearance to ward off predators as well, without developing the toxic chemical defenses, a bit of insect fraud.

As animals encounter, eat, and experience the toxic effects of the poison insects, they learn to avoid such prey, including the harmless mimics, in the future. Of course, if to many non-poisonous insects mimic the poison ones, the predators will not learn to avoid them. A fascinating game of cat and mouse played out over evolutionary time.


We had hundreds if not thousands of these False Milkweed Bugs all about our side garden. As this section of our gardens has no milkweed growing in it (we have plenty elsewhere) it was a pretty good clue as to their ID.


It is November and I still see them in the garden and on our deck. And as you can see from these images, there are both adults and young in various stages. They over winter as adults, so these youngins' better grow up quickly!

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You can find all of the Yard Critter of the Week posts listed here.

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