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A flock of cabbage
butterflies
(Pieris rapae)
©
Beatriz Moisset
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If
you see a pretty white butterfly, more likely than not you are seeing
an invasive species that was accidentally introduced to this country
and to many other parts of the world more than a century ago.
The
cabbage white butterfly is noticeable, pretty and soft, it visits
gardens, meadows, you name it. Perhaps the only places beyond its
reach are higher elevations. It starts flying early in the season and
produces several generations throughout the summer and fall. No
wonder it is seen so often.
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Cabbage butterfly
(Pieris rapae)
©
Beatriz Moisset
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The
name refers to the plant its caterpillar feeds on, cabbage. It also
eats other members of the mustard family, such as cauliflower and
kale and
it is regarded as a serious pest. It also feeds on a number of wild,
non cultivated mustards, including the invasive garlic mustard.
The
cabbage butterfly is related to a group of native butterflies, the so
called whites, yellows and sulphurs or family Pieridae. Their colors,
as the names indicate are either whites or yellows. The caterpillars
of most of them also feed on plants of the mustard family. A total of
58 species lived in North America before the arrival of this
newcomer. Nowadays, the cabbage white is seen as often as all of them
combined. One wonders if the growing numbers of this invader are
having an impact on the populations of native Pieridae butterflies.
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Orange sulphur butterfly
(Colias)
©
Beatriz Moisset
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In
summary, it has the qualities of so called weedy species, with high
rates of reproduction, very adaptable to different food sources and a
variety of habitats.
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Virginia
white butterfly
Pieris virginiensis
©
Beatriz Moisset
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The
cabbage butterfly reminds me of several insect species that were
brought to this country intentionally or accidentally and proceeded
to
become incredibly
widespread in a relatively short time. Now, some of them are
more abundant than any
of their
native relatives. Here are a few examples: the
Asian ladybug, the Chinese mantis, the giant resin bee, the European
paper wasp, the drone fly, and the brown marmorated stink bug.
David
Quammen, a distinguished journalist who has written extensively on
conservation and ecology, has coined the term “Planet of Weeds,”
meaning that the ecological changes caused by humans are having a
severe impact on the flora and fauna of the entire planet. We had
transported unprecedented numbers of species of plants, animals and
bacteria beyond their natural distributions with the consequence that
many of them have become established in their new surroundings. Not
only do they become established but spread out from the original
place of introduction, thus deserving the name of invasive species.
They impact the local flora and fauna, bringing up the extinction of
many species. In this way we are causing a mass extinction,
comparable to some of the most serious mass extinctions of the past.
Specialist
species are more vulnerable to extinction. The ones that have the
best chance for survival are the weedy ones, the adaptable
generalists. We are creating an impoverished world, gradually losing
precious biological diversity, biodiversity for short. It may take
millions of years for this biodiversity to raise back to the present
levels. The human species may never see that.
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Drone
fly (Eristalis tenax)
One
of many introduced, widespread species
©
Beatriz Moisset
© Beatriz Moisset. 2016
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I find it so odd that the scientific name of a butterfly can be the same as the scientific name of a plant! But thanks for writing about this, I didn't realize one of these guys was non-native.
ReplyDeleteThe name was chosen intentionally in this case; rapae is derived from rapa, the specific name of the host plant of this butterfly. The same thing happens with the oleander aphid, called Aphis nerii, in reference to the genus name of its favorite host, the oleander plant, Nerium. This is very common. On the other hand, sometimes plants and animals have the same name, just by accident. At Bugguide.net we have been collecting examples of this. You can see them here: Plants v. Animals (ICBN v. ICZN), http://bugguide.net/node/view/443579. Curiously, one example is this very butterfly. Pieris is also a plant in the family Ericaceae. Perhaps you were referring to it. See Wikipedia article: https://en.wikipedia.org/wiki/Pieris_%28plant%29
DeleteEllen - There are quite a few botanical-zoological genus name homonyms, in fact, and they are permissible under the codes of nomenclature.
DeleteAs for the cabbage white I have the impression from watching them a bit that, at least here in Missouri, they prefer to lay eggs on mustards of Eurasian origin, while native whites (checkered whites, and especially orange-tips) utilize mostly native mustards. Still checkered whites have declined in numbers in recent decades, and this may be related to the abundant presence of Pieris rapae. I wonder though, because the introduced butterfly was already quite abundant when I was a child, and it was one of the first butterflies I ever learned, but checkered whites were still quite abundant then, even after multiple decades of coexistence.
Beatriz, is it unusual in the butterfly world (here in North America) to have an alien invasive? Are there others?
ReplyDeleteI know two introduced skippers, Asbolis capucinus (Monk Skipper) (from Cuba) and Thymelicus lineola (European Skipper) (from Europe), and one hairstreak, Electrostrymon angelia (Fulvous Hairstreak) (possibly introduced from the West Indies). There may be more. As for Lepidoptera in general there may be more than 200 introduced species.
ReplyDelete