|
09-11-03
A Very Good Year for Painted Lady
Butterflies
To borrow a line from a song made famous by Frank Sinatra, "It was a
very good year!" Such a line could apply to wine, to winning sports teams
or even to the stock market. This year, it certainly applies to painted
lady butterflies, at least in the Midwest.
Painted lady butterflies seem to be everywhere. They are so common on
flowers that, when disturbed, the uprising resembles a dust storm. Roads
are covered with resting painted ladies. So much so that a drive in the
country often results in a car grill clogged with painted lady carcasses.
The painted lady is about 2 inches from wing tip to wing tip. It is orange-colored
with black patches and black wing tips. It also has four eye spots on
the back side of the hind wing. Painted ladies are one of the most common
butterfly species in the world. That is why they also are known as the
cosmopolitan butterfly. Painted ladies are found in temperate regions
around the world, except South America and Australia.
Even though the painted lady is widespread in temperate regions, it cannot
survive cold winters. These butterflies die off each winter in North America,
except in the Southwest. Each spring, these orange-and-black butterflies
migrate northward. Before the growing season is over, they can be found
everywhere except the most northern areas of Canada
and Alaska.
How do the butterfly populations build up so quickly? First, they have
a variety of food plants. The painted lady caterpillars can be found feeding
on many species of wildflowers. They are especially common on thistle.
In fact, painted ladies were once known as thistle butterflies. Their
populations can also build up rapidly because they can go through several
generations per year.
Because the populations can reach very high numbers in a short period
of time, the caterpillars have been known to defoliate their food plants.
One food plant is the soybean. When painted lady caterpillars are filling
their guts on this crop plant, they would be considered pests. But to
the delight of farmers, such an occasion is rare. Farmers would much rather
see these insects feeding on thistles!
Painted lady butterflies also are reared in the classroom to demonstrate
the metamorphosis of insects. In the classroom, the caterpillars feed
on an artificial diet that resembles solid pea soup with some fiber in
it. Once the caterpillar has completed feeding, it attaches itself to
the lid of the container to form the pupa. In the wild, the pupa would
be attached to the underside of a leaf or stem. Following emergence from
the pupa, the butterflies mate and lay eggs. The complete life cycle takes
less than three weeks.
The painted lady was given a scientific name by the famous founder of
the system of binomial nomenclature -- the practice of giving a genus
and species name to all living things. The name selected was Vanessa
cardui. Vanessa is the Old English word for butterfly, probably based
on the ancient goddess Venus. Cardui is based on Cardu, which is
Latin for thistle, so the name means the butterfly of thistle!
|
