April 23 – Imago that!

Today’s Factismal: An adult butterfly is called an imago.

Butterflies are weird little critters. They have taste buds in their feet, which they use to decide if the leaves they land on would make a good home for their children. They have eyes that see in the ultraviolet and infrared, so what we see as a white pansy is actually a multicolored neon “Eat Here!” sign to them. And they have noses on the end of their antennae, which they use to sniff out flowers that are full of nectar.

A butterfly tastes its landing place with its feet (My camera)

A butterfly tastes its landing place with its feet
(My camera)

But the weirdest thing about butterflies is that they have four different life stages. They are laid as eggs, each about the size of a grain of salt. After fertilization, the female butterfly lays the eggs on a leaf that she’s tasted with her feet to make sure that the caterpillars will be able to eat it. As she places each egg onto the leaf, the female butterfly glues it into place with a special secretion. She then flies off, never to see her children again.

A butterfly seeking a good place for its eggs (My camera)

A butterfly seeking a good place for its eggs
(My camera)

A butterfly in its egg is called an embryo. If it is winter, then the embryos rest in their eggs for a bit in a process known as diapause; this allows the caterpillars to hatch in the springtime when leaves abound instead of in the winter when they have nought but snow to eat. In the other seasons, the eggs hatch after a few weeks, giving rise to beautiful, bouncing, baby caterpillars.

An oversize caterpillar (My camera)

An oversize caterpillar
(My camera)

Technically called a larva, each caterpillar crawls along the leaf, eating as it goes. Though some species like to nibble on aphids and the like, most prefer the taste of leaves and other plant matter. Some of the caterpillars prefer to eat plants that contain toxins which then makes the bug taste bad; the most famous example of this is the Monarch Butterfly, which feeds on milkweed. All of this munching leads to rapid growth spurts; at the end of each one, the caterpillar has outgrown its old skin and must shed it. After the caterpillar has grown large enough, it starts to develop wings (and you thought Disney was kidding).

An adult butterfly (imago) emerging from its cocoon (My camera)

An adult butterfly (imago) emerging from its cocoon
(My camera)

Once wing development has begun and the caterpillar has grown fat enough, it spins a cocoon and turns into a pupa. Popular wisdom to the contrary, the caterpillar does not dissolve into a puddle of goo in the cocoon. Instead, it sheds some appendages and grows others. The wings continue development, appearing as origami-like folds of thin tissue. After a few weeks, the pupa has matured into an adult butterfly known as an imago (“image”).

An imago taking a rest (My camera)

An imago taking a rest
(My camera)

If you’d like to learn more about butterflies and help scientists as they learn more about them, too, then why not join one of these citizen science projects (or start one in your neighborhood)?
Illinois Butterfly Monitoring Network
Los Angeles Butterfly Survey
Loudoun Butterfly Count
Maine Butterfly Survey

2 thoughts on “April 23 – Imago that!

  1. Pingback: January 6 – Good News, Bad News, Butterfly News | Little facts about science

  2. Pingback: February 10 – Walking On Air | Little facts about science

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