A Butterfly's Flashy Colors

Male monarch butterfly

(Danaus plexippus)

© Beatriz Moisset

People fall in love with monarch butterflies because of their bright black and orange pattern. Many monarch enthusiasts are busily raising these butterflies in their gardens and homes. Some have become real experts on these insects and their life cycle. They are profoundly distressed when something goes wrong and one of them fails to make it to adulthood and freedom.

Some particularly despise butterfly enemies. If they catch a predatory bug sucking the juices out of an unfortunate caterpillar, they rage against the predator. Parasitic flies also generate a violent reaction. It is hard to believe, but monarchs owe their beautiful colors to their enemies. Here is the whole story.

Monarchs feed on milkweeds. They are dependent on these plants and cannot digest others. Milkweeds, like many plants produce powerful toxins as a defense against herbivores. These toxins go by the name of cardiac glycosides because they cause heart paralysis. As an additional defense they produce a sticky milky-looking substance that gives them their name. The milk is present in most tissues of the plant and bleed easily, gumming the yaws of a hungry attacker that tries to eat the milkweed plant.

This is enough to deter most plant eaters, but monarch butterfly caterpillars and more than a dozen other creatures have learned to overcome such defenses. Earlier milkweeds, millions of years ago, had milder forms of the toxins. That was all they needed, but some early insects learned to tolerate them and proceeded undeterred to feed from these plants. Thus, milkweeds were forced to create stronger and stronger glycosides and, in turn their feeders found ways to deal with the more powerful toxins. Arms races of this type abound in the natural world.

The monarch butterfly adapted itself to these plants by several means: it avoided the most toxic plants or their most toxic parts; it developed enzymes that could deal with the toxins, or it stored them in parts of its body where they could do no harm. In doing all this, it became dependent on milkweeds. This dependence added a bonus to the monarch's survival, its body is loaded with bad tasting, toxic glycosides, which constitute a powerful defense against its enemies. Most predators avoid the toxic butterfly. However a handful of these predators developed ways to handle the monarch's toxins by eating only the parts with less glycosides, or by evolving enzymes that neutralize these toxic substances. This is another case of the arms race at work.

This is not all. The monarch advertises its toxicity and horrid taste to possible predators. Birds who never saw a monarch butterfly before eagerly take a bite of one. The immediate reaction is that of disgust, spitting up the morsel and shaking their heads or rubbing their beaks in an effort to remove the unpleasantness. They have no trouble remembering the strikingly colored creature and its bad taste. They are not likely to repeat such experience.

Large milkweed bugs (Oncopeltus fasciatus)

on milkweed seed pod. Adults and nymphs

© Beatriz Moisset

Milkweed beetle (Tetraopes tetrophthalmus)

© Beatriz Moisset

The monarch butterfly is not the only animal that advertises its bad taste by sporting bright colors. Other insects that feed on milkweeds, like the milkweed beetles and milkweed bugs, are also colorful, in red and black; we can be sure that they are just as bad tasting. Similar cases abound in nature, not only insects but also vertebrates. Most frogs are green or have brown spots, colors that blend well with vegetation and help them remain unnoticed. The so-called poison dart frogs are the exception. Their backs are glossy red. The name tells you that these frogs produce powerful toxins, so much so, that native peoples use them to smear the tip of their darts in order to make them more lethal.

Dendrobatid frog, Peru

© Tim Ross. Wikicommons

Polished Lady Beetle (Cycloneda munda)

Ladybeetles are another example of

brightly colored bad tasting insects

© Beatriz Moisset

So, as I said at the start, a monarch's lovely colors are due to a constant battle with their enemies. In a perfect world (perfect for monarchs, that is) these butterflies wouldn't need to be loaded with toxins, nor would they need to tell their enemies to keep away. In such a perfect world, monarchs would have plain colors. Is this what we want?

The monarch caterpillar is also toxic

and also has bright warning colors

© Beatriz Moisset

Further readings:

List of articles
Monarchs and their Enemies
The Monarch's Breadbasket

Beginners Guide to Pollinators and Other Flower Visitors

© Beatriz Moisset. 2017

Flower Longhorn Beetles, the Elegant Crowd

Strangalia luteicornis on buttonbush
© Beatriz Moisset

 Most beetles we are familiar with are roundish or oval-shaped hard shelled insects. Think ladybugs or Japanese beetles. Others are a little longer and cigar-shaped. An entire group of beetles distinguishes itself for its elegant streamlined figure; these are the so called flower longhorns. The name refers to their love of flowers as a hangout and to their long antennae. No, they don't have real horns, just antennae like other insects. Sometimes these organs can be longer than their entire body.

Strangalia famelica, the hungry strangalia
© Beatriz Moisset

Flower longhorns are the fashion models of the beetle world. Their slender and highly stylized outline is reminiscent of that of wasps; although they would never be mistaken by such because they have the characteristic hard shell (elytra) of all beetles covering their membranous wings. In their elegance they would make a nice fashion parade. Some carry their slenderness to the extreme of appearing anorexic. In fact one of them was given the scientific name of famelica, which means starved one in Latin. By contrast, the banded longhorn (Typocerus) and Brachyleptura appear almost obese, although they are still rather slender when compared to most beetles.

Brachyleptura rubrica covered with pollen
© Beatriz Moisset

The banded longhorn, Typocerus velutinus on milkweed

© Beatriz Moisset

Flower longhorns love flat open blossoms of the umbrella type, such as the members of the carrot family. They also like flowers of the rose and aster family as well as wild hydrangea. They feed on their pollen. Sometimes you find several different types amiably mingling together on these flowers. They are regarded as lesser pollinators of such plants. It is not surprising, when you see some of them coated with pollen.

A couple of Metacmaeops vittata on wild hydrangea

© Beatriz Moisset

Their larvae don't have such wholesome habits. They are wood borers, meaning that they feed on wood. However none has been reported as a serious pest of trees. Perhaps trees have enough defenses against them or there are enough enemies to keep their numbers from getting out of control.

Analeptura lineola on wild hydrangea, with pollen on its back
© Beatriz Moisse

Flower longhorn beetles are a beautiful addition to the biodiversity of forests, well integrated with the remaining members of the community.

For more on pollinators and other flower visitors read the e-book:
Beginners Guide to Pollinators and Other Flower Visitors

List of articles

© Beatriz Moisset. 2014