At this time of year insects always get a bit spookier at Bug of the Week when we visit a few styling insects dressed in orange and black. Our first featured creature, the beautiful Argus tortoise beetle, is a denizen of morning glory plants where both the larvae and adults eat the tender green leaves of these weedy vines. Morning glories belong to a family of plants called the Convolvulaceae. In addition to their ornamental value some members of the morning glory family are important foods like the sweet potato. Curiously, the lovely morning glory has a dark side. Its leaves are protected from many animals that would like to make a meal of them by toxic compounds called alkaloids. Some alkaloids are potent nerve poisons and lethal to humans and other animals. Like the monarch butterfly, milkweed leaf beetle, and oleander aphid (LINK TO OCT 30, 2006) we met last Halloween, the Argus tortoise beetle likely gains protection from its own predators by storing in its own body some of the nasty alkaloids from the morning glory plant it eats. These compounds send a message to would-be predators that the delectable looking tortoise beetle is really a dangerous meal.
Another beautiful insect with a scary side is the oleander caterpillar. This caterpillar is the juvenile stage of a gorgeous moth sometimes called the polka-dot wasp moth. The moth has striking vermillion wings and an iridescent blue body stippled with white spots. She likely gains protection from her own predators by mimicking the appearance of a wasp. The male moth is a real sucker for a babe with a voice and the female polka-dot wasp moth attracts her mate by sending forth an ultrasonic song heard by her suitor, but not humans. After a brief courtship and romantic interlude, the female deposits eggs on the undersurface of an oleander leaf.
The caterpillars hatch and feed in a cluster while young. As they get older, caterpillars feed alone and consume vast amounts of oleander leaves before moving to a protected spot to spin a cocoon. Why the striking costume of orange and black? If you guessed protection from predators, you were right. As oleander caterpillars dine on leaves of oleander, they ingest highly toxic heart poisons called cardiac glycosides found in the leaves. These are the same type of chemical that helped milkweed leaf beetles, monarch butterflies, and dogbane beetles (LINK TO JULY 18, 2005) gain protection from their natural enemies.
The third member of our trio of Bugs in Orange and Black is a natural born killer, called the wheel bug (LINK TO AUG 1, 2005), Arilus cristatus. Upon hatching from their barrel-shaped eggs, nymphs of the wheel bug are a ghostly pale orange. Within a few hours, their exoskeleton hardens and the color scheme du jour is orange-black-orange with tip of the antennae pale orange, the body and legs jet black, and the rear end brilliant orange.
The business end of the wheel bug is the powerful beak or proboscis that is stored between the front legs of the beast when not in use. When the wheel bug spies a tasty morsel such as a fall webworm caterpillar, it casually approaches, embraces the victim with its long front legs, and impales the hapless caterpillar with the powerful beak. The beak is used to pump strong digestive enzymes into the victim. These enzymes liquefy the prey's body tissues. A pump is activated in the head of the bug and the liquid meal is slurped up through the beak. The common name of this bug, wheel bug, stems from the fact that this terror has a structure on its back that looks like a medieval torture wheel. The function of this wheel is known to Mother Nature and the wheel bug, but not to me. As you begin to plan your Halloween costume, why not consider dressing up like the oleander caterpillar, tortoise beetle, or maybe a wheel bug. Hardly anything is creepier than a bug on Halloween.
To learn more about the Argus tortoise beetle, oleander caterpillar, and the wheel bug please visit the following web sites. Have a creepy Halloween.