By Audrey F. Baker
Small but spectacular, Murgantia histrionica dazzles with brilliant red, orange and yellow markings defined in black.
While some call it the calico bug or fire bug, its most popular name, the harlequin bug, is an homage to the masked pantomime character of 16th-century Italian theater. Both dress in a diamond-patterned costume. A kaleidoscope of color and geometric markings make harlequin bugs one of the most easily recognized members of Pentatomidae, the black stinkbug family.
Part of its geometric decoration is created by the front pair of wings that overlap on the insect’s back, forming a distinctive “X.” The crossed wings, coupled with specialized mouthparts, denote the insect order harlequin bugs belong to – Hemiptera (true bugs).
The 3/8- to 1/2-inch shield bug is a year-round resident in Southern California and is frequently observed in the park. Adults and kids delight in detecting it on its host plants.
A harlequin may spend its entire life on one plant. While home may be Wild Radish, Shepherd’s Purse, and Pepperweed (mustard family members) or Telegraph Weed (sunflower family), center stage for viewing harlequin bugs at Mission Trails Regional Park is on Bladderpod (caper family). Many opportunities are afforded throughout the park. This California native plant boasts beautiful yellow flowers, peculiar bladder-shaped seed pods, and carries an odor appreciated by stinkbugs. It’s a lifestyle choice.
In both adult and nymph stages, the insects drain juices from leaves and stalks using their sharp needle-shaped mouth. Harlequins inject salivary secretions, liquefying plant tissue for easy ingestion. Unlike the butterfly or honeybee, the beak-like proboscis is non-retractable.
The harlequin bug life cycle consists of three stages: egg, nymph and adult — all achieved within 48 days. With adulthood, the lifespan for males is around 25 days and 41 for females.
One of the delights in observing the animal is glimpsing the eggs. They resemble upright black and white banded beer kegs sealed by convex lids. Each reproduction cycle produces six double rows laid together to form one batch. These are found on the underside of plant’s leaves.
The female fiercely defends her eggs from predators. Adults mate frequently, producing multiple egg batches of 12 eggs every three days. One female can lay 164 eggs.
When the eggs hatch, newborn nymphs begin feeding and progress through five or six molts (instars) before becoming adults.
It is through this process that nature finalizes her color palette. Abracadabra! Metamorphosis is now officially Incomplete. (Unlike a butterfly’s transformation, there is no pupa stage). Now winged and reproductively ready, another harlequin bug debuts on nature’s stage.
As the family feeds, they multi-task, isolating and sequestering odorous chemicals in their body to ward off predation. Just as monarch butterfly caterpillars ingest cardiac glycosides, a poisonous toxin, by consuming milkweed, Harlequin bug nymphs and adults ingest the same compounds from their host plants to make themselves distasteful to their predators.
Despite its diet and aposematic (warning) coloration, the harlequin bug is not poisonous. The chemicals it extracts and stores give an offending, spicy taste, comparable to hot mustard. Birds avoid spicy food! All part of classic stinkbug defense.
Our colorful bug has a colorful history. Native to Central America and Mexico, harlequin bugs were detected in Texas in 1864. Their range began extending over the southern United States just after the Civil War. It principally remains a coast-to-coast “southern insect,” but now boasts a northern range, and appears in Canada. In colder climes, they are limited to one generation per year.
In agricultural areas, harlequin bugs are considered a pest of cabbage and related crops. In more natural environments where plant variety abounds, natural predators work to control the balance of nature.
Harlequin bugs have their enemies and are equipped with ingenious defenses. A typical move when touched is to drop to the ground. Like other stinkbugs, they produce odors from their thoracic glands, and use them to fend off predators.
Parasitic wasps and flies are major adversaries. The pill bug (roly poly), once thought to be solely a decaying vegetation feeder, is now known as a nocturnal predator that feeds on harlequin bug eggs. Nature continues to amaze. Come see and hear!
—Audrey F. Baker is a trail guide at Mission Trails Regional Park. Check the MTRP events calendar published here or at mtrp.org or call 619-668-3281 for more information on the park’s free trail guide-led nature walks and opportunities to learn more about natural Southern California. Special walks can be arranged for any club, group, business or school by contacting Ranger Chris Axtmann at 619-668-2746 or at email@example.com.