**Golden Tortoise Beetles** (*Charidotella sexpunctata*) are small, strikingly beautiful beetles found in North America. They belong to the “tortoise beetle” group due to their shell-like, expanded, nearly transparent margins (flanges) that cover their head and legs, giving them a flattened, oval appearance. They are minor pests of plants in the morning glory family (Convolvulaceae), including **sweet potatoes**. The adult beetles are unique for their ability to **change color** from metallic gold to reddish-brown when disturbed or mating.
Taxonomy and Classification
Golden Tortoise Beetles belong to the family Chrysomelidae (leaf beetles) in the order Coleoptera. They undergo complete metamorphosis. The color change is a physical, not chemical, process, achieved by manipulating the hydration levels in the layered cuticle, which alters the reflection of light (iridescence).
Physical Description
Adult Golden Tortoise Beetles are small, about $1/4$ inch long, and nearly circular in shape.
- **Coloration:** Can shift from a brilliant, highly reflective **metallic gold** (appearing like a drop of molten metal) to a dull, coppery red or reddish-brown when stressed or dead.
- **Shape:** Possess a wide, thin shell-like margin that extends outward, concealing the edges of the body.
- **Larvae:** The larvae are spiny, flattened, yellowish-brown grubs that have a distinctive adaptation: they carry a protective shield of fecal matter and cast skins, called an **anal fork or fecal shield**, held over their backs.
Distribution and Habitat
Golden Tortoise Beetles are found throughout the eastern and southern United States and parts of Central America. Their habitat is restricted to plants in the morning glory family, including ornamental ivy, bindweed, wild morning glories, and cultivated sweet potatoes.
Behavior and Damage
Beetles have multiple generations per year in warm climates. Both adults and larvae feed on the foliage of their host plants.
- **Feeding:** They feed by chewing small, irregular holes or scraping the leaf tissue, a type of damage called **skeletonization**. They rarely cause serious economic damage unless populations are extremely high on young sweet potato transplants.
- **Fecal Shield Defense:** The larva’s fecal shield is believed to serve as camouflage and a physical barrier against predators like ants and spiders.
- **Color Change Defense:** The dramatic shift from highly reflective gold to dull red acts as a sudden warning or shock mechanism to deter predators when the beetle is handled or attacked.
Management and Prevention
Control is usually unnecessary, as their damage is primarily cosmetic and they are easily managed.
- **Hand Picking:** Due to their striking appearance and small host range, manual removal of adults and larvae from ornamental plants is highly effective.
- **Weed Control:** Eliminate the weed hosts, especially bindweed and wild morning glory, near cultivated areas to reduce the beetle population source.
- **Chemical Control:** If populations are damaging high-value crops (like young sweet potato plants), spot treatments with an appropriate, short-residual insecticide or neem oil may be warranted.
Conservation and Research
Golden Tortoise Beetles are managed as minor pests. Research focuses on the physiological mechanism of their color change and their fascinating larval defenses. They are also popular subjects for entomological photography.