Sparks of Beetle Light

by Beverly J. Letchworth | Apr 1, 2023 | 0 comments

Along the roadside in a mass of morning glory plants, specks of gold flitted among the leaves. They moved fast and were hard to focus on, but with the sunshine on them, they were like sparks of light. Not really sparks, but small ¼” (6 mm) insects. Beetles, to be exact—tortoise beetles—members of the leaf beetle family.

Why are they called tortoise beetles? They get their name because their hard back covers flatten out at the edge of their bodies like little shelves, causing them to resemble tiny turtles or tortoises.

Many tortoise beetles have bright metallic colors of gold or green or dark red that glisten in the sun. Some have added spots and resemble ladybugs; some are striped. Some species are among the most beautifully colored of all North American beetles.

Golden tortoise beetles (¼”) are bright brassy gold, indeed looking like flashes of light in the sun. One of the largest North American leaf beetles is the Argus tortoise beetle (½”).

Tortoise beetles range throughout the United States in meadows and roadsides. Adults and larvae feed on leaves and flowers, mostly those of the morning glory family, leaving many holes in the plants. They can become agricultural pests.

Adult beetles overwinter in leaf litter and emerge in summer to feed. Females lay many eggs, but in small groups, on the undersides of leaves. When the eggs hatch in one to two weeks, the tiny larvae begin to chow down. They will grow, and when they get too big for their skin, they’ll shed it and continue to grow larger.

Now something odd happens. The larvae carry their feces and shed skins over the top of their bodies! Two prongs on their hind ends hold the shed skin and feces on their backs. This stuff is called a fecal shield.

Sounds icky, but this shield seems to help keep them safe. If a predator, such as an ant, begins to threaten, it will back away when it detects the beetle’s fecal shield.

Finally, when the larvae have grown large enough, their outer skin hardens into a tough casing, and they are now called pupas. Inside they undergo remarkable changes. In a week or so, they emerge as adult beetles, sparkling the sun off their backs.

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