Bugs often exhibit bright colours that signify things like toxicity or help a bug blend in with its surroundings. When you see orange and black crawling around your plants, chances are, these bugs aren't meant to be eaten by predators. Many beetles feature orange and black colouring that makes them stand out against green plants or other vegetation.
Shiny Flea Beetle
The shiny flea beetle (Asphaera lustrans) stand out on plants due to their orange and black colouring. Shiny flea beetles are completely orange except for their blue-black elytra, or hardened front wings. These beetles, according to Bug Guide, feed on skullcap plants mainly. They grow to around 1/3 inch (8mm) long upon maturity. They can be found within Arizona, Louisiana, Iowa and Nebraska and were introduced into Florida, Mississippi and Georgia.
Burying beetles, or Sexton beetles, belong to the Nicrophorus genus of plants, within the carrion beetle family. These beetles reach between 1 and 1 1/2 inches (2.5 to 3.8cm) long and feature orange markings on their black bodies. Their antennae resemble clubs, with small orange balls at the end. The various species of burying beetles live throughout the country. Burying beetles earn their name thanks to their habit of burying carrion before eating it. These bugs often carry mites on them, usually within the genus Poecilochirus, according to Colorado State University's "Colorado Insect of Interest" fact sheet.
Beetles within the family Cantharidae bear the name soldier beetles or cantharids. Certain species within this family may also be known as leatherwings. Several of these beetles feature orange and black colouring, such as the goldenrod leatherwing (Chauliognathus pennsylvanicus) or the margined leatherwing (Chauliognathus marginatus). According to the University of Kentucky Critter Files, soldier beetles often live close to the ground or under logs and rocks. They reach around 3/4 inch (1.9cm) long. They prove beneficial to gardeners by eating aphids.
The Meloidae family of beetles, known as blister beetles, consists of thousands of species of bugs, though not all of them live within the United States. Several instances of blister beetles, such as Pyrota lineata and Epicauta vittata, bear orange and black markings, with the beetles commonly featuring orange and black vertical striping along the elytra. These bugs earn their name from their ability to create blisters on human skin upon contact.
Beetles in the family Cerambycidae are known as longhorn beetles, longicorn beetles and borer beetles. Several longhorn beetles are solid black, but some bear orange and black colouring. The long jawed longhorn beetle (Trachyderes mandibularis) features orange and black antennae, orange legs and orange and black elytra. The dogwood twig borer (Oberea tripunctata) also bears orange and black colouring. These beetles live all over the world and often feed on dying wood, though a few eat living plants and flowers.