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Common Name: Large Milkweed Bug
Scientific Name: Oncopeltus fasciatus

Kingdom: Animilia
Phylum: Arthropoda
Class: Insecta
Order: Hemiptera
Family: Lygaeidae
Genus: Oncopeltus
Species: O. fasciatus


The Oncopeltus fasciatus also known as the Large Milkweed Bug is an attractive black and orange plant sucking insect. This insect is commonly found on the seeds and tissues of the milkweed plant. Read on to find out more about this interesting insect.

The Large Milkweed Bug is generally 9-14mm long. These insects usually come in orange or yellow, and they have black spots. They don’t have mouths along with all True Bugs. Instead they have a tube-like beak for sucking fluids. Another characteristic of the Oncopeltus fasciatus is the stages they go through from hatching to maturity. They go through five nymphal stages as they get older. As the bug grows the wings grow darker, and eventually other markings appear on the bug. Soon the opposite sexes can be identified.

This bug is mainly found in the Southern-Eastern United States. They usually live for about a month. A female Oncopeltus fasciatus will usually lay about 2,000 eggs in her lifetime. The population of Large Milkweed Bugs is increasing. Milkweed bugs populate very quickly, and some people keep them as “pets” and watch them hatch.

The Large Milkweed Bug eats by sucking juices from milkweed plants. They do this by injecting digestive enzymes into the plant.  They also eat sunflower plants. The diet of the Milkweed Bug makes it toxic. The Oncopeltus fasciatus has few predators. Some small birds will try to eat the Milkweed Bug but most birds won’t try to eat this bug because of the foul taste that the toxic gives off. Also the bright color on this bug gives a warning to its predators.

Large Milkweed Bugs are important in regulating the population size of the Milkweed Plant.  One interesting fact about the Oncopeltus fasciatus is that it is a True Bug; all these insects don’t chew their food. Instead they have a rostrum. A rostrum is a tube like mouthpart that allows them to suck nutrients out of the Milkweed Plant.  Another interesting fact about the Milkweed Bug is that they live about a month. Also, they have an incomplete metamorphosis and they are born without their spots. Some people like to keep them as “pets” and watch them grow.

Author: Sara S
Published: 2/3/12

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