Aposematism is when an organism advertises to its predators that it is not worth eating
Unsurprisingly this photo of a large milkweed bug was taken on a milkweed plant. Their common name is in fact “large milkweed bug”. The scientific name for this insect is Oncopeltus fasciatus. The geographic range of this true bug, or hemipteran, is from Costa Rica north to Canada, across the entirety of the contiguous United States, and the Caribbean. They present some differences across their broad range, such as a difference in wing length.
The adult large milkweed bug is about 11 to 12 millimeters in length. As seen in this photo, they have a large orange-red “X” on their backs with an otherwise black body, antennae, and legs. The “X” is a form of aposematism. Aposematism is when an organism advertises to its predators that it is not worth eating. In the case of the large milkweed bug, the true bug is noxious to predators. The males and females can be distinguished by the markings on the fourth abdominal segment on the ventral side. For males, there is a black band; and for females, there are two black spots.
The life cycle of large milkweed bugs includes several instars, or growth stages. They make incomplete metamorphoses across these stages. Their life starts as eggs. From there they proceed through four nymphal stages over the course of 28-30 days. At the end of this period, they will molt and become adults.
Large milkweed bugs have a specialized diet. They primarily consume milkweed seeds. They are also known to eat aphids, monarch caterpillar eggs, and larvae. To eat the milkweed seeds, they will inject saliva into the seed through their rostrums. This will pre-digest the seeds, which they then suck up through their anterior pump and pharynx. When one adult feeds on a milkweed follicle, other large milkweed bugs are likely to follow. This may be because they signal to one another when they have found food.
They will inject saliva into the seed through their rostrums
Did you know?
- They are often used as model organisms in labs because they are easy to raise and handle.
- Some populations of large milkweed bugs are known to migrate.
- Most populations practice overwintering.
- These true bugs will lay as many as 50 eggs per clutch in their southern populations.
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