The Red Milkweed Beetle has a limited amount of interactions with other organisms. This is mostly due to the fact that this arthropod has a chemical defense, protecting it from most potential predators in its environment. The most crucial interaction that T. tetrophthalmus has is with Asclepias syriaca, the Common Milkweed plant (Lacourse, 1999). The Red Milkweed Beetle uses the Common Milkweed plant as its source of nutrition and shelter. Female beetles lay their eggs inside the stems of the plant for protection and safekeeping until the larvae is ready to become adults (Matter, 2009). As the young beetles grow throughout the fall and winter months, they rely on the Common Milkweed plant’s underground rhizomes to supply them with proper nutrients to continue growing (Matter, 2009). This specific species of beetle uses the A. syriaca as source of food throughout their whole lifetime. They consume nearly every part of the plant, including flowers, stems, and leaves. The Common Milkweed can only be consumed by a handful of organisms because of a toxic chemical that resides within the plant (Matter, 2009). The chemical is considered to be a cardiac glycoside, which means that it can have adverse health effects upon the heart of a potential predator (Lacourse, 1999). Since the Red Milkweed Beetle primarily consumes the Common Milkweed plant, the toxic chemical resides within the body of the beetle species. This means that the T. tetrophthalmus has a chemical defense against its predators, thus resulting in low rates of predation.

    The relationship between the Red Milkweed Beetle and the Common Milkweed is mutualistic, so both organisms receive a benefit from the relationship. During research studies, it has been proven that A. syriaca thrives in the presence of the Red Milkweed Beetle (Lacourse, 1999). The plant species has a higher rate of growth and produces more flowering structures when the T. tetrophthalmus is living on and within the plant (Lacourse, 1999).

       As mentioned earlier, the Red Milkweed Beetle has very few predators due to the toxic chemicals residing within its body. The beetle is only preyed upon by birds on accident (Lacourse, 1999). Certain bird species may mistake the Red Milkweed Beetle for another species of arthropod and mistakenly ingest it. The toxic chemical inside the beetles also creates a vulgar taste in the mouth of a predator attempting to eat it (Matter, 2009).

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