The thistle tortoise beetle exhibits multiple defense behaviors, such as a flexible shield, providing a barrier against the mandibles of predators, and an excretion that protects the eggs as well.

Its ability to massively consume and damage thistle plants has also made this beetle a well known biological control agent in many countries, including the United States, Canada, and Switzerland.

However, in some cases, the impact of these beetles has been limited due to parasitism preventing their accumulation in regions of thistle targeted for biological control.

This species is highly rounded, with green or yellowish-green elytra, sometimes with a small, dark triangular spot around the scutellum.

[4] The thistle tortoise beetle belongs to the Cassidinae subfamily, which is part of the Chrysomelidae family in the order Coleoptera.

Cassidinae species commonly serve as biological control agents for overgrown plants.

[5] This beetle inhabits North America and can be commonly found from South Dakota to Virginia within the United States.

Thistle beetle larvae mainly stay on the leaves they were hatched on throughout their development and feed on them.

The time it takes for them to begin feeding depends on a few factors relating to the leaf's structure.

The larvae wait until the thistle plants grow by 30% and for the nitrogen levels in the leaves to drop by 50% before feeding.

Later in development, the larvae's shield can protect them from ant attacks, but not from larger predators like lycosid spiders.

[9] In the Switzerland population of thistle tortoise beetles, the main predator of larvae is Polistes dominulus.

[11] In 1967, Thomas Eisner showed that thistle beetles without their shield were vulnerable to ants, which were able to attack them and bring them to their nests.

[4] In the South Virginia population of thistle beetles, it was predicted that parasitism was a top two reason for mortality.

Oviposition depends on many conditions, ranging from rain and wind to temperature and the length of the day.

This phenomenon could be explained by females sampling areas of leaves and choosing the most optimal place to lay their eggs to ensure that they will also have an abundance of high-quality food.

[10] This is thought to protect the eggs by serving as a physical barrier against the environment and enemies and also acting as concealment.

[4] It was found that this enclosure increased egg survival rates as it protected them from predators and parasites.

[4] The intromittent organ of male thistle leaf beetles is a long, tube-like structure that is called the flagellum.

These physical properties of the thistle beetle have been studied because the ability of a thin, flexible structure to penetrate without buckling or rupturing is mechanically challenging and may have important implications for the development of microscopic catheters in modern medicine.

As with hatching rate, larvae development is temperature-dependent and shows a positive relationship with increasing temperature.

[4] Cassida rubiginosa was introduced to New Zealand for use as a biological control agent against Cirsium arvense (Canada thistle) in 2006.

[17] In other regions of Canada, such as in the province of Quebec, it was found that these beetles were not sufficient in helping reduce thistle populations.

[14] It was found that parasites that inhibited the accumulation of thistle beetles when used as biological control agents were Tetrastichus rhosaces, Eucelatoriopsis dimmocki, Spilochalcis albifrons, Eupelmella vescicularis, and Itoplectis conquisitor.