Is it poisonous?

Understanding the Threat: Poisonous Caterpillars in Ontario



Ontario is currently facing an alarming increase in the population of poisonous caterpillars. These caterpillars, specifically from the Tussock Moth and Gypsy Moth species, are causing health concerns among residents. It is crucial to understand the threat posed by these caterpillars and take necessary precautions to mitigate the risks.

Types of Poisonous Caterpillars in Ontario

There are two main types of poisonous caterpillars found in Ontario: the Tussock Moth caterpillar and the Gypsy Moth caterpillar.

Tussock Moth Caterpillar

The Tussock Moth caterpillars have distinctive hair tufts on their bodies, which can cause irritation and allergic reactions in humans. Their hairs contain venomous substances that can cause skin rashes, itching, and even respiratory problems if inhaled.

Gypsy Moth Caterpillar

The Gypsy Moth caterpillars are known for their voracious appetite and ability to defoliate entire trees. Their hairs can cause skin irritation, similar to the Tussock Moth caterpillars. In addition, their droppings, known as frass, can contaminate outdoor spaces and pose a threat to public health.

Health Risks and Symptoms

Exposure to these poisonous caterpillars can lead to various health risks and symptoms, including:

  • Skin rashes
  • Itching and irritation
  • Respiratory problems
  • Allergic reactions
  • Asthma attacks (in individuals with asthma)
  • Eye irritation
  • Gastrointestinal issues (if ingested)

Preventive Measures

To protect yourself from the threat of poisonous caterpillars in Ontario, consider the following preventive measures:

  1. Avoid direct contact with caterpillars, their nests, or their hairs.
  2. Wear protective clothing, such as long sleeves, pants, and gloves, when working or spending time outdoors in infested areas.
  3. Keep windows and doors closed or use screens to prevent caterpillars from entering your home.
  4. Be cautious while gardening or handling plants, as caterpillars may be hidden among foliage.
  5. Use insect repellents containing DEET to deter caterpillars and other insects.
  6. Regularly inspect and clean outdoor furniture, play structures, and toys to remove any potential caterpillar presence.
  7. Seek medical attention if you experience severe symptoms or allergic reactions after exposure to caterpillars.


It is essential for residents of Ontario to be aware of the threat posed by poisonous caterpillars, particularly the Tussock Moth and Gypsy Moth caterpillars. By understanding the different types of caterpillars, their associated health risks, and implementing preventive measures, individuals can protect themselves and their communities from potential harm. Stay informed, stay cautious, and take appropriate actions to minimize the impact of these dangerous caterpillars.

Frequently Asked Questions

Q: How can I identify a Tussock Moth caterpillar?

A: Tussock Moth caterpillars have hair tufts or “tussocks” on their bodies, which can range in color from white to red or black.

Q: Are all caterpillars in Ontario poisonous?

A: No, not all caterpillars in Ontario are poisonous. However, it is advisable to exercise caution when encountering caterpillars and avoid direct contact.

Q: What should I do if I come into contact with a poisonous caterpillar?

A: If you come into contact with a poisonous caterpillar, immediately wash the affected area with soap and water. If symptoms persist or worsen, seek medical attention.

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