Parasa sp. (stinging slug caterpillar)

The Green Stinging Caterpillar of the Andes

This caterpillar belongs to the Limacodidae family, commonly called slug caterpillars. In Peru, it is likely a species related to the saddleback-type stinging caterpillars, known for their bright colors and sharp defensive spines.

The vivid green body, contrasting stripe down the back, and radiating yellow spines are all warning signals. This is not camouflage. It is a message.

Why this caterpillar is dangerous

Each spine is connected to a venom gland. When touched, the spines break off in the skin and release venom, causing an immediate reaction.

People who brush against it often experience:

• Sharp, burning or electric pain

• Redness and swelling at the contact site

• Pain that can intensify over the first hour

• Lingering sensitivity that may last a day or more

The sting is usually localized, but it can feel severe, especially on hands, arms, or the neck.

How people get stung

These caterpillars do not move much and cling tightly to leaves and stalks. Most stings happen by accident:

• Grabbing vegetation while hiking

• Leaning against tall plants

• Brushing past leaves without seeing it

• Children touching it out of curiosity

Their bright color makes them visible, but only if you are looking closely.

Traditional response: lemon juice

In rural areas, a common first response is lemon or lime juice applied to the sting site. While not a medical treatment, it is traditionally used to:

• Reduce the burning sensation

• Calm surface irritation

• Clean the skin after spine contact

The safest immediate steps are to avoid rubbing, gently remove any spines with tape if visible, apply lemon juice, and use a cold compress. Medical care is recommended if pain escalates or systemic symptoms appear.

A living warning sign

This caterpillar is a reminder that in Peru’s forests and fields, color often means caution. Bright does not mean harmless. It means defended.

Observe it, photograph it, and leave it undisturbed. In the Andes, respect for small creatures is part of staying safe.