A few weeks ago, a reader sent us the picture shown above, which features a very interesting looking specimen. The creature is orange, and has black spines covering its entire body. Our reader said she discovered this specimen on the leaves of a passion plant. What could it be?

We believe this is a caterpillar, or the larva of a moth or butterfly. There are estimated to be over 20,000 different species of caterpillars living around the world. We believe that the orange creature our reader discovered is a gulf fritillary caterpillar, also known as a passion butterfly larva. As the name suggests, this caterpillar matures into a gulf fritillary butterfly, or a passion butterfly. The name of this caterpillar gives a hint about their food source, but we will discuss that more in a bit!

This caterpillar grows to be about 4 centimeters, and is identified by its bright orange color and black spines. Despite their sharp appearance, these spines are soft to the touch and do not sting. However, the larva itself is poisonous if eaten. Most birds recognize the coloring of this caterpillar and avoid it, because they know it will harm them.

Gulf fritillary butterflies and larvae are common in the extremely southern United States. Besides the United States, they inhabit Mexico, Central America, and the West Indies. Female butterflies lay their yellow-colored eggs on passionflower leaves. When they hatch, larvae feed on the passionflower plants, and can defoliate entire plants quite rapidly. When the caterpillars are done eating, they enter the pupae stage before maturing into caterpillars. The pupa, or chrysalis, of the gulf fritillary is brown and resembles a dead leaf.

To summarize, a reader found a bright orange caterpillar with black spines on her passion plant. We have identified this caterpillar as a gulf fritillary larva, and it will eventually mature into a butterfly!