Gardening: Caterpillar season – with beauty can come pain

Eileen Ward
The colorful Io moth caterpillar is covered by fragile spines. Each contains a painful venom for anyone who physically contact this nocturnal moth’s larvae.

It is caterpillar season and if you love butterflies and are encouraging them in your yard this is an exciting time. However, we have several caterpillars that can harm you with their nasty sting so you should be aware of them. There was an article in the paper a while ago about the puss caterpillar but you should know there are others out there that inflict the same painful sting as the puss.

Stinging caterpillars sting via spines which are connected to poison glands. They feed on the foliage of many different plants. They do not usually inflict serious injury to the plants they feed on. However, their sting can be very painful when a person's skin comes in contact with them. Some people have severe allergic reactions and have to visit a doctor or emergency room. Most people just experience itching and burning pain from the contact. Following are the four most common stinging caterpillars for our area.

The puss caterpillar is short and stubby bodied about one inch long completely covered with gray to brown hair. It reminds me of the Adams Family character “Cousin It.” The poison spines are under the soft hair. When touched the spines break off in the skin and cause severe pain. Puss caterpillars prefer oaks and citrus.

The saddleback caterpillar is a very striking insect. It is brown with a distinctive green back and flanks with a conspicuous brown, oval central area. This spot looks like a saddle placed on a green saddle blanket, hence the name. It is also a short, stubby bodied caterpillar about one inch long. The main stinging hairs are on the back of fleshy protuberances toward the front and hind ends of the body. There is also a smaller row of stinging hairs along each side. You will find this caterpillar on many types of plants but especially palms.

The IO caterpillar is a beautiful pale green with yellow and reddish stripes. It can exceed two inches in length. Its’ stinging spines, which are usually yellowish with black tips, cover the body from tip to tip. Ixora, hibiscus, palm trees and roses are favorites of this caterpillar.

The hag caterpillar has nine pairs of variable length protrusions that bear stinging hairs extending from the body. These extensions are curved and twisted like the disheveled hair of a hag for which it is aptly named. Its’ sting is as intense as that of the saddleback. This caterpillar is found on various forest trees and ornamental shrubs. It is not as common as the other three mentioned.

Puss caterpillars.

The colors of these caterpillars camouflage them well on the plants. People who are stung are often left wondering what gave them that painful sting. Telltale signs of their presence include chewed leaves and defoliated branches. Also look for piles of brown to black pellets (fecal matter) on leaves of the affected plant. You should wear a long sleeve shirt, pants and gloves when working in infested areas.

Local reactions to the sting include severe burning, pain, numbness and swelling of the area of contact. You can also have rows or grids of marks on skin and possibly swelling on regional lymph nodes. You can treat by placing tape over the affected area and repeatedly stripping it off to remove poison spines. Apply ice packs to help reduce the stinging sensation and apply a paste of baking soda and water.

Allergy reactions include nausea, vomiting, fever, shock and convulsions. If you have a history of hay fever, asthma or allergy or if allergic reactions develop you should contact a physician immediately after being stung.

Saddleback caterpillar

These caterpillars are not usually numerous on plants and can be controlled by carefully removing them and squashing them. Also watch for the telltale sign that a natural predator, the parasitic wasp, has been there. You will see small white cocoons emerging from the body of the caterpillar. These are eggs which the female braconid wasp thrusts through the skin of the caterpillar. The young larvae will hatch from these eggs and eat within the body of the caterpillar thus killing it. People often mistake these cocoons for caterpillar eggs and destroy them thinking it will reduce the population of the caterpillars. My experience is that if you have the wasp present it will effectively control the current and future generations of the caterpillars. If the wasp is not present upon first inspection the telltale cocoons will almost always appear within one to two weeks and are worth waiting for.

If you feel you must use insecticides for control use the bacillus thuringiensis (Dipel or Thuricide) rather than Sevin so as not to harm the wasps if they are present.

More:Gardening: Your August ‘to do’ and ‘to watch’ list

Peter and Eileen Ward have sold Greensward of Marco after 40 years in the lawn and landscape business on Marco Island. You can reach Eileen with comments or questions on her columns via email at or call 239-269-0192.