Dorothy is a Master Gardener, former newspaper reporter, and the author of several books. Michael is a landscape/nature photographer in NM.
Dangerous Allergic Reactions Are Possible
Caterpillars may be cute and entertaining to watch, but they also have the ability to inflict a potentially dangerous sting. Their stings can cause minor symptoms but can cause dangerous allergic reactions in some people. The stinging nettle caterpillar, with colors that mimic the ones a clown might have, is no exception.
The physical effect on human skin is similar to that of exposure to fiberglass. Their spines release a mixture of irritating histamines produced by a poison gland. The spines release an irritant (a mixture of histamines) produced by a poison gland and that irritant is what causes the skin to burn and itch.
This particular caterpillar has a voracious appetite and a lengthy larval feeding stage, which makes it a major concern. The female can lay over 400 eggs and it has a very wide host range, making it even more of a concern.
If you have a heavy infestation of these caterpillars, they can cause serious defoliation, being able to destroy a potted plant in only a few days.
The Life Cycle of a Stinging Nettle Caterpillar
The lifespan of the stinging nettle caterpillar from egg to adulthood is from 75-99 days, depending on how many larval stages there are (from 8-11) and how long they are (from 45-72 days).
An adult female moth lives for approximately 10 days, and the male moth lives for approximately 11 days. The C-shaped embryos become clearly visible as the larvae develop over the seven-day incubation period. When ready the pupate, the larvae migrate toward the base of the host plant in order to find protection in dried leaves or other plant parts. Often, they pupate in clusters. Just before pupation, the larva's underside darkens to orange and it spins brown silk around itself, which will eventually form a hardened outer shell.
Pupation occurs within the cocoon after about five days.
Eggs - A female moth will deposit her eggs in small clusters or single lines on the underside of older leaves (usually). The eggs are flat, transparent ovals that will appear as a glossy sheen on the leaf surface, easily overlooked.
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Larva - The larva, usually about an inch long, is covered with several rows of stinging spines. The larvae can vary from white to a light gray color, with a long, dark stripe running longitudinally down the back. Larvae begin feeding about two days after hatching.
The pupal stage - The onset of pupation will depend on the availability of food and the surrounding environmental conditions. The pupal stage lasts from about 17 days to three weeks.
Adult stage - The adult stinging nettle moth is only about a half-inch long. Its forewing is separated (colorwise) by a white diagonal marking. The upper portion is rust colored and the lower portion is a lighter shade of brown. They begin mating about two days after they emerge. They are inactive during the day, retreating into nearby vegetation.
What to Do If You Get Stung
- Skin reactions vary from a red welt to severe swelling that can last a few days.
- Avoid any further contact with the caterpillar’s spines.
- If you are stung in the eye or have trouble breathing after being stung, get medical attention immediately.
- You should wash the area immediately with soap and water to reduce the initial pain.
- To stop any itching and swelling, an oral antihistamine or hydrocortisone cream may be effective.
Native to Southeast Asia
The stinging nettle caterpillar is native to China, Taiwan, Thailand, Malaysia, Java, and Borneo, although it has been observed many times in Hawaii. They are often distributed through nursery shipments and other cargo. They were first observed in Hawaii in 2001 and were said to have arrived in a shipment of palm seedlings from Taiwan. Since that time, they have spread to all of the main Hawaiian islands.
Evans, Arthur V. - Field Guide to Insects and Spiders of North America
https://dlnr.hawaii.gov/hisc/info/species/nettle-caterpillar/ (Retrieved from website on 4/26/2018)
https://www.ctahr.hawaii.edu/oc/freepubs/pdf/IP-22.pdf (Retrieved from website on 4/26/2018)
© 2018 Mike and Dorothy McKenney