Those fuzzy caterpillars are cute and hungry

I’ve had this thing lately about insects. The first creature I discussed wasn’t actually an insect.

The pillbug, it turns out, is a crustacean, but it still inhabits the same places we find most insects. Last week was all about the June bug, the stupidest bug, ever. This time I want to talk about the salt marsh caterpillar. These fuzzy insects aren’t poisonous, nor do they sting. However, they will devour your plants in next to no time.

The caterpillars will eventually turn into Tiger Moths, who can be quite large, with a wingspread that can span two and a half inches. Their wings are white with scattered black spots. Their bodies are yellow with black spots. The male’s hind wings will also be yellow, while the female will have all white.

The moths are present all over the U.S., and in most regions fly from May to September. However, since we’re so lucky in Texas, they fly all year long. That means the moths can have up to four breeding seasons a year here.

Aggressively hunting for food, even crossing roads, the Salt Marsh caterpillars are numerous this time of year. Aggressively hunting for food, even crossing roads, the Salt Marsh caterpillars are numerous this time of year. Tiger Moths are nocturnal, so breed during the evening. The female will lay one or more egg clusters the next evening, and live four or five more days. Each egg cluster contains from 400 to 1,000 eggs, which hatch in a week.

The caterpillars currently plaguing us are about ready to pupate. They live as caterpillars from 20 four to 37 days.

During this time, they will go through five growing stages, or instars, in which they change their coloring and gain in length. They begin caterpillar life brown in color, which changes as they mature. And they won’t all have the same coloring. It varies from creamy gray to yellowish-brown to almost black. They all have either long black or reddish hairs with black faces. By their fifth instar the caterpillars are about two inches long.

These guys are industrious, and move quite fast along the ground. Their habit of dispersing to wide areas in search of food is an uncommon trait among caterpillars. They will even cross the road in search of food. I actually lost count of the caterpillars crossing the highway as I drove the five miles from Milano east to the turn off to my road the other day. Yes, I saw them. I am not making that up.

The bigger they get, the more they eat. When they are young, the larvae eat together on the same plant, leaving it a mere skeleton of its former self. They become solitary as they mature, and also eat more, doubling their appetites after each instar. When they pupate, they build thin, brown cocoons in the soil. The adults emerge in 12 to 14 days.

Despite its name, the Salt Marsh caterpillar isn’t found solely in salt marshes, as many of us can attest. They prefer broadleaf weeds and wildflowers, but will attack vegetable and field crops if they find them.

They invade fields from nearby wild vegetation. Trenches with deep sides can deter a caterpillar invasion into field crops. The caterpillars do have some natural enemies, including a parasite. A few beetles, as well as assassin bugs will prey on them, but they don’t really do enough to regulate the population.

I have found most of the caterpillars on the wildflowers growing around my place, especially the red gaillardia. However, they really seem to like my Gregg’s Mistflower and zucchini.

I’m thinking that I may plant extra wildflower seeds around areas I want to protect, so next year they have more of the food they prefer, and maybe will leave my food and ornamentals alone.

El Camino Real Master Naturalists:

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2010-05-27 digital edition

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