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Inchworm invasion of the Highland Lakes


Inchworms are everywhere this spring in the Highland Lakes, mostly due to the February winter storms. iStock photo

Small green caterpillar ‘drops’ in on unsuspecting nature lovers

Walk through any park in the Texas Hill Country right now and you most likely will find a few inchworms taking your measure — more so than usual at this time of the year, according to the experts. 

Inchworms are so called because of the way they move. Their legs, called prolegs, are only on the front and back of their bodies — nothing in the middle. The front moves first, stretching out the inch-long body, and then waits for the back to catch up, folding the inchworm in two. It happens really quickly so the inchworm looks as if it is measuring. Those who find an inchworm on them are about to get new clothes, according to local folklore. 

Once through its metamorphosis, inchworms become gray-brown moths, part of the family Geometridae. 

The reason for so many of this sub-species of caterpillar, also known as cankerworms, is the winter ice and snowstorms that blasted Texas in mid-February. The eggs that are now hatched into inchworms were protected underground through the freeze. The arctic temperatures delayed leafing on plants that normally burst forth early in the season, putting a great deal of Mother Nature’s greenery on the same timetable. 

This is good — if not belated — news for what eats them, which includes birds, ants, and wasps. It’s actually not bad news for anyone, including the plants, since very few will be harmed by the hungry, hungry caterpillars. They eat a lot, but usually not enough to take down a healthy tree or shrub, their preferred habitat.

Once they have eaten enough, which usually takes about two to four weeks, they have to make it to the ground, where they form their cocoons and pupate (the process of becoming moths). 

As tiny, lightweight caterpillars, they are easily blown off leaves, so they attach themselves to their host plant via a tiny silk thread. When it’s time to go, they use that thread to drop out of the tree and sometimes onto people and animals who carry them off to new locations. 

How long they are in the ground depends on when they get there. Spring caterpillars become moths in two to four weeks. If they drop in the fall, they won’t emerge as an adult until the next spring, when they will mate with each other and the spring moths. 

The female moths, who do not fly, lay their eggs in tree bark, where they hatch at the first sign of new leaves and begin to eat. 

For more on caterpillars and which ones become what moths or butterflies, check out our story on