JULY
2013

 

By
Tom Turpin
 
Professor of
Entomology
Purdue University

 

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Flies in the face of fashion

What's Buggin You Now?

 

 

 

07-25-13

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Cabbage Caterpillars Loopy Chewers


There are more than 3,500 species of flowering plants included in the family Brassicacae. Most gardeners are familiar with this plant family because of the crucifers that are sometimes called cole crops. Cabbage, broccoli, cauliflower and Brussels sprouts are common garden plants that are scientifically classified as Brassicacae.

These garden crucifers end up on our tables in many ways. Corned beef and cabbage, sauerkraut and coleslaw are widespread usages of cabbage. Broccoli and cauliflower can be boiled, included in stir-fry recipes, or used as a fresh vegetable for dipping. I suspect that Brussels sprouts do not make the favorite-food list of many folks. But even the most hardened Brussels sprouts hater might like these little cabbages golden-crusted in olive oil and sprinkled with cheese or Dijon-braised.

Cabbage Butterfly
Cabbage butterfly
(photo credit: Univ. of California Davis)

Before we get to make a meal of any of the cole crops, we have to grow the plants. And that, as any gardener knows, means we are likely to encounter insects that feed on plants in the Brassicacae family. Yes, there are several species of insects that use the foliage of these plants as food. The list includes cutworms, flea beetles, beet armyworm, diamondback moth, cabbage maggot, cabbage looper and cabbage butterflies.

The worms that most people discover in their cabbage, or broccoli, are caterpillars of the cabbage looper or those of the cabbage butterflies. The caterpillars of these insects are smooth-bodied and green in color. Because they blend in with the plants on which they feed, people may not notice the worms until they come floating up when the food is being processed.

Cabbage worm
Cabbage looper

On occasion, caterpillars in cabbage or broccoli plants aren't discovered until the food is on the table. A worm in the food is sure to prompt a lively discussion. Such instances always remind me of the old joke that goes something like this: "What is worse than finding a worm in the apple you are eating?" The answer: "Finding half a worm in the apple that you are eating!"

Caterpillars of several species of butterflies feed on cabbage. These are all white butterflies and are known popularly as cabbage butterflies. One is likely the most common butterfly in the world - at least that's the case today. This butterfly's scientific name is Pieris rapae. It was originally found in Europe, Asia and North Africa and sometime around 1860, the insect was introduced into North America. Today, it's found in most parts of the world, including Australia and New Zealand. Because it isn't native to the United States, the insect is sometimes known as the imported cabbageworm.

The other type of caterpillar often found on cabbage or in broccoli is called the cabbage looper. This caterpillar turns out to be a moth in the adult stage. There is an entire group of moths that are called loopers. The name reflects the way the caterpillars crawl. They move along in a looping motion that creates a loop with their body. The caterpillar grasps the surface with two pair of fleshy protuberances called prolegs, situated near the rear end of the body. Then, it raises the forepart of its body off the surface and extends forward. Once its legs are on the surface, the proleg portion of the body is brought forward and a loop is formed.

There are other moth caterpillars that move in this looping motion as well. These are also sometimes called measuringworms, or inchworms, and are classified in the family Geometridae. One bit of folklore holds that if one of these worms crawls on you that you will be getting a new suit, because you are being "measured."

Every time I see a caterpillar crawling in a looping fashion, whether on the leaves of a cabbage plant or over a head of broccoli, I am reminded of the children's nursery rhyme song "Loop de Loop." It begins something like this: "Here we go loop de loop, here we go loop de lie."

The song was recorded by American pop singer Johnny Thunder and eventually became a sing-along for SpongeBob SquarePants. Here's the question. Do any of the kids watching SpongeBob and singing along with “Here we go loop de loop” know that they are describing the movement of a cabbage caterpillar?   

 

Writer: Tom Turpin
Editor: Olivia Maddox