Seeing Spots

Oct 22, 2008

If it looks like a duck, swims like a duck and quacks like a duck, then it probably is a duck.

That inductive reasoning (known as "the duck test") doesn't hold true for yellow bugs with black spots.

A yellow ladybug (ladybird beetle)  and a cucumber beetle look a little alike--at first glance. They're both yellow. They both have black spots.

But they're worlds apart. One is a beneficial insect. The other is a pest.

We spotted a spotted cucumber beetle (family Cerambycidae)  on our sunflower plant last summer. It's a common insect in California. It eats all kinds of flowers and leaves. It's often seen on plants in the squash family.  Figures. We had a squash plant in our garden. (Notice the "had.")

Ladybugs (family Coccinellidae) aren't always the classic reddish-orange color and they don't always have spots. They can be mellow yellow! But they're your buddies.  They feast on aphids, mealybugs, mites, and other soft-bodied insects.

I figure that between these two insects, the ladybugs are the bright spots in the garden.

By Kathy Keatley Garvey
Author - Communications specialist

Attached Images:

A yellow ladybug on sage. The ladybug (ladybird beetle) is a beneficial insect. (Photo by Kathy Keatley Garvey)

Yellow ladybug

The spotted cucumber beetle is a pest. It's often seen on plants in the squash family. (Photo by Kathy Keatley Garvey)

Spotted cucumber beetle