Insect Experiments

Goldenrods with Gall

What is inside goldenrods with gall? Insect larvae live inside the ball-like growths on the plants.

Fly and moth larvae frequently infect goldenrod plants, producing large shapes (like balls or ovals) called galls. To visualize this, think of larva entering your arm and swelling it to the size of a football!


What You'll Need:

  • Field with goldenrod plants
  • Safety scissors
  • Tweezers
  • Nylon mesh
  • Rubber bands

How to Make Goldenrods with Gall:

Step 1: Go into a goldenrod field, and observe the galls. Count how many are on a plant and how many plants are infected.

Step 2: Using a pair of scissors, cut open a gall and try to find the large cream-colored larva. When you find one, pull it out with tweezers. It will wiggle. Put it in the freezer for a few hours, and remove it. The larva mass won't move at first, but after warming up, it will wiggle again.

Step 3: Put nylon mesh around the gall. For round galls, do this in April or May; for oval galls, do it in August or September. Attach the mesh above and below the gall with rubber bands so that an insect cannot leave the netting after exiting the gall. Check your mesh net every week. What type of insect emerged from the gall?

Safety Tip: The gall should only be cut with adult supervision.

What Happened?

You will usually find only 1 gall on each plant. The number of infected plants varies from place to place. Since females lay about 70 eggs, the number of plants infected can be high. For example, a scientist collected 1,000 plants and found 264 with ball-shape galls.

The type of insect inside depends on the shape of the gall. Round galls contain fly larvae, while oval galls hold moth larvae. The larvae can withstand freezing because they have glycerol in their blood, which acts like antifreeze.

In the next experiment, study some bugs that jump.

For more crafty fun and animal-related activities: