Goldenrod Gall Fly

Eurosta solidaginis

Copyright, Dr. Warren Abrahamson and Paul Heinrich

The Goldenrod Gall Fly is a parasite on goldenrod plants. The fly's entire life, and death, is centered around Goldenrod.

This small brown fly is about five millimeters long. Males are slightly smaller than females. Females are easily identified by their ovipositor (egg-laying tube) extending from their abdomen.

Adult gall flies do not fly well, so they do most of their travelling by walking up and down goldenrods. The male will choose a bud on the plant and wait until a female shows up. When a female approaches, the male does a sort of "dance" to attract her.

After the flies mate, the female leaves to find a suitable spot on the goldenrod to lay eggs. To lay them, she injects her ovipositor into the goldenrod stem. Adult Goldenrod Gall Flies only live about two weeks.

Fly larvae will hatch from the eggs in about 10 days. The larvae will immediately begin to eat from inside the stem of the goldenrod. The saliva of the larvae has a chemical in it which causes the plant to grow abnormally, creating a ball-shaped "gall" that the larvae live in.

The larvae will stay in their galls for a full year before becoming adults. First, they will continue to eat from within, making the gall grow larger, until it is the size of a golf ball. When Fall approaches, the goldenrod stem and gall will turn brown and each larva will dig an escape tunnel to leave its gall, but will not use it until Spring. To prepare for Winter in the gall, the larvae will produce a chemical in their bodies which is similar to anti-freeze. It will keep them from dying from cold weather.

In the Spring, each larva will become a pupa (resting stage) before hatching into an adult. The adult will leave the gall and look for a mate. Adult Goldenrod Gall Flies do not eat.

Copyright, Dr. Warren Abrahamson and Paul Heinrich


Copyright, Dr. Warren Abrahamson and Paul Heinrich

Goldenrod Gall Flies have many predators, some even when they are in the larval stage in their gall. The gall is like protective armor against most predators, but some locate galls knowing there is a juicy snack inside. Downy Woodpeckers and Carolina Chickadees are two birds who seek out galls and break them to get the larvae out.

There is a beetle (Mordellistena unicolor-no common name) which burrows into the gall and eats the larva.

See a picture of this beetle below.

Copyright, Dr. Warren Abrahamson and Paul Heinrich

Copyright, Dr. Warren Abrahamson and Paul Heinrich

There are also two species of parasitic wasps (Eurytoma gigantea-no common name, pictured to the left; and Eurystoma obtusiventris-no common name) which prey on larvae of Goldenrod Gall Flies.

These wasps seek out galls and use their own ovipositors to inject eggs into the gall. When the eggs hatch, the wasp larva eats the gall fly larva.

Goldenrod Gall Flies only lay their eggs in goldenrod, and these two species of wasps only lay their eggs where there are Goldenrod Gall Flies. Therefore, these species both depend on goldenrod.

Additional Media

Goldenrod Gall Key
Link to Website
The Solidago Eurosta Gall Homepage

Relationships in N ature:



Carolina Chickadee


Goldenrod Pa

Downy Woodpecker

Parasitic Wasps (see above)

Mordellistena unicolor Beetle (see above)

Red-winged Blackbird

Rabid Wolf Spider

Wild Turkey

Goldenrod Spider

Daring Jumping Spider

Ruby-throated Hummingbird

Chinese Mantid

American Goldfinch


Common Yellowthroat

Relationship to Humans:

Goldenrod Gall Flies do not appear to have a direct impact on people. They don't bite or sting or become a pest, since they are only concerned with mating and goldenrods. They don't even hurt the goldenrod plants. They are a source of food for other species which people enjoy, such as woodpeckers and chickadees.


Eurosta solidignis


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