Insect Galls

Galls on Goldenrod Stems

If goldenrod, Solidago canadensis, grows in your community, you can easily find insect galls on it. The spherical goldenrod gall is caused by Eurosta solidaginis. Sometimes nearly every goldenrod stem Gall on Goldenrodhas one or two of these galls. These galls are nearly spherical in shape and about three centimeters in diameter. These galls are easily found in the winter and collecting some of them is a good way to begin your collection of insect galls. Goldenrod stems are strong and most will stand upright all winter. The galls are often located about 2/3 way up the plant stem.

Eurosta solidaginis is a pretty fly having pictured wings [flies have two wings]. The female lays her eggs on the surface of the goldenrod stems. The eggs hatch and the larvae wander a bit and then bore into the stems. The start of the galls is visible in June. By fall, the galls have the appearance of the goldenrod stem, but are greatly enlarged being the size of hickory nuts and nearly as hard when the stems are dry.

The above photo of a Goldenrod Gall Maggot inside a broken gall was provided by Nature North Zine which is online nature magazine about the plants and animals of Manitoba, Canada . They have a nice page on Goldenrod Gall Fly. They have an index to many pages of nature stories.

Starting a Goldenrod Galls Science Project

first have some simple projects, then end with the Journal papers. and web searches.

This is an example of a closed gall. Examine some and you will not find a hole unless there is a parasite or a woodpecker has dug a hole to eat the maggot. Baby flies, the larva, are called maggots or some times worms, but they are not true worms. The larvae remain inside the gall all winter. Some transform in the fall, but most wait for spring.

At least 12 other insects have been found in goldenrod galls. Some are parasites but others are true inquilines. After you have collected several of the galls, you can begin several studies. You can hold some galls until summer hoping to observe the adult coming from the gall. To be successful, you will need to hold the galls at suitable temperature and humidity. Leaving the galls outdoors in the normal weather (cold and rain) may be the best method. But any time from June to the following spring, you may open some of the galls and look for the contents. They are very strong and you are likely to injure yourself. Get your parent to help you. I have used sharp knives and pruning shears to cut the galls open. Pruning shears may be the safest tool. But you could cut a finger off. Be sure both hands and all your fingers are on the handles of the pruning shears. You should write down the findings for each goldenrod gall that you open.

----- to be continued.

Here is the results I found in opening 10 galls on 1998 Jan 10:

Gall # ....................... Observations

1 -5 had woodpecker holes (3 to 5 mm dia); inside these were wet and some rotten tissue.

7 - One small 1.5 dia hole that opened into a 2 mm dia chamber containing a mite. Gall seemed to just pith, but another cut revealed a cental chamber wit a maggot. its head pointed down. split the gall longitudinally. maggot was 3mm dia, 5 mm long. no hairs, smooth, making perstalic movements. pale yellow internal fluid with white fat bodies-- all this visible thru the skin. no legs, 2 black hooks at mouth as in Drosophila. I used 10x to 30X; all these very good for studying he organism. a smooth segmented bag. 6.3 mm was its longest length when it streched our once. wt 48.6 mg (0.0486 g). a nematode at the anus of maggot; perhaps nematode eats waste excreted by maggot, nematode crawled all over the maggot.

8 - no holes; small gall half as large as most. It had a maggot, maggot always in a slight C shape flexed. He was laying horizontal; maggot smaller than #7 chamber wall is fecal pellets packed 3 or 4 layers deep leaves a smooth clean chamber for maggot. maggot 2 x 4 mm; 11.9 mg.

9 - no holes; very small gall 1.2 x 2.5 cm. no central chamber. tiny chamber at edge of gall 1.8 mm from outside skin of the gall. Gall had the radial ray structure of all normal galls, but maggot chamber was at edge only. Thus the central chamber may not be reason for the radial design of galls. maggot was 0.7 x 3 mm 0.0005 gram wt.

10 - no holes, 2.1 x 3 cm gall. clean normal inside. maggot did not move; looked somewhat dehydrated maggot wt = .0024g.

plant stems were mostly 4 to 6 mm diameter. It had been rainy misty weather for 3 days. Galls were easily cut with sharp knife. Dry galls can be very hard to cut. I cut them with a rolling action; no fingers on gall. Then I snapped he gall apart, Thus if maggot in center, I would not cut it.

Web search via AltaVista goldenrod gall fly.

ACornell University essay on plant galls.

Kelleher, M.J., Rickards, J. and Storey, K.B. 1987. Strategies of freeze avoidance in larvae of the goldenrod gall moth Epiblema scudderiana: Laboratory investigations of temperature cues in the regulation of cold hardiness. J. Insect Physiol. 33, 581-586.



Abstract Laboratory manipulations of ambient temperature were used to investigate the role of temperature in triggering or modulating cold-hardiness adaptations supercooling-point depression and cryoprotectant accumulation, in larvae of the goldenrod gall moth, Epiblema scudderiana (Clemens), a freeze-intolerant species. Low temperature strongly facilitated cryoprotectant synthesis; larvae subjected to a 1C per day decrease In temperature showed a major increase in the rate of glycerol synthesis when temperature fell below 5'C with highest rates of synthesis, greater than 90 micromol/g/d, at temperatures between O and -10C. Conversely, abrupt rewarming of larvae from -18 to 23-C in mid-November stimulated a rapid loss of glycerol (from a starting level of 1763 + 278 micromol/g wet weight with a half time of only 1.5 days. Supercooling-point depression was not keyed to ambient temperature but appeared to be an endogenous event occurring over the same time interval in laboratory animals held at warm or cold temperatures, as well as in outdoor animals Rewarming of cold-adapted larvae in November resulted in only a small rise in supercooling point (and did not break diapause) but rewarming in February resulted in a 19C increase in supercooling point in 4 days, followed rapidly by pupation.

Michigan notes on galls. Excellent

Male, K.B. and Storey, K.B. 1982. Purification and properties of glutamate dehydrogenase from the cold hardy gall fly larva, Eurosta solidaginis. Insect Biochem. 12, 507-514.



Abstract Glutamate dehydrogenase (GDH) from the goldenrod gall fly larva, Eurosta solidaginis, was purified 500-fold to a final specific activity of 37.5 micromol NADH utilized/min/mg protein. The enzyme is a hexamer of mol. wt 350,000 + 30,000 and subunit size 57,000 + 5000. Both nicotinamide coenzymes were utilized with activity ratios, NADH/NADPH, of 3.5 at pH 6.75 and 11 at pH 7.5; NAD/NADP activity ratios were 7 at pH 7.5 and 15 at pH 8. Enzyme kinetic constants (S0.5) for NH4+, alpha-ketoglutarate and coenzyme were 210 + 10, 2.7 + 0.2 and 0.032 + 0.00l mM for the NADH linked reaction and 61 + 2.0, 0.56 + 0.06 and 0.060 + 0.003 mM for the NADPH reaction. Ammonium ion kinetics were distinctly sigmoidal. Metabolite effectors modified NH4+ kinetics, ADP activated, decreasing S0.5 for NH4+ four-fold and reducing n, the Hill coefficient. ATP inhibited the NADH linked reaction but activated the NADPH reaction. GTP inhibited the enzyme. GDH activity in the forward, glutamate oxidizing, direction was undetectable in the absence of ADP. S0.5 values for glutamate and coenzyme (at saturating ADP) were 3.1 + 0.2 and 0.22 + 0.02 mM for the NAD reaction and 3.8 + 0.3 and 0.20 + 0.02 mM for the NADP reaction. Inhibitors (GTP, ATP) modified both glutamate and coenzyme kinetics. Arrhenius plots were linear over the range 25-0C and temperature had little effect on enzyme substrate affinity. Inhibitor effects, however, were altered with temperature: I50 values for GTP and ATP decreased at low temperature and ADP reversal of GTP inhibition of the NADPH linked reaction was greater at 5C than at 25-C. Larval GDH appears well suited for a role in amino acid biosynthesis and may have an important role in the overwintering accumulation of proline in this freezing-tolerant insect.

Safety Precautions

Collecting and studying insect galls is an interesting, useful science project. An insect gall is any deformity caused by an insect. They are very common and were known by ancient man. Theophrastus, a greek, wrote about them 300 years before the birth of Christ. He wrote about their use in medicine. Some galls on animals are caused by insects, but this project is limited to galls on plants caused by insects and mites. Insects have six legs. Mites have eight legs and are not insects.

Any abnormal growth of a plant is a gall. Some of these are caused by limbs rubbing together or cutting or biting by animals. Fungi and viruses often cause witches'-broom. Nematodes, mites, and insects are the most common causes of galls on plants.