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Free
images of North American Wildflowers Note
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What are those strange growths on the Goldenrod plant?
Although they can be found on other plants as well, the
small tumour-looking bulges on the plant are called
"galls" and are actually hibernation dens for insects. Certain types of flies
lay their eggs on the stem of the plant.
The hatching larva dig themselves into the interior of the
stem. The swelling is
the plant’s response to the
insect living inside. The larva is laid in spring, and will live inside the plant
for the entire summer, wintering inside the stem.
Unless eaten by predators such as other insects or birds,
the larva turn into grubs and emerge next spring.
Although the galls aesthetically damage plants, they do not
do serious harm to the plant’s health. In order to defend
itself, the plant creates the Ball Gall to provide the grub with
more room. Note: Another name for Galls is "Cecidia" and they can also be caused by various other parasites including fungi, bacteria, insects and mites.
Goldenrod Gall (Gall-2) Medium - 640 x 480 Right click on above image and chose "save as". Large - 3883 x 2913 - Large files now only available by email request.
Goldenrod Gall (Gall-3) Medium - 640 x 480 Right click on above image and chose "save as". Large - 3017 x 2262 - Large files now only available by email request.
Goldenrod Gall (Gall-4) Medium - 640 x 480 Right click on above image and chose "save as". Large - 4608 x 3456 - Large files now only available by email request.
Goldenrod Gall (Gall-5) Medium - 640 x 480 Right click on above image and chose "save as". Large - 3456 x 4608 - Large files now only available by email request.
Goldenrod Gall (Gall-6) Medium - 640 x 480 Right click on above image and chose "save as". Large - 3456 x 4608 - Large files now only available by email request.
Goldenrod Gall (Gall-7) Medium - 640 x 480 Right click on above image and chose "save as". Large - 3766 x 2825 - Large files now only available by email request.
The following images are cross section cuts of newly developing galls. With the white pulpy material inside, it is difficult to see the grub living within.
Goldenrod Gall (Gall-8) Medium - 640 x 480 Right click on above image and chose "save as". Large - 4146 x 3110 - Large files now only available by email request.
Goldenrod Gall (Gall-9) Medium - 640 x 480 Right click on above image and chose "save as". Large - 4608 x 3456 - Large files now only available by email request.
Goldenrod Gall (Gall-10) Medium - 640 x 480 Right click on above image and chose "save as". Large - 4608 x 3456 - Large files now only available by email request.
A fly called the "Goldenrod Gall Fly" [Eurosta solidaginis] is a parasite and lays its eggs on the stem of a Goldenrod plant. The female fly injects her egg-laying tube called an "ovipositor" into the Goldenrod stem. In about 10 days the larvae hatch and begin to eat the inside of the Goldenrod stem. The swelling and creation of the round-shaped gall is the plant's response to the insect living inside. The larva is laid in spring and will live inside the plant for the entire summer. Sometimes the galls become very large - about the size of a ping-pong ball. As winter approaches, the larvae produce a chemical that prevents them from dying in the cold weather. This chemical is very much like anti-freeze. Unless eaten by predators such as other insects or birds, the larva turn into grubs and then adults that will emerge next spring. Many birds have learned to look for large galls in order to get a tasty meal. ► Did you know.... that there are two types of parasitic wasps - Eurytoma gigantea and Eurystoma obtusiventris that steal the galls made by the Goldenrod Gall Flies? These two wasps hunt for galls in which to lay their own eggs. The Eurytoma obtusiventris lays its eggs inside the Gall Fly larva while the Eurytoma gigantea eats the whole gall fly and takes its place in the gall.
Why are some galls round and some elliptical? Round galls are created by the Goldenrod Gall FLY, while elliptical galls are created by the Goldenrod Gall MOTH [Epiblema scudderiana]. The moth's life cycle is much the same as that of the fly, except that their galls are more camouflaged, and elongated. All images of galls below were made by Goldenrod Gall Flies.
Goldenrod Gall - 1 - Note the hole. Medium - 640 x 480 Right click on above image and chose "save as". Large - 4608 x 3456 - Large files now only available by email request.
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