Blackberry Knot Gall

November is a good time to take careful looks at trees and other plants for signs of bird or insect activity that were earlier hidden by leaves.

Recently I noticed an insect gall in a patch of thorny vines growing near a fallen tree. I had been in this area a number of times this Fall, but had not been aware of this gall before.

While recognizing this as an insect gall, I did not know anything more about it and do not remember seeing it previously. I took a couple pictures, confirmed that the brambles were blackberry (insects often select specific plant species for their eggs), and estimated the size of the gall (about 2 inches long). I could research it at home.

This is a photo from the underside.

The information I had was sufficient to identify this as a Blackberry Knot Gall. A small wasp deposits eggs into a blackberry stem in spring or summer and this stimulates the plant tissue to grow in this manner, making a case for multiple eggs. The gall is apparently better known than the wasp responsible for it because the wasp is named for the gall – the Blackberry Knot Gall Wasp.

That the gall is enlarged stem growth is evident from the fact that the gall has the same small thorns found on the rest of the stem.

On subsequent visits to Eliza Howell Park, I found two other galls on nearby blackbery plants. The shapes are a little varied, but here is little doubt that all three are the same species.

i am not familiar with this wasp and have no photos of it. While i usually use only my own photos or those of a photographer I know personally, I am not able to follow this practice here. This photo is from BugGuide.Net.

The eggs hatch and remain in the gall through the winter as larvae, emerging in the Spring.

Also on the now leafless blackberry canes are several Chinese Praying Mantis egg cases. These serve the same purpose — a sheltered environment for the eggs and larvae to develop before energing in the spring — but praying mantis egg cases are attached to the stems, not inside them.

Eliza Howell Park is about 250 acres in size. It is not surprising that I continue to discover flora and fauna that I have not seen (or paid attention to) here before. It’s a good reason to keep returning!

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