I took my secateurs and cut the gall off with two sets of leaves at the base of the gall.
Mossy hard mass. Really cool.
Took my secateurs and cut the gall in half. Found several larvae in sections. Each within their own chamber.
They are in fact larvae from a wasp.
Non-native - an European introduction called: Diplolepis rosae.
The most fascinating aspect is: how the heck did they get in there?
Adult wasps lay eggs on the plant and once a larva hatches, it begins to feed on leaf bud tissue, and an amazing process begins. The host plant is stimulated somehow with the feeding, where cells from the surrounding tissue multiply, adding layers of tissue - forming this gall. The larvae within, creates a microhabitat, where not only they are protected and housed, but the chambers they indwell also become their food source. A hotel with room service, if you will.