Egg sacs?

Egg sacs?

Observation - Egg sacs? - UK and Ireland. Description: I don't think the middle smooth brown sacs in my photo (each c. 3mm diameter) are part of this 6 foot high yew hedge - at any rate they seem different from the buds. There are many of them appear on all of the plants, though not all of the leaves. They

I don't think the middle smooth brown sacs in my photo (each c. 3mm diameter) are part of this 6 foot high yew hedge - at any rate they seem different from the buds.

There are many of them appear on all of the plants, though not all of the leaves. They are mostly located in the crux of where a leaf joins its stem but some are attached further along the leaf, which makes me think they are animals. They appear in mature leaves, not new growth.

The older ones (I presume) break off easily. They have a thin, flexible brown shell and are full of white flaky powdery substance, while others burst and are full of a viscous opaque straw-coloured liquid. Both odourless.