ROBIN'S PIN CUSHION

On this wild rose stem I spotted a strange red whiskery ball growing.

It's a Bedeguar Gall or Robin's Pin Cushion.  A tiny gall wasp lays several eggs on the rose stem and the plant responds by producing a swelling with all these short growths.

Inside, each grub has its own chamber to develop in.  Other insects come and lay their eggs, and their grubs live alongside the original inhabitants.  The name for these is inquilines.  Yet more insects parasitize those already in residence so a whole community develops inside the gall.  The grubs pupate inside the gall and new adults emerge in spring.