Heather Angel / Chalcid wasp (Gasteruption jaculator) nectaring on Yarrow (Achillea millefolium) cultivar, picking up pollen on legs and head. Long ovipositor used to lays eggs inside solitary bee nests. In garden, S...

Robert Thompson / Large blue butterfly (Phengaris arion) nectaring on Yarrow (Achillea millefolium). St Caterina di Valfurva Valfurva, Sondrio, Lombardy, Italy.

Colin Varndell / Yarrow (Achillea millefolium) flower. Dorset, UK, July.

Ernie Janes / Achillea millefolium Paprika' in flower in garden. England, UK.

Ernie Janes / Achillea millefolium Paprika' in flower in garden. England, UK.

Kim Taylor / Ruby-tailed wasp (Chrysis ignita) feeding on Yarrow (Achillea millefolium) Surrey, England, July.

Kim Taylor / Ruby-tailed wasp (Chrysis ignita) feeding on Yarrow (Achillea millefolium) Surrey, England, July.

MYN / Dirk Funhoff / High brown fritillary butterfly (Argynnis adippe) on Yarrow (Achillea millefolium), Lorsch, Hessen, Germany. June. Meetyourneighbours.net project

MYN / Dirk Funhoff / Yarrow (Achillea millefolium), Lorsch, Hessen, Germany. Meetyourneighbours.net project

Nick Upton / Spreading bellflower (Campanula patula) flowering alongside Common yarrow (Achillea millefolium) in alpine grassland, Zelengora mountain range, Sutjeska National Park, Bosnia and Herzegovina, July.

Nick Upton / Spreading bellflower (Campanula patula) flowering alongside Common yarrow (Achillea millefolium) in alpine grassland, Zelengora mountain range, Sutjeska National Park, Bosnia and Herzegovina, July.

Dave Bevan / Heath fritillary butterfly (Mellicta athalis) feeding from Yarrow flower (Achillea millefolium) Hungary, June.