The Common Darter Dragonfly, as its name indicates, is one of the most common dragonflies, not only in the UK but also throughout Eurasia.
The adult male (above left) has a reddish hue while the female (above right) is yellowy brown. Similar-looking subspecies include the Island Darter and the Highland Darter.
The "teneral" (recently-emerged) darter (above centre) is light yellow with lemon/lime yellow "pterostigma"
(the stained glass plane at the top outside edge of the wing).
Females darken (above right) progressively browner with age, occasionally with a red tinge, and males redden, but less red than the Ruddy Darter,
which has a clubbed end of abdomen ("tail").
The male's pterostigma reddens and there may be a reddish vein
A mating pair
A diagnostic feature, if close enough, is said to be the yellow stripe on the black leg, although the Red-veined Darter also has these.