These common green darners are Aeshnids, a worldwide family of mostly large, brightly-colored dragonflies (as in the related blue-eyed darner) that are even more specialized for flight than the rest of the order.   Most dragonflies occasionally perch on twigs or leaves, but Aeshnids spend hours on end in continuous flight.   Occasionally they will hover in one spot for a few seconds, and I was able to get a couple of shots of the ones in the two upper photos (using a long autofocusing telephoto lens) during hovering bouts.   They are males, as shown by the bright blue color on the abdomen; a close-up is at the bottom right of the page.   When dragonflies mate, the male grasps the female with his tail pinchers, and she swings her abdomen forward to contact the male's 'secondary' genitalia, which are somewhat surprisingly located at the base of the abdomen (below).   The 'real' male genitalia are in the standard place at the end of the abdomen.   The pair often stay hooked together for some time after mating (probably this helps the male guard against mating attempts by other males), and also while the female lays eggs in water (below, right).   Near the bottom of the page is a picture of a female at rest (she has some minor damage to the tops of her eyes, probably from the pinchers of a male).   At bottom right, an ovipositing female common green darner is being grabbed by a male blue-eyed darner in a misguided and very brief mating attempt.   Most of the images were taken in August, September, or early October at the San Jacinto Wildlife Area near Riverside, California; one photo was made in Palm Desert, California.