Pachydiplax longipennis

Blue Dasher

Pachydiplax longipennis, Blue Dasher

Family: Libellulidae

Length: typically 28 - 45 mm


Blue Dashers are often present at ponds in very large numbers, the males patrolling and clashing frequently with other males. Females are less conspicuous, but are often present in good numbers as well. Although not tiny, this species is smaller than many other species flying at the same time.

The mature male (shown in the first three photos) has a powder blue body, with the apex of the abdomen all black. As the photo just below shows, there are black and green lines on the sides of the thorax. The dasher typically holds its wings in a swept forward position. Males often have some amber to brown coloration in the wings.

Females and immature males (see bottom two photos on the page) are mostly brown in color, with a double row of yellowish lines down the dorsal surface of the abdomen. There are also yellowish markings down each side of the abdomen as viewed laterally. The eyes of the females are green to brown, and as with the males, the face is white.

Blue Dasher, Pachydiplax longipennis

Blue Dashers are usually seen at ponds, sometimes in swamps, but seldom along rivers and streams. They are also found in meadows near ponds. They have a long flight season, and interestingly, Dashers are typically larger in the springtime—by later in the summer the newly emerging ones are smaller.

McKinnon and May (1994) studied this species in the field in New Jersey. They reported that the nymphs emerge and undergo the final molt in mid-June. Within about eight days the adults were becoming sexually mature. Adults were on the wing through late September.

Males’ primary sexual cue seemed to be a female flying near the water (the males did not respond to a perched female). After mating, the male guarded the female as she oviposited, driving off any male that ventured too close.

The authors suggested the adult lifespan of Pachydiplax longipennis is fairly long, about thirty days.

Pachydiplax longipennis, Blue Dasher face
Blue Dasher, Pachydiplax longipennis

Above and below: Two views showing the coloration of the female and immature male Blue Dasher. The individual above is obelisking, a common pose for Blue Dashers, one that helps prevent overheating.

 Blue Dasher, Pachydiplax longipennis