Hagenius brevistylus

Dragonhunter
Hagenius brevistylus, Dragonhunter

 

Family: Gomphidae

Length: typically 80-85 mm

 

The Dragonhunter is the largest member of the Clubtail family. As its name implies, it is a bold predator. Dragonhunters often capture dragonflies nearly their own size. They also feed on butterflies, like the hapless Monarch shown here, and other large insects.

The eyes are green and widely separated. The face is yellow, and the overall size of the head is small compared with the robust thorax. Males and females are similar in color and markings.

Dragonhunters’ favored perches are along streams, although they may also be found some distance from water.

Males have a distinctive flight posture, with the abdomen often curved under so that the profile is that of the letter "J."

Dragonhunters have a wide distribution across the eastern United States and adjacent areas of Canada.

White and Sexton (1989) studied the predation of Hagenius brevistylus on Monarch butterflies, stating that they knew of no other records of an invertebrate that preys on Monarchs. Monarchs have unpalatable chemicals (cardenolides) sequestered in their bodies, and these chemicals ensure that predators leave them alone (or taste them only once).

White and Sexton showed how the Dragonhunters use their legs to rotate the Monarch, eating primarily the thorax where the cardenolides are not so noticeable. Dragonhunters may eat the Monarch’s abdomen, too, but will stop eating once they come to a significant amount of cardenolides. The dragonfly always fails to eat the Monarch’s wings, since the level of unpalatable chemicals is very high there.

While the study did not claim that Monarchs are the only prey of Hagenius brevistylus, the authors did state that in times of Monarch abundance Hagenius brevistylus seemed to feed on Monarchs alone. Monarchs apparently have learned to modify their behavior to avoid Dragonhunter predation. Though Monarchs are normally a sun-loving species, when Dragonhunters were around the Monarchs fed primarily in the shade, or if they were in the sun they flew to the shade if disturbed. Dragonhunters almost invariably hunt in the sun.


Dragonhunter, Hagenius brevistylus eating a Monarch
The yellow stripes are thin on the dorsal surface of the thorax, but thick on sides of the thorax. The eyes are green and widely separated. The face is yellow and may have a black stripe.

 

Dragonhunter, Hagenius brevistylus abdomen
The club on this member of the Clubtail family is relatively modest. Yellow spots adorn the sides of the abdomen. 

 

Dragonhunter, Hagenius brevistylus description and photograph
Markings on the top of the abdomen are spare. Typically these include thin yellow lines on top, and a yellow spot on segment eight.


American Insects site