Suborder Anisoptera
Family Synthemistidae

Family Synthemistidae figure 1

This family, which is closely related to the Corduliidae, is confined to Maluku, New Guinea, Australia and the South- west Pacific. Two genera are endemic to Australia. They resemble the Corduliidae but are very slender and display relatively weak flight. Like the Gomphidae and Aeshnidae (but unlike the Corduliidae and Libellulidae), the antenodal crossveins bridging the costal and subcostal spaces do not uniformly coincide where they meet the subcostal vein. The eyes meet in a seam at the top of the head, but not so long as in the Aeshnidae and Libellulidae.

Synthemistines represent an advance over the Gomphidae and Aeshnidae in that the triangle of the forewing has taken on the perpendicular axis found in more advanced groups such as the Corduliidae and Libellulidae. There is also the incipient development of an anal loop. The group is distinctive among the more advanced families in that there are one or more crossveins in the median (or mid-basal) space (as shown below). The abdomen is relatively long and cylindrical. The mesopleural suture is straight, without the pronounced S-curve found in that of the Libellulidae.



Family Synthemistidae figure 2
Anal loop (al), and crossveins in mid-basal space (mbs) (Eusynthemis).

Very little has been published regarding their behaviour or ecology. The females of some species have a well-developed ovipositor, but unlike the similarly-equipped Aeshnidae female synthemistines do not use it to bore into plant stems; instead, they fly over waterways, tapping their abdomens on the surface and dropping eggs in clusters, similar to many gomphids and libellulids. Though Synthemistines must, necessarily, spend a lot of their time perching, they are not found in this activity as Libellulidae commonly are; almost all synthemistines are captured on the wing.

One genus (Synthemis, with 10 species) is known from New Guinea, a second (Eusynthemis, with one species) from the Solomon Islands.