Synthemistidae

Wing venation : Crossveins are present in the forewing midbasal space, with more than two cubito-anal crossveins. The sectors of the arculus are fused for more than one-quarter, but less than half, of the arculus length. The hindwing triangle lies distinctly distal to the arculus, the anal loop is compact or ovate, and the forewing discoidal field widens strongly toward the wing margin. Adult morphology : Adults are medium-sized, generally dark dragonflies with a relatively slender abdomen. Male abdominal appendages are usually elongate and structurally distinctive, while the eyes meet dorsally. In Indonesian species, the body is commonly dark with pale yellow or cream markings. Male accessory genitalia : The posterior hamule is well developed, with distinct ventromedial and dorsolateral branches, while the genital lobe and anterior lamina vary among genera. The shape of the hamule and terminal appendages provides important diagnostic characters. Female morphology : The ovipositor and vulvar lamina vary within the family, ranging from reduced to relatively well developed. Female terminal structures and abdominal markings may also provide useful characters for distinguishing species. Vesica spermalis : The vesica spermalis is highly specialized. Its median process forms elongate, cylindrical, sclerotized cornua, often bearing paired distal horns. In Palaeosynthemis, the cornua are exceptionally long and may extend beyond the remaining length of the vesica spermalis. Larva : Larvae are generally robust and often hairy, with a broad, scoop-shaped labium and strongly developed labial-palpal teeth. They are predominantly associated with running-water habitats, particularly forest streams.