Hemigomphus comitatus is a small dragonfly with black and yellow markings. Its wingspan is 50-55mm and overall length is 40-45mm. The eyes of the adult are green and do not meet at the top of the head. The head of the female has a spine from the occiput just behind the eyes. The synthorax is strongly marked with black and yellow stripes, with the humeral stripe usually being continuous. A black mark along the suture of the synthorax is usually broken above and below the metastigma. The abdomen is black with prominent yellow bands, the appendages of the male are yellow and curve inwards at the tip. The wing margin at the base of the hindwing is folded in the male, but uniformly curved in the female.
Hemigomphus comitatus is known to inhabit streams and rivers, not necessarily in rainforest. The exemplar pictured here was found in suburban Cairns near a seasonal storm-water creek.