This is a small damselfly only up to 3.5 cm long. The males are blue on the sides of the thorax, and the upper side of the abdomen. Females are light blue on the thorax to greenish-yellow on the tail. The upper side of the abdomen is mostly black, except for segment eight, which is blue.
The nymph is about 2.5 cm long and has the typical slender shape of immature damselflies. They can range in color from green to light brown. The alkali bluet can be seen around river and creek estuaries where the water has a higher salt content. They can be found in all parts of Vancouver Island and they are quite common.
The nymphs eat a wide variety of aquatic insects, including mosquito larvae along with other aquatic fly larvae.
The adults eat a variety of small, soft-bodied flying insects such as mosquitoes, flies, and small moths.
The males stake out territories at choice breeding sites. After mating, the female alkali bluet oviposits on floating mats of decaying algae.