Maoridiamesa is the most common member of the Diamesinae, a subfamily of the Chironomidae. Like other chironomids the general body form is worm-like, but with a distinct head, and with paired prolegs under the head and at the end of the abdomen. Maoridiamesa larvae have a green or pale body, brown head with prominent hairs, and a distinct black collar. The eye can be a circular black mass or two joined spots.
Maoridiamesa larvae are found in a wide range of streams, particularly at sites with abundant streambed algae.
They are presumably collector-gatherers; feeding on algae and other fine organic matter.
Maoridiamesa can be common in good quality streams, but also in nutrient enriched streams with prolific streambed algae. They have tolerance values of 3 (hard bottom sites) and 4.9 (soft bottom sites).