H. relegatus can be found throughout the three main islands of New Zealand and visits the flowers of a wide variety of plant species, both native and introduced.

Black; head subopaque, very closely and finely punctured; the clypeus and inner orbits of the eyes, as high as opposite the insertion of the antennae, yellowish-white; the mandibles with a longitudinal white stripe.

Thorax : the disk closely and finely punctured; the metathorax with a triangular enclosed space at its base, which at its basal margin has a series of abbreviated striae; a spot on each side of the collar, and the tubercles, yellow; wings subhyaline and iridescent, the nervures black; the first recurrent nervure uniting with the first transverso-medial nervure; the second recurrent received near the apex of the second submarginal cell; the calcaria pale testaceous.

[1] The male of the species is between 5.7–7.7 mm in length with the face, apart from black lower margin, entirely yellow.

[1] This species is endemic to New Zealand and can be found in the North, South, Stewart, Chatham and Three Kings Islands.

[1] This species makes its nest by boring cells into wood, dead branches or even flax flower stalks.

[1] As of 2021, this species is not regarded as being at risk and was not mentioned in the most recent 2014 Threat Classification report for New Zealand Hymenoptera.