Lasioglossum exlautum vs Lasioglossum punctatum
I write this so that hopefully other users will not be as confused as I was.
An ongoing debate for some time that has utterly confused me has been which of the two species, L. exlautum or L. punctatum, is present in Australia.
From what I have learned, the issue originated from when it was decided that Homalictus with all its species was no longer recognised as a Genus separate from Lasioglossum and became a Subgenus under the latter. This Genus Homalictus contained the species Homalictus punctatum of Australia which became Lasioglossum (Homalictus) punctatum.
However, Lasioglossum (Ctenonomia) already had a L. punctatum which occurred in Indonesia. This meant that as L. (Homalictus) punctatum was the younger addition to Lasioglossum having just moved, its name had to be changed. A secondary name was found as (originally) Homalictus exlautus. So, the new L. (Homalictus) punctatum became Lasioglossum (Homalictus) exlautum.
L. (Homalictus) exlautum is the species recognised in Australia, and L. (Ctenonomia) punctatum is not, being an Indonesian species.
Professor Ascher summed it up in the following quote:
"Lasioglossum (Ctenonomia) punctatum (Smith, 1858) is from Sulawesi in Indonesia
Lasioglossum (Homalictus) exlautum (Cockerell, 1905) of Australia is the valid name for Halictus punctatus Smith, 1879
The junior name is Australian."
I hope this helps as I have been infuriated for months now and I hope others have not felt the same!