The amber specimens entombing H. scimitarus, and H. zigrasi were recovered from deposits in Kachin State, 100 kilometres (62 mi) west of Myitkyna town in Myanmar.

Burmese amber has been radiometrically dated using U-Pb isotopes, yielding an age of approximately 99 million years old, close to the boundary between the Aptian and Cenomanian.

[1] The amber is suggested to have formed in a tropical environment around 5° north latitude and the resin to have been produced by either an Araucariaceae or Cupressaceae species tree.

[2]The holotype of H. cerberus, specimen number "BMNH 20182" was deposited in the Natural History Museum Burmese amber collection in London.

Specimen number AMNH Bu-FB80 is the holotype for H. scimitarus and was part of an amber collection purchased from Federico Berlöcher by the American Museum of Natural History.

Unlike the other two species, at the time of description, the holotype for H. zigrasi, JZC-BuXX, was residing in the private collection of James Zigras and only loaned to the paleoentomologists for study.

[1] Despite its collection in the early 1900s fossils of the genus were not described until the Russian paleoentomologist Gennady M. Dlussky studied H. cerberus nearly 80 years later.

Overall the species of Haidomyrmex are gracile ants which range from 3.0 to 8.0 millimetres (0.12 to 0.31 in) in length and have a generally smooth exoskeleton.

The legs are very long and the pretarsal claw has a single tooth while the metasoma show telescoping segments and a fully retractable sting.

The protruding clypeus is large and has a roughly pentagonal shape and two pairs of long fine trigger hairs on the ventral side.