[3]: 61  Robert McLachlan commented that his peer Edmond de Sélys Longchamps proposed the separation of T. plagiata from the other members of the genus Gynacantha as a distinct subspecies that he labelled as Tetracanthagyna.

"[4]: 439  Ferdinand Karsch refused to recognize the proposed classification as a valid subgenus in his 1891 book Kritik des Systems der Aeschniden.

[5]: 79 [4]: 439  However, Robert McLachlan writing in the Transactions of the Royal Entomological Society of London, upon review of the available material stated that "not only is Tetracanthagyna valid, but also that its relationship to Gynacantha is perhaps not so intimate as has been thought."

[8] Tetracanthagyna plagiata has a variable distal transverse banding pattern on the forewings and hindwings, with males and some females sporting dark costal streaks.

[11] According to Leonard Tan of the blog Singapore Odonata, males lack the transverse brown patches near the wing tips that females have.

[6] Males have a pair of oreillets, lobes which help guide female genitalia into the proper position during mating,[13] on the second abdominal segment.

Watanabe (2003) recorded a female T. plagiata depositing its eggs into decaying wood, 150 centimeters above the water's surface.

[17]: 154  Larvae were found within Singapore's Central Catchment Nature Reserve at two separate sites (the MacRitchie Reservoir and the Nee Soon Swamp Forest).

[17]: 154  It is believed that the larvae feed on the shrimp species Macrobrachium trompii and Caridina temasek, as well as catfish, cyprinids, halfbeaks, and tadpoles in the wild.

Akin to other members of the family Aeshnidae, they display a crepuscular lifestyle, flying during the twilight period.

Streams in which Tetracanthagyna plagiata larvae were observed contained organic matter, including tree branches and leaf litter.

Female larvae are found in similar conditions, with vegetation such as sedges and ferns within the stream habitat in addition to trees providing shade.

The IUCN report stated that T. plagiata was potentially threatened by logging in its habitat, environmental degradation by mining developments, and by wood and pulp plantations.

[25] Leong et al. subsequently reported that the giant hawker has been seen multiple times outside of the Nee Soon Swamp Forest, being found within the broader context of the Central Catchment Nature Reserve within Singapore.

[11] In a 2016 revision of Murphy's previous work and an update of the national conservation status for various Odonata, T. plagiata was listed as "Restricted & Uncommon", receiving the designation of "Vulnerable".