Keith Wilson is an amateur naturalist who has contributed to the knowledge of Hong Kong's wildlife. A fisheries biologist by profession, he has devoted much of his free time since arriving in 1991 in Hongkong to studying dragonflies, helping boost the Hongkong's species total from 65 to 108 today. Among his finds have been several species which are new to science, like the Spangled Shadow-emerald Macromidia ellenae. Wilson made his discovery at Sha Lo Tung in the eastern New Territories, which is Hong Kong's main hotspot for dragonflies, and the world's only place that's home to two species of Macromidia, with a commoner relative sharing the streams. While a few more have been found at nearby Wu Kau Tang, Macromidia ellenae is one of just four dragonfly species that are known only from Hong Kong and Wilson suspects it may be truly unique to the Hong Kong.

In both a local and global context, Sha Lo Tung has very high ecological value. More species of dragonfly have been recorded here than anywhere else in Hong Kong: by 2003, at least 72 dragonfly species had been recorded; this figure represents 65% of the total for the whole of Hong Kong. One of the dragonfly species, Spangled Shadow-emerald (Macromidia ellenae), is endemic to Hong Kong. Sha Lo Tung is also the only site in the world to process two Macromidia species, namely South China Cruiser (Macromida katae) and Spangled Shadow-emerald (Macromidia ellenae).

Macromidia ellenae isn't spectacular to look at - it's only around 3 cm long, with yellow markings on its body. For much of the day, it rests on vegetation hanging over streams. But, if it's like close relatives, Macromidia ellenae becomes active as rain threatens or dusk approaches, circling and zigzagging low over streams and, its sharp eyes on the lookout for mosquitoes and other insect prey, flying long into summer nights.

It is a medium-sized forest dragonfly, has distinctive yellow spots on its thorax. the male is length around 32 mm from Abdomen to Anal Appendages with hindwing span 30.5mm, the female is length around 28.5 mm with hindwing span 29 mm. Distribution in Hong Kong: Double Island, Hok Tau, Luk Keng, Wu Kau Tang, Sha Lo Tung and Sheung Wo Hang. 

AFCD Assessment listed as Uncommon, Fellowes et al. (2002) listed as Global Concern