Diario del proyecto Dragonflies and Damselflies of Hong Kong

"Protosticta beaumonti" and "Agriomorpha fusca" are two different species of damselflies with similar appearance. Here's a comparison of their physical characteristics:

PLS refer to the photos at the links below.

Protosticta beaumonti
https://www.hkdragonfly.com/copy-of-91
https://www.inaturalist.org/taxa/110716-Protosticta-beaumonti/browse_photos

Agriomorpha fusca
https://www.hkdragonfly.com/copy-of-86
https://www.inaturalist.org/taxa/93565-Agriomorpha-fusca/browse_photos

Size: A. fusca is larger than P. beaumonti
Protosticta beaumonti is a relatively small damselfly species. Adult males typically have a total length ranging from 25 to 30 millimeters, while females can measure around 30 to 35 millimeters.
Agriomorpha fusca is larger, with males reaching about 35 to 40 millimeters in length and females measuring around 40 to 45 millimeters.

Coloration: P. beaumonti looks darker than A. fusca
Protosticta beaumonti males have a predominantly black or dark brown body. They may have pale yellow or cream-colored markings on their thorax and abdomen. Females of Protosticta beaumonti exhibit similar coloration but may have more prominent yellow or cream markings on their abdomen.
Agriomorpha fusca males have a primarily brown body coloration, ranging from light to dark brown, sometimes with hints of green. The thorax and abdomen may have darker brown or black markings. Their wings are usually transparent with a light brown or yellowish tint. Females of Agriomorpha fusca have a similar color pattern but with less distinct markings.

Wing Shape: P. beaumonti, pointed tips; A. fusca, slightly rounded.
Protosticta beaumonti damselflies have relatively narrow and elongated wings with pointed tips.
Agriomorpha fusca damselflies have broader wings with a slightly rounded appearance.

Last edit: 10:30am, Jun 9, 2023

There are two species of Genus Prodasineura in HK, they are P. croconota & P. autumnalis. The most distinctive feature of this genus is their very slim abdomen.

The female Orange-backed Threadtail (P. croconota) is virtually identical to the female Black Threadtail (P. autumnalis). The two cannot be reliably identified in the field unless in tandem with the very distinctive males. --- Reels & Zhang (2015).

The subspecies of B. chalybea seems to be promoted to species lately. The website of Agriculture, Fisheries and Conservation Department - Hong Kong Wetland Park updated its content and state the taxa as a species. From its URL, we still can tell its previously accepted taxa by the AFCD, the ssp, B. c. flavovittata.

https://www.wetlandpark.gov.hk/tc/biodiversity/beauty-of-wetlands/wildlife/brachydiplax-chalybea-flavovittata

Such a promotion is not inducted into the World Odonata List (yet), it's likely accepted in the near future or this is simply an error or an omission, which I would never consider a few years ago.

The survey (ウスバキトンボ全国マーキング調査) is conducted on the globe skimmers (Pantala flavescens, aka globe wanderer, 薄翅蜻蜓、黄蜻). According to the survey's homepage(1), till 21:45, Sept.14, there were 9,273 individuals(2) caught, marked then released and 52 of them re-caught.

In early August, NHK had been recruiting the volunteers for such a survey (3). It's a good example of citizen science project that ordinary people take parts in to help scientists reveal the secrets of the nature. If you are interested in the survey and feel like knowing better, pls visit its official homepage .
https://sites.google.com/view/usubaki/

Remarks:

(1) ウスバキトンボ全国マーキング調査 https://sites.google.com/view/usubaki/
(2) region breakdown: Okinawa 沖縄 1015、Kyushu 九州 2322、Shikoku 四国 44、Chūgoku 中国 56、Kinki 近畿 1339、Chyubu 中部 2773、Kanto 関東 1349、Tōhoku 東北 372、Hokkaido 北海道 3
(3)トンボ大調査　協力者募集します！
https://www.nhk.jp/p/darwin/ts/8M52YNKXZ4/blog/bl/p9oerqkz41/bp/pMjVEPW75M/

Though the subject, the San Francisco folktail (Ischnura gemina), is not about the species occurring in HK, it introduces the life of damselfly concisely. Specially, it's quite difficult for us to observe the life of damsel at nymph/larvae/naiad stage, so the footage about the submerged livelihood is quite precious. Besides, lots of close-up images allow us to see the features of damselfly clearly. I, therefore, think it a very nice video to watch. Let alone it's very well shot and the run time is only of 2 min 26 sec.