Cryptophaea vietnamensis (J.V. Tol & Rozendaal, 1995)

This Euphaeid was originally described in 1995 as Bayadera vietnamensis by Van Tol & Rozendaal from Vietnam (Nghe Tinh Province, altitude 100 m). In 2003, Wilson & Reels found it in Guangxi, southern China. They described for the first time the female and decided to place the species in the genus Schmidtiphaea. In 2003, Hämäläinen transferred it in the new genus Cryptophaea. 
Cryptophaea comes from the Greek Kryptos (=“hidden or concealed”) and refers to the fact that Cryptophaea species are rather elusive insects, inhabitants of shadowy streams. 

Cryptophaea species have a small and slender thorax, narrow hyaline wings and very long abdomen. Cryptophaea differs from Schmidtiphaea and Bayadera in many aspects (for more details, see Hämäläinen, 2003).

Full mature male.

The male show a shining black synthorax conspicuously patterned with blue and green. Dorsum of synthorax bears a crescent-shaped marking. 

Abdomen wholly black. Last abdominal segments pruinose in mature specimens.

Legs black, but anterior side of trochanters and femora blue-green. 

Anal appendages blackish; distal half of superiors strongly bent inwards and downwards, dorso-ventrally compressed. Inferiors short, acutely pointed.

With its bright orange patterned thorax, the mature female is really stunning. The first time I spotted it, at Cuc Phuong, I had absolutely no idea what it was. I sent a photo to Matti Hämäläinen who kindly answered me and identified it as Cryptophaea vietnamensis.  I was astonished by the differences in shape and colour pattern between the two sexes.

Prothorax matt black with large central lateral pale spot coloured bright orange. Synthorax black with bright orange pattern on dorsum, paler at sides.

Abdomen black with yellow-orange lateral stripes.

The strikingly colourful dimorphic female. 

Labrum, sides of face along the eyes glossy bright orange.

Female ovipositing in mossy rock.

Immature female. Orange synthorax/prothorax markings of the mature female replaced by violet. Abdomen darker.

A teneral male, also with violet markings

Unlike its name suggests, Cryptophaea vietnamensis is not an endemic of Vietnam. It has also been reported in southern China (Guangxi) and Laos.

I spotted this species at Ba Vi (Hanoi, 700m alt.), Cuc Phuong (Ninh Binh Province, 350m alt.), Mâu Son (Lang Son Province, 1000m) and Xuân Son (Phu Tho Province, 400m) National Parks, and also in the margin of Thuong Tiên Natural Reserve (Hoa Binh Province, 400-500m alt.). In Vietnam, this species is also known, qt least, from Tam Dao National Park (Vinh Phuc Province), Thanh Chuong district (Nghe An Province), Son Kim (Ha Tinh Province), Ngoc Linh mountain (Kon Tum Province) and Hon Ba Natural Reserve (Khanh Hoa Province). 
I found it along swift, well-shaded, rocky-bottomed streams or streamlets, in both relatively untouched or secondary forests. Most of the individuals have been observed perching on twigs along the streams when the sun poked through the canopy. Few individuals were seen when it was overcast.