Silhouette Dropwing, Trithemis hecate, Skraalvalvlerkie

Short description:

Silhouette Dropwing, Trithemis hecate, Skraalvalvlerkie is medium sized, blackish blue thorax and abdomen with dark maroon eyes and distinctly slender.

Family Libellulidae Leach, 1815

More Images:

Click on all images to enlarge or view more

Guides:

• Dropwings - General (Trithemis)
• By Colour - Blue
• By Colour - Red, Violet, Orange, Brown

Key identification features:

Male:

• Face brown. Labium light brown with large dark brown central area. Labrum dark brown. Anteclypeus light brown. Postclypeus dark brown. Frons light brown with dark brown margins. Frons and top of head dimpled, bright metallic mauve.
• Eyes are deep purple brown with a the lower part greyish mottled and a white band at the rear end of the eye. The outer edge of the back of the eye white. This is clearly visible. It consist of a narrow white band on the hind margin of the eye and white hair at the back of the eye and in the neck .
• Thorax dark blue, but pruinosity of thorax in life varies from pale to dark blue, brown or black. Ring of whitish hairs present on front of thorax and behind head, blackish hairs present on rest of thorax. Brown between the wings.
• Wings clear to slightly smoky with small dark orange/brown basal splash on hindwings. Venation is largely dark, brown to black, like veins of Pt. Ax veines 8½ to 9½. All wings with 2-8 cell doublings in radial planate (0-8). Front wing discoidal field Have 3-4 rows with 3-9 rows between anal loop and tornus. Arculus between Ax1-2, at most at Ax2 in hindwing
• Description of wing venation
• Pterostigmas buff between blackish veins, slightly lighter on underside, 2.9–3.0 mm.
• Abdomen segments 1 - 3 have brown markings  / This my become blue with age Abdomen blackish with light yellowish to brown, indistinct markings becoming almost invisible with age 

Female:

• Slender, yellowish and black.
• Face is pale yellow with black hairs. Top of head is metallic, with metallic band present on frons below top of head.
• Thorax has contrasting black and yellowish patches.
• Hindwings has small basal amber patch. Refer to male for wing venation.
• Abdomen is black with yellow dashes.

Habitat:

• Frequents standing and often temporary waters, but also flowing channels in marshes, in open landscapes. Often with emergent vegetation and a soft   muddy bottom.
• From 0 to 1700 m above sea level.

Behaviour:

• Very alert, perching on single reed stems, often far from the bank. It usually appears blackish, like a dark silhouette against the brightness of the open water.
• Female perches on twigs among trees, often far from water.

Compared with other species:

• When perching T. hecate appears dark blue to almost black with very dark eyes.
• A white band at the rear of the eye is clearly visible. This consist of a narrow white band on the hind margin of the eye and white hair at the back of the eye and in the neck .
• Halfshade Dropwing, T. aconite and T. Hecate are similar due to slender abdomen.
• Navy- T. Furva, Highlands T. dorsalis and Denim Dropwings T. donaldsoni, differ due to their broader abdomen.
  
• T. hecate has dullish brown abdominal marking, compared to yellowish markings on the abdomen of T.aconita and Orthetrum. trinacria. 
• Against the shiny water surface, the dark blue is not visible, and appearance is one of a black silhouette, looking like a small O. trinacria Long Skimmer.
• It’s very dark body, very slender abdomen and only 8½ - 9½ Ax (antenodal crossveins) are characteristic as is the notably large genital lobe.
• Female similar to Trithemis. stictica, Jaunty Dropwing,

Learn More about other Dropwings, (Trithemis) Species

Distribution:

South Africa:

• Occurs in coastal KwaZulu-Natal, MP and LP. 

Africa:

•  Botswana; Chad; Democratic Republic of the Congo; Gabon; Gambia; Guinee-Bissau; Kenya; Liberia; Mali; Mozambique; Namibia; Republic of South Africa; Senegal; Sierra Leone; South Sudan; Tanzania; Uganda; Zambia; Zimbabwe

Further reading:

Websites:
A Visual Guide to the Damselflies and Dragonflies of South Africa
The IUCN Red List of Threatened Species   Least Concern
African Dragonflies & Damselflies Online