Agriocnemis femina (Brauer, 1868)
Species: Agriocnemis femina (Brauer, 1868)
Common name(s): White-backed wisp, Variable wisp
Habitat: Water body (ponds, lakes, rivers) associated grassland
Distribution: Sylhet, Chittagong
Flight season: All over the year
Similar species: Agriocnemis pygmaea, Agriocnemis minima
Agriocnemis are the smallest damselflies of Bangladesh. A. femina shows different color variation in different developmental stages, this is why they are often called variable wisp. They are common however, due to their small size and difficulties to differentiate from A. pygmaea, they are often overlooked.
The male damselfly is a tiny one. The short abdomen measured 16-17 mm. Eyes of the damselflies is green with black capped above, blue or green post ocular spot present. Legs are pale yellow, the external side of the femora is black. The dorsum of the thorax blak with green or blue antehumeral stripe, that extends to the prothorax. Hind wing length 10-11 mm, wings are clear, pterostigma black. Abdominal segments are dorsally black , laterally blue or green. Anal appendages are orange. Below is a male with segment 8-10 dorsally black and orange ring in the apex of the segment.
The damselflies has two morph mainly, the blue morph and green morph. In blue morph, the antehumeral stripes, post ocular spots and lateral portion of the abdominal segments are blue. Abdominal segment 8-10 are completely orange.
The antehumeral stripes, post ocular spots and lateral portion of the segments are green, in green morph. Segment 8 black dorsally, yellow ventrally, segement 9 and 10 are yellow as well as anal appendages.
The pruinosed male of the species can be identified easily. As the male gets older, their thorax gets pruinosed.
The females of the species are difficult to identify. The female has two forms, red form and green form. The eyes are green, black cap above, no post ocular spot. Anterior lobe of the prothorax has a black spot, posterior lobe is large and elevated. Legs are whitish with black spine. Broad black stripe in the thorax, no clear antehumeral stripe. The wings are clear, yellow pterostigma. Abdominal segement 1-6 are red, broad black dorsal stripe present in segments 7-10.
I have photographed a female specimen which I believe is the intermediate form between the red morph and green morph. The antehumeral stripes are brick red, lateral portion of the thorax is turning into blue. Abdominal segments are yellow laterally.
The andromorph female is similar to male, the antehumeral black stripe absent and the terminal anal appendages are different,
I have documented a few matting pair of A. femina. Presented one is from Sylhet. In 12th October afternoon I spotted the pair from SUST campus. The male was not pruinosed and the female was the green form.
The copula with andromorph female, I have sighted from SUST campus at 19 May, 2015
It is very difficult to differentiate A. femina from A. pygmaea because they are very similar. Moreover, most often both species share the same microhabitat which makes it even more difficult. The best and simplest way to differentiate is by examining the anal appendages of the male specimen which are quiet different. The females are even more difficult to identify, however by close examining of the prothorax they can be differentiated. Finding a niche that contain either one of the species is an excellent way to study them. In Narsingdi, I found A. pygmaea only which makes it easy to monitor and study.