The genus Orolestes contains some striking species. O. selysi is interesting in that the male comes in two wing forms : hyaline or marked blackish-brown with white patches near the tip.
Male (patch-winged form / October 2012-Cat Ba Island)
Prothorax green. Pterothorax bronzy green above (almost brownish in old individuals), not metallic ; sides with 2 or 3 stripes of different shades of green - more or less bluish in very mature males.
Abdomen bronzed green on dorsum of segments 1 and 2, bronzed black on the remainder, but segments 3 and 4 with a medial bluish area (sometimes only S3) ; margins of segments 7 to 9 minutely spined apically; segment 10 slightly notched. S8, 9 and 10 bluish.
The male comes in two wing forms : hyaline or partly opaque blackish-brown with lacteous patches near the tip.
Females very similar to males in colour and pattern, but wings always hyaline.
Note the greenish labrum and bases of mandibles.
Anal appendages : superiors black half as long again as segment 10, slender, regularly curved and forcipate, so that the apices meet; outer border finely spined along apical half ; internally there is a robust basal tooth on inner side and a dilatation which extends along inner border nearly to apex and ends in a triangular, acute tooth.
Note the margins of S7 to 9 minutely spined apically; S10 slightly notched
Female insert eggs into tree branch. She choosed a vertically directed plant stem.
She performs oviposition accompanied by its mate.
Two or three times I spotted the male drive away other males who wanted to mate with the female.
She performs oviposition accompanied by its mate.
Two or three times I spotted the male drive away other males who wanted to mate with the female.
Height of oviposition : 1,70m. The tree (no idea of the species) was in a rather open, muddy area - but certainly under water during the rainy season (from June to September).
The female bent its abdomen, segments 3-4 and 4-5 forming a right angle. Before she started to insert her ovipositor in the plant, she touched the bark with the ovipositor, maybe to provide information leading to a choice of insertion site. Then ovipositor valves protruded and began to move alternately, gradually penetrating into plant tissue.
During ovipositor insertion, the female rotated its abdomen from side to side. When its cutting valves become entirely inserted in the plant, the female stayed motionless for some seconds ; the egg (eggs?) was probably laid into the prepared hole during this time. Then she removed the cutting valves from the hole, moved a bit around the bark and carried on doing the same process.
During ovipositor insertion, the female rotated its abdomen from side to side. When its cutting valves become entirely inserted in the plant, the female stayed motionless for some seconds ; the egg (eggs?) was probably laid into the prepared hole during this time. Then she removed the cutting valves from the hole, moved a bit around the bark and carried on doing the same process.
The female was carefully guarded by the male throughout the whole procedure - a good boy !
In August 2013, newly emerged tenerals were spotted at a small pond together with their exuviae.
After checking the area I found many larvae of O. selysi floating motionless near the surface, close to shoreline vegetation or fallen branches, and some of them even starting to climb out of the water.
I stayed there one hour and half with the hope to witness the whole larval emergence process, but without success. I think the emergence occurs at night or at dawn - I was there at 10 a.m., too late probably.
The mouthparts of nymphs are cleverly modified to form an elongate, prehensile structure known as the mask. This structure is hinged in the middle and bears a pair of terminal claws. The whole arrangement is called the mask because when not in use and folded back under the head, it conceals the rest of the mouthparts. When food is sighted, the mask is thrown forward and the prey is impaled on the claws.
Larvae of O. selysi floating near the surface.
O. selysi larva (August 11, 2013)
A Zygoptera larva is recognizable by the three feather-like gills extending from the tip of its abdomen that the animal uses to "breathe" in its underwater environment (Anisoptera larvae breathe by means of internal rectal hills). When it does move, it swims much like a fish by making lateral serpentine movements with their abdomens (Anisoptera larvae tend to walk though they can turn on the speed with jet propulsion by expelling water from their anal respiratory orifice).
The pond where these larvae were photographed. A small (less than 20m²) square-shaped, probably man-made pond at the foothills of Tam Dao (alt. 300m a.s.l.), in degraded forest. Other species breeding there include Coeliccia scutellum, Tetrathemis platyptera, Polycanthagyna erythromelas, Orthetrum triangulare, O. chrysis, Zyxomma petiolatum.
O.selysi is known to occur in India (Darjeeling), China (Guangxi, Hainan), Vietnam, Laos and Taiwan.
In Vietnam this species must be either scarce or very local. First published record : 1904, "in Tonkin" (= northern Vietnam) by Martin. Second one in 2004, at Cat Ba Island, Quang Ninh Province, by Dô Manh Cuong. O. selysi is actually known from several localities in northern Vietnam.
I bumped into this species at 4 lowland sites : a small marsh partially wooded surrounded by forest (Cat Ba NP), a small (less than 20m²) pond in heavily degraded forest (foothills of Mount Tam Dao) and 2 tiny pools along rocky, forest brooks (foothills ot Tam Dao, Cuc Phuong NP).
Orolestes selysi is a forest dweller but certainly does not need good forest habitats.
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