Many people will be familiar with the sight of dragonflies (and damselflies) ‘in tandem’, without knowing exactly what is going on! I came across a pair of mating green marsh hawks in northern Thailand (Huai Hong Khrai Royal Development Study Centre) and managed to get a few shots of them hanging on to a grass stem whilst in copula.
Orthetrum sabina, the green marsh hawk, or slender skimmer, has a very wide distribution, from SE Europe as far as Australia and the western Pacific. I took these photographs in Thailand, where it is very common, but was amazed to learn from my copy of Dijkstra and Lewington, that it occurs in southern Turkey and some Greek Islands. Male and female green marsh hawks are very similar, the only way to tell them apart is via the genitalia: the males appendages are closed together, whilst the females’ are splayed (see below).
Assuming the female is receptive, the male takes hold of the female’s thorax, then bends his abdomen round so that he can grasp her head (N.B. damselfly males hold on to the front of the female’s thorax: see below, final photo). From this point on they are attached ‘in tandem’. Apparently, the male hangs on the female so tightly – using his appendages – that it can leave scars! Before mating takes place, the male has already transferred a sperm package from his primary genital opening – which is located where you might expect to find it, near the end of his abdomen! – to his secondary genitalia (into a slit in this so-called, penis) near the base of his abdomen. So the sperm is there waiting for something to happen! Damselfly males do this whilst they are in tandem (perhaps they are not so confident of finding a mate as dragonflies?!).
To facilitate the transfer of sperm, the male curves his abdomen downwards, whilst the female bends hers upwards.
N.B. it almost looks as though the female is pressing her genital opening against the base of the male thorax (above), but this is not the case as the first few segments of the abdomen are rather bulbous in this species. Thus, the pair complete a circle (or ‘wheel’) – shown below – which can be heart-shaped, but it depends on the angle of view. This pair was at a slight angle to the camera. The female has to bring her genital opening into contact with the male secondary genitalia. The pair remain in copula like this for some time; I’m not sure for how long in this species.
In Orthetrum species, the pair remain perched close to each other for a short time, 1-2 minutes in this species, before the female commences to deposit the eggs. This short interregnum is called a post-copulatory rest (PCR) period! Reportedly, the male Green marsh hawk flies closely around the perched female several times, at the start of PCR period, making downwards dipping movements with the abdomen towards the water, apparently mimicking oviposition. It almost sounds like he is telling to get on with it! It is possible that the female is waiting for a few moments to look out for predators, or test how good the male will be in guarding her as she carries out her oviposition. The male hovers above the female and tries to prevent the attentions of other males, thereby protecting his paternity of their offspring.
According to Odonata expert Dennis Farrell, Green marsh hawks makes a rather loud ‘clacking’ sound when they takes off, not something that I heard.
The whole affair looks rather more elegant in the much ‘slimmer’ damselflies, I think! See below.
Miller, P. L., & Miller, A. K. (1989). Post-copulatory” resting” in Orthetrum coerulescens (Fabricius) and some other Libellulidae: time for” sperm handling”?(Anisoptera). Odonatologica, 18(1), 33-41.