If you ever have the opportunity to hike along streams, it shouldn’t be hard for you to spot a few dragonflies and damselflies hovering nearby . Of the 6400 species of Odonata (i.e. dragonflies and damselflies) described globally, 130 species have been recorded in Hong Kong, with the first species recorded back in the 1850s, being the black-banded gossamerwing, 𝘌𝘶𝘱𝘩𝘢𝘦𝘢 𝘥𝘦𝘤𝘰𝘳𝘢𝘵𝘢 Hagen 1853. It is a common damselfly in Hong Kong, also found around the coastal regions of Southern China . With a size of around 40 mm, they are skillful aerial predators which can feed on smaller insects like mosquitoes, butterflies, moths and bees up to a few meters above ground level.
The males and females of 𝘌𝘶𝘱𝘩𝘢𝘦𝘢 𝘥𝘦𝘤𝘰𝘳𝘢𝘵𝘢 are characterized by different patterns, with males having a signature black squared-shaped spot on their wings and a black body, while females generally have prominent yellow stripes along their bodies and lacking spots on their wings. This is an excellent example of sexual dimorphism, where males and females of a certain species exhibit significant differences in size and appearance. But why do individuals of the same species present such differences between sexes? Most damselfly species, as well as a good number of other animal species, have males being larger in size and bearing brighter colors than females, so that they can attract females with various visuals and behaviours to win a chance to mate with them .
During the mating season, male damselflies would secure a specific territory in streams and ponds to attract females . In some damselfly species, like the Common Dancing Jewel, 𝘗𝘭𝘢𝘵𝘺𝘤𝘺𝘱𝘩𝘢 𝘤𝘢𝘭𝘪𝘨𝘢𝘵𝘢, males even actively search for females to perform some prepared choreography in front of them - a bit of popping with wing vibrations, flexing their “abs” by bending their abdominal tip downwards … basically any steps you could think of to win the ladies’ hearts. Once a pair has been made, they are ready for their courtship ritual -- the “mating wheel”.
The male has a pair of claspers located at the tip of his abdomen which is used to grip onto the top of the female’s thorax - just like gripping onto someone by their neck. This is known as a “tandem linkage” , and it actually helps them to “communicate” ! Oftentimes the grooves on females are species-specific – meaning that if a male of another species has mistakenly clasped onto the wrong female, or if a particular males’s claspers doesn’t really fit well into the grooves, the female can decide whether to abandon this mating ritual or not. After forming a tandem linkage, the female would bend its abdomen with its ovipositor (the organ used for egg laying) at the tip to meet with the male’s genitalia (the sexual organs) located near the underside of its thorax, so that the male can then transfer its sperms to the female’s body. This mating position might seem one-of-a-kind, but to our eyes, it can appear like a romance - with their bodies forming a heart when mating!
When the mating ritual of 𝘌𝘶𝘱𝘩𝘢𝘦𝘢 𝘥𝘦𝘤𝘰𝘳𝘢𝘵𝘢 is complete, the female would then lay eggs onto submerged host plants in the water. To do so, the female will dive underwater , sometimes as deep as 10 cm, grasping the submerged plant leaf to resist current and break the water tension. There the female uses its ovipositor to lay eggs directly within the plant tissue, using their rear end to cut open plant tissues and lay eggs one by one, a strategy known as endophytic oviposition . This contrasts with most other species of Euphaea which usually lay their eggs on the plant surface, or on other substrates (e.g. logs ), which is referred to as exophytic oviposition. Throughout the process, the male protects her either by maintaining their tandem linkage or hovering around the female to make sure no strangers come around to disturb the egg-laying process . What a distinguished gentleman to protect the “damsels in distress” !
Next time you go on a wild adventure, try to keep your eyes on nearby aquatic plants to witness this beautiful mating ritual . In the meantime, visit the Hong Kong Biodiversity Museum to appreciate the diversity of damselflies and dragonflies (as well as their strange looking babies) and learn more about them!
Text: Rachel Au
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