"Click! Click!" What sound is it?🤔
Don't worry, nothing is about to explode—The culprit behind this clicking noise may be a click beetle🐞. You may have heard that beetles (Order Coleoptera) is the most diverse group of organisms (at least for pluricellular organisms), including over 400,000 described species worldwide! Within them, the click beetles (Elateridae family) is the 9th most diverse family, with over 10,000 species (nearly as many as birds). These insects also present an interesting and unique ability – when the click beetle is turned upside down (because of a bad fall to escape a predator for instance), it can flip over by flexing its body, and bounce off the ground with its own strength to get back into the right position. When they do this and "jump", they produce a clicking sound which gives them their name.
In Hong Kong, click beetle species have been recorded so far, in which the largest and probably most iconic one is the Jewel Click Beetle, a.k.a. Large Green Click Beetle, 𝘊𝘢𝘮𝘱𝘴𝘰𝘴𝘵𝘦𝘳𝘯𝘶𝘴 𝘢𝘶𝘳𝘢𝘵𝘶𝘴 (Drury, 1773). This diurnal insect is widespread in Southern China, and there is a chance you can see them when you go for a hike! All click beetles of the genus 𝘊𝘢𝘮𝘱𝘴𝘰𝘴𝘵𝘦𝘳𝘯𝘶𝘴 have on their bodies a metallic luster, and our Jewel Click Beetle has a green metallic body which is indeed as beautiful as a piece of jewel. 💎
Beetles are insects that undergo complete metamorphosis, also known as holometabolous insects. When the click beetles are still at the larval stage, they are called wireworms. The wireworms are slender and have hard bodies, and they live in the soil, feeding on the roots of trees and plants🌱. Some wireworms are predators feeding on other soil animals. However, the adult click beetle has a different diet (and shape). They feed mainly on nectar, pollen and flowers, but sometimes also on soft-bodied insects such as aphids.
So, what allows the click beetle to do their remarkable jump? The answer is in their unique thoracic structure. There is a small protuberance, which acts as a latch, on the underside of the beetle's bodies between the front and middle legs. The energy for jumping can be stored and released using this little latch–which allows the insect to load an internal spring, and while releasing the spring, the beetle rapidly flexes its body between the thorax and the abdomen, propulsing itself into the air.
The reasons behind the click beetle's jump and its evolution is still under research. It is hypothesized that they mainly use it as a defense mechanism. When the click beetles feel threatened, they will drop on the ground and immediately play dead💀. The jumping ability helps them to get back into position. On the other hand, when the body is being held, the clicking may make it harder for them to be grasped and can create impact to aid their escape; even through the creation of a surprise effect in the predators.
Next time when you visit the museum, don't forget to check out our beautiful Jewel Click Beetle specimens!😎
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