Encounters with new animals often represent enjoyable experiences, but in some cases, they can be very unpleasant to our noses. Indeed, several animal species are famous for the strong odours they produce, but one group of insects in particular, release such an awful smell that they have been named after it, - the stink bugs (Hemiptera, Pentatomidae). But let’s not judge these creatures too quickly. Instead, let’s explore why and how they produce such odours.
Just like you will, a predator will probably be absolutely disgusted by the smell or taste or a stink bug. So when these insects are in danger, they discharge this volatile secretion as a defensive weapon. Apart from giving out the foul odour, the secretion also produces a burning sensation and is considered distasteful. The predators would learn to leave the bugs alone after a previous unpleasant encounter. This secretion, however, has another maybe more surprising function. It is also used for triggering the aggregation or attraction of the opposite sexes- after all, all tastes are in nature!
The stinky secretion is produced by the scent glands found in the metathoracic region (hindmost part of the thorax) in adults, while those are found in the abdomen in nymphs (the term used to call the juvenile stage in Hemiptera). Take the lychee stink bug, 𝘛𝘦𝘴𝘴𝘢𝘳𝘢𝘵𝘰𝘮𝘢 𝘱𝘢𝘱𝘪𝘭𝘭𝘰𝘴𝘢 (Drury, 1770), as an example, their dramatic changes in the appearance between the nymphal and adult stages have already hinted at the different positions of the scent glands. We can see a hole in the thorax through which the smelly secretion is released, and a specialized area (evaporatorium) that promotes the spread of the scent.
Lychee stink bug 𝘛. 𝘱𝘢𝘱𝘪𝘭𝘭𝘰𝘴𝘢 loves sucking the sap and juice of 𝘓𝘪𝘵𝘤𝘩𝘪 𝘤𝘩𝘪𝘯𝘦𝘯𝘴𝘪𝘴 (lychee) and 𝘋𝘪𝘮𝘰𝘤𝘢𝘳𝘱𝘶𝘴 𝘭𝘰𝘯𝘨𝘢𝘯 (longan). Both of them are common fruit trees in Hong Kong and you are very likely to encounter a lychee stink bug. However, don’t stick your nose into the stink bug's life or you may regret it!
Text: Jennifer Poon
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