Abstract: 【Aim】 There are a variety of defense mechanisms used against predators in the animal kingdom. Some lepidopteran pupae can make a wriggling sound when they are mechanically stimulated. 【Methods】 We observed the morphology characteristics of acoustic 
organs of Papilio xuthus pupae under scanning electron microscope and analyzed the acoustic characteristics of captured sounds using Audacity software. 【Results】The pupae of P. xuthus produce a regular hissing sound by their acoustic organs located in the intersegmental membranes between their 4th-5th and 5th-6th abdominal segments. The sound-producing organs are composed of scrapers and plates, both of which are composed of multiple layers of chitin. There are totally 50-90 protuberances on scrapers and plates. When the abdomen of the pupae is stimulated by the antennae of the parasitoids for more than 30 s, the scrapers and plates will quickly rub against each other repeatedly wiggling from one side to another side of the pupal abdomen to make sounds. The sounds are detected to be composed of a series of short pulses that occur three times every 2 000-3 000 ms. The frequency band is very wide, mainly distributed in the 5-20 kHz range. The activity of fresh pupae is different from that of overwintering ones, resulting in different sound intensities. 【Conclusion】 We firstly described the structure of sound-producing organs of P. xuthus pupae with mechanical stimulation and the results support the hypothesis that the pupae of some butterflies have evolved a special defense mechanism (acoustic defense) against parasitoids. In addition, the sound-producing organs of the same species at different geological areas can generate dialectal phenomena by comparing the characteristics of the acoustic waves of P. xuthus pupae from two different habitats.

Key words: Papilionidae; Papilio xuthus, ultrasound, acoustic defense, morphology, dialect; adaptive evolution