Sound production by hawkmoth larvae and pupae through abdominal spiracles

Area of Science:

• Zoology
• Bioacoustics
• Insect Physiology

Background:

• Insects utilize defensive sounds for predator deterrence across various life stages.
• Understanding the ontogenetic variation in sound production mechanisms is crucial for insect communication research.

Purpose of the Study:

• To investigate differences in sound production characteristics, organs, and mechanisms between larvae and pupae of Phyllosphingia dissimilis.
• To compare the acoustic properties and anatomical sources of defensive sounds in different developmental stages of a single hawkmoth species.

Main Methods:

• Laboratory experiments involving tactile stimulation to simulate predator attacks on larvae and pupae.
• Analysis of sound pulses, including dominant frequency and sound pressure level, produced by each developmental stage.
• Identification of the specific spiracles utilized for sound generation in both larval and pupal stages.

Main Results:

• Final-instar larvae produce sounds (9.2–12.9 kHz; 50.2–62.4 dB SPL) by expelling air through the eighth abdominal (A8) spiracles.
• Pupae generate sounds (3.8–21.6 kHz; 42.0–53.5 dB SPL) by forcing air through abdominal spiracles A2–A7.
• Both larvae and pupae employ a comparable air-forcing mechanism for sound production, despite variations in spiracle usage.

Conclusions:

• The study reveals distinct abdominal spiracle involvement in sound production between Phyllosphingia dissimilis larvae and pupae.
• This research provides the first documented instance of sound production via abdominal spiracle airflow in insect pupae.
• The findings highlight ontogenetic plasticity in defensive sound production mechanisms within a single insect species.