What’s the buzz? Ultrasonic and sonic warning signals in caterpillars of the great peacock moth (Saturnia pyri)

Abstract

Caterpillars have many natural enemies and, therefore, have evolved a diversity of antipredator strategies. Most research focuses on those strategies (crypsis, countershading, and warning coloration) targeting visually guided predators. In contrast, defensive sounds, although documented for more than a century, have been poorly studied. We report on a novel form of sound production--chirping--in caterpillars of the common European Great Peacock moth (Saturnia pyri). Chirps are broadband, with dominant peaks ranging between the sonic (3.7 kHz) and ultrasonic (55.1 kHz) and are generated by a rapid succession of mandibular "tooth strikes." Chirp trains are induced by simulated predator attacks and precede or accompany the secretion of a defensive chemical from integumental bristles, supporting our hypothesis that these sounds function in acoustic aposematism. We propose that these caterpillars generate multimodal warning signals (visual, chemical, and acoustic) to target the dominant sensory modalities of different predators, including birds, bats, and invertebrates.

Whistling in caterpillars (Amorpha juglandis, Bombycoidea): sound-producing mechanism and function

“…According to this classification scheme, the walnut sphinx would be classified as a non-regurgitator. This is in contrast to previous studies of sound production in caterpillars, where sound is strongly correlated with the occurrence of a chemical defense and believed to be aposematic (Brown et al, 2007;Bura et al, 2009). …”

“…Forwidespread in soft-bodied larvae of holometabolous insects. In Lepidoptera, two recent studies (Brown et al, 2007;Bura et al, 2009) show that sounds made by the mandibles in silk-moth caterpillars are accompanied by chemical defenses, and these are thought to function as warning sounds. Other preliminary reports suggest that sound production is widespread in the superfamily Bombycoidea (reviewed in Brown et al, 2007).…”

Variation on a Theme: Vibrational Signaling in Caterpillars of the Rose Hook-Tip Moth,Oreto rosea

“…The only morphological structure employed by O. rosea to produce vibrational signals are the mandibles, which do not appear to be specifically differentiated for sound production. There is mounting evidence demonstrating that the use of mandibles for acoustic signaling may be common in caterpillars (Yack et al 2001; Brown et al 2007; Fletcher et al 2006; Bowen et al 2008; Bura et al 2009). Although mandible drumming and scraping have already been described in two other species of Drepaninae (Yack et al 2001; Bowen et al 2008), lateral tremulation has not been reported until now.…”

Individual bumblebees vary in response to disturbance: a test of the defensive reserve hypothesis

“…These workers may contribute to nest defense by producing an acoustic signal that may either alert nestmates of a potential threat (Fletcher, 2007;Rohrig et al, 1999;Sen Sarma et al, 2002) or act as a warning directed toward the intruder (Bura et al, 2009;Brown et al, 2007;Jeanne, 1981;Kirchner and Röschard, 1999). Cameron (1989) categorized defensive, or guarding, behaviors inside the nest as 'perching' (i.e., standing motionless with antennae raised to examine those who pass by them), 'patrolling' (rapid walking around the nest), and 'buzzing' (Cameron, 1989).…”