A synthesis of deimatic behaviour.

Deimatic behaviours, also referred to as startle behaviours, are used against predators and rivals. Although many are spectacular, their proximate and ultimate causes remain unclear. In this review we aim to synthesise what is known about deimatic behaviour and identify knowledge gaps.

Octopamine receptor gene influences social grouping in the masked birch caterpillar.

Objective: Group-living plays a key role in the success of many insects, but the mechanisms underlying group formation and maintenance are poorly understood. Here we use the masked birch caterpillar, Drepana arcuata, to explore genetic influences on social grouping. These larvae predictably transition from living in social groups to living solitarily during the 3rd instar of development.

What Does an Insect Hear? Reassessing the Role of Hearing in Predator Avoidance with Insights from Vertebrate Prey.

Insects have a diversity of hearing organs known to function in a variety of contexts, including reproduction, locating food, and defense. While the role of hearing in predator avoidance has been extensively researched over the past several decades, this research has focused on the detection of one type of predator-echolocating bats. Here we reassess the role of hearing in antipredator defense by considering how insects use their ears to detect and avoid the wide range of predators that consume them.

Transcriptome analysis of a social caterpillar, Drepana arcuata: De novo assembly, functional annotation and developmental analysis.

The masked birch caterpillar, Drepana arcuata, provides an excellent opportunity to study mechanisms mediating developmental changes in social behaviour. Larvae transition from being social to solitary during the 3rd instar, concomitant with shifts in their use of acoustic communication. In this study we characterize the transcriptome of D.

Hearing in caterpillars of the monarch butterfly ().

Many species of caterpillars have been reported to respond to sound, but there has been limited formal study of what sounds they hear, how they hear them and how they respond to them. Here, we report on hearing in caterpillars of the monarch butterfly (). Fourth and fifth instar caterpillars respond to sounds by freezing, contracting, and flicking their thorax in a vertical direction.

Bark beetles use a spring-loaded mechanism to produce variable song patterns.

Many insects vary their song patterns to communicate different messages, but the underlying biomechanisms are often poorly understood. Here, we report on the mechanics of sound production and variation in an elytro-tergal stridulator, male bark beetles. Using ablation experiments coupled with high-speed video and audio recordings, we show that: (1) chirps are produced using a stridulatory file on the left elytron (forewing) and a protrusion (plectrum) on the seventh abdominal segment; (2) chirps are produced by 'spring stridulation', a catch-and-release mechanism whereby the plectrum catches on a file tooth and, upon release, springs forward along the file; and (3) variability in chirp types is caused by introducing multiple catch-and-release events along the file to create regular interruptions.

In that vein: inflated wing veins contribute to butterfly hearing.

Insects have evolved a diversity of hearing organs specialized to detect sounds critical for survival. We report on a unique structure on butterfly wings that enhances hearing. The Satyrini are a diverse group of butterflies occurring throughout the world.

What does a butterfly hear? Physiological characterization of auditory afferents in Morpho peleides (Nymphalidae).

Many Nymphalidae butterflies possess ears, but little is known about their hearing. The tympanal membrane of butterflies typically comprises distinct inner and outer regions innervated by auditory nerve branches NII and NIII and their respective sensory organs. Using the Blue Morpho butterfly (Morpho peleides) as a model, we characterized threshold and suprathreshold responses of NII and NIII.

Vocalization in caterpillars: a novel sound-producing mechanism for insects.

Insects have evolved a great diversity of sound-producing mechanisms largely attributable to their hardened exoskeleton, which can be rubbed, vibrated or tapped against different substrates to produce acoustic signals. However, sound production by forced air, while common in vertebrates, is poorly understood in insects. We report on a caterpillar that 'vocalizes' by forcing air into and out of its gut.

Why do caterpillars whistle at birds? Insect defence sounds startle avian predators.

Many insects produce sounds when attacked by a predator, yet the functions of these signals are poorly understood. It is debated whether such sounds function as startle, warning or alarm signals, or merely serve to augment other defences. Direct evidence is limited owing to difficulties in disentangling the effects of sounds from other defences that often occur simultaneously in live insects.

A Comparative Analysis of Sonic Defences in Bombycoidea Caterpillars.

Caterpillars have long been used as models for studying animal defence. Their impressive armour, including flamboyant warning colours, poisonous spines, irritating sprays, and mimicry of plant parts, snakes and bird droppings, has been extensively documented. But research has mainly focused on visual and chemical displays.

Shaking Youngsters and Shaken Adults: Female Beetles Eavesdrop on Larval Seed Vibrations to Make Egg-Laying Decisions.

Egg-laying decisions are critical for insects, and particularly those competing for limited resources. Sensory information used by females to mediate egg-laying decisions has been reported to be primarily chemical, but the role of vibration has received little attention. We tested the hypothesis that vibrational cues produced by feeding larvae occupying a seed influences egg-laying decisions amongst female cowpea beetles.

What is the password? Female bark beetles (Scolytinae) grant males access to their galleries based on courtship song.

Acoustic signals are commonly used by insects in the context of mating, and signals can vary depending on the stage of interaction between a male and female. While calling songs have been studied extensively, particularly in the Orthoptera, much less is known about courtship songs. One outstanding question is how potential mates are differentiated by their courtship signal characteristics.

Hearing in the crepuscular owl butterfly (Caligo eurilochus, Nymphalidae).

Tympanal organs are widespread in Nymphalidae butterflies, with a great deal of variability in the morphology of these ears. How this variation reflects differences in hearing physiology is not currently understood. This study provides the first examination of hearing organs in the crepuscular owl butterfly, Caligo eurilochus.

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

Caterpillar defenses have been researched extensively, and, although most studies focus on visually communicated signals, little is known about the role that sounds play in defense. We report on whistling, a novel form of sound production for caterpillars and rare for insects in general. The North American walnut sphinx (Amorpha juglandis) produces whistle 'trains' ranging from 44 to 2060 ms in duration and comprising one to eight whistles.

The evolutionary origins of ritualized acoustic signals in caterpillars.

Animal communication signals can be highly elaborate, and researchers have long sought explanations for their evolutionary origins. For example, how did signals such as the tail-fan display of a peacock, a firefly flash or a wolf howl evolve? Animal communication theory holds that many signals evolved from non-signalling behaviours through the process of ritualization. Empirical evidence for ritualization is limited, as it is necessary to examine living relatives with varying degrees of signal evolution within a phylogenetic framework.

Variation on a theme: vibrational signaling in caterpillars of the rose hook-tip moth, Oreto rosea.

Vibrational communication in hook-tip moth caterpillars is thought to be widely used and highly variable across species, but this phenomenon has been experimentally examined in only two species to date. The purpose of this study is to characterize and describe the function of vibrational signaling in a species, Oreta rosea Walker 1855 (Lepidoptera: Drepanidae), that differs morphologically from previously studied species. Caterpillars of this species produce three distinct types of vibrational signals during territorial encounters with conspecifics--mandible drumming, mandible scraping and lateral tremulation.

Auditory mechanics and sensitivity in the tropical butterfly Morpho peleides (Papilionoidea, Nymphalidae).

The ears of insects exhibit a broad functional diversity with the ability to detect sounds across a wide range of frequencies and intensities. In tympanal ears, the membrane is a crucial step in the transduction of the acoustic stimulus into a neural signal. The tropical butterfly Morpho peleides has an oval-shaped membrane at the base of the forewing with an unusual dome in the middle of the structure.

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

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.

Hearing in a diurnal, mute butterfly, Morpho peleides (Papilionoidea, Nymphalidae).

Butterflies use visual and chemical cues when interacting with their environment, but the role of hearing is poorly understood in these insects. Nymphalidae (brush-footed) butterflies occur worldwide in almost all habitats and continents, and comprise more than 6,000 species. In many species a unique forewing structure--Vogel's organ--is thought to function as an ear.

The eyes of Macrosoma sp. (Lepidoptera: Hedyloidea): a nocturnal butterfly with superposition optics.

The visual system of nocturnal Hedyloidea butterflies was investigated for the first time, using light and electron microscopy. This study was undertaken to determine whether hedylids possess the classic superposition eye design characteristic of most moths, or apposition eyes of true butterflies (Papilionoidea), and, to gain insights into the sensory ecology of the Hedyloidea. We show that Macrosoma heliconiaria possesses a superposition-type visual mechanism, characterized by long cylindrical crystalline cones, a lack of corneal processes, 8 constricted retinular sense cells, rhabdoms separated from the crystalline cones forming a translucent 'clear zone', and tight networks of trachea that form a tapetum proximal to the retina and which also surround the rhabdoms to form a tracheal sheath.

Neuroethology of ultrasonic hearing in nocturnal butterflies (Hedyloidea).

Nocturnal Hedyloidea butterflies possess ultrasound-sensitive ears that mediate evasive flight maneuvers. Tympanal ear morphology, auditory physiology and behavioural responses to ultrasound are described for Macrosoma heliconiaria, and evidence for hearing is described for eight other hedylid species. The ear is formed by modifications of the cubital and subcostal veins at the forewing base, where the thin (1-3 microm), ovoid (520 x 220 microm) tympanal membrane occurs in a cavity.

Clicking caterpillars: acoustic aposematism in Antheraea polyphemus and other Bombycoidea.

Acoustic signals produced by caterpillars have been documented for over 100 years, but in the majority of cases their significance is unknown. This study is the first to experimentally examine the phenomenon of audible sound production in larval Lepidoptera, focusing on a common silkmoth caterpillar, Antheraea polyphemus (Saturniidae). Larvae produce airborne sounds, resembling ;clicks', with their mandibles.

The structure and function of auditory chordotonal organs in insects.

Insects are capable of detecting a broad range of acoustic signals transmitted through air, water, or solids. Auditory sensory organs are morphologically diverse with respect to their body location, accessory structures, and number of sensilla, but remarkably uniform in that most are innervated by chordotonal organs. Chordotonal organs are structurally complex Type I mechanoreceptors that are distributed throughout the insect body and function to detect a wide range of mechanical stimuli, from gross motor movements to air-borne sounds.