The evolution and functional morphology of hemipteran vibrational organs

Acoustic and vibrational signals are among the prevalent modes of arthropod communication, exploited by at least 230,000 species (Cocroft and Rodríguez, 2005). Vibroacoustic signals dominate hemipteran communication, being generated by stridulation, wing buzzing, percussion, membrane buckling and shaking of the body relative to the legs (tremulation). The last two mechanisms are produced by basi-abdominal organs known as tymbals in Cicadomorpha and tergal plates in Heteroptera, respectively, whose systematic distribution and homologies are poorly understood. Other groups, such as the planthoppers (Fulgoromorpha) and moss bugs (Coleorrhyncha), are more enigmatic, as they generate vibrations with mechanisms which have so far remained unexplored. In spite of limited available morphological evidence, it has been suggested that all hemipteran basi-abdominal organs are homologous and evolved once (Tymbalia hypothesis) (Wessel et al, 2014). The aim of this dissertation is to elucidate the evolution of hemipteran vibroacoustic organs by describing their biomechanics, morphology and systematic distribution, and to use the resulting data to test the claims of the Tymbalia hypothesis. I used a combination of state-of-the-art methods such as X-ray synchrotron microtomography and confocal laser scanning microscopy with more traditional techniques 10 (e.g. scanning electron microscopy), in order to describe the morphology of vibroacoustic organs from taxa selected from across hemipteran phylogeny. For experiments with living specimens, I used laser Doppler vibrometers to record their vibrational signals and high speed cameras to film the motion of the organs responsible for their production. I find that Fulgoromorpha produce vibrational signals with a novel mechanism I term the “snapping organ”, which is biomechanically and morphologically distinct from tymbals. Furthermore, re-examination of supposed stridulatory organs in derbid planthoppers reveals that they are instead more likely to be used in chemical signalling. I show that tymbals are ubiquitous in Cicadomorpha, and that their segmental affinities were misinterpreted by most previous studies. Finally, I document the tergal plate in a systematically important group of Heteroptera, and I challenge the evidence used to support the Tymbalia hypothesis. Overall, this dissertation documents the morphology and systematic distribution of hemipteran vibroacoustic organs in unprecedented detail, and provides a significant step towards resolving their evolutionary origins.</p

A New species of Henicocephaloides from Eastern Madagascar (Hemiptera: Heteroptera: Reduviidae)

Henicocephaloides raunoi sp. nov. (Hemiptera: Heteroptera: Reduviidae: Physoderinae) is described based on a single male specimen from Eastern Madagascar, which is deposited in the collection of the Moravian Museum, Brno. The newly described species is illustrated and compared to Henicocephaloides fulvescens Villiers, 1962. A revised generic diagnosis is also provided

A New species of Henicocephaloides from Eastern Madagascar (Hemiptera: Heteroptera: Reduviidae)

Henicocephaloides raunoi sp. nov. (Hemiptera: Heteroptera: Reduviidae: Physoderinae) is described based on a single male specimen from Eastern Madagascar, which is deposited in the collection of the Moravian Museum, Brno. The newly described species is illustrated and compared to Henicocephaloides fulvescens Villiers, 1962. A revised generic diagnosis is also provided

On the morphology and possible function of two putative vibroacoustic mechanisms in derbid planthoppers (Hemiptera: Fulgoromorpha: Derbidae)

A mechanism involving interaction of the metathoracic wing and third abdominal segment of derbid planthoppers was first discovered over a century ago, and interpreted as a stridulatory organ for sound production. Although referred to occasionally in later taxonomic works, the detailed morphology, systematic distribution, and behavioural significance of this structure have remained unknown, and its proposed use in sound production has never been corroborated. Here we examine the distribution and morphology of the supposed stridulatory organ of Derbidae and the recently-described vibratory mechanism of planthoppers – the snapping organ, across 168 species covering the entire taxonomic spectrum of the family. We find that many derbids possess snapping organs morphologically similar to those of other planthoppers, and find no evidence for the presence of tymbal organs, which were previously thought to generate vibrational signals in derbids. We find the supposed stridulatory mechanism to be widespread in Derbidae, and conclude that it provides several systematically and taxonomically important characters. Nevertheless, its morphology appears unsuitable for the production of sound, and we instead speculate that the mechanism plays a role in spreading chemical secretions or wax. Finally, we observe wax production by tergal glands in derbid larvae, and illustrate their external morphology in adults

Redescription of the Planthopper Bursinia genei (Dufour, 1849), with a new record from Greece (Hemiptera: Fulgoromorpha: Dictyopharidae)

Bursinia genei (Dufour, 1849) is the most widespread species of the planthopper subfamily Orgeriinae (Hemiptera: Fulgoromorpha: Dictyopharidae) in Europe, found from the Iberian Peninsula to the Western Balkans. However, its diagnostically important genitalia and biology have been insufficiently described. We employ state-of-the-art synchrotron X-ray microtomography and photomicrography to re-describe B. genei, and to study the morphology of both its sexes in unprecedented detail. By examining specimens from across the distribution of B. genei, we find that they probably belong to a single, broadly distributed morphospecies. Our morphological examination allowed us to make inferences on its jumping mechanism and capacity for vibrational communication. We also record B. genei for the first time from Greece, further extending the range of this elusive species. Detailed information on the habitat of B. genei is also provided

Redescription of the Planthopper Bursinia genei (Dufour, 1849), with a new record from Greece (Hemiptera: Fulgoromorpha: Dictyopharidae)

Bursinia genei (Dufour, 1849) is the most widespread species of the planthopper subfamily Orgeriinae (Hemiptera: Fulgoromorpha: Dictyopharidae) in Europe, found from the Iberian Peninsula to the Western Balkans. However, its diagnostically important genitalia and biology have been insufficiently described. We employ state-of-the-art synchrotron X-ray microtomography and photomicrography to re-describe B. genei, and to study the morphology of both its sexes in unprecedented detail. By examining specimens from across the distribution of B. genei, we find that they probably belong to a single, broadly distributed morphospecies. Our morphological examination allowed us to make inferences on its jumping mechanism and capacity for vibrational communication. We also record B. genei for the first time from Greece, further extending the range of this elusive species. Detailed information on the habitat of B. genei is also provided

The pregenital abdomen of Enicocephalomorpha and morphological evidence for different modes of communication at the dawn of heteropteran evolution

The internal and external anatomy of the posterior metathoracic region, pregenital abdomen, and associated nervous system of the heteropteran infraorder Enicocephalomorpha are thoroughly described, using an array of state-of-the art techniques. Based on morphology, it is hypothesised which modes of communication these insects use. This study is based primarily on an undescribed species of Cocles Bergroth, 1905 (Enicocephalidae) and another undescribed species of Lomagostus Villiers, 1958 (Aenictopecheidae), but additional representatives of the infraorder are also examined. Our results are compared with the literature on other Heteroptera. The metathoracic scent gland system of Enicocephalomorpha uses the same muscles as that of more derived Heteroptera, although the efferent system is different. The presence of a tergal plate and well-developed longitudinal musculature in the families Enicocephalidae and Aenictopecheidae, as well as a sexually dimorphic set of sclerites and membranes that allow an as yet undetermined type of motion, may indicate the presence of vibrational signaling in the infraorder, although experimental confirmation is required. Our findings raise new research questions regarding heteropteran functional morphology and communication

The pregenital abdomen of Enicocephalomorpha and morphological evidence for different modes of communication at the dawn of heteropteran evolution

The internal and external anatomy of the posterior metathoracic region, pregenital abdomen, and associated nervous system of the heteropteran infraorder Enicocephalomorpha are thoroughly described, using an array of state-of-the art techniques. Based on morphology, it is hypothesised which modes of communication these insects use. This study is based primarily on an undescribed species of Cocles Bergroth, 1905 (Enicocephalidae) and another undescribed species of Lomagostus Villiers, 1958 (Aenictopecheidae), but additional representatives of the infraorder are also examined. Our results are compared with the literature on other Heteroptera. The metathoracic scent gland system of Enicocephalomorpha uses the same muscles as that of more derived Heteroptera, although the efferent system is different. The presence of a tergal plate and well-developed longitudinal musculature in the families Enicocephalidae and Aenictopecheidae, as well as a sexually dimorphic set of sclerites and membranes that allow an as yet undetermined type of motion, may indicate the presence of vibrational signaling in the infraorder, although experimental confirmation is required. Our findings raise new research questions regarding heteropteran functional morphology and communication