The antennae of the ambrosia beetle Trypodendron lineatum (Olivier) were examined with the light and electron microscopes to determine the types, distribution, and structure of sense organs found thereon. At least six types of sense organs were found, with an additional seventh cuticular structure, the hypodermal gland pore, which is thought to be non-sensory. The sensilla are sensilla chaetica, three types of sensillum tri-choideum, sensilla basiconica, and sensilla campaniformia. Distribution maps of the various sensillum types and the gland pores are presented, for one each of female and male left antenna. Sensilla chaetica, evenly distributed over all parts of the antennae, as well as the rest of the body, consist of a long thick-walled hair 20 to 140 micra long which articulates in a socket composed of a hair root, socket lining, and spongy cylinder. A single bipolar neuron terminates in a scolo-pale attached at one side of the hair base. Sensilla trichoidea, Type I, situated at the base of the scape and the base of the first funicular segment, are short thin hairs articulating in a socket. Their fine structure and innervation are not known. Sensilla trichoidea, Type II, found on the distal periphery of the club only, consist of sharply pointed smooth hairs 18 to 25 micra long, the hair wall being thin and perforated. The hair is solidly joined to the body cuticle. The sensillum has two bipolar neurons, the dendrites of which extend, with slight branching, to the distal limits of the hair lumen. No dendritic endings could be demonstrated at the hair perforations. Sensilla trichoidea, Type III, are evenly distributed over the distal half of the anterior club surface. The hair is 26 to 36 micra long, blunt-tipped, and curved in reverse, with the result that the hairs protrude at right angles to the club surface and beyond all other vestiture. The hair articulates in a socket, and has a double lumen. The dendrites of four to seven bipolar neurons extend through the eccentric small lumen to the hair tip, where, presumably, they are open to the air. Sensilla basiconica cover both club surfaces. At least two types exist, one group being short pegs 6 to 8 micra long, and another group being longer pegs or hairs llj to 18 micra long. The long sensilla basiconica have a thin perforated hair wall, the openings being slit-shaped (700Å by 100 to 200Å). The two nerve cells of this sensillura send two distal processes into the hair where subsequent repeated branching occurs. The relationship of the dendrite branches to the hair perforations is not clear. Sensilla campaniformia are found in small numbers on all parts of the antennae, as well as other parts of the body. They consist of a short thin canal leading from the outside, to a sub-surface dome 3 micra in diameter, in the centre of which lies the nerve ending similar in appearance to the scolo-pale and nerve of the sensillum chaeticum. Also, a cross section of the antennal nerve in the proximal portion of the scape revealed about 2100 axons. A count of the sensilla, corrected for the number of sense cells present per sensillum, gave expected axon numbers of 1845 and 1921 for female and male antennae, respectively, with Johnston's organ not accounted for. Since more axons than expected are present, axon fusion is considered unlikely. This sudy may serve as the basis for further electrophysiological work to determine the functions of the various sense organs. / Science, Faculty of / Zoology, Department of / Graduate

The behaviour of the ambrosia beetle Trypodendron llneatum (Olivier) has been considered in respect to illumination, body moisture and host factors. The investigation was designed to study potential uses of this insect as a test instrument for chemical studies of host wood attractants. A preliminary study of host attractants was also conducted using a newly-proposed bioassay technique. Monochromatic light at the wavelength 543 millimicrons was found to be the sole peak of stimulation to this insect in the visible spectrum. Beetles displayed a positive photic response by walking toward the source of light. A decrease in sensitivity occurred on either side of this peak, and in the longer wavelengths the sensitivity to light diminished at 735 millimicrons. Evidence to date indicated a second peak of sensitivity in the ultraviolet region of the spectrum; the latter appearing to be much greater than the peak in the visible spectrum. The intensity of any wavelength was also found to be a limiting factor in affecting beetle response, although in the longer wavelengths the sensitivity appeared to be a function of wavelength alone. Monochromatic light as a standard has been proposed for future bioassay techniques to act in opposition to odour stimuli. Red illumination was found to be effective in simulating darkness to T. lineatum. ‘Green’ unattractive sapwood shavings of Douglas-fir after placement under oxygen deficient conditions became attractive to T. lineatum. Maximum attractiveness was indicated in wood placed under anaerobiosis for 20 to 26 hours. Beyond 30 hours, little sign of attractants was noted. Control wood series did not undergo any transition, this leading to the conclusion that a significant change occurred in wood as a result of the anaerobic treatment. The implications of this result have been discussed. The successful use of wood shavings has made possible further studies on the nature of origin of attractants. The use of the anemotactic behaviour of beetles of both sexes to an airstream carrying host odour was found to be a highly efficient technique of analysis. The role of greater quantities of light in attracting insects away from a source of olfactory stimulation became increasingly apparent from this study. Moisture loss of the insect apparently did not alter their response to white light. / Science, Faculty of / Zoology, Department of / Graduate

京都大学 / 0048 / 新制・課程博士 / 博士(農学) / 甲第20636号 / 農博第2243号 / 新制||農||1053(附属図書館) / 学位論文||H29||N5080(農学部図書室) / 京都大学大学院農学研究科地域環境科学専攻 / (主査)教授 北山 兼弘, 教授 田中 千尋, 教授 松浦 健二 / 学位規則第4条第1項該当 / Doctor of Agricultural Science / Kyoto University / DGAM

<p dir="ltr">Rapid ʻōhiʻa death (ROD) is a disease complex caused by two <i>Ceratocystis fungi</i>, <i>C. lukuohia</i> and <i>C. huliohia</i>, that is devastating the keystone tree of the Hawaiian Islands, ʻōhiʻa lehua (<i>Metrosideros polymoropha</i>). The causal agents of ROD were identified in 2015 and I began researching entomological aspects of the complex in 2016. Much like other <i>Ceratocystis</i> diseases, my colleagues and I suspected that beetles and frass might be involved in the system. Together, we identified four species of invasive ambrosia beetles (Coleoptera: Curculionidae) that contribute to the spread of ROD: <i>Xyleborinus saxesenii, Xyleborus affinis, Xyleborus ferrugineus</i>, and <i>Xyleborus perforans</i>. Both ROD-<i>Ceratocystis</i> fungi and the ambrosia beetles inhabit the xylem of ʻōhiʻa. When these beetles create their home galleries, they produce frass particles infested with resting chlamydospores that can be transported in the environment through the soil, wind, and water. Secondly, the beetles are capable of vectoring the fungi directly to stressed trees via viable propagules attached to their exoskeleton. The natural progression of this research was to investigate the chemical ecology of the system, therefore building the foundations for management strategies to reduce the spread of ROD. In addition, I satisfied my curiosity to explore the fungal mutualisms of these beetles through the use of phylogenetics.</p><p dir="ltr">In Chapter 1, I review the literature describing ROD and the four ROD-associated ambrosia beetle species. I report all of the research to date regarding ROD, including current monitoring and management strategies. Then, I introduce ambrosia beetles and the Xyleborini tribe, focusing on the life history of the ROD-associated beetles and current literature describing the use of semiochemicals to control them.</p><p dir="ltr">In Chapter 2, I determine the volatile organic compounds associated with the ROD <i>Ceratocystis</i> – ʻōhiʻa pathosystem and the response of the associated beetles to those compounds. I investigated the volatiles produced by <i>C. lukuohia</i> and <i>C. hulihia</i> in culture in addition to when inoculated into ʻōhiʻa seedlings. Then, I describe olfactometer assays to determine if the ROD-associated beetles are attracted to the volatiles emitted from ROD-<i>Ceratocysti</i>s in culture.</p><p dir="ltr">In Chapter 3, I investigate semiochemicals for attracting and repelling ambrosia beetles in ʻōhiʻa forests. I describe separate trapping experiments, first, testing the attraction of beetles to 100% ethanol and 1:1 methanol ethanol. Second, we investigate the use of two beetle repellent products, one with verbenone and the other with verbenone + methyl salicylate active ingredients.</p><p dir="ltr">In Chapter 4, I describe the testing of the repellent, verbenone, in the SPLAT^® Verb formulation, to deter ambrosia beetle attack from both healthy ʻōhiʻa trees and trees infested with ROD-<i>Ceratocystis</i>. Over two field seasons, we monitored ambrosia beetle attacks on trees treated with verbenone and measured the abundance of verbenone released from the repellents over time during the first season.</p><p dir="ltr">In Chapter 5, I investigate the ambrosia fungi of the ROD-associated beetles and native Hawaiian ambrosia beetles on the Island of Hawaiʻi. We isolated a dozen fungal symbionts from the mycetangia of ambrosia beetles, most of which are first reports in Hawaiʻi, and use phylogenetics to investigate putative new species of <i>Raffaelea</i> and <i>Ambrosiozyma.</i></p><p dir="ltr">Finally, in Chapter 6, I synthesize the results and future directions of the aforementioned chapters. Together, these dissertation chapters provide insights into ambrosia beetle monitoring and management strategies in Hawaiʻi and beyond. I describe the groundwork for understanding the pathosystem from a chemical ecology perspective and touch on the understudied world of Hawaiʻi fungi and potential pathogens.</p>