Determining whether mate-searching males use directional information from female signals in Umbonia crassicornis

Abstract only availableVibrational communication is widespread in insect social and ecological interactions. In fact, it has been estimated that thousands of insect species use vibrational signals as a primary source of communication. During many interactions, such as courtship and predator encounters, it is necessary for individuals to locate the source of the vibrational signal. Although localization of this sort is important, the mechanisms that small insects use to locate the source of the vibrational signal are not known. We are studying mate localization in thornbug treehoppers, Umbonia crassicornis. These are small sap-feeding insects in which mate-searching males produce vibrational signals that are transmitted along the stems and leaves of their host plant during courtship. First, the male produces a vibrational signal that is detected by the female. The female responds with her own vibration, creating a duet which is repeated until the male reaches the female. We hypothesize that the female's vibrational signals provide directional information to searching males. In order to test this hypothesis, we recorded the routes traveled and decisions made by mate-searching males as well as audio of the male-female duets. Our preliminary data suggest that female signals do influence the paths that males take to find females. Our results will guide future research on the actual mechanisms used by treehoppers to determine the direction of a substrate vibration and will continue to provide important insights into insect social behavior, ecology, and evolution.NSF Undergraduate Mentoring in Environmental Biolog

Determining whether mate-searching males use directional information from female signals in Umbonia crassicornis

Abstract only availableVibrational communication is widespread in insect social and ecological interactions. In fact, it has been estimated that thousands of insect species use vibrational signals as a primary source of communication. During many interactions, such as courtship and predator encounters, it is necessary for individuals to locate the source of the vibrational signal. Although localization of this sort is important, the mechanisms that small insects use to locate the source of the vibrational signal are not known. We are studying mate localization in thornbug treehoppers, Umbonia crassicornis (Hemiptera: Membracidae). These are small sap-feeding insects in which mate-searching males produce vibrational signals that are transmitted along the stems and leaves of their host plant during courtship. First, the male produces a vibrational signal that is detected by the female. The female responds with her own vibration, creating a duet which is repeated until the male reaches the female. We hypothesize that the female's vibrational signals provide directional information to searching males. In order to test this hypothesis, we recorded the routes traveled and decisions made by mate-searching males as well as audio of the male-female duets. Our preliminary data suggest that female signals do influence the paths that males take to find females. Our results will guide future research on the actual mechanisms used by treehoppers to determine the direction of a substrate vibration and will continue to provide important insights into insect social behavior, ecology, and evolution.NSF Undergraduate Mentoring in Environmental Biolog

A BIOLOGICAL MODEL FOR DIRECTIONAL SENSING OF SEISMIC VIBRATION

ABSTRACT There are many applications for a compact device that is capable of indicating the direction of propagation of substrate vibration. In order to develop effective devices for this purpose, it can be helpful to examine biological systems that have evolved specialized sensory systems for finding a vibration source. We are studying an insect model of vibration localization that provides an approach to directional vibration sensing over very small spatial scales. The treehopper Umbonia crassicornis communicates using vibrational signals transmitted along plant stems in the form of bending waves. The insect detects these substrate vibrations using sensors in the legs. Because the legs in this small species span a distance along the stem of only 5 mm, the insect is faced with a difficult localization problem: time-of-arrival differences between receptors on different legs are in the microsecond range, and wavelengths are an order of magnitude larger than the insect's own dimensions. To study this system we constructed a simulator that mimics the surface motion of propagating bending waves, then used the simulator to explore directional sensing mechanisms. Using laser vibrometry, we characterized the dynamic response of the insect's body (analogous to a mass on a set of springs) when driven with vibration of the substrate. We found a remarkable mechanical directionality in the response of the insect's body to substrate vibration, in which small time differences are converted to large amplitude differences across the insect's body. Preliminary evidence suggests that directionality results from the interaction of two modes of vibration in the insect's body: one that responds to the spatial gradient of the vibrational signal, and one that responds to the spatial average of the signal over the region sampled. This system generates a marked directionality in the amplitude response of the insect's body while sampling only 5 mm of a vibration gradient. We believe that a directional sensing system based on this insect model has direct applications to localization of other surface waves, such as those propagating along the surface of the ground

Predator hunting mode and host plant quality shape attack-abatement patterns of predation risk in an insect herbivore

Group formation reduces individual predation risk when the proportion of prey taken per predator encounter declines faster than the increase in group encounter rate (a ack-abatement). Despite a ack-abatement being an important component of group formation ecology, several key aspects have not been empirically studied, that is, interactions with the hunting mode of the predator and how these relationships are modi ed by local habitat quality. In 79 cage trials, we examined individual egg predation risk in di erent-sized egg clutches from the blue willow beetle Phratora vulgatissima for two predators with di erent hunting modes (consumption of full group [Orthotylus marginalis] vs. part group [Anthocoris nemorum]). Because these predators also take nutrients from plant sap, we could examine how the quality of alternative food sources (high- vs. low-quality host plant sap) in uenced a ack-abatement pa erns in the presence of di erent hunting strategies. For the O. marginalis predator, individual egg predation risk was largely independent of group size. For A. nemorum, egg predation risk clearly declined with increasing group size. However, approximately one-third of the grouping bene t was lost to an increase in group detectability. There were clear di erences in a ack-abatement pa erns between plants with high- vs. low-quality sap. When O. marginalis was the predator, there was no clear change in a ack-abatement in relation to host plant quality. However, for A. nemorum there was a clear reduction in overall predation risk and a stronger a ack-abatement pa ern with increasing group size when plant sap quality increased. This implies that the relative bene ts of prey grouping behavior for any species might show diurnal or seasonal changes as other aspects of resource/habitat quality change for the focal predator. Modulation of a ack-abatement by bo om-up e ects such as plant-based food resources is yet to be incorporated into general theory, despite the ubiquity of omnivorous predators and with omnivory being important for shaping food webs, ecosystem functions, and in biological control. Thus, ongoing re nement of a ack- abatement theory by focusing on bo om-up vs. top-down processes could have signi cant impacts on many important contemporary elds of study

Duración y éxito de eclosión en diferentes tamaños de nidadas de Crocodylus moreletii (Crocodylia: Crocodilidae)

Background. The Crocodylia begin their life by overcoming the incubation stage with group hatching. Incubation temperature is important for the development of the embryos and the duration of the hatching process, during which they emit sounds. Goals. The effect of the size of the clutch on the duration and success of hatching is reported for the first time, and the hatching process is described. Methods. We used four clutches supplied by the "Granja de Lagartos" farm in Tabasco, Mexico, from the 2010 breeding season, and each was distributed in containers to integrate three clutches of different size: large (15 eggs), medium (nine eggs), and small (one egg). We monitored the temperature, relative humidity, and the number of eggs hatched in each clutch. The duration of hatching and the incubation period were statistically compared, as well as hatching success among the three brood sizes. We made sure that incubation conditions were the same for all boxes. Results. The small clutches (? = 3340, ± 2794 min) and the medium-sized ones (? = 1844 ± 476 min) took less minutes to hatch, and both took less time than the large clutches (? = 9431 ± 768 min). The hatchings began with the vocalization of pre-hatching calls, heard up to a week before eclosion. Conclusions. The size of the clutch influences the duration of hatching, but is not related to hatching success.  Antecedentes. Los Crocodylia inician su historia de vida al superar la etapa de incubación con la eclosión en grupo. La temperatura de incubación es importante para el desarrollo de los embriones y el proceso de eclosión, durante el cual emiten sonidos. Objetivos. Reportar la influencia del tamaño de la nidada sobre la duración y el éxito de eclosión, y describir dicho proceso. Métodos. Se emplearon cuatro nidadas de Crocodylus moreletii de la Unidad de Manejo para la Conservación de la Vida Silvestre (UMA) Granja de Lagartos, en Tabasco, México. Con estas se integraron tres nidadas de diferente tamaño: grande (15 huevos), mediana (9 huevos) y pequeña (un huevo). Se monitorizó la temperatura, la humedad relativa y el número de huevos eclosionados y se compararon estadísticamente la duración de las eclosiones y el periodo de incubación, así como el éxito de la eclosión entre los tres tamaños de nidadas. Por último, se verificó que las condiciones de incubación fueran iguales para todas las nidadas. Resultados. Las nidadas pequeñas (? = 3340 ± 2794) y las medianas (? = 1844 ± 476) tardaron menos minutos en eclosionar en comparación con las nidadas grandes (? = 9431 ± 768). Mientras que el éxito de la eclosión (expresado en porcentaje) y la duración en días del periodo de incubación no mostraron diferencias entre los tres tamaños de nidada. Las eclosiones iniciaron con la emisión de los llamados preeclosionales, los cuales se escucharon una semana antes de la eclosión. Conclusiones. El tamaño de nidada influye en la duración de la eclosión, pero no influye sobre su éxito

The contribution of tympanic transmission to fine temporal signal evaluation in an ultrasonic moth

In lesser waxmoths Achroia grisella, pair formation and female mate choice involve very fine discrimination of male ultrasonic signals. Female A. grisella prefer male signals with longer pulses and longer 'asynchrony intervals', and evaluate differences in these characteristics in the range of 80-260 mu s. The first step in the evaluation of these characteristics is the tympanic transmission of stimuli. We used laser vibrometry to describe the mode of vibration, frequency tuning and stimulus transmission of the tympana of A. grisella. The tympanic response consisted of a rotational mode of vibration, in which the anterior and posterior sections moved out of phase; the posterior section of the tympanum vibrated with all points moving in phase and maximum displacement at the attachment point of the scoloparium that contains the receptor cells. The tympana of A. grisella were tuned to high ultrasonic frequencies and had an estimated time constant (i.e. the limit to their temporal acuity) of about 20-50 mu s. Pulse length and all but the shortest asynchrony interval were thus well resolved by the tympanum. We discuss implications for the evaluation of pulse length and asynchrony interval

Cold War : a Transnational Approach to a Global Heritage

Although within living memory, many countries now consider their surviving Cold War architecture as part of their heritage. It can even be a priority for heritage managers given that significant buildings are often suitable for reuse while extensive ‘brownfield’ sites such as airfields can be used for large-scale redevelopment. In a number of countries whose work we refer to here (notably the United Kingdom and elsewhere in Europe), agencies responsible for managing their country’s heritage have approached this priority by creating national inventories of sites and buildings with a view to taking informed decisions on their future. This paper presents the argument that the wider international context of the Cold War provides a more appropriate (or additional, higher-level) framework for such decision making. Such a ‘transnational’ approach would allow the comparison of similar (e.g. European) sites not merely within national borders but across the full extent of their western NATO1 deployment in Europe and North America. Taking this approach would also allow comparison with related sites in countries that formed part of the eastern-bloc Warsaw Pact.2 After outlining some examples of how national agencies have approached their Cold War heritage, this paper presents the four stages of this transnational approach making provision for an improved understanding and management of Cold War heritage sites wherever they occur. With a specific focus on the direct comparison between England and Russia, and also referring to sites surviving elsewhere within the former NATO and Warsaw Pact regions, as well as the United States, we argue that this four-stage approach: provides new understandings of a complex archaeological and architectural record; gives fresh perspectives on significance; and (importantly in a time of geopolitical instability) does so in a spirit of cooperation and friendship

Whispering to the Deaf: Communication by a Frog without External Vocal Sac or Tympanum in Noisy Environments

Atelopus franciscus is a diurnal bufonid frog that lives in South-American tropical rain forests. As in many other frogs, males produce calls to defend their territories and attract females. However, this species is a so-called “earless” frog lacking an external tympanum and is thus anatomically deaf. Moreover, A. franciscus has no external vocal sac and lives in a sound constraining environment along river banks where it competes with other calling frogs. Despite these constraints, male A. franciscus reply acoustically to the calls of conspecifics in the field. To resolve this apparent paradox, we studied the vocal apparatus and middle-ear, analysed signal content of the calls, examined sound and signal content propagation in its natural habitat, and performed playback experiments. We show that A. franciscus males can produce only low intensity calls that propagate a short distance (<8 m) as a result of the lack of an external vocal sac. The species-specific coding of the signal is based on the pulse duration, providing a simple coding that is efficient as it allows discrimination from calls of sympatric frogs. Moreover, the signal is redundant and consequently adapted to noisy environments. As such a coding system can be efficient only at short-range, territory holders established themselves at short distances from each other. Finally, we show that the middle-ear of A. franciscus does not present any particular adaptations to compensate for the lack of an external tympanum, suggesting the existence of extra-tympanic pathways for sound propagation

Temporal Processing of Vibratory Communication Signals at the Level of Ascending Interneurons in Nezara viridula (Hemiptera: Pentatomidae)

During mating, males and females of N. viridula (Heteroptera: Pentatomidae) produce sex- and species-specific calling and courtship substrate-borne vibratory signals, grouped into songs. Recognition and localization of these signals are fundamental for successful mating. The recognition is mainly based on the temporal pattern, i.e. the amplitude modulation, while the frequency spectrum of the signals usually only plays a minor role. We examined the temporal selectivity for vibratory signals in four types of ascending vibratory interneurons in N. viridula. Using intracellular recording and labelling technique, we analyzed the neurons' responses to 30 pulse duration/interval duration (PD/ID) combinations. Two response arrays were created for each neuron type, showing the intensity of the responses either as time-averaged spike counts or as peak instantaneous spike rates. The mean spike rate response arrays showed preference of the neurons for short PDs (below 600 ms) and no selectivity towards interval duration; while the peak spike rate response arrays exhibited either short PD/long ID selectivity or no selectivity at all. The long PD/short ID combinations elicited the weakest responses in all neurons tested. No response arrays showed the receiver preference for either constant period or duty cycle. The vibratory song pattern selectivity matched the PD of N. viridula male vibratory signals, thus pointing to temporal filtering for the conspecific vibratory signals already at level of the ascending interneurons. In some neurons the responses elicited by the vibratory stimuli were followed by distinct, regular oscillations of the membrane potential. The distance between the oscillation peaks matched the temporal structure of the male calling song, indicating a possible resonance based mechanism for signal recognition

(Im)material Culture : Towards an Archaeology of Cybercrime

Cybercrime is ubiquitous. People now inhabit a digital environment comprising permanent risk, exponential threats, and multiple virtual/physical harms, forming a global community of malefactors and the criminally exploited. The purpose of this paper is two-fold. First, through an archaeological lens, to characterize the new materiality of cybercrime (including its artefacts and architecture alongside digital/virtual manifestations). And second, to explore the potential for new perspectives on cybercrime borne out of this archaeological approach. In short: what is the archaeology of cybercrime and can new understandings emerge from an archaeological perspective? In undertaking this research we also challenge the long-held presumption that non-physical traces cannot be studied archaeologically. It is our contention that they can