The dispersal behaviour of apterous pea aphids, Acyrthosipon pi sum (Harris) was studied in the laboratory and field. In the laboratory, aphids exhibited two types of behaviour while on the ground, after dropping from plants in response to predators. Most aphids showed a high frequency of turning and tended to return to the plant they left, while a smaller proportion walked in straight lines and did not return to the plant they left. Adults and older nymphs had the highest proportion of individuals which showed the second type of behaviour and adults showed the greatest tendency to disperse to plants more distant than the nearest available plants. Young instar aphids were less successful at locating a host than older nymphs and adults. Aphids were placed on the central bean seedlings within plots, inside large field cages. Adult coccinellids were released into two of the cages while the other cage remained predator-free. Aphids in the cages with predators frequently moved between plants, while aphids in the predator-free cage did not. Adult aphids colonized more plants and had a lower mortality while on the ground than all other instars. Aphids did not show a preferred dispersal direction and the distance dispersed by aphid nymphs was proportional to the density of aphids on the plant they left. The importance of emigrating apterae in the exploitation of new resources and the regulation of aphid populations is discussed. Bean plants infected with an aphid transmitted virus were transplanted into the central position of bean plots in the field cages. Aphids were placed on the central infected plants and adult coccinellids were released into two of the three cages for three days. Aphids frequently moved to other plants from the centre infected plant in the two cages with predators but not in the predator-free cage. When plants were examined two weeks later, significantly more plants were infected with virus in the cages with predators than in the predator-free cage. New virus infections were correlated with plants that were visited or colonized by aphids from the central infected plant. The influence of predators in the spread of aphid transmitted diseases is discussed. In laboratory experiments, pea aphids from Vancouver were presented with alarm pheromone from irritated conspecifics. Adult and fourth instar aphids responded to the pheromone by either dropping, running or backing up. Instars one, two and three responded to the pheromone only when a vibratory stimulus accompanied it. A high proportion of all instars responded to the double stimulus by dropping. When adult aphids from Vancouver and Kamloops were presented with alarm pheromone, the Kamloops adults exhibited a more conservative reaction to alarm pheromone. Kamloops adults also were more conservative about leaving their plant when confronted by a coccinellid predator. A hypothesis is presented, which accounts for the differences in escape reactions between instars and biotypes. The hypothesis takes into consideration predation risk, escape behaviour repertoire and survival on the ground. Pea aphid adults resisted heat paralysis longer than first instars when subjected to high temperature treatments. All aphids succumbed to paralysis sooner at 42°C than at 37.5°C, but there appeared to be no difference in aphid survival in dry compared to moist conditions at high temperatures. Kamloops aphids were not more resistant to high temperatures. / Land and Food Systems, Faculty of / Graduate

Thesis (M.A.)--Kent State University, 2009. / Title from PDF t.p. (viewed Jan. 26, 2010). Advisor: Marilyn Norconk. Keywords: predation; anti-predator strategies; alarm calls. Includes bibliographical references (p. 111-120).

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Sound attenuation properties of the habitats occupied by two species of tree squirrels affect whether or not the squirrels will make alarm calls. Sound properties have been compared among habitats, microhabitats, weather conditions and seasons. In each case alarm calling activity is consistent with the hypothesis that calling behavior is acted upon by natural selection: calling occurs when squirrel calls carry well, and thus where the potential for communication is high.

Thesis (M.A.) -- University of Tennessee, Knoxville, 2006. / Title from title page screen (viewed on Sept. 20, 2006). Thesis advisor: Todd M. Freeberg. Vita. Includes bibliographical references.

The thesis is based on a multi disciplinary study involving both particulars regarding military history and certain psychological theories. In order to be able to discuss the psychological experiences of Boers during the guerrilla phase of the Anglo-Boer War, the first chapters of the thesis strive to provide the required background. Firstly an overview of the initial conventional phase of the war is furnished, followed by a discussion of certain psychological issues relevant to stress and methods of coping with stress. Subsequently, guerrilla warfare as a global concern is examined. A number of important events during the transitional stage, in other words, the period between conventional warfare and total guerrilla warfare, are considered followed by the regional details concerning the Boers’ plans for guerrilla warfare. These details include the ecological features, the socio-economic issues of that time and military information about the regions illustrating the dissimilarity and variety involved. In the chapters that follow the focus is concentrated on the psychological impact of the guerrilla war on the Boers. The wide range of stressors (factors inducing stress) are arranged according to certain topics: stress caused by military situations; stress caused by the loss of infrastructure in the republics; stress caused by environmental factors; stress arising from daily hardships; stress caused by anguish and finally stressors prompted by an individuals disposition. Then the psychological theories regarding an individual’s resistance resources (or general resistance resources ─ GRRs) and the means of using these resources to cope with stress are applied to the actual circumstances that the Boers were faced with. This discourse is arranged according to material resources, motivational issues and intrapersonal resources. Subsequently the complete guerrilla warfare phase is considered, the accent being placed on the psychological effect that the Boers’ strategies, as well as the British counter strategies, had on the republican forces. The phase is subdivided into four stages according to the course of the war, while still furnishing an overall account of the guerrilla phase ─ ranging from the initial successes on Boer side, the gradual decline in Boer initiatives to the final months, when the few successful encounters that the Boers launched, came too late to change matters. In the final chapter the impact of the guerrilla warfare on a selected group of Boers is examined in the form of case studies. The group includes President M.T. Steyn, whose health failed him in the end and Generals C.R. de Wet and J.C. Smuts, where their positive conduct is considered from a psychological perspective. The result of the continuous pressure on the young Commandant G.J. Scheepers is examined and the stress related experiences of Chief Field Cornet H.S. van der Walt, Burghers P.J. du Toit and R.W. Schikkerling are analysed. / Thesis (DPhil(History))--University of Pretoria, 2005. / Jurisprudence / unrestricted