Host-plant leaf surface compounds influencing oviposition in Delia antiqua

Summary. Delia antiqua (Diptera: Anthomyiidae) females lay eggs between the leaves of onion plants or in the soil around the base of the plants, then the maggots feed on the onion bulb and roots causing rapid secondary infection by fungi and bacteria. It is well known that the first sensory modality used by the onion fly is vision, therefore the shape (vertical narrow cylinders) and colour (yellow) of the plant play a crucial role in the recognition of a potential host plant. In the past it has been shown that n-dipropyl disulfide (Pr₂S₂), a typical component of onion volatiles, is an important chemical host plant cue. We extracted host leaf surface to verify if Pr₂S₂ is the major chemical oviposition stimulant and to determine if other as yet unknown substances may play a role in host-plant selection. We confirmed that the females laid more eggs around onion plants with leaves than when only the onion bulb was present and that the odour of chopped onion stimulates oviposition. Extraction of the surface of onion leaves revealed that only the apolar fraction contained substances that stimulate egg-laying in D. antiqua. GC-EAD analysis indicated that a minor constituent, Pr₂S₂, is perceived by the olfactory receptor on the antennae of the onion fly females. This confirmed the importance of Pr₂S₂ as oviposition stimulant. Contact with the polar fraction did not stimulate egg-laying behaviour in this Delia species. We discuss the oviposition strategy of D. antiqua in comparison with its closely related species, D. radicum, in which the oviposition behaviour is stimulated mainly through contact with the cabbage leaf surface and only partially by the host volatiles.     

Differential timing of spring migration in northern wheatears Oenanthe oenanthe: hurried males or weak females?

In a field experiment on the island of Helgoland (southeast North Sea), we investigated whether migration strategy or competition between the sexes cause the differential timing of spring migration of male and female northern wheatears (Oenanthe oenanthe) (males migrating earlier). The study included two subspecies, heading towards Greenland/Iceland and Scandinavia, respectively, and is based on colour-ringing and remote weighing of individuals. Despite food offered ad libitum, most Scandinavian birds left the island on the day of arrival or stayed only 1–3 days, whereas more than half of Greenlandic/Icelandic birds stayed for up to 12 days and refuelled rapidly. In the latter subspecies, males showed a positive correlation of departure fuel load and fuel deposition rate, resembling time-minimizers in optimal migration theory. In contrast, females departed irrespective of fuel deposition rate, with an approximately constant level of fuel stores. This level was lower than in males, but sufficient to enable by-passing of stopover sites en route, allowing us to regard females as time-minimizers also. Since females are not able to reach Greenland without additional refuelling elsewhere and males appeared to have a larger potential for by-passing stopover sites, time-selection seems to be more pronounced in males and may be the reason for earlier migration of males. Intraspecific aggressive interactions between colour-ringed birds were predominantly won by the initiator, by males and by larger birds, whereas fuel load and subspecies did not affect the outcome. Although compared to females, males were more often dominant at the feeding stations or held territories, refuelling patterns could not be explained by dominance. Subordinate or non-territorial birds did not refuel at a lower rate or depart with lower fuel loads than dominant or territorial birds. In non-territorial birds, the restricted access to feeding stations was made up with larger doses of food taken per visit, leading to the same energy intake as that of dominant and territorial birds. Therefore, competition during stopover could be eliminated as the reason for differential timing of migration of male and female wheatears, but this result may be species-specific.Communicated by W. Wiltschko     

人员可靠性与系统安全

论述了人员可靠性对系统安全的影响，分析了它的特点和应采用的研究方法，介绍了笔者近年来在核电站人员可靠性基础研究方面的情况，并对研究的发展趋势进行了展望。     

A fungus infecting domestic flies manipulates sexual behaviour of its host

The Enomopathogenic fungus Entomophthora muscae infects and kills domestic flies Musca domestica, and rates of transmission are higher at high population densities. I tested whether features of parasitized hosts increased the likelihood of transmission of the fungus in a series of experiments. Individual flies contacting an infected conspecific had a much higher probability of becoming infected than had flies contacting a dead fly without signs of infection. Males especially were attracted to and behaved sexually towards dead, infected flies even when a choice was available between a dead, infected fly and a dead, uninfected individual. The abdomen of infected flies swelled considerably as a consequence of infection, and uninfected female flies with larger abdomens are more fecund than the average female and maybe more attractive. Experiments in which abdomens of infected and uninfected flies were cut off and glued back on other flies demonstrated that the abdomens of infected flies were highly attractive to males. When the size of the abdomen of infected and uninfected individual flies was held constant, infected dead flies were still more attractive than corpses of uninfected flies. This result suggests that features other than the size of the swollen abdomen enhanced the attractivity of infected flies. Features of infected hosts therefore increased the likelihood of transmission of the parasitic fungus.     

Factors affecting adolescents’ use of urban public spaces in their leisure time: an exploratory study from the city of Vienna

Urban public spaces are important areas for leisure, recreation and physical activity and therefore contribute to the quality of life in cities. In particular, for adolescents they provide important spaces to meet with their peers, away from parental or school control. In many cities worldwide, public spaces have undergone severe developmental processes, and often a withdrawal from public space is noted. With regard to the opportunities those spaces provide for adolescents, it is necessary to investigate their current meaning for adolescents in a leisure context. In this article, qualitative research methods were used to investigate factors affecting adolescents’ use of public spaces in Vienna, Austria. In total 45 adolescents were interviewed. Results show that public open spaces are not regarded as important leisure spaces, and data reveal a strong retreat to private areas for leisure purposes. Perceived insecurities and fears support these processes and often result in avoidance of public spaces but also the wish for more control by authorities.     

Assessing the bio-psychosocial correlates of flood impacts in coastal areas of Lagos,Nigeria

This paper explores the complex heterogeneous experiences of flood impacts based on a bio-psychosocial model of socio-economic, demographic, behavioural and environmental factors. Using ordinary least squares regression on a cross-sectional survey of 1003 individuals, flood impacts in three contiguous coastal neighbourhoods in Lagos, Nigeria, were modelled. The results show that approximately 52% of the variability in flood impact was accounted for by education, age, family structure, ethnicity, personal health concern and income. While involvement in coping was not a significant predictor of flood impacts, relocation emerged as a strong predictor. The inclusion of behavioural factors did not change the magnitude and significance of the relationship between demographic factors and flood impacts. However, the effects of age, education and personal health concern disappeared when environmental factors were controlled. The overall importance of the predictors for determining flood impact in decreasing order is as follows: income > coping strategies > ethnicity = participation in community development > family structure > personal health concerns > housing quality > reasons for living in residential locality > neighbourhood vulnerability to flood > housing vulnerability to flood.     

Who's greener? Comparing urban and suburban residents' environmental behaviour and concern

While various studies have compared metropolitan and rural residents' displays of environmentalism, recent shifts in the housing and energy markets make intra-metropolitan differences in urban and suburban attitudes and actions more interesting. The housing market crash and accompanying rise in fuel costs are prompting a return of centralisation to many communities and, it is believed, are drawing environmentally conscious residents downtown closer to work and play. Past research has found that this trend – demonstrated by a re-centralising housing market – was already underway, pre-crash, in Louisville, Kentucky over the “boom” period from 2000 to 2006. Drawing on original 2006 survey data for Louisville, this study regresses two components of environmentalism (behaviour and concern) on socio-demographics and residence. Findings show urbanites in Louisville are indeed significantly more environmentally friendly in their behaviour but not in their concern. Countering some claims, residents of single-family homes also exhibit significantly higher levels of environmental behaviour and concern than those residing in apartments and condominiums. Finally, in a surprise finding, recent movers from the suburbs to the city do not differ in their behaviour and are significantly less concerned about the environment than urbanites, suburbanites, and all metropolitan residents.     

Community acceptance of policy options for managing the maintenance of rainwater tanks

This research examined community acceptance of policy instruments that could be used to promote ongoing maintenance of domestic rainwater tank systems. Using an online survey of 533 tank owners in South East Queensland, Australia, the research investigated four sets of factors that influence policy acceptance: features of the policy, judgements of policy fairness and effectiveness, contextual framing, and individual attitudes and motivations towards tank maintenance. An experimental design incorporating choice modelling was employed. Results demonstrated that perceptions of policy fairness and effectiveness are important to acceptance. Policies that include enabling features associate with increased perceptions of effectiveness, and policies that use incentives are linked to increased perceptions of both fairness and effectiveness. Individual attitudes and motivations regarding tank maintenance were significant predictors of policy support. Perceptions of a person's own ability to undertake tank maintenance tasks were negative predictors of policy intervention, suggesting that people who believe they can carry out maintenance themselves may not see the need for a policy that encourages tank maintenance to exist. The findings are discussed in relation to issues of policy design.     

The effect of larval and early adult experience on behavioural plasticity of the aphid parasitoid <Emphasis Type="Italic">Aphidius ervi</Emphasis> (Hymenoptera,Braconidae, Aphidiinae)

The relevance of the integration of preimaginal and eclosion experiences on the subsequent habitat preferences and mate finding by the adult has been rarely tested in holometabolous insects. In this work, the effect of larval and early adult experiences on the behavioural responses of adult males of the aphid parasitoid, Aphidius ervi, towards volatiles from the host–plant complex (HPC) and from conspecific females were evaluated. Two experience factors were considered: host diet (normal diet=ND; artificial diet=AD), and eclosion, i.e. extraction or non-extraction of the parasitoid larva from the parasitised aphid (extracted=EX; non-extracted=NE). Thus, four treatments were set up: ND/NE, ND/EX, AD/NE and AD/EX. Glass Y-tube olfactometers were used to investigate the responses of adult A. ervi males to the odour sources used. Males from the ND/NE treatment showed a shorter latency to the first choice of olfactometer arms, displayed a marked preference towards the HPC olfactometer arm, and spent more time in the HPC arm than males from the other treatments. Only the interaction of host diet and eclosion experiences proved to be relevant in explaining the differences in latency to first choice, time spent in olfactometers arms, and behaviours displayed in the olfactometer arms. These results show the importance of the integration of larval and eclosion experiences in the development of stereotyped responses of the adults. This process may involve memory retention from the preimaginal and emergence period, but further research is needed to disentangle the contribution of each stage. The response to conspecific females was much less affected by the treatments in relation to first arm choice and times in olfactometer arms, suggesting a pheromone-mediated behaviour, even though a prompter and more intense wing fanning courtship behaviour was registered in the ND/NE males compared to males from the AD/NE treatment. These results show that sexual behaviours are less affected by early experiences than behaviours related with finding a HPC for foraging or oviposition. Taken together, our results demonstrate for first time that larval and eclosion experiences affect in a differential way the early responses of the adult towards environment-derived cues and mate related cues.     

Territorial meadow pipit males (<Emphasis Type="Italic">Anthus pratensis</Emphasis>; Passeriformes) become more aggressive in female presence

Although mate guarding as prevention of extra-pair copulation is common among birds, evidence for aggressive behaviour involving physical contact related to mate guarding in passerines is scarce and cases of the presence of one partner directly influencing the aggressiveness of the other are lacking. We investigated the intra-specific territorial behaviour of male meadow pipits (Anthus pratensis; Passeriformes: Motacillidae) at the beginning of the breeding season by placing a pipit model accompanied by an intra-specific song playback in the territory of socially paired males and compared the responses of males whose mates were physically present during trials with those whose females were out of sight. The level of aggression of males was significantly higher in the presence of the female; half of the males in this group physically attacked the model (the most intense and risky aggressive behaviour). Physical attacks did not occur among males whose female was absent during the trial; response to the playback by most of these males was only weak. This pattern may be related to the prevention of extra-pair copulation; if the risks involved in the conflict are outweighed by potential loss of paternity, such aggressive mate guarding may pay off. The apparently overlooked effect on the territorial behaviour of a partner’s passive physical presence during conflict should be further evaluated because it may be important for the design and interpretation of results of behavioural experiments.