title: Aspects of the ecology of Scolypopa australis (Walker) (Homoptera:Ricaniidae) and its parasite Centrodora scolypopae (Valentine) (Hymenoptera: Aphelinidae)

authors: Gerard, Philippa Jane

abstract: The ecology, population dynamics and interaction, of natural populations of the univoltine passion vine hopper, Scolypopa australis Walker, and its egg parasite, Centrodora scolypopae Valentine, were studied in a bracken and blackberry filled gully near Hamilton, New Zealand, from 1980-85. The S. austral is egg population was estimated using a height frequency vegetation sampling method and the nymphal and adult stages by direct counting. The S. australis nymphal populations ranged from 200-400/m² in the first three generations studied, then fell to below 100/m² after a cold summer in 1982-83. 
S. australis overwintered as eggs laid mainly in blackberry and bracken stems. Parasitism by C. scolypopae was found to be the main cause of egg mortality, followed in importance by fungae, then stem boring insects. Egg mortality varied with height above ground and increased over winter. Host plant had a strong influence on egg survival, mainly because eggs were laid at greater depths in blackberry than in bracken, and thus were less susceptible to parasitism. 
Rate of S. austraiis nymphal development differed markedly between years and aspects in response to temperatures experienced. It was slower on blackberry than bracken. 
Time specific life table analysis showed that parasitism by C. scolypopae was the key factor determining fluctuations in the population of S. australis. The next most important factors were variation in natality and adult loss. Neonate loss was the largest cause of mortality and nymphal loss the smallest. No density dependent mortalities were found.
The developmental stages of C. scolypopae are described. The larval instars all show a reduction in morphological differentiation when compared with other Aphelinidae. The first instar retains the egg chorion and lacks visible mouthparts, segmentation or tracheae. The third instar has four pairs of spiracles. Adult nutrition, internal and external reproductive systems and mating behaviour are described.
Although C. scolypopae females were shown to discriminate between parasitised and nonparasitised host eggs, superparasitism was common in years of high percentage parasitism of host eggs. The progeny of the first oviposition is dominant and eliminates the younger individuals by physiological suppression.
The low temperature threshold for S. australis egg eclosion was 10°C and the thermal requirement for completion of the life cycle was estimated between 1500-1900 day degrees. The low temperature threshold for C. scolypopae varied with the developmental stage. Egg eclosion required at least 10°C while 14•5°C was needed for the initiation of pupation and adult emergence. C. scolypopae was demonstrated to have a facultative diapause in the prepupal stage, that is influenced by both light and temperature.
Life table analysis shows that mortality of overwintering larvae, caused by fungae, twig loss and stem boring insects, was the key factor in the population dynamics of C. scolypopae. The 'area of discovery' of C. scolypopae was related to both host and searching female density. The mutual interference constant was approximately 1, indicating high levels of interference between searching females. Parasite density was highly dependent on the number of available host eggs. The partial refuge of S. australis eggs in blackberry would increase the stability of the host-parasite interaction.

text: Aspects of the ecology of Scolypopa australis (Walker) (Homoptera:Ricaniidae) and its parasite Centrodora scolypopae (Valentine) (Hymenoptera: Aphelinidae) The ecology, population dynamics and interaction, of natural populations of the univoltine passion vine hopper, Scolypopa australis Walker, and its egg parasite, Centrodora scolypopae Valentine, were studied in a bracken and blackberry filled gully near Hamilton, New Zealand, from 1980-85. The S. austral is egg population was estimated using a height frequency vegetation sampling method and the nymphal and adult stages by direct counting. The S. australis nymphal populations ranged from 200-400/m² in the first three generations studied, then fell to below 100/m² after a cold summer in 1982-83. 
S. australis overwintered as eggs laid mainly in blackberry and bracken stems. Parasitism by C. scolypopae was found to be the main cause of egg mortality, followed in importance by fungae, then stem boring insects. Egg mortality varied with height above ground and increased over winter. Host plant had a strong influence on egg survival, mainly because eggs were laid at greater depths in blackberry than in bracken, and thus were less susceptible to parasitism. 
Rate of S. austraiis nymphal development differed markedly between years and aspects in response to temperatures experienced. It was slower on blackberry than bracken. 
Time specific life table analysis showed that parasitism by C. scolypopae was the key factor determining fluctuations in the population of S. australis. The next most important factors were variation in natality and adult loss. Neonate loss was the largest cause of mortality and nymphal loss the smallest. No density dependent mortalities were found.
The developmental stages of C. scolypopae are described. The larval instars all show a reduction in morphological differentiation when compared with other Aphelinidae. The first instar retains the egg chorion and lacks visible mouthparts, segmentation or tracheae. The third instar has four pairs of spiracles. Adult nutrition, internal and external reproductive systems and mating behaviour are described.
Although C. scolypopae females were shown to discriminate between parasitised and nonparasitised host eggs, superparasitism was common in years of high percentage parasitism of host eggs. The progeny of the first oviposition is dominant and eliminates the younger individuals by physiological suppression.
The low temperature threshold for S. australis egg eclosion was 10°C and the thermal requirement for completion of the life cycle was estimated between 1500-1900 day degrees. The low temperature threshold for C. scolypopae varied with the developmental stage. Egg eclosion required at least 10°C while 14•5°C was needed for the initiation of pupation and adult emergence. C. scolypopae was demonstrated to have a facultative diapause in the prepupal stage, that is influenced by both light and temperature.
Life table analysis shows that mortality of overwintering larvae, caused by fungae, twig loss and stem boring insects, was the key factor in the population dynamics of C. scolypopae. The 'area of discovery' of C. scolypopae was related to both host and searching female density. The mutual interference constant was approximately 1, indicating high levels of interference between searching females. Parasite density was highly dependent on the number of available host eggs. The partial refuge of S. australis eggs in blackberry would increase the stability of the host-parasite interaction.

year: 1985

title: The marginal willingness-to-pay for attributes of a hypothetical HIV vaccine

authors: Cameron, Michael Patrick

subjects: HIV vaccine

abstract: This paper estimates the marginal willingness-to-pay for attributes of a hypothetical HIV vaccine using discrete choice modeling. We use primary data from 326 respondents from Bangkok and Chiang Mai, Thailand, in 2008–2009, selected using purposive, venue-based sampling across two strata. Participants completed a structured questionnaire and full rank discrete choice modeling task administered using computer-assisted personal interviewing. The choice experiment was used to rank eight hypothetical HIV vaccine scenarios, with each scenario comprising seven attributes (including cost) each of which had two levels. The data were analyzed in two alternative specifications: (1) best-worst; and (2) full-rank, using logit likelihood functions estimated with custom routines in Gauss matrix programming language. In the full-rank specification, all vaccine attributes are significant predictors of probability of vaccine choice. The biomedical attributes of the hypothetical HIV vaccine (efficacy, absence of VISP, absence of side effects, and duration of effect) are the most important attributes for HIV vaccine choice. On average respondents are more than twice as likely to accept a vaccine with 99% efficacy, than a vaccine with 50% efficacy. This translates to a willingness to pay US$383 more for a high efficacy vaccine compared with the low efficacy vaccine. Knowledge of the relative importance of determinants of HIV vaccine acceptability is important to ensure the success of future vaccination programs. Future acceptability studies of hypothetical HIV vaccines should use more finely grained biomedical attributes, and could also improve the external validity of results by including more levels of the cost attribute.

text: The marginal willingness-to-pay for attributes of a hypothetical HIV vaccine This paper estimates the marginal willingness-to-pay for attributes of a hypothetical HIV vaccine using discrete choice modeling. We use primary data from 326 respondents from Bangkok and Chiang Mai, Thailand, in 2008–2009, selected using purposive, venue-based sampling across two strata. Participants completed a structured questionnaire and full rank discrete choice modeling task administered using computer-assisted personal interviewing. The choice experiment was used to rank eight hypothetical HIV vaccine scenarios, with each scenario comprising seven attributes (including cost) each of which had two levels. The data were analyzed in two alternative specifications: (1) best-worst; and (2) full-rank, using logit likelihood functions estimated with custom routines in Gauss matrix programming language. In the full-rank specification, all vaccine attributes are significant predictors of probability of vaccine choice. The biomedical attributes of the hypothetical HIV vaccine (efficacy, absence of VISP, absence of side effects, and duration of effect) are the most important attributes for HIV vaccine choice. On average respondents are more than twice as likely to accept a vaccine with 99% efficacy, than a vaccine with 50% efficacy. This translates to a willingness to pay US$383 more for a high efficacy vaccine compared with the low efficacy vaccine. Knowledge of the relative importance of determinants of HIV vaccine acceptability is important to ensure the success of future vaccination programs. Future acceptability studies of hypothetical HIV vaccines should use more finely grained biomedical attributes, and could also improve the external validity of results by including more levels of the cost attribute.

year: 2013

title: Kuta (Eleocharis sphacelata, Cyperaceae), a locally important and highly valued weaving plant

authors: Wehi, Priscilla M.

subjects: Northland (N.Z.)

abstract: This article introduces and discusses kuta (Eleocharis sphacelata, Cyperaceae), a tall spikerush found on the margins of shallow lakes in New Zealand, which, although often overlooked, is considered in Northland to be a valuable weaving resource.

text: Kuta (Eleocharis sphacelata, Cyperaceae), a locally important and highly valued weaving plant This article introduces and discusses kuta (Eleocharis sphacelata, Cyperaceae), a tall spikerush found on the margins of shallow lakes in New Zealand, which, although often overlooked, is considered in Northland to be a valuable weaving resource.

year: 2006