The third trophic level of plant defence: neotropical social wasps\u27 use of odours of freshly damaged leaves when hunting

An important aspect of the hunting strategy of neotropical social wasps (Hymenoptera: Vespidae) is where they hunt. Three species used two behavioural components in their selection of a place to search for prey. The wasps uti lizcd the odour of freshly damaged leaves as cues (which could be synomones) to select which leaves to inspect and also they remembered a place to which they were strongly attracted to hunt recently and returned there. Polybia ignobilis (Haliday, 1836) and Polistes satan Bequaert, 1940 hunted on a lawn of Digitaria diversinervis Stapf immediately after it was mown in significantly larger numbers than at other times. P. ignobilis and Polistes versicolor (Olivier, 1791) hunted in significantly greater numbers on freshly cut leaves of passion vine (Passiflora edulis Sims) than on uncut leaves. Sometimes wasps inspected cards rubbed with freshly crushed leaves of P. edulis, but not control cards. Preliminary data suggest that several other species of social wasps around Brasilia hunt in a similar manner on native and exotic plants. Apparently the production of ephemeral odours by freshly cut leaves attract generalist insectivorous predators which perceive these scents and the social wasps investigated are members of the third trophic level of the plants' defence against attacks by herbivores. Available information suggests a difference between the behaviour of generalists and that of specialist arthropod predators which arc attracted to the odour emitted after their particular prey have damaged the leaves

Avaliação de cultivares de amendoim para resistência a Spodoptera frugiperda

Este trabalho teve por objetivo identificar cultivares de amendoim com resistência a Spodoptera frugiperda (J. E. Smith) (Lepidoptera: Noctuidae), determinando os graus de resistência por meio da análise univariada e multivariada. Utilizaram-se cultivares de amendoim de hábitos de crescimento ereto (IAC 5, IAC 8112, IAC 22 e IAC Tatu ST) e rasteiro (IAC 503, IAC 505, IAC 147, IAC 125, IAC Caiapó e IAC Runner 886), semeadas em campo. Lagartas de primeiro ínstar foram individualizadas em placas de Petri forradas com papel filtro umedecido e mantidas sob condições controladas de temperatura (25 ± 2 °C), umidade (60 ± 10%) e fotofase (12 horas). Utilizaram-se cinco repetições de dez lagartas (recém-eclodidas), em delineamento inteiramente casualizado. Diariamente, foram fornecidos folíolos novos, lavados com solução de hipoclorito de sódio a 1%. Avaliaram-se a duração (dias), a massa (mg) e a viabilidade (%) dos períodos larval e pupal, a razão sexual, longevidade e fecundidade. Os dados foram submetidos à análise de variância (teste F) e as médias comparadas pelo teste de Tukey (p<0,05), além da análise de agrupamento e de componentes principais. As cultivares de hábito de crescimento ereto, IAC 22, e rasteiro, IAC Runner 886, foram menos adequadas ao desenvolvimento do inseto, interferindo nas fases larval e pupal de S. frugiperda, demonstrando resistência moderada do tipo antibiose