We tried to measure the effects that a native parasite may cause to its native host by studying some biological properties of the specialist weevil Trichosirocalus troglodytes in relation to the impact on its host Plantago lanceolata. Density and activity of the weevil were estimated in four different ways: Tullgren, sweep net, capture-recapture and counting feeding holes in the leaves. The sweep net gave reliable information on relative densities and on presence of the weevil on the spikes, but the results were much influenced by the diurnal and seasonal activities of the weevil. Most eggs were laid during spring in the oldest leaves and most larvae were found in the caudex of the plant. Weevils of the new generation appeared from July onwards and developed flight muscles. The impact of 0, 3, 6 and 12 larvae on the spikes and the rosette of different P. lanceolata genotypes was investigated. The number of seeds per spike decreased linearly with the number of larvae added to the spikes. No effect on plant performance was found when the larvae were added to the rosette. The weevil spreads its risks by using different plant parts as oviposition sites during a prolonged period, hereby softening the ''pain'' put upon the plant. [KEYWORDS: insect herbivore; impact; weevil; Plantago lanceolata; density; oviposition; flight muscles Spatial autocorrelation; generalist caterpillars; behavior; curculionidae; evolutionary; coleoptera; preference; specialist; goldenrod; insects]
Original languageEnglish
JournalActa Oecologica
Journal publication date1995

ID: 145801