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Structural refuges in two stem‐boring weevils on Rumex crispus
Author(s) -
FREESE GUNTER
Publication year - 1995
Publication title -
ecological entomology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.865
H-Index - 81
eISSN - 1365-2311
pISSN - 0307-6946
DOI - 10.1111/j.1365-2311.1995.tb00467.x
Subject(s) - biology , rumex , parasitoid , weevil , host (biology) , braconidae , parasitism , botany , curculionidae , ecology
.1 Differences in feeding positions, parasitoid complexes and parasitization rates of the two dominant insect species in stems of Rumex crispus were investigated. Apion miniatum (inhabiting the lower 10% of the stem) and Apion violaceum (occurring all along the stem) exploited distinctly different feeding positions, partly due to differences in time of oviposition. 2 A.miniatum suffered less parasitization than A.violaceum , measured both by number of parasitoid species and parasitization rates. Its feeding position constitutes a refuge. 3 Parasitization of A.violaceum was least in individuals feeding in basal, thick parts of the stem. There is a trend that the developed refuge increases with increasing stem diameter. 4 The refuge of A.violaceum in basal positions only affected idiobiont ectoparasitoids, because koinobiont endoparasitoids attack the weevils before they enter the stem. Moreover, the koinobiont did benefit from the refuge itself by avoiding hyperparasitism. 5 Densities of A.violaceum increased with plant size, whereas percentage parasitism did not differ. Its three most abundant parasitoid species showed small‐scale density‐independent patterns of attack over all plants. Therefore a constant proportion of weevil larvae mine within the refuge independent of its potential size. 6 Synchronization between weevils and plants, as well as between parasitoids and hosts, appears to be the dominant factor for the spatial community structure of the stem borers of Rumex crispus and their enemies.