The Insect Complexes Associated with the Stems of Seven Thistle Species

Abstract

The complexes of phytophagous insects associated with the stems of Cirsium arvense (L.) Scop. 1772, Cirsium vulgare (Savi) Ten. 1835-1838, Cirsium palustre (L.) Scop. 1772, Cirsium oleraceum (L.) Scop. 1769, Cirsium eriophorum (L.) SCOP.. 1772, Carduus acanthoides L. 1753 and Carduus mutans L. 1753 (Asteraceae) and their parasitoids were studied in northern Bavaria (FRG), lower Austria and the Alsace (France). The structure of the food-webs is discussed for all host species. A total of 25 phytophagous and 44 parasitoid species was found. 12 herbivorous species were associated with C. arvense, 15 with C. vulgare, 11 with C. eriophorum, 10 species each with C. nutans, C. acanthoides and C. palustre and 4 species with C. oleraceum. None of these species occurred on all plants investigated. Ceutorhynchus litura (Fabricius 1775), C. cf trimaculatus (Fabricius 1775) (Coleoptera: Curculionidae) and Urophora cardui (Linnaeus) 1758 (Diptera: Tephritidae) were monophagous. Out of the other species, the oligophagous Melanagromyza aeneoventris (Fallen) Hendel 1920 (Diptera: Agromyzidae) and Mordellistena cf parvuloides Ermisch 1956 (Coleoptera: Mordellidae) were dominant. Agapanthia villosoviridescens DeGeer 1775 (Coleoptera: Cerambycidae), Myelois cribrumella (Hubner 1796) (Lepidoptera: pyralidae), Cheilosia albipila (Meigen 1838), C. fraterna (Meigen 1830) (Diptera: Syrphidae), Apion onopordi Kirby 1808, A. gibbirostre Gyllenhal 1813 and Lixus elongatus Goeze 1777 (Coleoptera: Curculionidae) were each abundant herbivores on some of the host plants. Average infestation (% stems attacked) by all phytophaga was high, reaching 68% in C. arvense and 90 to 100% in the other thistles. The size of the host plant species influenced the average number of individuals per plant. The phytophagous insects used four different parts of the resource: (1) the pith, with some species depending on a pith channel, (2) self induced gall-tissue, (3) meristematic tissue, (4) roots or root collars. Resource utilization of the main phytophages showed some overlap in time for C. vulgare and C. palustre, but little for C. arvense. A comparison with the Cardueae flowerhead system showed similar patterns in guild tructure in spite of a distinct taxonomic composition