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|Title:||Auchenorrhyncha of a calcareous grassland.|
|Authors:||Cook, A. A.|
|Abstract:||1) The Auchenorrhyncha of the Deeps, an area of calcareous grassland in Northamptonshire, were surveyed. Two contrasting sites within grassland, one with taller (50 - 70 cm) vegetation dominated by Brachypodium pinnatum and the other with shorter (10-20 cm) vegetation dominated by Festuca spp., were sampled with both an Univac vacuum sampler and a sweep net between April 22 and September 9, 1987. On two occasions sticky traps were also used. Most of the commoner species showed a marked preference for one or other of the sampling sites. The majority of the 40 species of Auchenorrhyncha recorded from the site during the entire study was found during the survey. 2) The nymphs of the commoner species of Cicadellidae encountered during the study were identified and described. Most of the identifications were made by rearing the nymphs to maturity by confining them in clip-cages on grasses, which were grown in plastic pots in a greenhouse. A key to the nymphs, illustrated by drawing and photographs, was constructed. 3) Choice experiments were conducted in a greenhouse on two of the common species of cicadellid recorded at the Deeps; Adarrus multinotatus and Turrutus socialis. Adult specimens of the two species were collected from the field and released into a cage with seven species of the commoner grasses found at the Deeps. Collections of the leafhoppers made from the grasses indicated that A. multinotatus was specific to Brachypodium pinnatum and Turrutus socialis had a wide host range, with a preference for Avenula pubescens and Festuca rubra. 4) Choice experiments were conducted in the field over a three year period (1990 -1992). Replicated grass species, grown in plastic pots, were sunk into the ground in both the sites initially surveyed at the Deeps. Auchenorrhyncha were collected from the grasses at intervals by carefully removing pots from the ground and brushing the plant inside a muslin cage. Auchenorrhyncha removed from the grasses in this way were collected from the cage with pooters. The data obtained from this aspect of the study indicated that a number of species of Auchenorrhyncha were specific to one grass species or genus, a few species were associated with a well defined range of grasses and a third group (the largest) had a wide host range. 5) During the first year of the field choice experiments an investigation into the role of plant nitrogen in host selection by Auchenorrhyncha was undertaken. The response of Auchenorrhyncha to the 'natural' range of total leaf nitrogen found in unfertilised grasses grown in pots and their response to grasses fertilised with NH4NO3 were studied. Total leaf nitrogen was measured using a micro-Kjeldahl digestion. Although this aspect of the study was limited, the results indicated that only a few species at the Deeps selected plant hosts with a high nitrogen content. 6) Greenhouse no-choice experiments were conducted on the survival and oviposition of Adarrus multinotatus and Turrutus socialis and the survival of Criomorphus albomarginatus on a range of potential host grasses. The survival and oviposition of specimens contained in clip-cages on potential host grasses grown in plastic pots was monitored. The results obtained supported the results of the choice experiments, indicating that A. multinotatus was specific to B. pinnatum, T. socialis had a wide host range, and C. albomarginatus was specific to F. rubra. 7) Observations were made on the oviposition behaviour of a number of species, in addition to those described in 6) above, which were confined on host plants in clip-cages. Dead or living leaf sheaths were most commonly used for oviposition, although flower stems and leaves were also used. Generally, the species observed appeared to be specific in their choice of oviposition site.|
|Rights:||Copyright © the author. All rights reserved.|
|Appears in Collections:||Theses, College of Medicine, Biological Sciences and Psychology|
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