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Seasonal Abundance (seasonal + abundance)
Selected AbstractsSeasonal abundance, spatial distribution and sampling indices of thrip populations on cotton; a 4-year survey from central GreeceJOURNAL OF APPLIED ENTOMOLOGY, Issue 7-8 2002P. N. Deligeorgidis Thus, in a cotton field (1.1 ha) in central Greece, 45 leaves were collected (one leaf per cotton plant) at 10-day intervals from May to September, for four consecutive growing seasons (1995,98). Five species of thrips were found: Frankliniella intonsa was the most abundant species followed by Thrips angusticeps, Thrips tabaci, Frankliniella occidentalis and Aeolothrips intermedius. Although considerable differences were observed in the population fluctuations among species, the highest population densities, for all species found, were recorded in July and August. As indicated by Taylor's power law estimates, all species presented aggregated distribution among sampling units. As this type of spatial pattern indicates, the accuracy obtained in estimating mean population density increased with the increase of the mean. Furthermore, the increase of the mean caused an exponential decrease in sample size. However, the precision level is acceptable only in high mean values, while at the same time the benefit from an increase in sample size is of no practical value. [source] Broadleaf privet, Ligustrum lucidum Aiton (Oleaceae), a late-season host for Nezara viridula (L.), Plautia affinis Dallas and Glaucias amyoti (Dallas) (Hemiptera: Pentatomidae) in northern New South Wales, AustraliaAUSTRALIAN JOURNAL OF ENTOMOLOGY, Issue 4 2004Marc Coombs Abstract Seasonal abundances of the pentatomids Nezara viridula, Plautia affinis and Glaucias amyoti were monitored on the introduced weed, broadleaf privet, Ligustrum lucidum from January 1998 to July 2000 at Moree, New South Wales, Australia. All developmental stages (eggs, nymphal instars and adults) of N. viridula, P. affinis and G. amyoti were recovered from privet. For all species, adult and nymphal densities peaked from February to May, coincident with privet fruiting. Nymphs of each species successfully developed when fed L. lucidum berries in the laboratory. The importance of L. lucidum as a host is discussed in relation to its role in maintaining populations of pentatomid pest species and in particular as a late-season host prior to overwintering. [source] Effect of stinging nettle habitats on aphidophagous predators and parasitoids in wheat and green pea fields with special attention to the invader Harmonia axyridis Pallas (Coleoptera: Coccinellidae)ENTOMOLOGICAL SCIENCE, Issue 4 2009Ammar ALHMEDI Abstract The relative occurrence and seasonal abundance of aphids and their natural enemies were visually assessed between May and July 2005,2006 in four types of habitats located in Gembloux (Namur province, Belgium): green pea, wheat and stinging nettle either planted in or naturally growing in woodland adjacent to these crops. Results showed that: (i) Acyrthosiphon pisum Harris, Sitobion avenae F. and Microlophium carnosum Buckton were the most common aphid species, respectively, on green pea, wheat and stinging nettle either in or near field crops; (ii) stinging nettle and field crops shared several important aphidophagous insect species such as the ladybird Coccinella septempunctata L., hoverfly Episyrphus balteatus De Geer and braconid wasp Aphidius ervi Haliday; (iii) the shared beneficial species were typically recorded earlier on stinging nettles than on crops; and (iv) the spatial occurrence of the invasive ladybird Harmonia axyridis Pallas was distinctly associated with stinging nettles, particularly in 2005. Stinging nettles and field crops partially coincide in time, enabling the movement of natural enemies among them. These findings suggest that the presence of stinging nettles in landscapes seems to enhance the local density of aphidophagous insect communities necessary for aphid biocontrol in field crops. [source] Effects of the non-indigenous cladoceran Cercopagis pengoi on the lower food web of Lake OntarioFRESHWATER BIOLOGY, Issue 12 2003Corey L. Laxson Summary 1. In North America, the invasive predatory cladoceran Cercopagis pengoi was first detected in Lake Ontario. We explored the impact of Cercopagis on the lower food web of Lake Ontario through assessments of historical and seasonal abundance of the crustacean zooplankton, by conducting feeding experiments on the dominant prey of the invader, and by estimating its food requirements. 2. Between 1999 and 2001, a decrease in the abundance of dominant members of the Lake Ontario zooplankton community (Daphnia retrocurva, Bosmina longirostris and Diacyclops thomasi) coincided with an increase in the abundance of Cercopagis. Daphnia retrocurva populations declined despite high fecundity in all 3 years, indicating that food limitation was not responsible. Chlorophyll a concentration generally increased, concomitant with a decline in the herbivorous cladoceran zooplankton in the lake. 3. Laboratory experiments demonstrated that Cercopagis fed on small-bodied species including D. retrocurva and B. longirostris. 4. Consumption demand of mid-summer populations of Cercopagis, estimated from a bioenergetic model of the confamilial Bythotrephes, was sufficient to reduce crustacean abundance, although the degree of expected suppression varied seasonally and interannually. 5. Predatory effects exerted by Cercopagis on the Lake Ontario zooplankton, while initially very pronounced, have decreased steadily as the species became established in the lake. [source] Larval habitats and seasonal abundance of Culicoides biting midges found in association with sheep in northern Sardinia, ItalyMEDICAL AND VETERINARY ENTOMOLOGY, Issue 2 2010C. FOXI Between January 2005 and December 2006, the larval habitats and seasonal abundances of 21 species of Culicoides (Diptera: Ceratopogonidae) found in association with livestock on a farm in northern Sardinia were studied. Culicoides were collected using two light traps (one placed in a sheep shed and the other near water ponds) and reared from mud collected in and along the margins of a small and a large water pond. The mammalophilic Culicoides imicola Kieffer and Culicoides newsteadi Austen were the most prevalent (>95%) of 20 species in the sheep shed, whereas the ornithophilic Culicoides univittatus Vimmer, Culicoides sahariensis Kieffer, Culicoides festivipennis Kieffer, Culicoides circumscriptus Kieffer and Culicoides cataneii Clastrier were most abundant in the traps set at the ponds (73%) and in 16 species of Culicoides reared from laboratory-maintained mud samples retrieved from three microhabitats (a non-vegetated pond shoreline, 20 cm above a pond shoreline, the shoreline of a secondary, permanently inundated, grass-covered pool). The species reared most abundantly from along the pond shoreline were C. festivipennis, C. circumscriptus and C. sahariensis, whereas those most prevalent at the grassed pool were C. cataneii and C. festivipennis. C. imicola was found to breed preferentially in mud 20 cm above the pond shoreline, whereas C. newsteadi was restricted almost entirely to the grassed pool, which had a high organic matter content. Using the light trap and adult emergence data, the seasonal abundance patterns of the eight species of Culicoides were determined. In general, there was good correspondence between light trap catches and emergence trends. Well-defined emergence peaks indicate four or five generations for C. festivipennis and C. circumscriptus and three generations for C. cataneii, C. newsteadi and Culicoides jumineri Callot & Kremer. The emergence trends for C. imicola and C. sahariensis were unimodal, but, because they stretched over several months, indicated that a number of overlapping generations had occurred. Adults of C. imicola were reared and captured only sporadically in the first half of the year, gradually building to a peak in autumn. Conversely, C. newsteadi was reared throughout the year and displayed three clearly defined peaks (in winter, spring and autumn); captures of C. newsteadi in the light traps peaked in May,June and again to a lesser extent in autumn. In Sardinia the late seasonal peak in the abundance of C. imicola occurs in synchrony with outbreaks of bluetongue (BT) in sheep, which is consistent with earlier findings elsewhere in the Mediterranean basin and in Africa that it is the principal vector of bluetongue virus (BTV). Although the status of C. newsteadi as a vector of BTV is not known, its low-level presence in winter and heightened abundances in spring may provide a pathway along which the virus can overwinter. [source] | ||||||||||