摘要:

The influence of substrate composition on spatial distribution patterns of final instar larvae in a single-cohort population of the limnephilid caddisflyDicosmoecus gilvipes(Hagen) was examined in a pool of the McCloud River, Shasta Co., California. Four distinct substrate habitats were identified; three strata, each composed of different stone sizes, had low variability (sorting coefficient = 1.0), whereas the 4th was composed of highly mixed stone sizes (SC = 1.7). Each stratum was divided into 0.093-m2quadrats and Surber samples were collected in all areas where depth was<1 m. Sampling efficiency was optimized by incorporating the surface-dwelling behavior and large size ofD. gilvipeslarvae into sampling design. Considering the pool as a single habitat,D. gilvipesexhibited an aggregated spatial pattern fitting a negative binomial distribution, with large numbers of samples necessary to estimate accurate mean density. However, within each of the uniform substrate ribbons, the spatial pattern ofD. gilvipeswas non-aggregated and counts from the samples followed a Poisson series. Accordingly, sampling variability was low and fewer samples were necessary to estimate mean densities within each of these areas. In the unsorted substrate ribbon, an aggregated distribution was again exhibited, resulting in high sampling variability. Habitat stratification may reduce sampling variability within the constituent strata. Integration of life history features of study populations into sampling design may result in reduced sampling effort and greater accuracy.

ISSN:1754-5692    

DOI:10.1093/ee/8.3.561

出版商:Oxford University Press    

年代:1979

数据来源: OUP

摘要:

The populations of 6 sympatric species of detrivorous beetles were sampled over a 4-yr period at a site in the northern Mojave Desert. Data on precipitation, ambient temperature, soil moisture, and plant biomass were gathered simultaneously. The amount of summer rainfall was found to be a factor associated with the abundance of all species. Temperatures affected the phenology of spring emergent species. None of the populations responded to radical changes in plant productivity.

ISSN:1754-5692    

DOI:10.1093/ee/8.3.568

出版商:Oxford University Press    

年代:1979

数据来源: OUP

摘要:

Experiments were conducted on colonies of 3 selected ant species that are abundant in corn fields in the Nebraska Sandhills to determine their predatory potential on eggs of western corn rootworms (WCR)Diabrotica virgiferaLeConte.Lasius neonigerEmery was not found to be a predator on WCR eggs under test conditions.Myrmica americanaWeber andPheidole bicarinata longulaEmery did remove WCR eggs from filter paper placed upon the surface of their colonies.M. americanadid not locate and remove eggs placed beneath the soil in the colonies. Location of WCR eggs in soil appears to be due to chance; thus significant reduction of WCR egg populations in the field is questionable.

ISSN:1754-5692    

DOI:10.1093/ee/8.3.575

出版商:Oxford University Press    

年代:1979

数据来源: OUP