摘要:

The biological motivation for a stochastic model for life history data arising from naturally occurring single-generation insect populations, composed of single or multiple cohorts, is discussed. The parameters of the model, in addition to having biological interpretations, can be conveniently and simultaneously estimated using standard statistical packages. Several life history quantities of interest are expressed as simple functions of the model parameters and can therefore be estimated in a straightforward manner. Examples of the method are provided.

ISSN:1754-5692    

DOI:10.1093/ee/21.6.1229

出版商:Oxford University Press    

年代:1992

数据来源: OUP

摘要:

We studied the effect on nontarget birds, mammals, and insects of 2% carbaryl bran bait applied for grasshopper control in western North Dakota. Total bird density did not differ 2, 10, or 21 d or 1 yr after application. Though carbaryl is an acetylcholinesterase (AChE) inhibiting chemical, we found no evidence of depressed brain AChE in birds or small mammals collected from the treated area. We sampled arthropod biomass on the treated and untreated areas with pitfall traps and stickyboards. Grasshopper densities were estimated with ring counts. Biomass of Coleoptera declined on the treated relative to the untreated area 2 and 10 d and 1 yr after treatment. Biomass of ants (Formicidae) and arthropods consumed by birds declined 2 d after treatment but recovered during later sampling periods. Grasshopper numbers declined on the treated area between the before and after 2-d count and remained unchanged during later counts. We found no evidence of a decline in Halictid bees, which are the primary pollinators of some native plant species, but our inferences regarding changes in arthropod numbers are limited because we did not identify insects to species. These results indicate that low rate (1.68 kg/ha) carbaryl bait applications have minimal potential for direct toxic effects on birds and mammals but may have limited indirect effects on species that depend on certain arthropod groups for food or seed dispersal. It has been suggested that bait applications are less hazardous to wildlife than liquid sprays because there is less exposure to nontarget organisms. Our results generally support this hypothesis, but there is potential for indirect effects on some species.

ISSN:1754-5692    

DOI:10.1093/ee/21.6.1239

出版商:Oxford University Press    

年代:1992

数据来源: OUP

摘要:

Four fields of birdsfoot trefoil,Lotus corniculatusL., were sweep sampled May through August during 1984–1987 in northern Wisconsin to assess the dispersion patterns of three plant bug pests and to calculate optimum sample size for these mirids in trefoil. Counts of the alfalfa plant bug,Adelphocoris lineolatus(Goeze), the tarnished plant bug,Lygus lineolaris(Palisot de Beauvois), andPlagiognathus chrysanthemi(Wolff) were aggregated for nymphs and adults of all three species. Nymph-dominated populations that occur early in the growing season required larger sample sizes to achieve a given precision level than did adult-dominated populations later in the season. A sample size of 10 sets of 20 sweeps provided a 25% precision level at ≥3 plant bugs per sweep and a 10% precision level at 2:20 bugs per sweep for all plant bug species and stages combined through the entire season (May through August).

ISSN:1754-5692    

DOI:10.1093/ee/21.6.1248

出版商:Oxford University Press    

年代:1992

数据来源: OUP

摘要:

The spatial relationships between density ofKorscheltellus gracilis(Grote) larvae, canopy species, and forest structure (gaps; gap edges; dense, young tree stands; and older tree stands) were investigated. Larvae at 1,000-m elevation on Camels Hump Mountain, Huntington, VT, were associated with dense, young stands of regenerating balsam fir(Abies balsamea[L.]) and fir defining the edges of wood fern(Dryopterus campylopteraClarkson) gaps. The consequences of these associations on life-table sampling methods and gap dynamics are discussed.

ISSN:1754-5692    

DOI:10.1093/ee/21.6.1253

出版商:Oxford University Press    

年代:1992

数据来源: OUP

摘要:

Between July and December, pits (30 em deep) were excavated in sugar maple forests to determine the vertical distribution of pear thrips,Taeniothrips inconsequens(Uzel). In well-drained, fine sandy loam, 67.3% of the larvae occurred in the upper 10 cm and40% of the thrips were located in t∼e upper 4 cm, whereas during dormancy, only 21% of the thrips were found that deep. In early June, when larvae reenter the soil, thrips were commonly found in the litter, but by mid-June, vertical distribution had stabilized, suggesting that downward movement of thrips into the soil had ceased.

ISSN:1754-5692    

DOI:10.1093/ee/21.6.1258

出版商:Oxford University Press    

年代:1992

数据来源: OUP

摘要:

A potential mosquito control agent, xanthan gum powder, was applied to a still water surface in laboratory pans to determine its efficacy in killingAedes atropalpus(Coquillett) pupae. The ED50of xanthan gum was 6.18gm/m2,and the LT50was 14.2 min. When xanthan gum was applied at a rate of 22.47gm/m2, water depth had no effect on the level of pupal mortality. The xanthan surface layer prevented access by the pupae to the air-water interface. The layer did not significantly decrease the levels of dissolved oxygen in the test pans.

ISSN:1754-5692    

DOI:10.1093/ee/21.6.1267

出版商:Oxford University Press    

年代:1992

数据来源: OUP

摘要:

Spatial distributions of Russian wheat aphid,Diuraphis noxia(Mordvilko), populations on preferred and nonpreferred hosts, as predicted by a spatial simulation model, were evaluated using geostatistics. The purpose was to assess effects of different hypothesized plant-to-plant movement behaviors on population spatial structure and to determine which behavior produced spatial structures (associations) most similar to those observed experimentally. The simulation model predicted location, chronological age, reproduction, movement, and mortality of individual aphids, at 1-d time intervals, within a 25-by-25 plant grid of preferred (wheat) or nonpreferred (oat) hosts. Three aphid movement behaviors were simulated: random, directional, and aggregative. Aggregativc movement produced spatial dynamics closest to the observed experimental data of the three simulated behaviors. Directional movement was the most sensitive to stochasticity in the model. The Taylor power law was tested and found to be not useful for assessing the spatial simulation. We question the utility of this method for assessing spatial relationships and patterns; however, indices of aggregation are useful for the design of sampling protocol. This study demonstrates the utility of geostatistics for assessing the ability of a spatial simulation to model dynamics of a spatial phenomenon.

ISSN:1754-5692    

DOI:10.1093/ee/21.6.1271

出版商:Oxford University Press    

年代:1992

数据来源: OUP

摘要:

The seasonality and diversity of members of the beetle family Leiodidae were determined for an old-growth and a 40-yr-old forest in New Hampshire. Thirty-four species were found at each site for a combined total of 39 species. Diversity was calculated using log series index α, Shannon-Wiener index, coefficient of community, and percent similarity. Seasonality is lengthily unimodal for the Cholevinae, which feed on carrion and fungi. The Leiodinae feed on slime molds and fungi and are more narrowly unimodal.Anisotomaspp. exhibit broadly overlapping abundance peaks, whereas some members ofAgathidiumandLeiodeshave abundance peaks at different times, indicating the possibility of resource partitioning. The greater leaf litter depilis and amount of woody debris at the old-growth site are presumed to lead to the production of more food resources for the leiodids. The difference in forest ages and the disturbance by selective cutting has not lowered species richness, but the diversity indices used reflect a difference between the sites based on greater abundance in the old-growth forest. The dispersal ability of leiodids is presumed to lead to rapid recolonization of the younger forest as food sources become available.Anisotoma inopsBrown is a potential indicator species for old-growth forests in northeastern North America.

ISSN:1754-5692    

DOI:10.1093/ee/21.6.1283

出版商:Oxford University Press    

年代:1992

数据来源: OUP

摘要:

Densities of larvalCulex tarsalisCoquillett andAnophelesspp. populations were monitored in experimental plots of white rice,Oryza sativaL., and wild rice,Zizania palustrisL., in Lake County, CA, during the spring and summer of 1989. Plant height, floral debris drop, water quality, and bacterial counts were measured and contrasted between the two systems.Anophelesspp. and C.tarsalispopulations in wild rice were 6 and 2.6 times higher, respectively, than in the white rice over the entire season. A significantly greater number of notonectids and hydrophilid larvae were sampled in the wild rice treatments and did not appear to be responsible for the difference in larval mosquito populations. A positive correlation was found between average larval density and plant height forAnophelesspp. in both wild and white rice and for C.tarsalisin wild rice during the early growing season. In the latter half of the growing season, onlyAnophelesspp. densities showed a significant correlation with plant height. A significant positive correlation was demonstrated between the number of shed wild rice anthers and larval densities for bothAnophelesspp. and C.tarsalis.No significant differences were noted in either water quality factors or bacterial counts between white and wild rice treatments. In the field, development of C.tarsalislarvae was slower in wild rice than in white rice plots before flowering but faster during flowering. However, temperature-adjusted developmental times were significantly shorter for the wild rice group only during flowering. In the laboratory, C.tarsaliscompleted development from second instar to adult when fed only wild rice pollen. These results suggest that wild rice pollen serves as a nutrient source for larvae in the field. In addition, the floral components of wild rice may serve as an oviposition attractant and structural refuge for the immature stages.

ISSN:1754-5692    

DOI:10.1093/ee/21.6.1294

出版商:Oxford University Press    

年代:1992

数据来源: OUP

摘要:

A study of the association betweenMelanoplus occidentalis(Thomas) and the prickly pear cactus,Opuntia polyacanthaHaw., was conducted on native rangeland in southeastern Wyoming. During the study, the grasshopper population density was 14.5 ± 3.7 m-2, of which 52% were M.occidentalisin cactus patches and 16%were M.occidentalisin the surrounding rangeland. Surveys of prickly pear flowers showed that 54% of the flowers had one or more (up to four) grasshoppers, of which 96% were M.occidentalis.Females of this species comprised 72% of the individuals within the cactus patches and 33% of the individuals captured in surrounding rangeland. Of the insects found in prickly pear flowers, grasshoppers accounted for 87%of the biomass; meloids (ll %)and nitidulids (2%)made up the balance. Crop content analysis of the 10 dominant grasshopper species collected from cactus patches revealed that only M.occidentalishad fed on prickly pear flowers. Within this species, 37% of all individuals had detectable levels of prickly pear cactus tissue in their crops, including 41%of the adults (58% of the females and 28% of the males) and 23% of the nymphs. Behavioral observations revealed that M.occidentalisfed on prickly pear stamens in short (10–15 min) bouts, which were frequently interrupted by aggressive physical interactions between individuals. Evaluation of the cactus stamens of flowers in the area revealed that 20% were completely or heavily damaged, 75% were moderately to slightly damaged, and 5% were undamaged by grasshopper feeding.

ISSN:1754-5692    

DOI:10.1093/ee/21.6.1301

出版商:Oxford University Press    

年代:1992

数据来源: OUP