Detecting invertebrate responses to fire depends on sampling method and taxonomic resolution

New knowledge about the responses of species to fire is needed to plan for biodiversity conservation in the face of changing fire regimes. However, the knowledge that is acquired may be influenced by the sampling method and the taxonomic resolution of a study. To investigate these potential sampling biases, we examined invertebrate responses to time since fire in mallee woodlands of southern Australia. Using a large‐scale replicated study system, we sampled over 60 000 invertebrates with large pitfall traps, wet pitfall traps and sweep nets, and undertook analyses at morphospecies and order level. Large pitfalls and sweep nets detected several strong fire effects, whereas wet pitfall traps detected few effects. Invertebrate abundance in sweep nets was highest shortly after fire because of grasshopper outbreaks. Several additional morphospecies showed strong preferences for different stages in the post‐fire succession. In contrast with morphospecies effects, analyses at order level either failed to detect fire effects or were driven by the most abundant species. For fire research to produce credible results with the potential to guide management, it must use a range of sampling techniques and undertake analyses at (morpho)species level. Homogeneous fire management, such as fire suppression in fragmented landscapes or widespread frequent burning for asset protection, is likely to cause declines in fire‐affected invertebrates.     

Detecting impacts of non‐native species on associated invertebrate assemblages depends on microhabitat

Invasive plants that displace native floral communities can cause changes to associated invertebrate species assemblages. Using a mini‐review of the literature and our own data we add to the still considerable debate about the most effective methods for testing community‐level impacts by invasive species. In endangered saltmarshes of southeast Australia, the non‐native rush Juncus acutus L. is displacing its native congener J. kraussii Hochst., with concurrent changes to floral and faunal assemblages. In two coastal saltmarshes, we tested the hypothesis that the ability to detect differences in the invertebrate assemblage associated with these congeneric rushes depends on the microhabitat of the plant sampled. We used three sampling methods, each targeting specific microhabitats: sweep netting of the plant stems, vacuum sampling of the plant tussock, and vacuum sampling of the ground directly below the plants. Over 3800 individuals and 92 morphospecies were collected across four main taxa: gastropods, crustaceans, hexapods and arachnids. Detection of differences in invertebrate density, richness and composition associated with native compared with non‐native rushes was dependent on the microhabitat sampled and these differences were spatially variable. For example, at one saltmarsh the stems and tussock of J. acutus had a lower density and richness of total invertebrates and hexapods than those of the native J. kraussii. In contrast, crustaceans on the ground were in greater abundance below J. acutus than J. kraussii. This study demonstrates that on occasions where overall differences in the assemblage are not detected between species, differences may become apparent when targeting different microhabitats of the plant. In addition, separately targeting multiple microhabitats likely leads to a greater probability of detecting impacts of invasion. Comparing the invertebrate assemblage without differentiating between or sampling an array of microhabitats can fail to determine the impact of invasive species. These results highlight that a combination of methods targeting different microhabitats is important for detecting differences within the invertebrate community, even for phylogenetically related species.     

The beetle fauna of remnant eucalypt woodlands from the Northern Plains Victoria Australia

The abundance, richness and trophic structure of beetle assemblages (Insecta: Coleoptera) from remnant eucalypt woodlands of the Northern Plains, Victoria, is documented. Three sampling methods (pitfall trapping, direct searching, sweep netting) were used to sample beetles in four seasons over a year. A total of 4487 beetles were sorted into 342 morphospecies from 46 families. Pitfall trapping alone caught the greatest number of families (72%), morphospecies (56%) and specimens (50%). However, direct searching and sweep netting yielded a large number of morphospecies not caught by pitfall trapping. Sampling in summer yielded the greatest number of families (78%) and morphospecies (55%) but the most specimens (31%) were caught during winter. The proportions of different trophic groups varied little across different seasons but greatly for sampling methods. Pitfall trapping caught a higher proportion of predators and a lower proportion of herbivores than other sampling methods. Direct searching caught mostly herbivores, whilst sweep netting captured a large number of fungivores. The results have implications for the design of sampling sets for inventory surveys of invertebrate groups.     

Comparing the precision,accuracy, and efficiency of branch clipping and sweep netting for sampling arthropods in two Jamaican forest types

ABSTRACT Devising methods for sampling arthropods presents many challenges, including understanding possible differences in results obtained by different individuals (precision), investigating differences between estimates and the actual variable of interest (accuracy), and assessing the effort and cost of a given method (efficiency). We assessed the precision, accuracy, and efficiency of sweep netting and branch clipping, two common methods of sampling arthropods, in mangrove and second‐growth scrub forests in Jamaica, West Indies, in 2009. Three individuals used both methods sequentially to sample arthropods in the territories of American Redstarts (Setophaga ruticilla). We found that both branch clipping and sweep netting lacked precision because different individuals produced different estimates of either arthropod abundance (number of individuals per sample) or biomass. In both forests, more arthropods were sampled with sweep netting, in terms of biomass and abundance, and several orders of arthropods were collected that were missed by branch clipping. We also detected the absence of a predictable habitat‐based difference in arthropod biomass with sweep netting, but not with branch clipping. Sweep netting took longer overall (field and processing time combined) and was therefore less efficient. Despite problems with precision and efficiency, our results suggest that sweep netting may be a more accurate method than branch clipping for sampling foliage arthropods in some forest habitats. Our study also reveals the importance of recognizing and controlling for individual bias and of choosing arthropod sampling methods most appropriate to each study species and habitat type.     

A laboratory technique to speed processing of samples with large numbers of invertebrates

The amount of time needed to process samples with large numbers of terrestrial invertebrates in the laboratory has been a long‐standing obstacle impeding progress in invertebrate conservation biology and applied ecology. Laboratory subsampling of samples with large numbers of invertebrates is one method that saves time and reduces processing cost. In this study, a laboratory vacuum processing technique, consisting of a vacuum pump, aspirator and voice recognition software, was compared with a subsampling technique, and a conventional whole sample counting method. Vacuum processing was the most efficient technique; on average, more than five times more insects were processed per minute compared with whole sample counting and subsampling techniques. Differences in efficiencies among techniques were affected by trap type and invertebrate abundance. The vacuum technique was most efficient when processing high abundance pitfall trap samples, and was less efficient in processing pan trap samples that had invertebrates entangled by algae and other materials. Caution should be exercised when using the technique on soft‐bodied or poorly preserved specimens; a subsampling technique may be more appropriate in these cases, especially if specimens must be identified to genus or species level at a later time. The efficiency of the vacuum technique is reduced relative to the amount of time it takes to locate invertebrates in a sample; therefore, the technique does not save substantial time when processing samples with large amounts of substrate or debris, such as is the case with some aquatic invertebrate samples. However, if flotation or another method that separates invertebrates from other materials is used first, then the vacuum method would be useful for these types of samples as well.     

Measuring Spider Richness: Effects of Different Sampling Methods and Spatial and Temporal Scales

Assessing the richness of invertebrate taxa to aid conservation and management requires a better understanding of the potential sources of error. Patterns of richness for heathland spiders at the species and family levels were compared across three sampling methods, four spatial scales, and monthly intervals (for 16 months). A total of 33 families and 130 species was collected: pitfall traps collected 94% of species, sweep net, 25%, and visual search, 41%. The sampling methods produced variable results. Pitfall trap and sweep net techniques identified significant, yet contrasting spatial differences in the number of families and species at one spatial scale. Pitfall trap data reflected strong temporal variation that influenced spatial patterns in richness (across one spatial scale for families and two for species). The use of broader temporal scales introduced a potential failure to detect significant differences in the richness of ground active spiders, and this risk varied spatially. The sweep net is not recommended for this habitat, although a method that targets the foliage is required for a more complete faunal assessment. Visual searches detected no significant patterns in richness, yet given its potential and increasing use for rapid biodiversity surveys, ways to improve sampling efficiency are suggested.     

Use of both benthic and drift sampling techniques to assess tropical stream invertebrate communities along an altitudinal gradient, Costa Rica

1. Two sampling techniques were used to characterize invertebrate communities in eight, low-order streams along an altitudinal gradient in Costa Rica that represents the last continuous tract of primary forest spanning such extremes in elevation (i.e. near sea level to 2900 m a.s.l.) along the Caribbean Slope of Central America. A standard Surber sampler was used to sample invertebrates on the stream bottom, and drift sampling nets were used to sample invertebrates drifting in the stream flow. 2. Sites were established at 30, 50, 700 1800 and 2700 m a.s.l. In one to two streams per site, six Surber samples were collected, and drift was sampled every 3 h over one 24-h period between April and August 1994. All sites were in primary forest, with the exception of the lowest elevation site (30 m) which was located in banana plantations. 3. Both sampling techniques indicated that Diptera (Chironomidae) and Ephemeroptera were the dominant insect groups at all sites. Disturbed streams draining banana plantations were dominated by Chironomidae and had lower taxon richness and diversity than other sites. 4. While data from benthic samples indicated that insects were the major faunal component (> 90%) at all sites, drift samples were dominated by larval shrimps (> 50%) at the 30 m and 50 m sites. 5. Drift periodicity of invertebrates was observed at those sites characterized by predaceous fishes: nocturnal drift densities were higher than diurnal densities at 30, 50 and 700 m a.s.l., however, no periodicity was observed at 1800 and 2700 m a.s.l. where fish were absent. 6. This study shows the importance of measuring invertebrate drift, in addition to directly sampling the benthos. Drift sampling provided data on a major community component (shrimps) of lowland tropical streams, that would have been overlooked using traditional benthic sampling techniques, and in some cases provided additional information on taxon richness. 7. Based on results of the present study, it is recommended that drift sampling be included as a standard complementary tool to benthic sampling in biological assessments (e.g. bioassessment protocols) of tropical streams, which are often characterized by migratory invertebrate species such as shrimps. Drift samples provide critical information on the presence or absence of shrimps and also on the timing and magnitude of their migration which is an important link between many tropical rivers and their estuaries.     

Towards the development of a macroinvertebrate sampling technique for palustrine wetlands in South Africa: a pilot investigation in the KwaZuluNatal midlands

A study was undertaken in November 2003 to derive a suitable sampling technique for collecting a representative sample of aquatic macroinvertebrates from a selected emergent vegetation biotope in a palustrine wetland, Melmoth Vlei, KwaZulu-Natal, South Africa. The aim was to undertake a preliminary investigation on the development and testing of a macroinvertebrate sampling technique for use in emergent sedge-dominated palustrine wetlands (sensu Cowardin et al. 1979), which could contribute to the development of a South African wetland health biomonitoring programme. Sweep nets and activity traps were evaluated for their effectiveness in terms of macroinvertebrate collection. Sweep net sampling was tested over a range of sweep intensities to determine the minimum number of sweeps required to collect a representative sample. Sampling efficiency of activity traps placed at four depths was tested, and taxon diversity and composition of sweep net and activity trap samples were compared to determine whether activity traps are required to supplement sweep net data. A total of 32 taxa (identified mainly to family level) were identified in the samples collected. Taxon diversity and composition did not differ in the activity traps placed at the four depth locations. Taxon diversity did not differ significantly between different sweep intensities. This may be a result of high variability of macroinvertebrate distribution within a wetland. There is evidence, however, to suggest that this result is due to an inadequate sample size. There was a significant difference in taxon composition between the different sweep intensities (P < 0.05) and between activity trap and sweep net samples (P < 0.05). Sixty-eight percent of taxa appeared more frequently in sweep net sampling than in activity trap sampling. Two taxa were found exclusively in activity traps, although the numbers of these taxa collected were not significant, and they do not represent any unique trophic group. Based on these findings, it was concluded that activity traps are not required to supplement sweep net data, and a technique using a sweep net with a sweep intensity of five would be suitable for collecting a representative sample of macroinvertebrates from a palustrine wetland.     

Sweeping beauty: is grassland arthropod community composition effectively estimated by sweep netting?

Arthropods are critical ecosystem components due to their high diversity and sensitivity to perturbation. Furthermore, due to their ease of capture they are often the focus of environmental health surveys. There is much debate regarding the best sampling method to use in these surveys. Sweep netting and pan trapping are two sampling methods commonly used in agricultural arthropod surveys, but have not been contrasted in natural grassland systems at the community level. The purpose of this study was to determine whether sweep netting was effective at estimating arthropod diversity at the community level in grasslands or if supplemental pan trapping was needed. Arthropods were collected from grassland sites in Montana, USA, in the summer of 2011. The following three standardized evaluation criteria (consistency, reliability, and precision) were developed to assess the efficacy of sweep netting and pan trapping, based on analyses of variations in arthropod abundances, species richness, evenness, capture frequency, and community composition. Neither sampling method was sufficient in any criteria to be used alone for community‐level arthropod surveys. On a taxa‐specific basis, however, sweep netting was consistent, reliable, and precise for Thysanoptera, infrequently collected (i.e., rare) insects, and Arachnida, whereas pan trapping was consistent, reliable, and precise for Collembola and bees, which is especially significant given current threats to the latter's populations worldwide. Species‐level identifications increase the detected dissimilarity between sweep netting and pan trapping. We recommend that community‐level arthropod surveys use both sampling methods concurrently, at least in grasslands, but likely in most nonagricultural systems. Target surveys, such as monitoring bee communities in fragmented grassland habitat or where detailed information on behavior of the target arthropod groups is available can in some instances employ singular methods. As a general ecological principle, consistency, reliability, and precision are appropriate criteria to evaluate the applicability of a given sampling method for both community‐level and taxa‐specific arthropod surveys in any ecosystem.     

The influence of sampling method on the classification of wetland macroinvertebrate communities

Macroinvertebrate communities sampled by a corer, plankton net and sweep net from five wetlands on the Swan Coastal Plain were compared. The composition of the fauna collected in sweeps and tows was generally similar and differed from that collected in the cores. Cores caught fewer species than tows and sweeps at all wetlands and did not capture fast swimming hemipterans or less abundant taxa. The highest species richness was recorded in sweep samples in four out of the five wetlands. Classification (TWIN-SPAN) and ordination (SSH) of the samples collected in sweeps and tows gave good separation of the wetlands, whereas classification of core samples did not. Coring appeared to be the least suitable sampling method for describing the major components of the macroinvertebrate communities of these wetlands. Plankton tows were useful if the time available for sorting was limited as these samples were free of sediments and generally gave similar results to those obtained with sweeps. Sweeps appeared to be the most useful method for a large classification study as they collected more species and resulted in the best discrimination amongst wetlands.     

Sampling methods, dispersion patterns, and fixed precision sequential sampling plans for western flower thrips (Thysanoptera: Thripidae) and cotton fleahoppers (Hemiptera: Miridae) in cotton

A 2-yr field study was conducted to examine the effectiveness of two sampling methods (visual and plant washing techniques) for western flower thrips, Frankliniella occidentalis (Pergande), and five sampling methods (visual, beat bucket, drop cloth, sweep net, and vacuum) for cotton fleahopper, Pseudatomoscelis seriatus (Reuter), in Texas cotton, Gossypium hirsutum (L.), and to develop sequential sampling plans for each pest. The plant washing technique gave similar results to the visual method in detecting adult thrips, but the washing technique detected significantly higher number of thrips larvae compared with the visual sampling. Visual sampling detected the highest number of fleahoppers followed by beat bucket, drop cloth, vacuum, and sweep net sampling, with no significant difference in catch efficiency between vacuum and sweep net methods. However, based on fixed precision cost reliability, the sweep net sampling was the most cost-effective method followed by vacuum, beat bucket, drop cloth, and visual sampling. Taylor's Power Law analysis revealed that the field dispersion patterns of both thrips and fleahoppers were aggregated throughout the crop growing season. For thrips management decision based on visual sampling (0.25 precision), 15 plants were estimated to be the minimum sample size when the estimated population density was one thrips per plant, whereas the minimum sample size was nine plants when thrips density approached 10 thrips per plant. The minimum visual sample size for cotton fleahoppers was 16 plants when the density was one fleahopper per plant, but the sample size decreased rapidly with an increase in fleahopper density, requiring only four plants to be sampled when the density was 10 fleahoppers per plant. Sequential sampling plans were developed and validated with independent data for both thrips and cotton fleahoppers.     

Invertebrate diversity on

Despite the global importance of New Zealands invertebrates, relatively little is known about them and their relationships with plants and plant communities in native habitats. Invertebrate diversity was examined by beating randomly chosen shrubs of the species Olearia bullata (Asteraceae) and Coprosma propinqua(Rubiaceae). Invertebrate taxon richness was assessed initially using morphospecies, which were identified subsequently by expert taxonomists. Though the taxon richness of invertebrates recorded from O. bullata was not significantly higher than that on C. propinqua (except for the orders Diptera and Hemiptera), there was a clear indication that O. bullata hosts a higher diversity of invertebrates. Mean number of taxa per shrub for O. bullata was higher in all cases (except Coleoptera), and so was the maximum number of taxa per shrub. Overall, O. bullata yielded 115 invertebrate taxa compared with 93 for C. propinqua. Moreover, 50 invertebrate taxa were restricted to O. bullata compared with 28 for C. propinqua. Since at least ten species of Oleariaare threatened or uncommon, this could be cause for concern with respect to the maintenance of invertebrate diversity. Therefore, sites where Oleariaspecies are still present are likely to be of significance for invertebrate conservation.     

Comparing four simple,inexpensive methods for sampling forest arthropod communities

Terrestrial arthropods are diverse, and quantifying their availability to consumers is important for understanding both consumer and insect distribution, abundance, and communities. However, characterizing arthropod communities in complex forest ecosystems is challenging. We compared arthropod communities in a wet‐limestone forest in Jamaica during the dry season sampled by four methods: branch clips, sweep netting, and sticky traps applied to tree trunks and hanging free of vegetation. We found no effect of relative height in the canopy for the two methods that could be used at different heights, i.e., hanging sticky traps and branch clips. In addition, the arthropod community sampled changed over time (season) for sweep nets and branch clips. We also found that branch clips and sweep nets sampled more arthropod taxa than the two sticky‐trap methods. In addition, branch clips and sweep nets sampled more ants and spiders than the two sticky‐trap methods, whereas collar sticky traps on tree trunks sampled more bark lice (Psocoptera), and hanging sticky traps more flies (Diptera) than the other methods. Percentages of flying insects and strong‐flying insects sampled did not differ between sweep netting and branch clipping, but a higher percentage of both groups were captured with collar and hanging sticky traps. Because we found that the different methods sampled different subsets of the arthropod community, both taxonomically and in terms of aerial versus non‐aerial taxa, investigators should choose the arthropod sampling methods that most closely align with their focal species and study questions. For example, investigators might use collar traps for studies of bark gleaners, hanging sticky traps for aerial foragers, and branch clips or sweep nets for foliage gleaners. Alternatively, if a focal species is known to prefer certain prey items, investigators may instead select a method that effectively samples those prey taxa. Finally, for some studies, using multiple sampling methods may be the best option.     

Conservation implications of grazing practices on the plant and dipteran communities of a turlough in Co. Mayo,Ireland

Turloughs, which are classified as priority habitats under the European Habitats Directive, are seasonally flooded depressions found almost exclusively in Ireland. In 2001, three adjacent fields with different stocking densities were selected and plant/dipteran communities within the same vegetation zone of each field (site) were investigated using quadrats and sweep netting, respectively. There was a significant positive relationship between Diptera morphospecies richness/Diptera abundance and mean vegetation height (P < 0.001). However, no significant relationship between Diptera morphospecies richness and plant species richness was found. Median Diptera morphospecies richness per sweep was lower at the site with the highest stocking density (17) than at the other two sites (22 and 31, respectively). Total species richness of Sciomyzidae was greater at the least grazed site (7) than at the more heavily grazed sites (2 and 1, respectively). The results suggest that an evaluation of turlough management practices based on plant communities alone is not sufficient and that at least some areas within the turlough basin remain ungrazed on a rotational basis to ensure maximum diversity of Diptera.     

Toward an optimal sampling protocol for Hemiptera on understorey plants

There are no standardised sampling protocols for inventorying Hemiptera from understorey or canopy plants. This paper proposes an optimal protocol for the understorey, after evaluating the efficiency of seven methods to maximise the richness of Hemiptera collected from plants with minimal field and laboratory time. The methods evaluated were beating, chemical knockdown, sweeping, branch clipping, hand collecting, vacuum sampling and sticky trapping. These techniques were tested at two spatial scales: 1 ha sites and individual plants. In addition, because efficiency may differ with vegetation structure, sampling of sites was conducted in three disparate understorey habitats, and sampling of individual plants was conducted across 33 plant species. No single method sampled the majority of hemipteran species in the understorey. Chemical knockdown, vacuum sampling and beating yielded speciose samples (61, 61 and 30 species, respectively, representing 53, 53 and 26% of total species collected). The four remaining methods provided species-poor samples (<18 species or <16% of total species collected). These methods also had biases towards particular taxa (e.g., branch clipping and hand collecting targeted sessile Hemiptera, and sticky trapping were dominated by five species of Psyllidae). The most time-efficient methods were beating, sweeping and hand collecting (200 minutes of field and laboratory time yielded >7 species for each technique). By comparison, vacuum sampling, sticky trapping, branch clipping and chemical knockdown yielded <5 species for the same period. Chemical knockdown had further disadvantages; high financial cost and potential spray drift. The most effective methods for a standardised sampling protocol to inventory Hemiptera from the understorey are beating and vacuum sampling. If used in combination, these methods optimise the catch of understorey hemipteran species, as their samples have high complementarity.     

Assessment of Littoral Benthic Invertebrate Communities at the Land–Water Interface in Lakes Recovering from Severe Acid- and Metal-Damage

Benthic invertebrate communities within confluence sites, or areas of sediment deposition, are shaped by the input of catchment products including coarse woody debris, organic and inorganic particulates, and contaminants, but these sites also appear to be potential “hotspots” where recolonization of severely damaged ecosystems begins. Two species of leaf packs and a sweep netting technique were used to assess benthic invertebrate communities across a gradient of 14 confluence sites in 3 recovering lakes near the copper and nickel smelters in Sudbury, Canada. Environmental variables including delta habitat composition, delta area and length, and composition of deposited materials were used to detect spatial patterns in littoral benthic invertebrate communities. Benthic invertebrate community relationships with water chemistry were also assessed. Partial redundancy analysis (pRDA) showed that all sampling methods detected similar gradients of increasing invertebrate community richness and diversity as area and length of the sediment delta and the surface organic matter abundance increased. Two-way nested ANOVAs showed significant differences (p < .05) in taxa richness and diversity metrics among sites. Of the three methods, the benthic invertebrate community measurements from the birch leaf packs provided the strongest correlations with measures of organic matter inputs or habitat characteristics of the confluence zones. These correlations suggest that tree planting in riparian areas, or organic matter or macrophyte additions to littoral zones, may enhance littoral benthic invertebrate richness and diversity in acid and metal damaged lakes.     

Cave invertebrate assemblages differ between native and exotic leaf litter

Abstract Allochtonous leaf litter is an important source of energy and nutrients for invertebrates in cave ecosystems. A change to the quality or quantity of litter entering caves has the potential to disrupt the structure and function of cave communities. In this study, we adopted an experimental approach to examine rates of leaf litter decomposition and the invertebrate assemblages colonizing native and exotic leaf litter in limestone caves in the Jenolan Caves Karst Conservation Reserve, New South Wales, Australia. We deployed traps containing leaf litter from exotic sycamore (Acer pseudoplatanus) and radiata pine (Pinus radiata) trees and native eucalypts (Eucalyptus spp.) in twilight zones (near the cave entrance) and areas deep within the caves for 3 months. Thirty‐two invertebrate morphospecies were recorded from the litter traps, with greater richness and abundance evident in the samples from the twilight zone compared with areas deep within the cave. Sycamore litter had significantly greater richness and abundance of invertebrates compared with eucalypt and pine litter in samples from the twilight zone, but there was no difference in richness or abundance among litter samples placed deep within the cave. Relative rates of decay of the three litters were sycamore > eucalypt > pine. We discuss the potential for the higher decomposition rates and specific leaf area in sycamores to explain their higher invertebrate diversity and abundance. Our findings have important implications for the management of exotic plants and the contribution of their leaf litter to subterranean ecosystems.     

Determination of Oebalus pugnax (Hemiptera: Pentatomidae) spatial pattern in rice and development of visual sampling methods and population sampling plans

Commercial rice, Oryza sativa L., fields in southeastern Texas were sampled during 2003 and 2004, and visual samples were compared with sweep net samples. Fields were sampled at different stages of panicle development, times of day, and by different operators. Significant differences were found between perimeter and within field sweep net samples, indicating that samples taken 9 m from the field margin overestimate within field Oebalus pugnax (F.) (Hemiptera: Pentatomidae) populations. Time of day did not significantly affect the number of O. pugnax caught with the sweep net; however, there was a trend to capture more insects during morning than afternoon. For all sampling methods evaluated during this study, O. pugnax was found to have an aggregated spatial pattern at most densities. When comparing sweep net with visual sampling methods, one sweep of the "long stick" and two sweeps of the "sweep stick" correlated well with the sweep net (r2 = 0.639 and r2 = 0.815, respectively). This relationship was not affected by time of day of sampling, stage of panicle development, type of planting or operator. Relative cost-reliability, which incorporates probability of adoption, indicates the visual methods are more cost-reliable than the sweep net for sampling O.     

The Amazonas‐trap: a new method for sampling plant‐inhabiting arthropod communities in tropical forest understory

Methods to quantify plant‐insect interactions in tropical forests may miss many important arthropods and can be time consuming and uneven in capture efficiency. We describe the Amazonas‐trap, a new method that rapidly envelops the target plant for sampling arthropods. We evaluated the efficiency of the Amazonas‐trap by comparing it with two commonly used sampling methods to collect arthropods from plants: the beating tray and manual collection. Samples were collected in 10 permanent plots, in the Ducke forest reserve, Manaus (Amazonas, Brazil). In each plot we sampled 18 plant individuals of Protium sp. (Burseraceae): six by a beating tray, six by manual collection, and six using the Amazonas‐trap. All insects were identified to the family level and those belonging to the order Hymenoptera were identified to the species and morphospecies level. The new method sampled more insect families and more Hymenoptera species than tree beating and manual collection. Of the 75 total families collected, 20 were sampled exclusively by the Amazonas‐trap, seven were only collected with a beating tray, and seven were sampled exclusively with manual collecting. A similar pattern was found for abundance: Amazonas‐trap sampled more individuals, followed by the beating tray and manual collection. Small and winged arthropods were more abundant in Amazonas‐trap, explaining the highest richness of Hymenoptera and insect families sampled with this method. The new method sampled more spiders, wood‐fungi feeders, sap suckers, omnivorous, parasitoids, and insect predators than the other methods, but was equally effective in sampling leaf‐feeders and ants. Amazonas‐trap was more time consuming in the field, but for all diversity parameters evaluated, the new method showed better performance for collecting invertebrates on plants.     

Entomofauna associated to horticultural crops under organic and conventional practices in Córdoba, Argentina

Farming practices and the addition of chemical synthetic substances in conventional agroecosystems are detrimental mainly to natural enemies of phytophagous insects, diminishing the natural regulation of pest insects. On the other hand, in organic agriculture, biological processes and care of the environment are favoured, hence an increase in insect biodiversity is predicted in this type of systems. In this work, abundance, richness of insects and proportion of functional groups were compared through a single quantitative sampling of insects in horticultural crop fields, three under organic and three under conventional management practices. Insect species richness, total and for guilds (phytophagous and entomophagous insects) were significantly higher in organic orchards, and also was the abundance of entomophagous insects. Richness and abundance of all insect orders (with exception of Homoptera abundance), were higher in orchards under organic management, being significative the differences for richness of Coleoptera and richness and abundance of Hymenoptera. Similar tendencies were observed in data obtained through sweep net in weeds. These results suggest that organic practices increase the diversity of species, particularly that of natural enemies.