Ant sampling: the importance of pitfall trap depth as a bias factor

When sampling with pitfall traps, possible bias factors should be considered. In this study we compare traps of two depths. The results show that, on average, deeper traps captured more ant species (Hymenoptera: Formicidae) and higher numbers of workers, and that the relative abundances of the species were different depending on the depth of the trap, regardless of the type of habitat.     

Activity traps and the corer: complementary methods for sampling aquatic invertebrates

We compared the picture of aquatic invertebrate fauna given by three types of sampling methods: the corer as well as bottom and mid-water activity traps. The corer mainly caught benthic animals (89%), the most numerous groups of which were chironomids and sphaerids. Nekton was more abundant in activity traps (77% in bottom and 63% in mid-water), the most numerous groups were Cladocera and water mites. The size distributions in catch of the corer and the activity traps differed but there was no difference between the two types of activity traps. In activity traps, individuals of the smallest size class were most abundant, wheras animals of the second smallest size class were most numerous in the corer. We suggest that activity traps and the corer could be used as complementary methods to sample aquatic invertebrate communities.     

陷阱法的改进及其在稻田蜘蛛取样中的应用

在稻田保水的情况下,使用传统的取样方法调查地面活动的节肢动物存在很大的困难。为了准确监测稻田地面活动节肢动物的物种及其个体数量和时间动态,对陷阱法在水稻田的应用进行了改进。以稻田地面活动的优势种狼蛛(Lycosidae)为监测对象,采用改进的陷阱法——"土堆陷阱法"取样,并以常用的吸虫器法作对比,验证土堆陷阱法的应用效果。建议以土堆陷阱法作为稻田地面节肢动物的调查采样方法。     

Development of an exposure-free bednet trap for sampling Afrotropical malaria vectors

An exposure-free bednet trap (the 'Mbita trap') for sampling of Afrotropical malaria vectors was developed during preliminary studies of mosquito behaviour around human-occupied bednets. Its mosquito sampling efficiency was compared to the CDC miniature light-trap and human landing catches under semi-field conditions in a screen-walled greenhouse using laboratory-reared Anopheles gambiae Giles sensu stricto (Diptera: Culicidae). When compared in a competitive manner (side by side), the Mbita trap caught 4.1+/-0.5 times as many mosquitoes as the CDC light-trap, hung beside an occupied bednet (P < 0.000 1) and 43.2+/-10% the number caught by human landing catches (P < 0.0001). The ratio of Mbita trap catches to those of the CDC light trap increased with decreasing mosquito density. Mosquito density did not affect the ratio of Mbita trap to human-landing catches. In a non-competitive comparison (each method independent of the other), the Mbita trap caught 89.7+/-10% the number of mosquitoes caught by human landing catches (P < 0.0001) and 1.2+/-0.1 times more mosquitoes than the CDC light trap (P = 0.0008). Differences in Mbita trap performance relative to the human landing catch under noncompetitive vs. competitive conditions were explained by the rate at which each method captured mosquitoes. Such bednet traps do not expose people to potentially infectious mosquito bites and operate passively all night without the need for skilled personnel. This trap is specifically designed to catch host-seeking mosquitoes only and may be an effective, sensitive, user-friendly and economic alternative to existing methods for mosquito surveillance in Africa.     

An improved technique for sampling lotic invertebrates

The electrophoretic characterization of an Artemia population from a saline lake of the Chilean Andes with unusual ecological features (Salar de Atacama, 23° 30′ S; 68° 10′ W) was carried out with the aim of comparing its genetic variation with, and genetic similarity to, representative populations of A. persimilis (Buenos Aires, Argentina) and A. franciscana (San Francisco Bay, USA). Based on the analysis of 22 loci it is concluded that the Chilean population and that from San Francisco are conspecific (D = 0.144), while the Chilean strain and A. persimilis are congeneric species (D = 1.171), differing in more than 40% of the loci. Parameters measuring genetic variation (e.g., percentage of loci polymorphic, mean number of alleles per locus, mean heterozygosity per locus) demonstrate that values for the Chilean Artemia (50.0, 1.68, 0.126, respectively) are within the range for bisexual Artemia in general and A. franciscana in particular.     

A light trap design for stratum-specific sampling of reef fish larvae

The vertical distribution of late stage reef fish larvae may potentially influence their dispersal, recruitment success and energetic expenditure during the recruitment process. To date, methods of examining the vertical distribution of reef fish larvae either under-sample late stage individuals, or are incapable of discretely sampling the water column. The aim of this study was to develop a light trap able to sample a narrow depth range enabling fine scale patterns of vertical distribution to be examined. The experimental traps radiated light in a relatively narrow beam with a maximum vertical angle of radiation of 7.5°, indicating that the traps could be placed 4.8 m apart and still sample discrete depth strata. Their catch efficiency was similar to conventional light traps, indicating that they are adequate sampling units. Preliminary data showed that most families are more abundant near the surface, although many have significant numbers of individuals lower in the water column. Some families (inc. Apogonidae) occurred in higher abundance at greater depths. Our experimental light traps permit increased resolution of the vertical distribution of late stage larval reef fishes in the field.     

A new type of collapsible insect-surveillance light trap for sampling Diptera

The newly designed Army Collapsible Insect Surveillance trap for nocturnal collection of flying Diptera that are attracted by light is described. A polyvinyl chloride construction increases durability, while the capability to collapse from a height of 92.1 cm to 24.1 cm facilitates transportation and storage.     

Evaluation of aerial sampling methods for detecting waterbird colonies

ABSTRACT Estimating the number of waterbird colonies in a given area can have important conservation implications, including assessment of the regional or global importance of an area and the impacts of conservation efforts (e.g., habitat restoration) and human disturbance (e.g., oil spills). Our objective was to examine differences in estimates of the number of waterbird colonies determined using strip‐transect (ST) surveys, distance sampling, and adaptive cluster sampling (ACS), and to compare these estimates to the minimum number of known colonies (MNKC) obtained using point‐to‐point surveys. We conducted aerial surveys in May 2004 and May and June 2005 at two sites in southern Louisiana: the Atchafalaya Basin (AB), a large forested wetland, and the Barataria‐Terrebonne estuary (BTE), a large coastal marsh with isolated clumps of woody vegetation suitable for nesting. In AB, we detected nine and eight colonies using the ACS and ST/distance sampling methods, respectively. Neither ACS estimator of number of colonies (Horvitz–Thompson and Hansen–Hurwitz) was within the 95% confidence interval of the estimate determined from ST; ST estimated—two to three times more colonies than either ACS estimator. The MNKC for the AB was 33, well within the 95% confidence interval of ? by ST sampling. For the BTE, ACS estimators (?_HT= 20.49, CI = 9.3–31.7; ?_HH= 14.15, CI = 2.3–26.0) were similar to the MNKC (20), whereas the ST (?= 87.94, CI = 82.9–92.9) and distance sampling (?= 60, CI = 31–113) methods produced much larger estimates. Our results suggest that the ACS method performed better when waterbird colonies were spatially clumped (BTE) and the ST method performed better in areas where colonies were more uniformly distributed (AB). Depending on management objectives, a complete, systematic survey of a study area may be required if the potential for missing large colonies is unacceptable. If surveying an area with no previous information about colony location or dispersion, we recommend a coarse‐scale analysis of the availability and contiguity of habitat likely to contain waterbird colonies; this analysis will help determine the most appropriate survey method.     

Comparison of two methods for sampling invertebrates: vacuum and sweep‐net sampling

ABSTRACT With numerous invertebrate sampling techniques available, deciding which technique to use under certain circumstances may be difficult. Many researchers interested in invertebrate abundance and availability relative to the foraging ecology of birds may use a technique (e.g., vacuum sampling or sweep‐netting) without understanding the impacts their choice may have on the samples collected and the ability of the method to meet research objectives. We compared the characteristics, including overall biomass, morphospecies richness, average size, diversity, and body length categories, of invertebrates collected using a sweep‐net and a Dietrick vacuum sampler along paired transects in Woodward County, Oklahoma, from May to July 2007 and 2008. These sampling techniques differed in the taxa collected, with the orders Diptera, Homoptera, and Hymenoptera dominating vacuum samples and the orders Homoptera, Orthoptera, and Araneae dominating sweep‐net samples. Although morphospecies richness was similar for the two techniques, the mean size of invertebrates collected and overall invertebrate biomass were greater for sweep‐netting than vacuum sampling. Vacuum sampling was more effective at collecting small (e.g., <5 cm) invertebrates, whereas sweep‐netting captured large (>5 cm) Orthopteran and Lepidopteran larvae at higher rates. Thus, our results indicate that neither sampling method effectively sampled all invertebrate families and investigators should be aware of the potential biases of different sampling techniques and be certain that the technique selected will allow study objectives to be met.     

An improved probe for sampling soil atmospheres

A probe for the extraction of soil gases is described. Novel features are the way the probe aperture within the soil can be manipulated from above, and the design of the tip to maximize gas extraction.     

Experimental evaluation of a minnow trap for small lotic fish

A minnow trap that operates in various flow regimes in streams and allows sampling of small fish from stream bed microhabitats was developed. In laboratory and field tests, the most efficient trap design for capturing and retaining various species of fish had one funnel oriented downstream, a plexiglass body, and commercial trout food as bait. These lightweight traps can be set in a wide range of current velocities and depths, and can be useful in investigations that examine the microhabitat use, diel activity patterns or population densities of small lotic fish. Guidelines for the trap's use and for quick verification of capture success in new situations are suggested.     

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.     

Development of a novel sticky trap for container-breeding mosquitoes and evaluation of its sampling properties to monitor urban populations of Aedes albopictus

Collection methods currently used for large-scale sampling of adult Stegomyia mosquitoes (Diptera: Culicidae) present several operational limitations, which constitute major drawbacks to the epidemiological surveillance of arboviruses, the evaluation of the impact of control strategies, and the surveillance of the spreading of allochthonous species into non-endemic regions. Here, we describe a new sticky trap designed to capture adult container-breeding mosquitoes and to monitor their population dynamics. We tested the sampling properties of the sticky trap in Rome, Italy, where Aedes (Stegomyia) albopictus is common. The results of our observations, and the comparison between sticky trap catches and catches made with the standard oviposition trap, are presented. The sticky trap collected significantly larger numbers of Ae. albopictus females than any other Culicidae species representing >90% of the total catches. A maximum of 83 An. albopictus females was collected in a single week. A high correlation (Pearson correlation coefficient r= 0.96) was found between the number of females and the number of eggs collected by the traps. The functional relationship between the number of eggs and the number of adult females was assessed by major axis regression fitted to log(1 +x)-transformed trap counts as y= 0.065 + 1.695x. Trap samples significantly departed from a random distribution; Taylor's power law was fitted to the trap samples to quantify the degree of aggregation in the catches, returning the equations s(2)= 2.401 m(1.325) for the sticky trap and s(2)= 13.068 m(1.441) for the ovitrap, with s(2) and m denoting the weekly catch variance and mean, respectively, indicating that eggs were significantly more aggregated than mosquitoes (P < 0.0001). Taylor's power law parameters were used to estimate the minimum number of sample units necessary to obtain sample estimates with a fixed degree of precision and sensitivity. For the range of densities encountered in our study area during the Ae. albopictus breeding season, the sticky trap was more precise and sensitive than the ovitrap. At low population densities (c. < 0.1 mosquito/trap), however, the ovitrap was more sensitive at detecting the presence of this species. Overall, our results indicate that our new model of sticky trap can be used to sample Ae. albopictus females in urban environments, and, possibly, other container-breeding Stegomyia mosquitoes (e.g. Aedes aegypti). The technical properties of the new trap are discussed with respect to its possible application in monitoring the population dynamics of container-breeding mosquitoes, in studying their bionomics, and in vector surveillance and, possibly, control.     

Comparison of several techniques for sampling macroinvertebrates in different habitats of a North Iberian pond

Several habitats of a Mediterranean pond were sampled for macroinvertebrates using different techniques: quantitative methods, semiquantitative hand-net sweep sampling and a qualitative protocol based on hand-net sweeps with fixed counts of individuals. The taxonomic composition was analyzed by DCA and several indices based on taxon composition or percentage of individuals were calculated. The aim of the study was to compare the results provided by these techniques and, in particular, to check if the qualitative approach could be an appropriate low-cost methodology for use in biomonitoring. The results provided by the three sampling methods in relation to submerged macrophytes were very similar. In soft sediment, certain differences were found between the quantitative and semiquantitative techniques. The qualitative protocol applied to single habitats collected fewer taxa than the corresponding quantitative or semiquantitative techniques. However, the overall protocol, consisting of samples from three habitats, provided higher richness values than all the quantitative and semiquantitative methods together, with 59 taxa out of the 70 collected during the study. It is concluded that this qualitative methodology performed reasonably well since it offers a reliable view of the community and it misses few taxa. Moreover, it is not so time consuming as other techniques and can be applied in a variety of habitats. It, therefore, seems to be an efficient method for bioassessment of the macroinvertebrate communities of ponds or the littoral zone of lakes.     

Colour-coded sampling: the pan trap colour preferences of oligolectic and nonoligolectic bees associated with a vernal pool plant

1. Pan traps or water traps have been used widely to sample agricultural insect pests, but no formal studies have assessed the utility of these traps as sampling devices for bees. 2. Coloured pan traps, used as flower models, can efficiently and selectively sample an oligolectic bee, Andrena (Hesperandrena) limnanthis, and other bees associated with white-flowered Limnanthes douglasii rosea. 3. Females and males of A. limnanthis unexpectedly exhibit different colour preferences. Females are strongly attracted to white and blue traps, but discriminate against yellow traps. Males prefer white traps over blue and yellow traps. Consequently, blue traps are selective for females only, while white traps are selective for both sexes. 4. Non-A. limnanthis bees were caught in significantly greater numbers in yellow than in blue or white traps. These bees included generalists, as well as specialists that are oligolectic on mostly yellow-flowered species. 5. Colour of traps had a significant effect on the numbers of A. limnanthis females and males, and non-A. limnanthis bees caught in traps. These results indicate that quantitative sampling of bees by pan trap methods can be highly sensitive to trap colour.     

A simple design for a rain-resistant pitfall trap

Summary. Heavy rain causes major problems with using pitfall traps to collect ants and other surface-active arthropods. A simple design for a rain-resistant pitfall trap is described. The trap is constructed by grinding a hole in the side of a plastic vial and then covering it with fine-gage wire screen. This hole allows excess water to drain out the side of the trap. A method for quickly setting small-diameter pitfalls into the ground with an auger and a battery-powered drill is also described.Received 23 December 2003; revised 23 July 2004; accepted 7 October 2004.     

Potential of pigeon pea as a trap crop for control of fruit worm infestation and damage to okra

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