Determination of an Optimal Pitfall Trap Size for Sampling Spiders in a Western Australian Jarrah Forest

Pitfall trapping is a sampling technique extensively used to sample surface foraging invertebrates for biological diversity studies and ecological monitoring. To date, very few invertebrate studies have considered what trap size is optimal for sampling spiders. This study presents preliminary findings from a single short sampling period on the role of trap size in sampling spiders in a Western Australian Jarrah forest. Four different trap diameters (4.3, 7.0, 11.1 and 17.4 cm) were examined (4 trap sizes × 15 replicates = 60 traps). Two-way ANOVAs revealed no significant interaction effects between trap size or the spatial positioning of transects within the study site along which the pitfall traps were arranged. Post-hoc tests revealed abundance, family richness and species richness increased with increasing trap sizes for traps 7.0 cm. No significant differences in these dependent variables occurred between 4.3 and 7.0 cm traps, or for species richness between 11.1 and 17.4 cm traps. Determination of an optimal trap size was undertaken by bootstrapping and calculating species accumulation curves for increasing numbers of traps used. Three different criteria were considered: equivalent number of traps (15), standardized sampling intensity (cumulative trap circumference, approximately 207 cm) and standardized cumulative handling time (approximately 1 hour 17 minutes). The largest trap size (17.4 cm) was most efficient in terms of number of traps and trap circumference. For the same number of traps, it caught 19 species whereas all other trap sizes caught ten species. At the standardized circumference, it caught seven species whereas all other trap sizes caught five. For handling time, however, the two largest trap sizes (17.4 and 11.1 cm) were optimal. Both caught nine species whereas all other traps caught 相似文献   

Thermal dependence of trap building in predatory antlion larvae (Neuroptera: Myrmeleontidae)

Trap-building predators remain under strong selection from thermal microenvironments. To address how soil temperature and body size affect trap building, we conducted a laboratory experiment using larvae of the antlion Myrmeleon bore at six ecologically relevant temperatures. Larger larvae built larger traps, and warmer soil led to more and larger traps. Body mass did not alter the dependence of trap building on temperature. Our results suggest that the physiological capacity of antlion larvae, which is affected by larval size and body temperature, is the major determinant of trap building. This effect should be considered when assessing interactions between antlions and prey.     

Modelling the interplay between pest movement and the physical design of trap crop systems

Abstract 1 The interplay between pest movement and trap crop physical design is modelled in a situation where the pest moves by a random walk with spatially variable mobility. Questions addressed are: (i) how does the proportion of trap crop area of the total field area influence the equilibrium distribution of pests among the crop and the trap crop and (ii) how do crop patch size and shape influence the speed of pest redistribution from the crop to the trap crop. 2 When pest mobility in the trap crop is clearly lower than that in the crop, the pest population in the crop decreases very sharply for small trap crop proportions. When mobility in the trap crop is slightly closer to that in the crop, the pest population in the crop decreases much more gradually with increasing trap crop proportion. Thus finding a trap crop that the pest distinctly prefers over the crop appears to be crucial for developing efficient trap crop systems. 3 The rate of decay in the pest population in the crop increases with increasing perimeter to area ratio of the crop patch. Hence, designing field layouts to increase the perimeter to area ratio of crop patches may be beneficial.     

The Tauber Pollen Trap,a Discussion of Its Usefulness in Pollen Deposition Studies

In connection with pollen deposition studies some discrepancies between Tauber traps and open collectors were discovered. Field observations showed that the aerodynamic lid of the Tauber trap itself acted as a pollen trap by redeposition e.g. because of rainsplash. In an experiment coal dust in the size range of pollen was introduced in a turbulent air stream passing over the trap. Great quantities of coaldust were captured on the aerodynamic lid. By exposure to artificial rain it was observed that the splashing effect of raindrops brought coal dust into the sampler. By application of Corylus pollen on the aerodynamic lid and exposure to rain, it was found that great amount of pollen is transferred by raindrop splash to the trap. This contamination of the pollen contents of the trap is so serious that the usefulness of the Tauber trap for quantitative evaluation of the pollen deposition is doubted unless the trap is protected in some way. Further tests of this effect have been planned.     

Comparison of several traps for catching German cockroaches (Dictyoptera: Blattellidae) under laboratory conditions

German cockroach, Blattella germanica (L.) (Dictyoptera: Blattellidae), catch by five types of traps and modifications of each, were tested under controlled laboratory conditions. Cockroach catch differed significantly among traps. Lo-line trap caught the greatest number of cockroaches in the test arena for each size class (23% small nymphs, 39% of gravid females, and 60% of other size classes in the experimental arena). Jar traps caught the least number of cockroaches in the test arena for each size class (range, 7-23% of each size class trapped). Modifications of traps also altered catch of cockroaches. Food bait tablets increased catch significantly; however, increases were small (<10%). Size of traps did not affect catch; whole traps or half traps caught the same number of cockroaches. Jar traps were much less effective than sticky traps, catching only half the number of cockroaches as sticky traps. A thin layer of petrolatum was a more effective barrier in jar traps to cockroach escape than powdered Olancha clay. Traps with petrolatum caught about twice as many cockroaches as traps with clay. Trapping of any of six life stages was not significantly affected by catch of any of the other stages. Rather, trap catch of each life stage was dependent on the number of that life stage available in the experimental arenas. In conclusion, of the traps tested, the Lo-line trap was the most sensitive for measuring cockroach catch, whereas the Detector trap (one third of trap) was the most economical trap (greatest sensitivity for lowest cost).     

Defining the fire trap: Extension of the persistence equilibrium model in mesic savannas

Mesic savannas are dominated by trees that are strong resprouters caught in a frequent fire trap. Persistence within this fire trap has been described by a resprout curve of SizeNext ~ f(Pre‐fire size), defined by the Michaelis‐Menten function. A key feature of this resprout curve is a stable persistence equilibrium that represents the size of individual plants upon which a population will converge over successive inter‐fire time steps under a given fire regime. Here, we contend that such a resprout curve does not adequately describe resprout tree dynamics in frequently burnt mesic savannas because it is constrained to an asymptote. We propose a new framework for modelling the resprout curve, which recognizes that local environmental stochasticity and growth patterns can interact to change the growth response function entirely, and thus more readily reflect the range of feasible resprout responses. Importantly, we define an unstable equilibrium representing the size above which individuals have escaped the fire trap and explore mechanisms that can shift an individual from persistence to escape. Through a case study from northern Australia, we confirm that our framework provides a simple yet practical approach to defining these critical aspects of savanna tree growth dynamics: persistence and escape.     

Functional characteristics of traps of aquatic carnivorous Utricularia species

Firing and resetting of traps in aquatic Utricularia species are associated with water flow and trap volume changes. In this study, trap thickness was used as a measure of water flow and was monitored automatically using an electronic position sensor. The basic characteristics of mechanically stimulated firing and resetting were measured in isolated traps from 13 aquatic Utricularia species and in two trap size categories in Utricularia reflexa. This allowed to study the relationship between these trap functions and trap thickness and length (criteria of trap size). Additionally, the characteristics of spontaneous firings (without any mechanical stimulation) were compared for U. reflexa traps fed or denied prey during a 1-day period. On the absolute scale, the 13 Utricularia species differed considerably in their firing and resetting rates. Significant interspecific differences were also found in the magnitude of firing (in total 3.7–4.2 times) and resetting rates (10–24 times) per unit trap thickness or length. Overall, traps of Utricularia australis, Utricularia stellaris and Utricularia inflata showed the greatest firing and resetting rates. The relative magnitude of firing per unit trap thickness or length showed a highly significant negative correlation with both trap thickness and length and the same also held for the relative resetting rates. Smaller and narrower traps are thus relatively more effective at trap firing and resetting than larger traps. Neither firing nor resetting characteristics were significantly different between unfed and prey-fed traps of U. reflexa and this was also true for the occurrence of spontaneous firings. A strict linear resetting rate, without any lag-period, was found during the first 3 min after trap firing in U. reflexa. This suggests that water is pumped out of the trap continuously and probably recirculates. Given the concepts of spontaneous firing and water recirculation, an ecological model based on the literature data has been devised to quantify the daily N and P gain from the ambient water by Utricularia traps devoid of animal prey. The model shows that the total N and P content estimated in the trap fluid is too high to be accumulated from only the ambient water. This implies that the prey-free traps do not take up N or P from the trap fluid but rather exude a quantity of these nutrients to the fluid to support the microbial community. Therefore, the trap microorganisms behave more as parasites than commensals and represent an additional ecological cost for trap maintenance.     

Efficiency of six different octenol-baited traps for collecting horseflies (Diptera: Tabanidae)

The efficiency and the potential species preference for six different horsefly trap types was studied. A total of 2401 horseflies were collected during this study. The most effective trap was the modified box trap with (27.9%), followed by the Nzi trap with (24.5%), Malaise trap (Townes design 1972) with (22.5)%, canopy trap with (17.9%), modified small canopy trap with (7.0%) and Malaise trap (Townes design 1962) with (0.2%). The Nzi and Malaise trap (Townes design 1972) did not differ significantly in the number of collected horseflies. The comparison of all other traps revealed significant differences in the number of collected horseflies. Tabanus bromius was the most abundant species with (58.6%) of the collected sample. The modified box trap was the most successful in collecting of T. bromius, while the Malaise trap (Townes design 1972) was the most successful in collecting the species Haematopota pluvialis, T. maculicornis and T. tergestinus. This study demonstrated that different trap designs influenced the quantity, species and taxonomic diversity of horseflies that were collected. Variables in the trap design included cloth type and colour and size and shape of trap. More detailed studies should be done to determine which factor or factors are most significant.     

Evaluation of a sampling trap for Dermanyssus gallinae (Acari: Dermanyssidae).

Traps made by rectangular pieces of 3 mm thick corrugated cardboard of four different sizes, 200 by 140 (A), 140 by 100 (B), 100 by 70 (C), and 200 by 40 mm (D), were evaluated as a sampling device for the chicken mite, Dermanyssus gallinae (De Geer). Mites were trapped during 2, 4, 6, 8, and 10 d, respectively, in a poultry house heavily infested with the parasite. Significantly greater numbers of mites were collected by trap B. Additionally, significantly more mites were collected during the sampling periods 6-10 d than by 2 and 4 d. However, with regard to trap size and sampling period, trap C, used for 2 d, collected significantly more mites per day and trap area than any of the other traps. Therefore, such a trap was suggested for monitoring population trends of chicken mites in poultry houses. The larger traps contained significantly higher numbers of mites per trap and may therefore be feasible to use in alternative, nonchemical control programs. Optimum sample size, or number of traps required to monitor population trends of D. gallinae, was also calculated. At a relative variability of 20%, and at densities of 2,000-20,000 mites per trap, approximately 11-16 of trap B and 11-19 of trap C would be adequate to monitor mites.     

Methods to Reduce Avian Bycatch in Small Mammal Studies Using Snap Traps

ABSTRACT Avian bycatch, a common and undesired occurrence in small mammal studies, should be minimized by researchers. We examined effects of trap covering, treadle color (copper or yellow plastic), trap size (mouse or rat), and trap weathering (traps <1 yr or ≥ 1 yr old) on avian bycatch during 3 years. We found that covered traps caught 81% fewer birds and 70% fewer small mammals than did uncovered traps, that mouse traps caught 30% more birds and 38% more small mammals than did rat traps, and no capture differences for treadle color or trap weathering. Covered traps effectively reduced avian bycatch and should be used when reduced small-mammal capture rates are acceptable.     

Density estimation in live-trapping studies

Unbiased estimation of population density is a major and unsolved problem in animal trapping studies. This paper describes a new and general method for estimating density from closed-population capture–recapture data. Many estimators exist for the size (N) and mean capture probability ( p ) of a closed population. These statistics suffer from an unknown bias due to edge effect that varies with trap layout and home range size. The mean distance between successive captures of an individual (     ) provides information on the scale of individual movements, but is itself a function of trap spacing and grid size. Our aim is to define and estimate parameters that do not depend on the trap layout. In the new method, simulation and inverse prediction are used to estimate jointly the population density (D) and two parameters of individual capture probability, magnitude (g₀) and spatial scale (σ), from the information in     , p and     . The method uses any configuration of traps (e.g. grid, web or line) and any choice of closed-population estimator. It is assumed that home ranges have a stationary distribution in two dimensions, and that capture events may be simulated as the outcome of competing Poisson processes in time. The method is applied to simulated and field data. The estimator appears unusually robust and free from bias.     

Effects of population density on alienicolae of Aphis fabae Scop.: V. Variations in size, relative wing length and numbers of antennal sensorla of field alatae

Size, relative wing length and numbers of antennal sensoria of alate Aphis fabae caught in a suction trap 12.2 m above ground and of migrants, flyers and non-flyers among alate A. fabae from field infestations on beans and beet are compared. The size of aphids in successive samples decreased throughout the period of colonization but, on average, beet aphids were bigger and broad bean aphids were smaller than field bean aphids. There were very few migrant alatae among the very large or the very small aphids from any of the crops, neither were aphids of these extreme sizes caught in the suction trap. Non-flyers and beet aphids generally had relatively shorter wings than migrants and bean aphids respectively. The numbers of antennal sensoria differed more between aphids from the three crops than between classes of alatae from the same crop, although trap aphids, presumed to be migrating from field beans had more sensoria than alatae taken from that crop. The mean dry mass of flyers was usually less than that of migrants of a similar size, although if the mass of nymphs deposited before flight is added, it is apparent that a flyer would be heavier than a migrant of the same size at maturity. This additional mass is thought to be due to increased development of the embryos in the ovarioles of flyers at this time and indicative of their greater adaptation for reproduction.     

Entrapment Bias of Arthropods in Miocene Amber Revealed by Trapping Experiments in a Tropical Forest in Chiapas,Mexico

All entomological traps have a capturing bias, and amber, viewed as a trap, is no exception. Thus the fauna trapped in amber does not represent the total existing fauna of the former amber forest, rather the fauna living in and around the resin producing tree. In this paper we compare arthropods from a forest very similar to the reconstruction of the Miocene Mexican amber forest, and determine the bias of different trapping methods, including amber. We also show, using cluster analyses, measurements of the trapped arthropods, and guild distribution, that the amber trap is a complex entomological trap not comparable with a single artificial trap. At the order level, the most similar trap to amber is the sticky trap. However, in the case of Diptera, at the family level, the Malaise trap is also very similar to amber. Amber captured a higher diversity of arthropods than each of the artificial traps, based on our study of Mexican amber from the Middle Miocene, a time of climate optimum, where temperature and humidity were probably higher than in modern Central America. We conclude that the size bias is qualitatively independent of the kind of trap for non–extreme values. We suggest that frequent specimens in amber were not necessarily the most frequent arthropods in the former amber forest. Selected taxa with higher numbers of specimens appear in amber because of their ecology and behavior, usually closely related with a tree–inhabiting life. Finally, changes of diversity from the Middle Miocene to Recent time in Central and South America can be analyzed by comparing the rich amber faunas from Mexico and the Dominican Republic with the fauna trapped using sticky and Malaise traps in Central America.     

A sex pheromone‐baited trapping system for management of sweetpotato weevil,Cylas formicarius (Coleoptera: Brentidae)

A potent male attractant of sweetpotato weevil helps in monitoring and control of sweetpotato weevil in many production areas around the world. At present, it has not been used in Malaysia. Cost of the components of a trapping system is a major constraint in the adoption of male lure‐baited trapping by growers in Malaysia. Seven field trapping experiments were conducted from February 2013 to November 2015 as part of an effort to develop a simple, easy to construct, cost‐effective and efficient sex pheromone‐baited trap acceptable for use by farmers in Malaysia for monitoring and control of sweetpotato weevil (Cylas formicarius Fabricius). Overall, sweetpotato weevil trap catch was significantly affected by the number of windows in the trap, the killing agent used in the trap and the position of the trap relative to sweetpotato foliage, while trap size and trap colour did not significantly affect trap catch. Trap catch was best in plastic pole traps made from polyethylene terephthalate, with four window opening to facilitate weevil entry, with detergent solution as a killing agent and with the trap positioned from 0 to 40 cm above the crop canopy level. In a comparison study with commercial trap designs, sex pheromone‐baited plastic pole traps caught 60%–78% more weevils than were caught in sex pheromone‐baited delta traps, wing traps or unitraps. Optimization of trap characteristics is important for improving the performance of pheromone‐baited traps for use in population monitoring or mass‐trapping efforts to minimize crop damage by sweetpotato weevil infestation.     

Dung beetles in a Central Amazonian rainforest and their ecological role as secondary seed dispersers

Abstract 1. The role of several factors that affect the composition of the dung beetle assemblages in an Amazonian rainforest was quantified, together with the effect of these factors on the role that dung beetles play as secondary seed dispersers. 2. A total of 61 dung beetle species was captured during 3360 h of trapping. During nocturnal trapping periods, more dung beetles, of larger mean size, and more species were captured per trap than during diurnal trapping periods. 3. During the rainy season, more dung beetle species were captured per trap than during the dry season, but the number of individuals and their mean size did not vary between seasons. 4. Bait size had a significant effect on the mean number of beetles and mean number of species but not on mean beetle size. As bait size increased from 5, 10, 25, to 50 g, more beetles and more species were captured per trap. 5. Between 6 and 73% of plastic beads, used as seed mimics, were buried by dung beetles at depths that ranged from 0.5 to 7 cm. Both the proportion of beads buried and burial depth decreased with increasing bead size, and increased with increasing amounts of dung surrounding each bead (5, 10, and 25 g). 6. The proportion of buried seeds for three species varying in size between 5 and 27 mm, increased with increasing dung beetle size, using beetles of seven sizes, varying between 10 and 25 mm. 7. Seeds surrounded by dung were buried more often and more deeply when placed on the forest floor during the late afternoon than when placed during the early morning. Seeds were also buried more often when placed on the forest floor during the rainy season than when placed during the dry season, but season had no effect on burial depth. 8. Forests in Central Amazonia hold a rich dung beetle community that plays an active role in secondary seed dispersal, and consequently in plant regeneration. The interaction between seeds and beetles is complex because it is affected by many factors.     

How Does Spatial Study Design Influence Density Estimates from Spatial Capture-Recapture Models?

When estimating population density from data collected on non-invasive detector arrays, recently developed spatial capture-recapture (SCR) models present an advance over non-spatial models by accounting for individual movement. While these models should be more robust to changes in trapping designs, they have not been well tested. Here we investigate how the spatial arrangement and size of the trapping array influence parameter estimates for SCR models. We analysed black bear data collected with 123 hair snares with an SCR model accounting for differences in detection and movement between sexes and across the trapping occasions. To see how the size of the trap array and trap dispersion influence parameter estimates, we repeated analysis for data from subsets of traps: 50% chosen at random, 50% in the centre of the array and 20% in the South of the array. Additionally, we simulated and analysed data under a suite of trap designs and home range sizes. In the black bear study, we found that results were similar across trap arrays, except when only 20% of the array was used. Black bear density was approximately 10 individuals per 100 km(2). Our simulation study showed that SCR models performed well as long as the extent of the trap array was similar to or larger than the extent of individual movement during the study period, and movement was at least half the distance between traps. SCR models performed well across a range of spatial trap setups and animal movements. Contrary to non-spatial capture-recapture models, they do not require the trapping grid to cover an area several times the average home range of the studied species. This renders SCR models more appropriate for the study of wide-ranging mammals and more flexible to design studies targeting multiple species.     

Two ways of trapping seeds in alpine environments, Lapland, Sweden

Seed dispersal in two habitats was investigated in the mid-alpine Latnjajaure valley, in northernmost Swedish Lapland. The seed rain size was measured using artificial seed traps and natural snowbed at a heath and a meadow site, c. 1000 m a.s.l. The average seed rain size trapped in the snowbeds varied from 18 seeds m^-2 at the heath site, to 96 seeds m-² at the meadow site. On average, the heath trap station had 177 seeds m-² and the meadow station, 218 seeds m². At each site, the vegetation was inventoried within a circular area with a radius of 20 m. Overall, the species assembly in the seed rain reflected the surrounding vegetation. However, there were additional species in the seed rain as well. At the seed trap station on the wind-exposed heath, 78% of the seeds originated from sites outside the homogeneous vegetation around the trap. These seeds were dispersed from locations at least 150 m from the trap site. By trapping a higher number of species than artificial traps and a higher number of seeds per unit area, snowbeds served as effective 'seed traps'. However, the location of the sampling spot in the snowbed is crucial due to a decrease in seed density towards the edge. In this study, with the aim of trapping the main dispersing species in the area, the optimal artificial seed trap size appears to be - 1.5–2.0 m². There was also a positive correlation between the mean July and August temperature, the seed rain size, and the number of species found. Thus, through brief visits to remote locations, the study of seed dispersal can be accomplished effectively when snowbeds are present on the landscape.     

Impact of a glossy collard trap crop on diamondback moth adult movement, oviposition, and larval survival

One component of developing a systematic approach for deployment of trap crops is to understand how the trap crop modifies pest behavior. Glossy‐leafed collards, Brassica oleracea L. var. acephala (Brassicaceae), were evaluated as a potential trap crop for diamondback moth, Plutella xylostella (L.) (Lepidoptera: Plutellidae), because they are attractive to P. xylostella adults and are a poor host for P. xylostella larvae compared to cabbage, Brassica oleracea L. var. capitata. We used large field plots to measure the changes in adult, egg, and larval P. xylostella densities in cabbage when the trap crop was planted in the field. Furthermore, we planted the trap crop in dispersed and concentrated spatial arrangements to determine the impact of trap crop arrangement on the behavior of P. xylostella. In 2002, results showed that the presence of collards within a cabbage field reduced larval density on cabbage. In 2003, neither trap crop arrangement had a significant impact on P. xylostella larval density on cabbage. Adult moths aggregated in proximity to collards in 2002, but not in 2003. Egg and larval data in both years in all treatments showed that total oviposition was highest near a central release point, indicating that females lay many eggs before dispersing very far when suitable host plants are available. The mean direction of P. xylostella movement and oviposition from a central release point was not consistent or correlated to wind direction. Plant size of the trap crop in relation to the main crop and environmental factors may have been responsible for the inconsistent effectiveness of the trap crop.     

The use of drop traps to estimate the efficiency of two beam trawls commonly used for sampling juvenile flatfishes

The efficiencies of a 2-m and a 1·5-m beam trawl for catching newly settled flatfish and brown shrimp were compared with that of a 1-m² drop trap that was assumed to be 100% effective. Low and variable trawl efficiencies were recorded but the trawls were not size selective within the size range of individuals captured.     

Development of a Gravid Trap for Collecting Live Malaria Vectors Anopheles gambiae s.l.

Background

Effective malaria vector control targeting indoor host-seeking mosquitoes has resulted in fewer vectors entering houses in many areas of sub-Saharan Africa, with the proportion of vectors outdoors becoming more important in the transmission of this disease. This study aimed to develop a gravid trap for the outdoor collection of the malaria vector Anopheles gambiae s.l. based on evaluation and modification of commercially available gravid traps.

Methods

Experiments were implemented in an 80 m² semi-field system where 200 gravid Anopheles gambiae s.s. were released nightly. The efficacy of the Box, CDC and Frommer updraft gravid traps was compared. The Box gravid trap was tested to determine if the presence of the trap over water and the trap’s sound affected catch size. Mosquitoes approaching the treatment were evaluated using electrocuting nets or detergents added to the water in the trap. Based on the results, a new gravid trap (OviART trap) that provided an open, unobstructed oviposition site was developed and evaluated.

Results

Box and CDC gravid traps collected similar numbers (relative rate (RR) 0.8, 95% confidence interval (CI) 0.6–1.2; p = 0.284), whereas the Frommer trap caught 70% fewer mosquitoes (RR 0.3, 95% CI 0.2–0.5; p < 0.001). The number of mosquitoes approaching the Box trap was significantly reduced when the trap was positioned over a water-filled basin compared to an open pond (RR 0.7 95% CI 0.6–0.7; p < 0.001). This effect was not due to the sound of the trap. Catch size increased by 60% (RR 1.6, 1.2–2.2; p = 0.001) with the new OviART trap.

Conclusion

Gravid An. Gambiae s.s. females were visually deterred by the presence of the trapping device directly over the oviposition medium. Based on these investigations, an effective gravid trap was developed that provides open landing space for egg-laying Anopheles .