How reliable are light traps in estimating biting rates of adult Anopheles gambiae s.l. (Diptera: Culicidae) in the presence of treated bed nets?

The sampling efficiency of light trap catches relative to human bait catches in estimating biting rates of the mosquito Anopheles gambiae Giles was investigated in two types of community in southern Sierra Leone: (i) where most of the inhabitants slept under treated bed nets; and (ii) where most of the inhabitants slept without bed nets. The number of female A. gambiae mosquitoes caught in these communities by light trap was strongly correlated (r > or = 0.72) with those from corresponding human biting catches performed either on the same or adjacent nights. It was found that the relative sampling efficiency of light traps varied slightly but significantly with mosquito abundance in villages with treated bed nets, but not in those without them. Nevertheless, the relationship between relative sampling efficiency and mosquito abundance did not differ significantly between the two types of village. Overall, there was insufficient evidence to show that the presence of treated nets altered the relative efficiency of light traps and any bias was only slight, and unlikely to be of any practical importance. Hence, it was concluded that light traps can be used as a surrogate for human bait catches in estimating biting rates of A. gambiae mosquitoes in the two communities.     

Comparison between anopheline mosquitoes (Diptera: Culicidae) caught using different methods in a malaria endemic area of Papua New Guinea

The mosquito sampling efficiency of CDC (Centers for Disease Control) miniature light traps hung adjacent to mosquito nets, was compared with that of both indoor and outdoor human-bait collections in ten villages in the Wosera area of Papua New Guinea. The most frequently collected anopheline in the matched indoor and light trap samples was Anopheles koliensis Owen, followed by A. punctulatus D?nitz, A. karwari (James), A. farauti Laveran (sensu lato), A. longirostris Brug and A. bancroftii Giles. All species were much less frequent in the light traps than in landing catches. The hypothesis that the numbers of mosquitoes in light traps are proportional to human landing catches was examined using regression models that allowed for sampling error in both entomological measurements. Light traps under-sampled A. punctulatus and A. farauti s.l. at high densities. The models indicated that the ratio of light trap to landing catch females of A. koliensis and A. karwari increased with increasing mosquito density. Light trap catches of A. longirostris were proportional to indoor landing rates but when outdoor landing rates were high this species was under-sampled by light traps. Numbers of A. bancroftii in light traps were found to be proportional to those in outdoor landing catches, but were negatively related to those attempting to bite indoors. Circumsporozoite positivity rates for both Plasmodium falciparum Welch and P. vivax (Grassi & Feletti) in A. punctulatus and A. farauti s.l. were significantly higher in light trap collections than in either indoor or outdoor landing catches, suggesting that light traps may selectively sample older mosquitoes of these species.     

A preliminary study of insect abundance on West Island,Aldabra Atoll,Indian Ocean

• 1 Heath and Rothamsted light traps and a Johnson-Taylor suction trap were used to sample flying insects on Aldabra Atoll.
• 2 The present study extended over two wet seasons. The pattern of relative monthly insect activity resembled the rainfall pattern. Catches were greatest during the months when there was a sudden marked increase in precipitation.
• 3 Lepidoptera dominated light trap catches and Diptera suction trap catches, the total monthly insect numbers therefore reflecting the abundance of these two orders. Hemiptera, Coleoptera and Hymenoptera were also common.
• 4 Predominant families were represented by only a few or even only one dominant species. These species were present throughout the study period although their monthly totals varied considerably, different species dominating the catches during different months.
• 5 The composition and size of catches in the three light traps was affected by the type of light source and surrounding vegetation.
• 6 A comprehensive list of families and selected common species is given with their relative monthly abundance in the light traps.
• 7 Suction trap catches were segregated on an hourly basis to give a broad indication of insect flight periodicity.

     

Sphaeroceridae (Diptera) caught in light traps at Rothamsted Experimental Station, Herts., 1980–83

ABSTRACT.

• 1 A total of 7063 specimens of Sphaeroceridae representing forty species were caught in four light traps, two in woodland and two in the open, at Rothamsted Experimental Station between December 1980 and December 1983.
• 2 A complete list of species and the numbers of individuals of each is provided.
• 3 The catches in the two traps in woodland were less diverse than the catches in the two traps in the open.
• 4 Two-way analysis of variance demonstrated a significant difference in catch from trap to trap.
• 5 When their similarities were compared, the four light trap catches formed two groups, corresponding with habitat type.
• 6 The majority of the catch were Copromyza similis (Collin) (5555 specimens or 78.64% of the total). The species was most abundant in winter from mid-December to early February, although there were slight differences in times of maximum abundance between open and woodland habitats.

     

Short-term effects of mowing on insect communities in Japanese peach orchards

A population survey of insects was conducted at peach orchards in Okayama Prefecture, western Japan, every 2 weeks during May–October in 2011. Pitfall traps were used to sample more than 4000 insects at 10 orchards: 8 orchards where ground vegetation had been managed by mowing and 2 with management by herbicide application. Numbers of insect species (species richness) and numbers of insects captured in pitfall traps (trap catches) were greater after mowing. Details of the effects of mowing on insect communities were examined at four orchards that had been mowed. Results suggest that species richness and trap catches increase up to 5 days after mowing and then return to their original state. Increased species richness and trap catches were mainly attributable to the increase of ants (Formicidae) and carabids (Carabidae). These results suggest that ants and carabids actively seek prey animals that have been killed, injured, or damaged by mowing.     

THE COMPARISON OF SUCTION TRAP, STICKY TRAP and TOW-NET FOR THE QUANTITATIVE SAMPLING OF SMALL AIRBORNE INSECTS

The sticky trap and stationary aerial 'tow-net' catch insects which alight or fly on to them or are blown against them by the wind. It would be expected that such traps would be inefficient in light winds or in calm weather; and even though their efficiency should increase with stronger winds, errors of unknown magnitude may occur not only in estimations of density and of proportions of species in the air, but also with comparisons of actual catches. These errors are due to unknown degrees of weighting as the traps sample by means of a variable wind from a changing population density. The suction trap, on the other hand, samples a constant quantity of air in all relevant wind-speeds and does not appear to suffer so seriously from these disadvantages. It also works efficiently in perfectly calm weather when maximum densities of insects are often in the air.
The performances of the three traps in the field operating over a range of wind-speeds are described. Particular attention has been paid to aphids, for which the sticky trap and tow-net are generally used and for which the suction trap was primarily designed. Density estimates of these insects in winds below about 3 m.p.h. are much larger when calculated from suction trap catches as compared with estimates from sticky trap and tow-net catches. There is reason for the belief that the suction trap is neither attractive nor repellent to aphids to a significant extent, and that it catches these insects at random by virtue of its air stream alone; weighting of catches due to variable quantities of air being sampled does not occur. It is considered, therefore, that the suction-trap values of density are likely to be the more accurate ones. Sampling of other small insects is also discussed.     

Xestia communities (Lepidoptera, Noctuidae) in eastern Finnish Forest Lapland as indicated by light trap sampling

Xestia moths (Lepidoptera, Noctuidae, subgenera Anomogyna and Pachnobia ) were collected with eleven light traps installed in various virgin habitats in the Värriötunturi fell area, E Finnish Forest Lapland (67° 44'N, 29° 37'E). Seven Xestia species were caught during the years 1978–84. The most abundant species, X. tecta and X. alpicola inhabited the widest range of habitats, from spruce-covered ravines up to the treeless summit. The other species were almost entirely caught in the sprucecovered ravine. The largest catches were obtained in odd years, although some moths were also caught in the even years. There was a striking male dominance. The trap catches were separated into three groups, corresponding to the original classification of the trap habitats. Of the habitats, the open pine forest was nearest to the summit and the spruce forest farthest away. X. alpicola and X. tecta appear to be ecologically related species, while X. gelida and X. laetabilis are located at the other end of this ecological scale.     

Trapping sand flies (Diptera: Psychodidae) in the Emilia-Romagna region of northern Italy.

The efficiency and practicality of two trapping methods for adult Phlebotomine sand flies in two areas of the Emilia-Romagna region (Italy) were evaluated. Suction traps (CO2) and sticky traps (ST) were used to collect sand flies every two weeks, from June to September, 1999, from 16:00 to 07:00. Two CO2 traps were activated at the same time for each area (one with light and one without light), whereas 38 (four with light and 34 without lights) and 48 (four with light and 44 without) sticky traps were activated in Borghi and Longiano, respectively. An Index of Apparent Abundance (IAA) was calculated for each trap type and area. A total of 2,253 sand flies was trapped over the four-month period, with 1,765 collected from Borghi and 488 from Longiano. Phlebotomus perfiliewi was the most abundant species collected, comprising 99.6% and 84.6% of the total flies trapped in Borghi and Longiano, respectively. Other species were also collected within the two areas (Phlebotomus perniciosus and Phlebotomus mascittii) but were not considered for further analyses due to low catches. Significantly more specimens were caught using CO2 than sticky traps and the addition of a light source also improved the catches, however, a significantly greater number of female specimens were collected by a CO2 trap without a light source. Phlebotomus perfiliewi thus appears to show a photophobic reaction in the case of females when trapped using CO2/light attractants.     

Efficiency of Malaise traps and colored pan traps for collecting flower visiting insects from three forested ecosystems

Pan and Malaise traps have been used widely to sample insect abundance and diversity, but no studies have compared their performance for sampling pollinators in forested ecosystems. Malaise trap design and color of pan traps are important parameters that influence insect pollinator catches. We compared pan trap (blue, yellow, white, and red) and Malaise trap catches from forests in three physiographic provinces (Piedmont, Coastal Plain, and Blue Ridge) of the southeastern United States. Similarities in trap performance between sites were observed with blue pan traps being most effective overall. Our results showed that various pollinator groups preferred certain pan trap colors and that adding color to Malaise traps influenced insect pollinator catches. However, pan traps generally caught more pollinators than Malaise traps. Because of their low cost and simplicity, using several colors of pan traps is an effective way to sample relative abundance and species richness of flower-visiting insects.     

Effect of light colours and weather conditions on captures of Sogatella furcifera (Horváth) and Nilaparvata lugens (Stål)

To study the phototactic responses of white‐backed planthopper, Sogatella furcifera (Horváth) and brown planthopper, Nilaparvata lugens (Stål) to different wavelengths, four colours of light traps (blue, green, yellow and red light‐emitting diodes) were placed in the same rice field along with a traditional black light trap. This study revealed that S. furcifera and N. lugens are more attracted to blue and green lights than that to yellow and red lights. During the 24 nights, compared with the black light trap, the blue LED trap could catch more rice planthoppers at 17 nights. Furthermore, catches of other species (moths and beetles) were substantially reduced in blue LED light traps. Multiple regression models were developed to assess the effect of weather factors on light trap catches of rice planthoppers. Rainfall and mean air temperature at a night mainly affected light trap catches of S. furcifera. Higher rainfall and lower temperature increased light trap catches of S. furcifera. However, wind speed was the main factor affecting the catches of N. lugens, and the lower incidence of catches was found in the night when wind speed exceeded 3.08 m/s. S. furcifera may be flying against wind at light wind nights by 0.3–1.5 m/s, whereas N. lugens may be flying down at strong wind nights by 1.5–3.08 m/s. Relative humidity did not significantly influence on trap catches. Consequently, light wavelengths, precipitation, average temperature and wind should be considered when monitoring rice planthoppers by light traps. Therefore, the blue LED light traps are worth using for monitoring planthoppers.     

Quantifying the spatial dependence of Culicoides midge samples collected by Onderstepoort-type blacklight traps: an experimental approach to infer the range of attraction of light traps

The emergence of bluetongue disease in Europe has led several countries to rapidly establish large-scale entomological surveys of its vectors, which are midges belonging to the genus Culicoides Latreille, 1809 (Diptera: Ceratopogonidae). These surveys have largely been based on the use of Onderstepoort-type blacklight traps. However, the range of attraction of the traps and the spatial dependence of the samples they provide are unknown, which somewhat complicates subsequent analyses. This paper investigates spatial interaction between Onderstepoort-type blacklight traps based on catches at a central trap placed close to two traps set in consecutive on/off modes. The spatial interaction is inferred from the drop in the number of midges collected in the central trap when nearby traps positioned at 50 m, 100 m or 200 m are turned on. The results showed a significant spatial interaction between traps separated by 50 m for female Culicoides obsoletus/Culicoides scoticus and Culicoides dewulfi. No significant interaction was found for female Culicoides of other species, for male Culicoides, or for traps spaced at ≥100 m. Based on the experimental design geometry and on simple assumptions on the distribution of Culicoides midges in the neighbourhood of the traps, the paper also presents a method to infer the range of attraction of the traps.     

First use of pheromones to detect phenology patterns and density relationships of pine sawflies in German forests

1 Monitoring studies of pine sawflies with pheromone traps were performed for the first time in Germany. Pheromone traps baited with species‐specific pheromone substances were installed in pine forests at different locations in Bavaria, Brandenburg and Lower Saxony during two years. 2 It was possible to track the flight phenology of Diprion pini, Gilpinia pallida and Neodiprion sertifer reliably and to get information about the number of generations of these species in 1997 and 1998. 3 A clear relationship between trap catch and population density could not be detected, but qualitative changes in trap catch caused by different density levels were observed. 4 For D. pini, trap catches were different among endemic populations of different forest types. Furthermore, catches of males reflected the results from the regular cocoon collections by foresters during the previous winter. 5 For N. sertifer, trap catches in endemic populations were well separated from trap catches on sites with higher sawfly densities. However, no significant correlation between trap catch and sawfly density or defoliation level could be found. These results suggest that the efficacy of the pheromone traps probably varied with biological features (sex ratio, density level, immigration) of the particular population.     

Visual Responses of Adult Asian Citrus Psyllid (Hemiptera: Liviidae) to Colored Sticky Traps on Citrus Trees

The effects of five differently-colored sticky traps in capturing adult Diaphorina citri were evaluated in citrus orchards. Trap catches of D. citri were monitored fortnightly on blue, green, red, white and yellow sticky cards placed on three citrus varieties during D. citri active flight period from April to July in south Texas. Evaluation of mean trap catches of each color by repeated measures analysis of variance produced three separate groups: yellow traps caught significantly more D. citri adults than the other four traps; red and green traps caught significantly more D. citri than blue and white traps, which were not significantly different. Although the number of adult psyllid captured on all trap types significantly increased with time during the trapping period, the performance of traps did not change with time. Trap catches were also significantly influenced by the citrus species; traps placed on lemon trees captured more D. citri than those placed on sweet orange and grapefruit, suggesting that plant preference exhibited by D. citri may influence the performance of traps. The ratio of trap reflectance between the 680 to 700 nm and the 450 nm was significantly correlated with total trap catches in all host species studied. Thus, this index was a good indicator of the attractiveness of adult D. citri to colored traps. Additionally, we compared the reflectance values of young versus mature flush shoots of the three host plants used in this study as related to densities of D. citri recorded in colored traps. We discussed the importance of visual cues in the host finding behavior of adult D. citri.     

Efficacy of CC traps and seasonal activity of adult Bemisia argentifolii (Homoptera: Aleyrodidae) in Imperial and Palo Verde Valleys, California

Adult whitefly Bemisia argentifolii Bellows & Perring trap (CC trap) catches were compared with suction type trap catches. CC trap catches were significantly correlated to the suction trap catches. Higher numbers of B. argentifolii adults were caught in CC traps oriented toward an untreated, B. argentifolii-infested, cotton field as compared with traps oriented toward Bermuda grass fields, farm roads, or fallow areas. CC trap catches at five heights above ground (from 0 to 120 cm) were significantly related to each other in choice and no-choice studies. CC trap catches were low in the Imperial and Palo Verde Valleys from late October to early June each of 1996, 1997, and 1998. Trap catches increased with increasing seasonal air temperatures and host availability. Trap catches were adversely affected by wind and rain. Abrupt trap catch increases of 40- to 50-fold for 1-2 d in late June to early July followed by abrupt decreases in adult catches suggest migrating activity of adults from other nearby crop sources.     

Sheep Skin Odor Improves Trap Captures of Mosquito Vectors of Rift Valley Fever

In recent years, the East African region has seen an increase in arboviral diseases transmitted by blood-feeding arthropods. Effective surveillance to monitor and reduce incidence of these infections requires the use of appropriate vector sampling tools. Here, trapped skin volatiles on fur from sheep, a known preferred host of mosquito vectors of Rift Valley fever virus (RVFV), were used with a standard CDC light trap to improve catches of mosquito vectors. We tested the standard CDC light trap alone (L), and baited with (a) CO₂ (LC), (b) animal volatiles (LF), and (c) CO₂ plus animal volatiles (LCF) in two highly endemic areas for RVF in Kenya (Marigat and Ijara districts) from March–June and September–December 2010. The incidence rate ratios (IRR) that mosquito species chose traps baited with treatments (LCF, LC and LF) instead of the control (L) were estimated. Marigat was dominated by secondary vectors and host-seeking mosquitoes were 3–4 times more likely to enter LC and LCF traps [IRR = 3.1 and IRR = 3.8 respectively] than the L only trap. The LCF trap captured a greater number of mosquitoes than the LC trap (IRR = 1.23) although the difference was not significant. Analogous results were observed at Ijara, where species were dominated by key primary and primary RVFV vectors, with 1.6-, 6.5-, and 8.5-fold increases in trap captures recorded in LF, LC and LCF baited traps respectively, relative to the control. These catches all differed significantly from those trapped in L only. Further, there was a significant increase in trap captures in LCF compared to LC (IRR = 1.63). Mosquito species composition and trap counts differed between the RVF sites. However, within each site, catches differed in abundance only and no species preferences were noted in the different baited-traps. Identifying the attractive components present in these natural odors should lead to development of an effective odor-bait trapping system for population density-monitoring and result in improved RVF surveillance especially during the inter-epidemic period.     

Associations of aquatic insects (Ephemeroptera,Plecoptera, and Trichoptera) in a network of subarctic lakes and streams in Québec

As part of an impact assessment of large hydroelectric projects in the James Bay drainage in Northwestern Québec, the aquatic insect communities were studied in a network of rivers, lakes and streams during the summer of 1975. Thirty-eight emergence traps operated over the ice-free season yielded 10 888 insects (5559 Ephemeroptera, 2817 Plecoptera, and 2512 Trichoptera), representing 148 species (respectively 44, 18, and 86), most of temperate and boreal afinities. There was no arctic element.Similarity analyses and clustering procedures on the emergence series revealed the existence of distinct insect communities in the river (fast and slow sections), the streams (fast and slow), the lakes and the bogs, each characterized by a particular assemblage of species. Many of the species were more or less ubiquitous and differences between communities were marked more by changes in the dominance of the species and differences in the frequency distributions, than absolute shifts in the species lists. The yields in the traps set in fast water were much greater than those in slow running water, and these in turn greater than those of standing water.By comparison with more southerly sites, the seasonal succession of species was retarded in the spring and early summer, but was not shortened appreciably in the fall. The usual emergence patterns associated with these taxa was observed, namely those of spring, summer and autumn species.     

Evaluation of funnel traps for characterizing the bark beetle (Coleoptera: Scolytidae) communities in ponderosa pine forests of north-central Arizona

Lindgren funnel traps baited with aggregation pheromones are widely used to monitor and manage populations of economically important bark beetles (Coleoptera: Scolytidae). This study was designed to advance our understanding of how funnel trap catches assess bark beetle communities and relative abundance of individual species. In the second year (2005) of a 3-yr study of the bark beetle community structure in north-central Arizona pine (Pinus spp.) forests, we collected data on stand structure, site conditions, and local bark beetle-induced tree mortality at each trap site. We also collected samples of bark from infested (brood) trees near trap sites to identify and determine the population density of bark beetles that were attacking ponderosa pine, Pinus ponderosa Douglas ex Lawson, in the area surrounding the traps. Multiple regression models indicated that the number of Dendroctonus and Ips beetles captured in 2005 was inversely related to elevation of the trap site, and positively associated with the amount of ponderosa pine in the stand surrounding the site. Traps located closer to brood trees also captured more beetles. The relationship between trap catches and host tree mortality was weak and inconsistent in forest stands surrounding the funnel traps, suggesting that trap catches do not provide a good estimate of local beetle-induced tree mortality. However, pheromone-baited funnel trap data and data from gallery identification in bark samples produced statistically similar relative abundance profiles for the five species of bark beetles that we examined, indicating that funnel trap data provided a good assessment of species presence and relative abundance.     

The relationship between CDC light-trap and human-bait catches of endophagic sandflies (Diptera: Psychodidae) in the Peruvian Andes

Abstract. A study was carried out in the Peruvian Andes to test the suitability of CDC light traps for monitoring changes in the human-landing rate of endophagic phlebotomine sandflies, following house-spraying with pyrethroid insecticide. On four pairs of consecutive nights, sandflies were caught inside eight sprayed and eight unsprayed houses, either by human bait or by CDC light traps. The sandflies collected were Lutzomyia verrucarum (97%) and Lu. peruensis (3%), both probable vectors of Leishmania peruviana , and the species composition was unaffected by house-spraying. A non-linear relationship was detected between light-trap and human-bait catches, but the relationship did not diverge significantly from linearity within the range of sandfly abundance found in most houses in the endemic area (i.e. between 3 and 200 sandflies/house-night), and did not differ significantly between sprayed and unsprayed houses. However, light trap catches had a significantly lower proportion of blood-fed females in sprayed than in unsprayed houses, probably due to an insecticidal effect on post-blood-feeding behaviour. The proportion of Lu. verrucarum was significantly higher in light trap than in human bait catches, indicating that Lu. peruensis is either more anthropophilic or less phototropic than Lu. verrucarum.     

The ability of synthetic sex pheromone traps to forecast Plutella xylostella infestations depends on survival of immature stages

The potential for using synthetic sex pheromone traps as a simple and practical method of monitoring population densities of insect pests has been investigated in many crop systems. Yet, factors enabling the forecast of infestations based on pheromone trap catches are not fully understood. This study tested the prediction that high survival of immature stages of the target pest is a pre‐requisite for trap catches to correlate well with future infestations on the crop. The influence of parasitoids, as an important natural mortality factor of diamondback moth, Plutella xylostella (L.) (Lepidoptera: Plutellidae), larvae and pupae in South Africa, on the ability of pheromone traps to forecast infestations was investigated continuously at weekly intervals over 6 years on unsprayed cabbage. During late October–May, when parasitism levels were high (≥50%), infestations and trap catches were significantly lower than during low parasitism (<50%) observed during June–early October. Because infestations were negatively related to parasitism level, trap catches correlated with infestations better when observations were made in the same week during periods of high parasitism. Conversely, when survival of P. xylostella immature stages was high due to low parasitism levels, trap catches correlated with future infestations well for up to 2 weeks. Thus, trap catches can be used to forecast infestations during September–October, a period that coincides with high P. xylostella infestations as a consequence of low natural control by parasitoids. This is the first study to show that the ability of pheromone trap catches to forecast infestations depends on survival of the immature stages of the target pest.     

Effect of trap design, trap size and pheromone dose on male capture of two pine bast scales species (Hemiptera: Matsucoccidae): implications for monitoring and mass-trapping

Abstract 1 The effects of pheromone dose, trap size and trap design on the capture of male Matsucoccus feytaudi were studied in maritime pine forests of Portugal, France and Italy, and Matsucoccus josephi in Aleppo pine stands of Israel. 2 Males of both species respond to racemic mixtures of the respective sex pheromone at a dosage as low as 25 µg. However, for low population densities of M. feytaudi, a 50 µg dosage was needed to guarantee male catches significantly different from the control trap. 3 Male capture increased with increasing dosage up to a threshold level for both species. Overdose repellence was not observed even with baits containing 1600 and 2200 µg of the pheromone of M. josephi and M. feytaudi, respectively. 4 For M. feytaudi, a higher dose–response was observed at medium population densities, whereas lesser captures were registered at low and high population densities, suggesting female competition in the latter case. 5 Catches of M. feytaudi males were not affected by trap design, whereas M. josephi males were caught in significantly greater numbers in delta traps. Large traps caught significantly more males of both species. 6 The relative higher male catches in the marginal zone of the sticky traps is probably related to males landing behaviour in the vicinity of the pheromone source. 7 The shape and size of the trap did not affect the bias of the estimates of male catches. However, the plate traps provided higher precision. Both bias and precision improved with increasing dose.