Aerial Nets Research Articles

An aerial netting study of insects migrating at high altitude over England

Day and night sampling of windborne arthropods at a height of 200 m above ground was undertaken at Cardington, Bedfordshire, UK, during July 1999, 2000 and 2002, using a net supported by a tethered balloon. The results from this study are compared with those from the classic aerial sampling programmes carried out by Hardy, Freeman and colleagues over the UK and North Sea in the 1930s. In the present study, aerial netting was undertaken at night as well as daytime, and so the diel periodicity of migration could be investigated, and comparisons made with the results from Lewis and Taylor's extensive survey of flight periodicity near ground level. In some taxa with day-time emigration, quite large populations could continue in high-altitude flight after dark, perhaps to a previously underrated extent, and this would greatly increase their potential migratory range. Any trend towards increases in night temperatures, associated with global warming, would facilitate movements of this type in the UK. Observations on the windborne migration of a variety of species, particularly those of economic significance or of radar-detectable size, are briefly discussed.

DIET OF THE NESTLING TREE SWALLOW

Abstract Dietary samples from nestling Tree Swallows (Tachycineta bicolor) in northwestern Minnesota were compared to invertebrate availability as measured by aerial tow nets. The majority of the biomass in the nestlings' diet was adult insects with larval stages of aquatic origin, while absolute numbers of insects of both aquatic and terrestrial origin were similar. Orders of invertebrates in the diet and available were similar in number but not in biomass. Diet showed little variation by time of day, date of sampling or the age of the nestling. The mean number of odonates in the nestling Tree Swallows' diet increased exponentially as the percentage of open water and open water + cattail marsh increased within a 400-m foraging radius. Dieta de los Pichones de Tachycineta bicolor Resumen. Se compararon muestras dietarias de pichones de la golondrina Tachycineta bicolor tomadas en el noroeste de Minnesota con la disponibilidad de invertebrados medida con redes aereas. La mayor parte de la biomasa en la die...

Collection of wind-borne haematophagous insects in the Torres Strait, Australia.

Circumstantial evidence has implicated wind-borne mosquitoes (Diptera: Culicidae) in the introduction of Japanese encephalitis (JE) virus into Australia from the New Guinea mainland. A study was initiated on Saibai Island in the northern Torres Strait, during January and February 2000, to identify the potential source of insects collected in aerial (kytoon) and surface-level traps. Wind speed and direction were recorded to determine wind profiles during insect sampling. Northerly winds capable of carrying insects from New Guinea to Saibai Island were only present on three out of 18 nights sampled. Only three male mosquitoes, comprising two Verrallina funerea (Theobald) and one Ochlerotatus vigilax (Skuse), were collected in aerial samples, and were most likely of local origin. Culicoides midges were also collected in aerial nets and included gravid/parous C. bundyensis Lee and Reye, and one parous C. histrio Johannsen. Highest densities of arthropods (up to 1562/million m3) were on 30 January 2000 when NW winds, sustained for six hours, probably introduced midges from the New Guinea mainland. Adult mosquitoes (including three female Ve. funerea and a single female Ficalbia) and Culicoides (including two gravid C. bundyensis and one parous C. cordiger Macfie) were also collected in 2 m high mast nets during northerly surface winds. Although the results do not provide evidence that wind-blown mosquitoes introduced JE from New Guinea into Australia, they do not preclude that strong N winds associated with low pressure systems SW of the Torres Strait could have done so. However, results suggest that Culicoides were more likely than mosquitoes to reach high altitude and travel long distances during the light N winds experienced during the study.

High‐altitude migration of the diamondback moth Plutella xylostella to the U.K.: a study using radar, aerial netting, and ground trapping

Abstract 1. The high‐altitude wind‐borne migration of the diamondback moth Plutella xylostella in the U.K. in 2000 was investigated (a) by direct monitoring of insect flight by vertical‐looking radar and by aerial netting, and (b) through evidence of temporal variation in P. xylostella abundance deduced from a network of light traps.2. Migrating P. xylostella were identified by a unique combination of size and shape data derived from the continuously operating vertical‐looking radar.3. Radar‐detected migratory overflights correlated significantly with associated peaks in abundance of P. xylostella estimated by catches in a U.K.‐wide light trap network; however the correlation was stronger when light trap catches were lagged by 1 day.4. The first notable catches of P. xylostella in the U.K. occurred in early May, and were accompanied by migrations over the radar from the east.5. Radar data and back‐tracking indicated that a major wind‐borne migration of P. xylostella from The Netherlands to southern England took place in early May, and that this was responsible for the establishment of the U.K. population.6. The origin of early‐season P. xylostella occurring in Britain is discussed.

Seasonal variation in the windborne movement of insect pests over northeast India

This paper describes the use of a kytoon-supported net to sample the insect fauna flying at about 150 m above a site in West Bengal, India. The sampling took place during four periods of the year: March, May, October and November. Amongst the insects captured were some economically important rice pests (Nilaparvata lugens, Sogatella furcifera, Nephotettix spp. and Cnaphalocrocis medinalis), some of their natural enemies, and also pest aphids (e.g. Lipaphis erysimi, Aphis gossypii and Rhopalosiphum rufiabdominalis). We found thatinsectaerialdensities aloftoften remained high untillate in the night, and we deduced from this that migration over distances of tens, or even hundreds of kilometres was in progress-movements which would lead to redistribution of both pest and beneficial insects over large areas of northeast India. Differences between aerialdensities and migration rates found for the 4 months are interpreted in terms of seasonal cropping patterns and weather, and aerial densities of N. lugens, C. medinalis, aphids, and the mirid Cyrtorhinus lividipennis are compared with values found from aerial netting studies in other geographical regions.

Evidence from flagelliform silk cDNA for the structural basis of elasticity and modular nature of spider silks

Orb-web weaving spiders rely on their aerial nets to entrap flying prey. A key mechanical feature of orb-web design is the high elasticity of the capture spiral. We report the cloning of substantial cDNA for flagelliform gland silk protein, which forms the core fiber of the catching spiral. Like all silks, the flagelliform protein is composed largely of iterated sequences. The dominant repeat of this protein is Gly-Pro-Gly-Gly-X, which can appear up to 63 times in tandem arrays. This motif likely forms Pro2-Gly3 type II β-turns and the resulting series of concatenated β-turns are thought to form a β-spiral. We propose that this spring-like helix is the basis for the elasticity of silk. The variable fifth position of the motif (X) is occupied by a small subset of residues (Ala, Ser, Tyr, Val). Moreover, these X amino acids occur in specific patterns throughout the repeats. This ordered variation strongly suggests that with hydration, the β-spirals form hydrogen-bonded networks that increase the elasticity of flagelliform silk. The self-assembly of flagelliform protein monomers into silk fibers may be promoted by β-spiral/β-spiral interactions. Additionally, the other two motifs in the flagelliform protein, Gly-Gly-X and a spacer that disrupts the glycine-rich regions, may contribute to the alignment of monomers into fibers.The flagelliform protein cDNA was compared to the other members of the spider silk gene family. We show that all spider silk proteins can be characterized as sets of shared structural modules. The occurrence of these modules among the proteins is inconsistent with the phylogenetic relationships inferred from the C-terminal regions. This observation, along with the high level of variation among individual flagelliform protein repeats, but striking lack of such variation in the other silk proteins, suggests that unusual homogenization processes are involved in silk protein evolution.

Observations of the autumn migration of the rice leaf roller Cnaphalocrocis medinalis (Lepidoptera: Pyralidae) and other moths in eastern China

AbstractThe autumn migration of the rice leaf roller moth, Cnaphalocrocis medinalis Guenée, in eastern China was studied at two sites (one in southern Jiangsu Province and one in northern Jiangxi Province), using radar and aerial netting. It was confirmed that C. medinalis is a high-altitude nocturnal windborne migrant, with large numbers of moths taking-off at dusk and flying continuously for several hours. Migration was post-teneral and the females had immature ovaries. Maximum densities of the moths typically occurred between 250 and 550 m above ground, and layering was intense on some nights. Moth layers often occurred at an altitude where there was a wind-speed maximum. In early September, migrant C. medinalis from southern Jiangsu Province were carried on the winds in an approximately westward direction. However, the winds prevailing in late September and October took migrants from both sites towards the south-west or south. Forward trajectories for C. medinalis and other insects emigrating from northern Jiangxi during October indicated that they were able to reach the tropical rice-growing areas near the south China coast, where year-round breeding would be possible. Incidental observations on the migratory flight of other lepidopteran pests, including Mythimna separata (Walker), Spodoptera litura (Fabricius), Ctenoplusia agnata (Staudinger) and Agrotis ipsilon (Hufnagel) (all Nocturidae), Spoladea recurvalis (Fabricius) and particularly Omiodes indicata (Fabricius) (both Pyralidae) are presented.

Observations on the autumn migration of Nilaparvata lugens (Homoptera: Delphacidae) and other pests in east central China

AbstractRadar, aerial netting and ground sampling were used to study the autumn migration of Nilaparvata lugens (Stål) in Jiangsu Province in east central China. Emigration of macropterous adults increased from late August until late September as the main rice crop matured and was harvested. In early and mid September, the resulting windborne migrations carried the planthoppers mainly towards the west, although the migration directions ranged (within the western sector) from south to north. By late September, however, displacements were predominantly to the south-west on the then prevailing north-east monsoon winds: migration was particularly rapid when the north-easterlies were reinforced by typhoons. Although in late September such movements to more southerly latitudes are essential for the survival of the planthoppers' progeny, we found no definite evidence for preferential emigration on winds blowing towards the south. There were, however, indications that when winds towards the north occurred, the duration of migratory flight was curtailed. Irrespective of any possible preference for migration on northerlies, a large proportion of the N. lugens population would normally be carried in an adaptive southwards direction, because the advent of the north-east monsoon occurs at a time when the number of flight-ready planthoppers approaches its peak.

Aerial Dispersal of Insects Between and to Islands in the Galápagos Archipelago, Ecuador

Active or passive movement of insects through the air is probably their most common means of dispersal to oceanic islands. Use of aerial nets suspended on boats documents the presence of insects in the air between the islands of the Galápagos Archipelago during the 1991–1992 El Niño climatic event. At least 50 species of terrestrial arthropods in nine orders were captured. The most abundant families were Aphididae, Aleyrodidae and Psyllidae (Homoptera), Encyrtidae and Formicidae (Hymenoptera), and Sciaridae and Ceratopogonidae (Diptera). The moist conditions and winds during a strong El Niño probably create the most favorable circumstances for aerial movement of insects between islands of the Galápagos and for movement from the tropical American mainland to the Archipelago.

Downstream drift of the larvae of Chironomidae (Diptera) in the River Chew, S.W. England

The drift of larval Chironomidae (Diptera) was investigated at two sites on the River Chew, using a pump filtration system with 50 µm mesh-aperture aerial nets, situated on the river bank.

Traps for Collecting Live Euphasiopteryx depleta (Diptera: Tachinidae) at a Sound Source

After Wolcott (1940) reported rearing the tachinid Euphasiopteryx depleta (Wied.) from a Scapteriscus mole cricket (Orthoptera: Gryllotalpidae), interest has been shown in using this fly in introductions for the biological control of Scapteriscus. Fowler and Kochalka (1985) reported attracting E. depleta to the synthesized broadcast calls of S. acletus Rehn & Hebard in Paraguay. Using similar synthesizers (Walker 1982), Fowler and Garcia (1987) reported additional captures of E. depleta, and of rearing it from S. acletus, S. vicinus Scudder and S. abbreviatus Scudder. In those studies, attracted female E. depleta were captured with an aerial net over the synthesizer and larvae taken from them were placed on mole crickets to achieve laboratory parasitism. Subsequently, aerial nets were replaced with a sheet of plastic covered with Tanglefoot?, and large numbers of female E. depleta were obtained. However, in the laboratory, often the Tanglefoot would interfere with obtaining larvae, as many were killed in the female's body through asphyxiation, or were gummed and died as they left the female's body. Also, for some laboratory studies, healthy, gravid females were needed, which could not be obtained by sticky trapping. Using flashlights and aerial nets to capture females at sound synthesizers was not highly productive, as E. depleta tended to avoid lighted areas. To overcome these problems, two traps were designed and field tested (Fig. 1). Both traps were inexpensive, consisting of a wire frame, with muslin sides and funnels, which were used to direct flies into the trap. Cardboard baffles mounted on wire were used to hinder fly escape after capture (Fig. 1). The muslin base was built so that the trap could easily fit over a sound synthesizer (Walker 1982) or over a tape player. Trap designs were evaluated by comparison of the numbers of flies caught in each with the numbers caught on sticky traps. In December 1984, three sound synthesizers broadcasting S. vicinus songs were placed in the field in Rio Claro, state of Sao Paulo, Brazil. One synthesizer was fitted with sticky plastic sheeting, and the other two with the two trap designs. After each night, the location of each was switched. Each synthesizer was separated by 30 m from its neighbor. The sticky trap caught 132 flies during 2 weeks of trapping. Trap B, fitted with 5 funnels, of which 4 were lateral, was about 2.5 times as efficient as design A, consisting of only 1 funnel (Fig. 1). Trap B was about a third as efficient as the sticky trap. Field observations indicated that flies alighted on the muslin and walked extensively over the trap's external surface until they were channeled into its interior through the funnels. Many flies departed without ever reaching the trap's interior. This explains why the numbers of female E. depleta caught in the traps were much less than with sticky traps. If large numbers of flies are required, sticky traps should be used. If, however, viable healthy females are required, then trap design B should be used. Sticky traps are recommended for population monitoring. I thank Joao Justi and Madelena Lima Costa for their assistance with the field portion of this project. This study was funded in part by a grant, USDA No. 83-CRSR-2-

The migration of Nilaparvata lugens (stål) (delphacidae) and other hemiptera associated with rice during the dry season in the Philippines: a study using radar, visual observations, aerial netting and ground trapping

AbstractThe migratory flight behaviour of Nilaparvata lugens (Stål), other delphacid and cicadellid pests of rice and some of their heteropteran predators was investigated during the dry-season crop in an irrigated rice-growing area of the Philippines. A combination of radar (including an X-band and a newly-developed Q-band system (8 mm wavelength)), aerial netting, ground trapping and visual observations was used to determine diel changes in aerial density and composition of arthropods in flight over the study site. The most abundant migrant caught in the aerial nets was Cyrtorhinus lividipennis Reuter (a mirid predator of N. lugens), with Nephotettix spp. and Nilaparvata lugens the next most abundant species. Flight activity in all migrants was found to be very largely confined to periods of about 30 min at dusk and dawn, with minimal activity at other times of the day and night. Migration distance in the dusk flight was generally limited to 6–30 km, depending on wind speed, and the dawn migration covered shorter distances due to the lighter winds. Small numbers of rice cicadellids and delphacids including N. lugens were occasionally detected later in the night, and these may have had the potential to migrate longer distances.

Seasonal Distribution of Northern New York State Anthropophilic Tabanidae (Diptera) and Observations on the Dispersal of Several Species

In a 154 km2 area of Franklin Co., N.Y., 47 sites were monitored biweekly or weekly for two consecutive adult Tabanidae seasons. Investigators used standard aerial insect nets and captured 10,969 tabanids during 1,380 10-min sweeps. Four genera and 37 species were collected, with Chrysops ater (43%) and C. mitis (15%) dominating. The collection method was more selective of Chrysops (96% of total Tabanidae) than Hybomitra , Stonemyia , or Tabanus . In addition, over 600 C. dawsoni , a species only recently detected in New York, were captured at this location. New extensions of nuisance activity were documented for seven species. In addition to seasonal distribution data on 37 northern New York Tabanidae species and relationships of major species collected to habitat, we also report observations on the dispersal of C. ater and C. mitis recaptured at sites ≤7 km from the release site and dispersed to other sites at a rate of ≥1.2 km/h. Sixteen of 520 (3.1%)marked and released Chrysops were recaptured.

Observations on the biology of Mansonia perturbans (Walker) (Diptera: Culicidae) in the Nova Scotia–New Brunswick border region

Aerial sweep netting of mosquitoes in the Nova Scotia – New Brunswick border region during the summers of 1973–1975 revealed that Mansonia perturbons (Walker) is the most abundant species in this region. This mosquito is univoltine; adult emergence commences in late June; peak abundance occurs about mid-July; peak activity of blood-seeking females occurs at or near darkness. Observations were made of swarming adults, and the immature stages were associated with at least seven species of aquatic plants. Mansonia perturbans appears to have become a relatively recent pest in this region.

A Comparison of Malaise Trapping and Aerial Netting for Sampling a Horsefly and Deerfly Community 1 , 2

A comparison was made of the effectiveness of malaise trapping and aerial netting for sampling a community of 50 species of Tabanidae collected near Deer Lake, Boonton, NJ during 1974. Five sites in the study area were sampled by malaise traps and by netting about the head with an insect net. Comparisons were made of 4 community and 4 population parameters. No significant difference existed between the species richness of the community of flies sampled by each method, but malaise traps sampled the tabanid community with greater diversity and evenness than did netting. The species composition of the community trapped by each method differed substantially. Hybomitra and Tabanus were sampled in significantly greater numbers by malaise traps while netting favored the dominant Chrysops species. Seasonal niche breadths, seasonal ranges and seasonal distributions were measured concordantly by each sampling method. Neither trapping method should be used alone in studies concerning the entire tabanid community, but can be used effectively together.