V. A. Drake

Insect migration : tracking resources through space and time

Part I. Insect Migration in Relation to Weather and Climate: 1. Long-range insect migration in relation to climate and weather: Africa and Europe D. E. Pedgley, D. R. Reynolds and G. M. Tatchell 2. Insect migration in North America: synoptic-scale transport in a highly seasonal environment S. J. Johnson 3. Migration of the brown planthopper Nilaparvata lugens and the white-backed planthopper Sogatella furcifera in East Asia: the role of weather and climate R. Kisimoto and K. Sogawa 4. Migration of the oriental armyworm Mythimna separata in East Asia in relation to weather and climate. I. Northeastern China R. -L. Chen, Y. -J Sun, S. -Y. Wang, B. -P. Zhai and X. -Y. Bao 5. Migration of the oriental armyworm Mythimna separata in East Asia in relation to weather and climate. II. Korea J. -H. Lee and K. -B. Uhm 6. Migration of the oriental armyworm Mythimna separata in East Asia in relation to weather and climate. III. Japan K. Hirai 7. Insect migration in an arid continent. I. The common armyworm Mythimna convecta in eastern Australia G. McDonald 8. Insect migration in an arid continent. II. Helicoverpa spp. in eastern Australia P. C. Gregg, G. P. Fitt, M. P. Zalucki and D. A. H. Murray 9. Insect migration in an arid continent. III. The Australian Plague Locust Chortoicetes terminifera and the native budworm Helicoverpa punctigera in Western Australia K. J. Walden Part II. Adaptions for Migration: 10. Migratory potential in insects: variation in an uncertain environment A. G. Gatehouse and X. -X. Zhang 11. Insect migration in heterogeneous environments K. Wilson 12. The regulation of migration in Helicoverpa armigera J. Colvin 13. Physiological integration of migration in Lepidoptera J. N. McNeil, M. Cusson, J. Delisle, I. Orchard and S. S. Tobe 14. Aerodynamics, energetics and reproductive constraints of migratory flight in insects R. Dudley Part III. Forecasting Migrant Pests: 15. Operational aspects of forecasting migrant insect pests R. K. Day and J. D. Knight 16. Geographic information systems and remotely sensed data for determining the seasonal distribution of habitats of migrant insect pests T. P. Robinson 17. Forecasting systems for migrant pests. I. The brown planthopper Nilaparvata lugens in China B. -H. Zhou, H. -K. Wang and X. -N. Cheng 18. Forecasting systems for migrant pests. II. The rice planthoppers Nilaparvata lugens and Sogatella furcifera in Japan T. Watanabe 19. Forecasting systems for migrant pests. III. Locusts and grasshoppers in West Africa and Madagascar M. Lecoq Part IV. Overview and Synthesis: 20. Forecasting migrant insect pests J. I. Magor 21. Insect migration: a holistic conceptual model V. A. Drake, A. G. Gatehouse and R. A. Farrow Index.

Radar observations of moths migrating in a nocturnal low‐level jet

Abstract. 1. Radar observations of insects migrating at night over central‐western New South Wales have detected an instance of migration in a low‐level wind jet.

Radar observations of the spring migration into northeastern China of the oriental armyworm moth, Mythimna separata, and other insects

Abstract. 1. The spring migration of the oriental armyworm moth, Mythimna separata (Walker), and other insects into northeastern China was observed by radar at a site in central Jilin province. Samples of the migrants were obtained in a net flown from a kite, and M.separata populations in the surrounding region were monitored with a trap network.

THE VERTICAL DISTRIBUTION OF MACRO-INSECTS MIGRATING IN THE NOCTURNAL BOUNDARY LAYER: A RADAR STUDY

A special-purpose radar has been used to observe the vertical distribution of large, strong-flying insects migrating in the nocturnal boundary layer over the central-western plains region of New South Wales. During the period of take-off flight at dusk, the density of insects decreased monotonically with height, and a distribution of this type persisted for much of the night in the zone of steady temperature lapse extending from the top of the inversion layer to the flight ceiling at about 1 km. Later in the night, the insects often became concentrated in the warm air at the top of the inversion layer. The lower boundary of this concentration sometimes became sharply defined, but above the zone of maximum insect density there was usually a smooth decrease of insect numbers with altitude. When the boundary layer was disturbed by an atmospheric density current, the direction and vertical distribution of the migration was permanently changed; solitary wave disturbances, however, had only a transient effect.

The nocturnal migration of the Australian plague locust, Chortoicetes terminifera (Walker) (Orthoptera: Acrididae): quantitative radar observations of a series of northward flights

Night migrations of insects above the surface boundary layer were studied by direct observations with an entomological radar, and by direct aerial sampling with a kite-borne net, in an area in New South Wales inhabited by large fledging populations of Chortoicetes terminifera (Wlk.). The aerial catches and radar echo-modulation observations suggested that the majority of migrants detected by the radar were locusts, and this conclusion was supported indirectly by light-trap catches and by observations of take–off at dusk. Night flights of locusts began at dusk with a mass take-off and continued on a diminishing scale until about midnight. Displacements were all approximately downwind and to the north, under the influence of a southerly airflow which prevailed throughout the six-day study period. A quantitative radar observation procedure was used to estimate locust aerial densities and migration rates, and to observe the variations of these quantities with height and time; typical and extreme values for all the principal migration quantities are presented. The flight paths of the locusts were estimated from radar observations of target tracks, and probable source areas at distances of up to 200 km to the south were identified; a major overflight which probably originated 150 km away was detected on one occasion. Northward movements of C. terminifera during anticyclonic conditions may help to explain how populations are redistributed in the periods between the long-range southward invasion movements for which this species is well-known.

Insect monitoring radar: remote and network operation

A network of two remote Insect Monitoring Radars (IMRs) connected to a base-laboratory node computer has been operating in inland eastern Australia since late 1999. The IMRs, which incorporate ancillary meteorological observing equipment, operate automatically under the control of a microcomputer that both acquires the data and analyses it. The microcomputer is linked to the node computer via a modem and a connection to the public telephone network. This link is used both to retrieve observation data and to carry out remote servicing and fault diagnosis. An automatic system has been developed to analyse the radar and meteorological data and to generate daily statistical summaries and graphical representations of the activity observed by the radar during the previous night. The summaries and graphs show the intensity, altitude, speed, and displacement direction of the migrations, the orientation, size, and wingbeat frequencies of the migrants, and the surface weather conditions, at each site. These summaries are downloaded to the node computer and incorporated automatically into standard World Wide Web (WWW) pages, which are normally available to users by early afternoon of the following day. The network is being used in studies of the spatial ecology of mobile insect populations and of the utility of migration-monitoring information for operational pest forecasting. The methods developed to operate the radars over the network, and to make the observations available to users promptly and in a readily accessible and interpretable form, are described. Some examples of the information products generated are presented.

Collective orientation by nocturnally migrating australian plague locusts, Chortoicetes terminifera (Walker) (Orthoptera: Acrididae): a radar study

The collective orientation of Chortoicetes terminifera (Wlk.) migrating at night in New South Wales was studied with a radar. Measurements of the distribution of insect echoes on the radars plan-position-indicator display provide information about the variation of both the direction and the degree of orientation with both height and time. A quantitative analysis procedure used in a detailed study of one particularly interesting series of observations is described. It was found that collective orientation occurred frequently, and that it sometimes became very well-developed. The direction of orientation remained approximately constant for long periods, but did not appear to be consistently related to any obvious directional cue; changes in direction were observed on occasions, however, and one such change was clearly associated with a change in the direction of the wind. The degree of collective orientation was a rather more variable quantity than the direction, and increases in degree were sometimes associated with increases in the number of locusts arriving at the observation site.

Insect monitoring radar: stationary-beam operating mode

Abstract Radars employing the zenith-pointing linear-polarised conical-scan (ZLC) configuration can be adapted to operate in a second mode in which the beam remains stationary and a time-series of echo intensity is recorded as a target traverses the beam. When the targets are insects, the intensity time-series incorporates a slow variation due to the traverse and usually also a modulation that arises from changes in the targets radar cross-section (RCS) due to its wingbeating. A number of target parameters can be retrieved from these time-series: the traverse speed, the wingbeat frequency, the depth of wingbeat modulation and the harmonic content. A lower limit on the targets RCS can also be set. Stationary-beam observations are now incorporated into the operating schedule of two ZLC-configuration insect monitoring radars (IMRs) deployed in inland eastern Australia and datasets of parameter retrievals are routinely produced for several thousand targets per night during periods of heavy migration. This paper describes the stationary-beam mode of IMR operation and presents an analysis of the results for 1 night of heavy migration when Australian plague locusts Chortoicetes terminifera are believed to have been the predominant target. Wingbeats were detected for over 68% of the 6631 echoes that were sufficiently strong to be selected for analysis, and strong and quite narrow peaks around 27–31 Hz, as expected for C. terminifera , were present in the frequency distributions. Harmonic incidence, modulation depth, target speed and the lower-limit of the RCS were also retrieved with good statistics. Speeds and RCS values were consistent with those from the nights conical-scan observations and, in the case of speed, may be somewhat more reliable. The distributions of most of these quantities varied somewhat with height, in some cases because of range-dependent factors in the radars performance and in others probably because of differences in environmental conditions and/or the insects’ behaviours. The wingbeating parameters all appear to have the potential for discriminating between targets of different types and the results presented here indicate that an IMR can generate datasets of these parameters that are large enough for reliable inferences to be drawn from them.

Solitary wave disturbances of the nocturnal boundary layer revealed by radar observations of migrating insects

Four solitary wave disturbances of the nocturnal boundary layer have been detected during radar observations of insect migration over central-western New South Wales. Three of the disturbances took the form of trains of long waves of elevation of large relative amplitude, and these were manifested as propagating variations of the highly stratified vertical distributions of the migrating insects; in the fourth disturbance, which appeared as an evenly spaced series of steadily advancing insect line concentrations, the waves almost certainly contained regions of closed circulation in which large numbers of insects had become entrained. Wave profiles have been reconstructed from the radar observations, and measurements of the length and speed of the wave components have been compared with theoretical values determined from upper air data.

Target density estimation in radar biology

Abstract The fundamental problems associated with radar methods of estimating the intensity of aerial biological activity are discussed. An equivalent number density is defined and adopted as a convenient and useful measure of activity. Three target concentration types are identified, and methods of density estimation for each type are described. A detailed study of the signal analysis aspects of the estimation problem for the intermediate concentration type is presented. The intermediate concentration problem is shown to be general, and to include the high and low concentration problems as its limiting forms. The precision of the estimates and the applicability of the estimation methods are discussed, and a number of comparisons with related results from radar meteorology are drawn.