Identification of Flying Insects in the Spatial, Spectral, and Time Domains with Focus on Mosquito Imaging

Insects constitute a very important part of the global ecosystem and include pollinators, disease vectors, and agricultural pests, all with pivotal influence on society. Monitoring and control of such insects has high priority, and automatic systems are highly desirable. While capture and analysis by biologists constitute the gold standard in insect identification, optical and laser techniques have the potential for high-speed detection and automatic identification based on shape, spectroscopic properties such as reflectance and fluorescence, as well as wing-beat frequency analysis. The present paper discusses these approaches, and in particular presents a novel method for automatic identification of mosquitos based on image analysis, as the insects enter a trap based on a combination of chemical and suction attraction. Details of the analysis procedure are presented, and selectivity is discussed. An accuracy of 93% is achieved by our proposed method from a data set containing 122 insect images (mosquitoes and bees). As a powerful and cost-effective method, we finally propose the combination of imaging and wing-beat frequency analysis in an integrated instrument.

Wing damage affects flight kinematics but not flower tracking performance in hummingbird hawkmoths

ABSTRACTWing integrity is crucial to the many insect species that spend distinct portions of their life in flight. How insects cope with the consequences of wing damage is therefore a central question when studying how robust flight performance is possible with such fragile chitinous wings. It has been shown in a variety of insect species that the loss in lift-force production resulting from wing damage is generally compensated by an increase in wing beat frequency rather than amplitude. The consequences of wing damage for flight performance, however, are less well understood, and vary considerably between species and behavioural tasks. One hypothesis reconciling the varying results is that wing damage might affect fast flight manoeuvres with high acceleration, but not slower ones. To test this hypothesis, we investigated the effect of wing damage on the manoeuvrability of hummingbird hawkmoths (Macroglossum stellatarum) tracking a motorised flower. This assay allowed us to sample a range of movements at different temporal frequencies, and thus assess whether wing damage affected faster or slower flight manoeuvres. We show that hummingbird hawkmoths compensate for the loss in lift force mainly by increasing wing beat amplitude, yet with a significant contribution of wing beat frequency. We did not observe any effects of wing damage on flight manoeuvrability at either high or low temporal frequencies.

Wing damage affects flight kinematics but not flower tracking performance in hummingbird hawkmoths

The integrity of their wings is crucial to the many insect species that spend distinct portions of their life in flight. How insects cope with the consequences of wing damage is therefore a central question when studying how robust flight performance is possible with such fragile chitinous wings. It has been shown in a variety of insect species that the loss in lift-force production resulting from wing damage is generally compensated by an increase in wing beat frequency rather than amplitude. The consequences of wing damage for flight performance, however, are less well understood, and vary considerably between species and behavioural tasks. One hypothesis reconciling the varying results is that wing damage might affect fast flight manoeuvres with high acceleration, but not slower ones. To test this hypothesis, we investigated the effect of wing damage on the manoeuvrability of hummingbird hawkmoths (Macroglossum stellatarum) tracking a motorised flower. This assay allowed us to sample a range of movements at different temporal frequencies, and thus assess whether wing damage affected faster or slower flight manoeuvres. We show that hummingbird hawkmoths compensate for the loss in lift force mainly by increasing wing beat amplitude, yet with a significant contribution of wing beat frequency. We did not observe any effects of wing damage on flight manoeuvrability at either high or low temporal frequencies.

Mosquito counting system based on optical sensing

Mosquitos, sometimes carrying deadly diseases such as malaria, zika, and dengue fever, cause much concern. To control mosquitos, it is important to effectively monitor their presence and behavioral trends. We have constructed two optical sensing systems for insects based on light attenuation and light backscattering, respectively. The systems, which were tested with the potentially dangerous Aedes albopictus and Culex pipiens, were able to extract the wing-beat frequency, when they passed impinging light, derived from light-emitting diodes. We could achieve distinction between the sexes of A. albopictus and C. pipiens based on the wing-beat frequency. Finally, we propose a statistical method suitable for the system to improve the accuracy of counting.

Sustained hovering, head stabilization and vision through the water surface in the Pied kingfisher (Ceryle rudis)

Pied kingfishers (Ceryle rudis) capture fish by plunge diving from hovering that may last several minutes. Hovering is the most energy-consuming mode of flight and depends on active wing flapping and facing headwind. The power for hovering is mass dependent increasing as the cube of the size, while aerodynamic forces increase only quadratically with size. Consequently, birds above a certain body mass can hover only with headwind and for very short durations. Hummingbirds are referred to as the only birds capable of hovering without wind (sustained hovering) due to their small size (ca. 2-20 gr), high wing-beat frequency and unique anatomy.We studied the hovering characteristics of pied kingfishers in relation to wind and sun orientation, in 139 hovers. Furthermore, plunge diving necessitates the coping with the visual effects of light at the air/water interface. The kingfishers oriented their body axis towards the wind more than towards the sun. Hovering in little or no wind was common. With increased wind speed (a) orientation precision increased, (b) wing beat amplitude did not change, (c) wing beat frequency decreased and (d) body tilt became more horizontal. The head was highly stabilized and with orientations that indicated monocular viewing of prey.We conclude that pied kingfishers achieve sustained hovering. This is despite their being significantly heavier than the theoretical maximum and showing ordinary kinematics and morphology. Head stabilization is a means of aiding viewing of submerged prey across the interface.

Bombus impatiens (Hymenoptera: Apidae) display reduced pollen foraging behavior when marked with bee tags vs. paint

Numbered bee tags, developed for marking honey bees (Apis mellifera Linnaeus), are glued to the mesosoma of many bees to uniquely identify them. We recorded whether or not bees sonicated to collect pollen after being marked, and we compared the sonication frequency, sonication length, and wing beat frequency of Bombus (Pyrobombus) impatiens Cresson that were tagged with bee tags vs. marked with paint. We found that bees with tags glued to their mesosoma had no significant change in wing beat frequency, sonication frequency, or sonication length, relative to bees that were marked with paint; however, we found that the probability of collecting pollen via sonication after being marked was much lower for bees marked with bee tags vs. paint.