Take-off Behaviour Research Articles

CRY1 is involved in the take-off behaviour of migratory Cnaphalocrocis medinalis individuals

BackgroundNumerous insect species undertake long-distance migrations on an enormous scale, with great implications for ecosystems. Given that take-off is the point where it all starts, whether and how the external light and internal circadian rhythm are involved in regulating the take-off behaviour remains largely unknown. Herein, we explore this issue in a migratory pest, Cnaphalocrocis medinalis, via behavioural observations and RNAi experiments.ResultsThe results showed that C. medinalis moths took off under conditions where the light intensity gradually weakened to 0.1 lx during the afternoon or evening, and the take-off proportions under full spectrum or blue light were significantly higher than that under red and green light. The ultraviolet-A/blue light–sensitive type 1 cryptochrome gene (Cmedcry1) was significantly higher in take-off moths than that of non-take-off moths. In contrast, the expression of the light-insensitive CRY2 (Cmedcry2) and circadian genes (Cmedtim and Cmedper) showed no significant differences. After silencing Cmedcry1, the take-off proportion significantly decreased. Thus, Cmedcry1 is involved in the decrease in light intensity induced take-off behaviour in C. medinalis.ConclusionsThis study can help further explain the molecular mechanisms behind insect migration, especially light perception and signal transmission during take-off phases.

Female bias in an immigratory population of Cnaphalocrocis medinalis moths based on field surveys and laboratory tests

Sex ratio bias is common in migratory animals and can affect population structure and reproductive strategies, thereby altering population development. However, little is known about the underlying mechanisms that lead to sex ratio bias in migratory insect populations. In this study, we used Cnaphalocrocis medinalis, a typical migratory pest of rice, to explore this phenomenon. A total of 1,170 moths were collected from searchlight traps during immigration periods in 2015–2018. Females were much more abundant than males each year (total females: total males = 722:448). Sex-based differences in emergence time, take-off behaviour, flight capability and energy reserves were evaluated in a laboratory population. Females emerged 0.78 days earlier than males. In addition, the emigratory propensity and flight capability of female moths were greater than those of male moths, and female moths had more energy reserves than did male moths. These results indicate that female moths migrate earlier and can fly farther than male moths, resulting more female moths in the studied immigratory population.

Variability and genetic basis for migratory behaviour in a spring population of the aphid,Aphis gossypiiGlover in the Yangtze River Valley of China

The population dynamics, development of gonads, takeoff and flight behaviour of Aphis gossypii Glover were investigated in order to test whether there was variation of migratory ability in the spring population. Field surveys showed that not all the aphids overwintering on hibiscus migrated to the secondary host plants, and the host-alternating and host-specific life-cycle forms coexisted in Nanjing, China. Substantial variation in flight capacity of winged individuals, development of gonads and takeoff behaviour were found within the spring population. The frequency distribution of flight duration and the number of ovarioles per individual alatae exhibited two peaks, representing the migratory and sedentary genotypes, respectively. Significant response to directional selection on takeoff behaviour demonstrated the additive genetic component of this variation. Selection for 'takeoff' individuals caused a significant increase in takeoff angle from 39.8 degrees in the first selection to 68.7 degrees in the fifth; and, hence, screened out the migratory genotype (M), while selection for the sedentary individuals increased the rate of non-takeoffs significantly, and screened out the sedentary genotype (S). The reciprocal cross, M(female) x S(male), produced hybrid offspring performing significantly steeper takeoff angles compared with those from the cross S(female) x M(male), suggesting the presence of a maternal effect. On the other hand, takeoff rate was ranked as M(female) x S(male)=S(female) x M(male)>M>S, involving no sex-linkage and maternal effect. The coexistence of host-alternating and host-specific life-cycle forms of A. gossypii on the primary host has, as deduced from the present studies, a genetic basis.

The buzz-run: how honeybees signal ‘Time to go!’

The explosive take-off of a honeybee swarm when it moves to its new home is a striking example of an animal group performing a synchronized departure for a new location. Prior work has shown that the nest-site scouts in a swarm prime the other bees for flight by producing piping signals that stimulate all the bees to warm up their wing muscles in preparation for flight, but how the bees are ultimately triggered to take flight remains a mystery. We explored the possibility that the buzz-run signal is the critical releaser of flight. Using slow-motion analyses of videorecordings, we made a detailed description of this signalling behaviour: a buzz-runner runs about the swarm cluster in great excitement, tracing out a crooked path, buzzing her wings in bursts, bulldozing between idle bees and periodically performing a conspicuous wiggling movement. It seems likely that the buzz-run signal is a ritualized form of a bee's take-off behaviour, with the wing buzzing greatly exaggerated and other behavioural elements (running, butting and wiggling) added to increase the signal's detectability. The immediate effect of the signal is to disperse and activate otherwise lethargic bees; the long-term effect is probably to stimulate the recipients to launch into flight. It turns out that the scout bees from the chosen nest site are responsible for producing both the piping signal to prime a swarm for take-off and the buzz-run signal to trigger the take-off. We suggest that these bees produce the signal that triggers take-off because they travel throughout the swarm cluster while piping and so are able to sense when the entire swarm is hot enough to take flight. The mechanisms mediating take-offs by honeybee swarms appear to present us with a rare instance where an action of a large social insect colony is controlled by a small set of individuals that actively monitor the global state of their colony and produce a signal triggering the colony's action in a timely way.

A review of the evolution and mechanisms of ballooning by spiders inhabiting arable farmland

This paper complements and updates a review of spider ballooning literature by WEYMAN (1993), with expanded discussion of the possible causative factors of ballooning by spiders that inhabit arable farmland. Results relating to other taxonomic groups (especially Acari) are also described, where these help to illuminate the processes underlying the phenomenon of ballooning. Changes in air movement are proposed as an immediate trigger for take-off behaviour, and food deprivation is confirmed as a short-term moderator affecting ballooning frequency. Seasonal changes in ballooning motivation of spiders inhabiting arable farmland have not been found. Within species, ballooning frequency can vary with the growth stage and sex of the spider but variations may also represent a mixed strategy within the population. Differences in ballooning frequency between species are difficult to detect if sample size is low, trapping period is short, or the results are not controlled for the physiological states of the spider populations being compared. Where real inter-specific differences in ballooning frequency occur, they may be related to foraging strategies, physiological adaptations to exploit transient food resources, or dispersal selection pressures in the origin habitats of each species. Ballooning by spiders found on arable farmland is suggested to have evolved primarily as a risk-spreading strategy to maximise survival in unpredictable habitats. In addition to reducing the risk of being confined in deteriorating habitats, ballooning could confer on spiders the opportunity to exploit (in advance of less dispersive predatory invertebrates) ephemeral blooms of prey organisms. Areas for further research are suggested.

Take-off and Flight Behaviour of the Tiger-Beetle Species Cicindela hybrida in a Hot Environment (Coleoptera: Cicindelidae)

Take-off and flight behaviour of Cicindela hybrida Linnaeus 1758, living on a small sandy spot was recorded during a very hot period of mid august. Timing of take-off to flight sequence-ducking, jumping, elytra opening, first wing-beat - is described. This sequence is stereotype and very fast, lasting only 0.12 s, even when taking off after copulation. Distance-, velocity- and acce-leration-time-functions are given and compared to the start - to - run sequence. The flight-path angle at take-off is usually around 40°. Mean speed and maximum acceleration are around 0.6 m s -1 and 7 m s -2 for flight and approximately 1/4 of this value for running. A take-off jump is carried out with mainly the pedes-II. By the time the end of a jump has been reached the P-I are stretched out to support the outspread elytra in a slightly positive V-position and a moment later they are aided by the P-II. Wing-beat frequency at take-off averages 100 Hz during the hottest time of day (13.00 hours, S-Tp T s ≤ 50°C) and 70 s -l in the evening when, normally, they no longer take-off (20..30 hr, T s 24°C). Flight lasts only a few seconds, maximum flight speed is ≥ 3 m s -1 , maximum flight height and length is generally 50 cm and 5 m. The elytra, which do not beat, are held almost horizontally, still supported by the pedes-I and -II. Distal parts of the P-II are stretched forward obliquely, P-III are stretched backward, the tarsi touching each other. Wing-beat frequency (under hot environmental conditions) is around 100 Hz and amplitude between 150 - 180°, or slightly more. At the upper turning region the wing tips often touch each other, executing near clap and fling, but they do not touch at the lower turning point. A phase shift between coupled beating and rotational oscillations is clearly visible.

Synomone-induced suppression of take-off in the phytoseiid mite Phytoseiulus persimilis Athias-Henriot

Plant-inhabiting predatory mites in the family Phytoseiidae are known to disperse passively on air currents. In this article ww analyse observations on the behaviour that initiates aerial dispersal, the so-called take-off behaviour. When starved for 24 hours at 25°C and 35% RH, about 80% of the females of Phytoseiulus persimilis Athias-Henriot became airborne during 10 minute exposure to wind velocities of 2 ms-1 or higher. However, take-off was suppressed when females were exposed to volatile chemicals emanating from leaves that had been infested by two-spotted spider mites (Tetranychus urticae Koch) during one day preceding the experiments. This result is the first unambiguous proof that phytoseiid mites exert control over take-off. Interestingly, the females of the predator strain under study did not show the characteristic upright posture that was hypothesized to be important for take-off in two other species of phytoseiid mites (Amblyseius fallacis Garman and Metaseiulus occidentalis (Nesbitt)). These observations shed new light on the behaviour involved in controlling take-off. It is suggested that take-off control is exerted mainly via the grasp of the claws and the adhesive empodia in a way reminiscent of that described for aphids.