摘要:

Abstract.The free‐flight behaviour ofBemisia tabaci(Gennadius) (Homoptera: Aleyrodidae), the sweet potato whitefly, was investigated in a vertical flight chamber. A mercury‐vapour lamp presented from above induced a phototactic flight response. Although flight propensity was comparable from 06.00 to 19.00 hours, flight duration was maximum between 06.00 and 10.00 hours. Males flew longer than females and their mean flight duration remained constant throughout the day. Females flew longer from 06.00 to 13.00 hours than from 13.00 to 19.00 hours. Both sexes were capable of sustaining flight for more than 2h, although less than 5% of those tested did so.Flight activity also was influenced by age and by host quality. The propensity to take off, proportion exhibiting phototactic orientation and flight duration varied with the age of the whitefly. Host quality influenced the timing of flight behaviour. Whiteflies reared on senescing plants exhibited greater take‐off rates and initiated longer phototactic flights up to 4 days following adult eclosion when compared to individuals reared on vegetative plants. Thereafter, individuals reared on vegetative plants exhibited greater response levels. Whiteflies reared on vegetative plants weighed more and survived longer than did individuals reared on senescing plants.Whiteflies that responded to the overhead light initially exhibited a strong photokinetic and phototactic response. Over the course of the flight, these responses declined and flight instability increased, as indicated by an overall decrease in the mean rate of climb, accompanied by an increase in the variability of this parameter and an increase in horizontal displacement. Although males and females displayed similar flight characteristics, females exhibited a greater rate of climb than did males, and for both sexes, individuals that flew longer than 25 min had a greater rate of climb than did individuals that flew for less than 2

ISSN:0307-6962    

DOI:10.1111/j.1365-3032.1993.tb00592.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

Abstract.The adipokinetic hormone (Grb‐AKH) content in the corpora car‐diaca of the house cricket,Acheta domesticus, varied during a day with two peaks in the scotophase and one peak in the photophase. There were two distinct peaks of total lipid concentration in the blood, one early in the photophase and the other early in the scotophase. Fat body sensitivity to adipokinetic hormone also varied in close synchrony with the lipid rhythm. It was not possible to attribute the rhythm of blood lipid titre unequivocally to either the rhythm of adipokinetic hormone content in the corpora cardiaca or to the rhythm of sensitivity of the fat body to the hormone. In adult crickets the blood carbohydrate titre had two peaks in adult females, one towards the end of scotophase and another in the late photophase (c. 12h apart), but a single peak at the end of scotophase was apparent in last instar larvae. The blood carbohydrate rhythm persists in DD and is therefore endogenous. Carbohydrates were not mobilized by the Grb‐AKH, therefore could not be involved in the blood carbohydrate rhythm. Exposure to various day lengths caused shifts in the patterns of the carbohydrate rhythms, but imposition of a cyclic temperature regime had no effect on the r

ISSN:0307-6962    

DOI:10.1111/j.1365-3032.1993.tb00593.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

Abstract.Both oscillator and hourglass features are found in the photoperiodic response that controls the pupal winter diapause ofMamestra brassicae.The expression of oscillatory response to extended long‐night cycles is temperature dependent, i.e. circadian resonance appears at 23 and 25oC but not at 20 and 28oC. At 20oC, scanning of extended scotophases by a short light pulse does not reveal any clear circadian rhythmicity. However, a circadian feature of the photoperiodic response is indicated even at 20oC by a bistability phenomenon, i.e. either one of the two dark periods in symmetrical skeleton photoperiods determines the diapause response depending on the phase angle with the preceding (entraining) light‐dark cycles. At 20 and 25oC, the incidence of diapause increases as a function of the number of light–dark cycles regardless of the cycle length(T), ifTis 24 h or 2 X 24h (with a 12 h light period). A non‐diel cycle (r=36h) is less effective, suggesting that disturbance of the circadian organization partly impairs the diapause‐inducing function. The inductive effect of a long night is largely affected by temperature, and becomes saturated with eight cycles at 20oC and 14 cycles at 25oC. Presumably, an hourglass mechanism measures the dark time, and a circadian component involved in some later sequence of the photoperiodic response may or may not be expressed depending on the mode of interaction bet

ISSN:0307-6962    

DOI:10.1111/j.1365-3032.1993.tb00594.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

Abstract.A strain of the red flour beetleTribolium castaneum(Herbst) was selected separately for resistance to hypoxia and hypercarbia. At the 21st generation, adults and pupae of the line selected for resistance to hypoxia were significantly heavier than those selected for resistance to hypercarbia and the unselected line. It also exhibited a more prolonged developmental range than the unselected line. The line selected for resistance to hypercarbia was also significantly heavier than the unselected line. When the selected and unselected lines were subjected to starvation at the 26th generation, metabolism in both selected lines proceeded at a lower rate than in the unselected line and consequently the selected lines survived for much longer periods.

ISSN:0307-6962    

DOI:10.1111/j.1365-3032.1993.tb00595.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

Abstract.The olfactory orientation of adult cabbage seed weevils(Ceutorhynchus assimilisPayk.) from a distance of 20 m to extracts of oilseed rape(Brassica napusL.) was studied in the field using mark–release–recapture experiments. Male and female weevils dispersed upwind from the centre of a circular array of traps baited with Oilseed rape extracts. In the absence of host‐plant odour, female weevils dispersed randomly, and male weevils downwind. Percentage recapture of weevils was significantly greater in traps baited with rape flower than rape leaf extracts. Significantly fewer weevils were recaptured in unbaited traps compared to traps baited with rape flower or leaf extracts. We suggest that seed weevils can use odour‐mediated upwind anemotaxis to locate their host‐plants from distances of at l

ISSN:0307-6962    

DOI:10.1111/j.1365-3032.1993.tb00596.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

Abstract.Juvenile Hormone III (JH‐III) production by corpora allata (CA) of sexually mature female locusts(Locusta migratoria migratorioides(R.&F.)) was maintainedin vitrofor up to 30 days in an agar‐solidified medium. Hormone production was measured periodically with a short‐term radiochemical assay. Low‐activity CA increased their activity significantly after 24–48 h incubation in the long‐term medium, but high‐activity glands did not. Variations in activity were considerable among glands tested on the same day and among measurements from the same gland on different days. Farnesoic acid‐stimulated rates of JH‐III production were always higher than the basal rates, suggesting that the CA were not maximally activated. However, freshly excised low‐activity CA, whose hormone production increased in the long‐term conditions, showed similar farnesoic acid‐stimulated rates of JH‐III production to those of freshly excised high‐activity glands, suggesting that at the time of excision of the corpora allata rate‐limiting step(s) preceding farnesoic acid biosynthesis were inhibited or ref

ISSN:0307-6962    

DOI:10.1111/j.1365-3032.1993.tb00597.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

Abstract.The mating system ofProkelisia dolusWilson (Homoptera: Delphacidae) was characterized by determining: if males and females multiply mate; when transitions occur in female sexual receptivity, what triggers sexual refractoriness; and what behaviours characterize unreceptive virgins, receptive virgins, and unreceptive mated females. Males copulated with up to six females in less than 1 h, but completely inseminate, on average, only the first four females. Females rarely mated more than once, unless males were depleted of sperm due to previous copulations or if copulation was interrupted (if duration was<2 min). Male and female calling was associated (100% and 91%, respectively) with sexual receptivity and resultant matings. The transition from unreceptive virgin to receptive (calling) mature virgin occurred 48 h posteclosion, and all were mated by day 4. Females that were sexually immature and those completely inseminated did not call. Rejection of males by females included walking away from approaching males (65%), female kicking (7%), and abdominal lifting (5%). Rejection of males was observed by immature, mature and calling, and mated females. Sexual refractoriness was not triggered by acoustic and visual stimuli or mechanical stimulation of genitalia. Refractoriness was also not triggered by reception of small quantities of sperm because some females laid a few viable eggs yet calling was not terminated. Sexual refractoriness was activated by a substance in the ejaculate as demonstrated by injection into the haemocoel of male accessory glands or testes and homogenates of seminal vesicles. This is the first study that documents the role of male ejaculate in inhibiting female sexual receptivity in Hemiptera (Homoptera).

ISSN:0307-6962    

DOI:10.1111/j.1365-3032.1993.tb00598.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

Abstract.The circadian locomotor (walking) rhythms of forager honeybees(Apis mellifera ligusticaL.) were entrained to eight different 24 h light‐dark cycles. The phases of activity onset, peak activity, and offset were correlated with the lights‐off transition, suggesting lights‐off as the primary zeitgeber for the rhythm. Further support for this hypothesis was provided by LD 1:23 experiments, in which entrainment occurred when the light pulse was situated at the end, but not at the beginning, of the subjective photophase. Steady‐state entrainment of the locomotor rhythm was achieved with square‐wave temperature cycles of 10oC amplitude under constant dark: most of the activity occurred within the early thermophase. Smaller amplitude temperature cycles yielded relative coordination of the rhythm. Interactions of temperature and light‐dark cycles resulted in entrainment patterns different from those elicited in response to either cycle alone or those formed by a simple combination of the two separate responses. Furthermore, temperature cycles having amplitudes insufficient for entrainment of the rhythm nevertheless modified the pattern of entrainment to light ‐ dark cycles, suggesting a synergism of light and temperature effects on the underlying circadian

ISSN:0307-6962    

DOI:10.1111/j.1365-3032.1993.tb00599.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

Abstract.The temporal dynamics of host‐marking behaviour in the tropical tephritid fly,Anastrepha ludens(Loew), is described and used to formulate a model of control of marking behaviour. The following temporal patterns in host‐marking behaviour were observed. Time spent marking increased asAludensfemales deposited clutches in a given fruit previously marked zero, one, two or three times. This trend was paralleled by an increase in the number of pauses in marking behaviour within the host‐marking bout (and hence an increase in the number of sub‐bouts separated by such pauses). Finally, within any given marking bout, the length of a sub‐bout diminished progressively. The length of a pause, by contrast, showed no significant trend. Based on these results, we propose that host‐marking pheromone, or HMP, while deterrent to females prior to egg‐laying, actually stimulates continued host‐marking behaviour after egg‐laying. We argue that host‐marking is regulated by sensory adaptation or habituation to HMP in conjunction with a dosage‐dependent restoration of inhibition of the motor pattern. Functional aspects of this pattern of motor

ISSN:0307-6962    

DOI:10.1111/j.1365-3032.1993.tb00600.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

Abstract.The physiological basis of phagodeterrence was studied electrophy‐siologically and behaviourally in the phytophagous caterpillarsManduca sextaandManduca quinquemaculata.The model unacceptable non‐host plant was the canna lily,Canna generalis.A strongly deterrent extract was obtained from fresh leaves of canna by extraction with hot ethanol or ethyl acetate in a blender. Behavioural rejection of these extracts was similar to that of fresh leaves, although less intense. In contrast, blender extracts using other solvents, as well as leaf surface rinses, were phagostimulant or neutral. Chromatographic fractionation of the deterrent ethanolic extract showed the active principles to be moderately polar and separable into two fractions.Previous ablation experiments had shown that the medial maxillary styloconica and epipharyngeal sensilla are the two most important chemosensory organs in mediating behavioural rejection of canna leaves; if only one of these organs is spared, the animal completely rejects canna. We investigated the neural responses of the medial styloconica and their contribution to the sensory coding responsible for this phagodeterrence.The active fractions of the deterrent ethanolic extract elicited a vigorous response from one chemosensory neurone in the medial styloconica. This neurone is distinguishable from others in the medial styloconica by its unique temporal response parameters and the characteristic shape changes of its action potentials. The response frequency of this neurone correlates with the degree of phagodeterrence in a dose‐dependent manner. Threshold deterrence occurs at a concentration of extract (1%) that elicits firing in this neurone at a rate ofc.50 spikes/s peak instantaneous frequency and 30 total spikes in the first Is.We conclude that this is a ’deterrent neurone’ in the sense that vigorous response from this neurone is a sufficient sensory code for behavioural rejection of canna. Thus input from a single sensory neurone is capable of blocking feeding, since only one (unilateral) medial styloconicum is needed to mediate this

ISSN:0307-6962    

DOI:10.1111/j.1365-3032.1993.tb00601.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY