Response of Eretmocerus eremicus to skylight and plant cues in a vertical flight chamber

In the southwestern United States, Eretmocerus eremicus (Hymenoptera: Aphelinidae) is a native parasitoid of the Bemisia complex (Homoptera: Aleyrodidae). However, little information currently exists on its potential as a biological control agent of whiteflies or on the factors that influence its tendencies to disperse. In this study, we examined the flight behavior of male and female E. eremicus in response to skylight (here simulated by a mercury-vapor lamp) and plant cues (a 550-nm filtered light) in a vertical flight chamber. Approximately 90% of the parasitoids took off in response to the skylight cue. Both sexes were capable of sustained flights in excess of 60 min; however, males had higher rates of climb than females (3.31±0.17 and 2.63±0.19 cm s^–1, respectively). When a plant cue was presented during the parasitoid's phototactic flight, four relatively distinct responses were observed. Fifty-one percent of the individuals responded to the plant cue throughout their flight by flying toward or by landing on the cue. The majority of these parasitoids were females. Approximately 12% of the wasps exhibited an intermittent, positive response to the plant cue. Twenty percent exhibited a `migratory' response. These parasitoids, which were predominantly males, failed to respond to the plant cue until they had flown for a considerable period. Finally, 17% failed to respond to the target during their flight. Approximately 37% of the individuals that showed a positive response to the plant cue actually landed on it and the majority of these were female. The differential response to the plant cue by male and female parasitoids could be, in part, because females are driven to locate hosts in which to oviposit, and males are driven to find mates.     

Environmental and physiological factors influencing phototactic flight of Bemisia tabaci

Abstract. Experiments were conducted in a glasshouse and in the laboratory to determine the environmental and physiological parameters that affect flight behaviour of Bemisia tabaci (Gennadius) (Homoptera: Aleyrodidae). The number of whiteflies taking off and exhibiting a positive response to sky light in the glasshouse was greatest from 08.30 to 10.00 hours. During peak flight activity less than 5% of the population engaged in phototactic orientation. Temperature was the best single predictor for the phototactic response, accounting for 75% of the variability in whitefly ascent. Sex ratios were determined for individuals remaining on poinsettia, Euphorbia pulcherrima (Willd.), and for individuals that exhibited phototactic orientation; both groups deviated from an expected 1:1 ratio. Males were more prevalent on the plants (1:0.76), whereas females were much more prevalent (1:3.02) among the whiteflies responding to sky light. A higher percentage of the females displaying a phototactic response contained eggs when compared to females remaining on poinsettia (87 v 65%). The two groups of females did not differ significantly in their weights, but males that remained on the plants were heavier than males that responded to sky light. Mark–recapture studies and experiments where phototactic individuals were removed from the population established that the response was short-lived. Whiteflies exhibiting a phototactic response in the glasshouse were more likely to exhibit long-duration, phototactic flights in a vertical flight chamber when compared to individuals that remained on poinsettia (80.7 ± 6.7 v 36.0 ± 5.8% phototactic response; 7.0 ±3.2 v 0.7±0.2min flights). There was also less deviation in flight across the horizontal plane among the individuals that exhibited a positive response to sky light in the glasshouse in comparison to individuals that remained on their host. However, initial rates of climb were not significantly different between the two groups of whiteflies.     

Flight behaviour of Bemisia tabaci in a vertical flight chamber: effect of time of day, sex, age and host quality

Abstract. The free-flight behaviour of Bemisia 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 25 min.     

Sexual differences in the flight performance of the oriental fruit moth, Cydia molesta

Cydia molesta Busck (Lepidoptera: Tortricidae), a major pest of stone fruits and an increasingly important late season pest of apple, is predominately monitored by pheromone trapping of male moths. We investigated flight performance in relation to sex, age, and mating status using computer-linked flight mills, and also examined the relationship between female flight and reproduction. The crepuscular flight pattern of the experimental moths in relation to photointensity was very similar to that reported from field studies. Female moths significantly outperformed males in all measured flight parameters including total distance flown, distance of longest single flight, and velocity. The proportion of long-flying females (categorised as those completing an unbroken flight of greater than 1 km) was three to six times greater than that of males. Female flight performance was not related to mating status, but mated males displayed significantly greater flight than unmated males. The maximal flight period of mated females commenced on the third day after eclosion, following 30% egg deposition. Male flight was not significantly related to age. The data suggest that a limited proportion of the population, in particular females, may have the capacity to make inter-orchard flights. The limitations of monitoring C. molesta populations in apple orchards solely by pheromone trapping of males are discussed.     

Tethered flight of the potato moth, Phthorimaea operculella

ABSTRACT. The effects of sex, age and mated state on average flight speed, duration and distance were determined for potato moths, Phthorimaea operculella (Zeller) (Lepidoptera, Gelechiidae), tethered to flight mills. Moths were classified as non-fliers (NFs), good-fliers (GFs) and remaining-fliers (RFs) on the basis of their performance over the first two flights. Some moths flew for over 5 h non-stop, while others tethered overnight flew between 20 and 30 km. Speed, duration and distance flown were greater during the first flight. First flight duration and distance flown by females decreased with age, whereas no trend was evident for males. Mated males and females flew slower first flights with increasing age, whereas virgin moths showed no marked trend. The analysis of fliers and NFs revealed that GFs were heavier than both RFs and NFs, GFs were faster than RFs, the percentage of NFs increased with age especially for mated females, and the percentage of GFs decreased with age. Age and mated state are important factors influencing flight performance especially for female moths. The relevance of these results to the field situation and the possible application of tethered flight to tests of potato moth quality are discussed.     

Avoidance of natural enemies by adult whiteflies, Bemisia argentifolii, and effects on host plant choice

In this study we asked whether, in the context of a trap crop system, differential predation risks among plants influence host choice patterns of adult whiteflies, Bemisia argentifolii. We investigated whether adult whiteflies avoid natural enemies inhabiting poinsettia (a cash crop) and whether this behavior can be used to increase the movement of whiteflies to cucumber (a trap crop). The potential of cucumber as a trap crop was first evaluated and we found that significantly more whiteflies were attracted to cucumber when the whiteflies were released between the two plants. However, the accumulation of whiteflies on cucumber substantially diminished if the insects had first settled on poinsettia. Under such circumstances, we investigated whether movement of adult whiteflies to cucumber could be increased by creating conditions that would cause the whiteflies that had settled on poinsettia to leave the plant. A mechanical disturbance, consisting of shaking the plant, was first used to test this hypothesis. The shaking caused more whiteflies to leave poinsettia and move onto the trap crop, compared to undisturbed whiteflies. We then asked whether the presence of natural enemies on the cash crop could induce whiteflies to leave the cash crop and move onto the trap crop. Three natural enemies were tested: two predators, Amblyseius swirskii and Delphastus catalinae, and a parasitoid Encarsia formosa. The presence of D. catalinae on poinsettia induced significantly more whiteflies to disperse to cucumber compared to poinsettia with no natural enemies, whereas A. swirskii and E. formosa did not result in a significant increase. Predator avoidance behavior by adult whiteflies should be investigated further in the context of trap cropping and other crop-habitat alterations designed to help manage whitefly abundance.     

Chemical ‘generalists’ and behavioral ‘specialists’: a comparison of host finding by Stelidota geminata and Stelidota octomaculata

Host orientation by two nitidulid beetles was compared: Stelidota geminata (Say), which is very broad in its' host range, and Stelidota octomaculata (Say), a species whose feeding is restricted primarily to acorns. In a no-choice assay, both species responded to all food substrates offered and neither showed a significant preference among substrates (except banana versus wood fungi for S. octomaculata), or between aseptic and inoculated treatments; however, S. geminata readily displayed both phototactic flights and host-orienting flights, whereas S. octomaculata never exhibited phototactic flight and never responded to food odors by flying to the source. Furthermore, when upwind-walking response was compared, S. octomaculata walked to the source at a rate of 0.16±0.01 cm/s, which was significantly lower than that of S. geminata, with a rate of 0.54±0.02 cm/s. Turning frequency on the way to the source also differed between the two species, whereas distance traveled, number of pauses, and duration of pauses did not differ significantly. We submit that both species represent olfactory generalists, and that the restricted host range of S. octomaculata compared to S. geminata is not mediated by differences in long-range response to host odors, but rather is due to differences in other behaviors such as a reduced rate of locomotion, post-landing behavior, and possibly ecological factors.     

Behavior of Carpophilus hemipterus in a vertical flight chamber: transition from phototactic to vegetative orientation

The freeflight behavior of Carpophilus hemipterus (L.) (Coleoptera: Nitidulidae) was investigated in a vertical flight chamber to measure takeoff propensity relative to beetle age and to determine the effect of food odors on phototactic orientation. A high-pressure sodium lamp presented from above induced a phototactic flight response, especially in beetles 3–7 days old. The majority of phototactic flights lasted less than 15 min for both males (73%) and females (85%), but ranged up to 100 min. A bimodal periodicity in flight propensity was recorded during the photophase with a small peak in activity occurring 14–10 h prior to scotophase and a large 4 h peak occurring from 3 h prior to scotophase to 1 h after when the onset of scotophase would normally have occurred. Beetles maintained with water as adults usually displayed higher levels of flight activity than did beetles maintained with artificial diet.After a period of vertical flight, photokinetic and phototactic response 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 measure and an increase in horizontal displacement.When food odor (apple cider vinegar) was introduced the rate of climb dropped rapidly and beetles usually landed regardless of how long they had been in flight. When the food odor was removed, takeoff occurred and the beetle returned to its previous rate of climb. When food odor was repeatedly introduced during the same flight, there was no apparent cumulative effect, and each time it was removed, the beetle re-initiated phototactic flight. Unlike true migratory flight in which response to vegetative cues is temporarily inhibited until the insect has engaged in a period of phototactic flight, C. hemipterus flight could be better characterized as extended foraging in which phototactic flight is readily interrupted by encounters with food odor.

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Résumé Le comportement de vol libre de C. hemipterus L. a été examiné dans une chambre à vent verticale pour déterminer la tendance au vol après l'émergence et observer l'influence de l'odeur d'aliments sur le vol phototactique. Une lampe à haute pression de sodium induit une réponse de col phototactique, qui débute le 3^e jour et reste puissante jusqu'au 8^e jour. La majorité des vols phototactiques duraient moins de 15 pour les mâles (73%) et les femelles (85%), mais pouvait se prolonger jusqu'à 100. Les femelles nourries sur régime artificiel présentaient la plus forte proportion de vol dépassant 35. Cependant, les adultes maintenus exclusivement en présence d'eau ont présenté un niveau d'activité de vol encore supérieur. Une tendance au vol à périodicité quotidienne bimodale a été notée avec un petit pic d'activité à 14–10 heures avant la scotophase et un grand pic durant 4 heures, de 3 heures avant la scotophase à une heure après le début de la scotophase.Après une période de vols verticaux, les réactions photocinétiques et phototactiques ont diminué, et l'instabilité des vols augmenté comme en a témoigné la diminution du taux total d'ascensions et l'accroissement de la variabilité de ce paramètre et des déplacements horizontaux. L'introduction d'odeurs d'aliments pendant le vol phototactique provoque une diminution immédiate du taux d'ascension et conduit généralement à un atterrissage indépendamment du temps antérieur de vol. Quand l'odeur était supprimée le décollage avait lieu et l'insecte retrouvait sont taux antérieur d'ascension. Quand la même odeur d'aliment a été réintroduite à répétition pendant le même vol, il n'y a pas eu d'effets cumulatifs apparents. Par opposition avec d'autres insectes présentant un véritable comportement migrateur pour lesquels la désinhibition des réactions végétatives ne se produit qu'après une longue période de locomotion continue, le vol de C. hemipterus est mieux caractérisé comme un comportement de prospection pour lequel les aliments inhibent immédiatement la dispersion.

     

Investigations of the oogenesis-flight syndrome inAnthonomus grandis (Coleoptera: Curculionidae) using tethered flight tests

This paper investigates the relationship between oogenesis and flight duration and the use of tethered flight as an indicator of tendency to migrate inAnthonomus grandis grandis Boheman (Coleoptera: Curculionidae), the boll weevil. When boll weevils were flown to exhaustion in tethered flight tests, many flew between 2 and 3 h, with several flying more than 4 h. To test the validity of the tethered flight test as an indicator of tendency to migrate, comparisons of mean flight duration were made between boll weevils trapped in pheromone traps far from any cultivated cotton and those trapped at the edge of heavily infested, flowering cotton fields. There was a significant difference in mean flight time between the two groups, supporting the assumption that long-duration tethered flight in the laboratory reflects the tendency to make long-distance flights in the field. Groups of weevils of different ages were killed after flight testing, and the degree of ovarian development and fat body status were determined and related to duration of tethered flight. Insects with undeveloped or partially developed ovaries were the most likely to make long flights. Weevils with ovaries bearing chorionated eggs made very few long flights. Flight duration was positively correlated with degree of fat body development. In contrast, there were no significant differences in the degree of ovarian development with fat body status. We conclude from these experiments thatA. grandis grandis is capable of long-distance flight, that this species displays some behavioral and physiological characteristics typical of many insect migrants including an oogenesis-flight syndrome, and that a tethered flight test is an appropriate means of measuring migratory tendency in this species.     

Orientation of male gypsy moths,Lymantria Dispar (L.), to pheromone sources: The role of olfactory and visual cues

The role of olfaction and vision in the close-ranging flying and walking orientation of male gypsy moths, Lymantria dispar(L.), to females was studied in the forest and in the laboratory. In the forest, feral males found an isolated pheromone source as readily as one supplemented with female visual cues; dead, acetonerinsed females deployed without pheromone received virtually no visitations. In flight tunnel choice experiments using cylinders as surrogate trees and pheromone in different spatial configurations, visual attributes of the female did not influence either the males' choice of landing site or the efficiency with which they located the female. Rather, the presence of pheromone on the cylinder was necessary to elicit orientation as well as landing and walking on the cylinder. When a female visual model was placed in various positions around a pheromone source, walking males oriented primarily to the chemical stimulus. There were, however, indications that males would alter their walking paths in response to female visual cues over short distances (<5 cm), but only if they continued to receive pheromone stimulation. When visual and chemical cues were abruptly uncoupled by altering the trajectory of the pheromone plume, most males responded to the loss of the odor cue rather than to visual cues from the female. Temporal pheromone stimulation patterns affected male walking orientation. When stimulated by pheromone, males oriented toward the source; loss of the odor cue prompted an arearestricted local search characterized by primarily vertical and oblique movements with frequent reversals in direction. Presumably these maneuvers enhance the likelihood of recontacting the plume or serendipitously encountering the female. The apparent lack of visual response to the female is discussed in light of morphological and behavioral evidence suggesting that gypsy moths were formerly nocturnal.     

Flight Speed of Tethered Reticulitermes flavipes (Kollar) (Isoptera: Rhinotermitidae) Alates

Alates of the Eastern subterranean termite, Reticulitermes flavipes (Kollar) were collected over two flight seasons (2002 and 2004) and flown on flight mills. Data were collected to test if alate mass, colony origin, or gender influenced flight speed. Flight speed ranged from 3.14 to 69.12 cm s⁻¹ and the maximum distance flown by an alate was 458.3 m. Alate mass (P = 0.9406), gender (P = 0.3976), colony origin (P = 0.1244), and the interaction of gender and colony (P = 0.7093) did not significantly influence flight speed. Additionally, an electronic counting device was used to provide instantaneous flight speeds and allowed flight speed to be modeled during acceleration, cruising, and deceleration periods of flight. Mean (±SEM) flight speeds in 2004 were 20.64 (±2.21) cm s⁻¹ (n = 13) for males and 17.76 cm s⁻¹ (n = 1) for the single female flown, falling within the range of the 2002 values.     

Localized migration and dispersal by the sweet potato whitefly,Bemisia tabaci

Laboratory populations of the sweet potato whitefly, Bemisia tabaci, have been shown to consist of both migratory and trivial flying morphs. The behavior of these forms as part of the process of short-range migration was examined under field conditions. Insects were marked in a field of melons using fluorescent dust during two consecutive growing seasons. During the first growing season, passive traps used to collect living whiteflies, were placed along 16 equally spaced transects radiating from the field to a distance of up to 1.0 km. Wind out of the north-east consistently carried migrating whiteflies to traps placed along transects in the south-western quadrant because cold air drainages dictate wind direction during early morning hours in the desert South-west. For this reason, during the second season traps were laid out over fallow ground in a rectangular grid extending 2.7 km to the south-west of the marked field. If dispersal was entirely passive, patterns could be described using a diffusion model. Statistical examination of the data, howèver, demonstrated that the distribution on all days was patchy. Geostatistical techniques were used to describe the observed patchiness. Traps in the immediate vicinity of the marked field caught more whiteflies than the daily median. Large numbers were also collected from near the periphery of the grid. White-flies were far less prevalent in the grid's center. As a result, the distribution of captured whiteflies can be described as bimodal. These patterns confirm behavior observed in the laboratory, i.e., a portion of the population are trivial fliers that do not engage in migration and are consequently captured in traps near the field, and a portion initially respond to cues associated with skylight, ignoring cues provided by the ground, and fly for a period of time before landing in distant traps. During both years movement out of the field had an exaggerated directional component on 13 of 14 days.     

Flight initiation in the egg parasitoid Trichogramma minutum: Effects of ambient temperature, mates, food, and host eggs

Emergence, preening, and flight initiation were studied in laboratory-reared Trichogramma minutum Riley (Hymenoptera: Trichogrammatidae). Male parasitoids emerged first and flew before females. When both sexes were present in flight cylinders, female parasitoids flew before males. Flight propensity in males was negatively related to the number of emerging females, while flight propensity in females was independent of the number of males present. Ambient temperature significantly affected the propensity and timing of flight; between 70–80% of the parasitoids flew at 25 and 30 °C while less than 4%, mostly males, flew at 20 °C. No flights were observed at 15 °C. The presence of fresh host eggs caused a reduction in the proportion of female parasitoids that flew and a delay in the time to flight for the females that did fly. The presence of food increased the flight propensity of female parasitoids, but did not affect the timing of flight. The relationship between flight behaviour and the efficiency of mass-reared Trichogramma is discussed in terms of its importance for inundative release programmes.     

Sexual dimorphism inAnastrepha suspensa (Loew) and other tephritid fruit flies (Diptera: Tephritidae): Possible roles of developmental rate,fecundity, and dispersal

Larger male Caribbean fruit flies are more likely to be chosen as mates and defeat rivals in territorial contests. Yet males are smaller than females. Adaptive explanations for relatively small male size include (1) acceleration of male development to maximize female encounter rates, (2) selection for greater female size to increase fecundity, and (3) selection for body sizes most suitable for sexually dimorphic degrees of mobility, speed, and distance flight. None of these unambiguously accounts for the degree of sexual dimorphism. Male development is not accelerated relative to that of females. On average, males remain inside fruit longer than females and those males with extended development periods are smaller than more rapidly developing individuals. There is no evidence that female enlargement alone, presumably for greater fecundity, has generated the degree of dimorphism in the Caribbean fruit fly or other fruit flies. The relationship between dimorphism and mean female body size in 27 species of Tephritidae is the opposite of what would be predicted if differences in dimorphism were due to differences in unilateral female enlargement. Larger size in a species or in one sex of a species may be an adaptation for extensive flight. In general, among 32 species of fruit flies, as body size increases, wing shape becomes progressively more suited for distance flight. However, there are important exceptions to this correlation. Both sexual selection and nonadaptive allometries may contribute to the range of dimorphisms within the family.     

Herbivore host plant selection: whitefly learns to avoid host plants that harbour predators of her offspring

Evidence is accumulating that herbivorous arthropods do not simply select host plants based on their quality, but also on the predation risk associated with different host plants. It has been suggested that herbivores exclude plant species with high predation risk from their host range. This assumes a constant, predictable predation risk as well as a rather static behaviour on the part of the herbivore; plants are ignored irrespective of the actual predation risk. We show that adult females of a small herbivore, the whitefly Bemisia tabaci, can learn to avoid plants with predatory mites that attack only juvenile whiteflies, while they accept host plants of the same species without predators. Predatory mites disperse more slowly than whiteflies; they cannot fly and walk from plant to plant. Hence, by avoiding plants with predators, the whiteflies create a temporary refuge for their offspring. We suggest that the experience of arthropod herbivores with risks associated with host plants plays an important role in their host plant selection.     

Effect of physiological state and fungal inoculation on chemically modulated host-plant finding by Carpophilus hemipterus and Carpophilus lugubris

Host orientation by Carpophilus hemipterus L. and Carpophilus lugubris Murray (Coleoptera: Nitidulidae) was investigated in a horizontal wind tunnel to ascertain if these species differ in their response to aseptic and fungal-inoculated hosts, and also to determine how age, nutritional status, diel period, and locomotory opportunity affect these behavioral responses. Both species responded to food odors beginning on Day 3 of adult life by walking upwind to the source; flight activity and flights to the odor source began for C. hemipterus on Day 4, but C. lugubris continued to walk to the source and rarely flew regardless of age. Both species displayed maximum response to food odors from 6 to 9 days after emergence and showed bimodality in host orientation during the photophase. C. hemipterus maintained with artificial diet took flight as frequently as when maintained with water only, as long as they were deprived of diet for 36 h before the test; however, after takeoff, beetles maintained with diet were less likely to fly to food odor in comparison to beetles maintained with water. C. lugubris maintained with diet until 36 h before the test displayed a reduction in walks upwind to sources of food odor compared to beetles maintained with water. Three hours of unrestricted locomotion under a high-pressure sodium lamp did not enhance upwind orientation to host odors by C. hemipterus maintained with diet or water, or by C. lugubris maintained with water; however, such preexposure to a sodium lamp resulted in reduced takeoffs in C. hemipterus maintained with artificial diet. Both species were attracted to all fruit and vegetable substrates offered; however, aseptic substrates were less attractive than were substrates inoculated with Saccharomyces cerevisiae Hansen or Candida krusei (Castellani) Berkhout for C. lugubris. Despite the broad host range exhibited by these two nitidulid species, each responded to chemical cues from longrange (2.5 m), a trait once assigned to specialists.     

Sexually differentiated flight responses of the Mexican bean beetle to larval and adult nutrition

Summary Flight of male and female Mexican bean beetle adults was examined in laboratory tests. The experimental design made it possible to examine flight behavior not only with respect to different types of hosts (young vs senescent common bean foliage) but also with respect to effects due to their utilization during particular stages of beetle development. The median flight time of males was significantly affected by the adult host, but not by the juvenile host; whereas, the median flight time of females tended to be more affected by the juvenile than by the adult host. These different effects of hosts on the flight times of males and females resulted in sexual dimorphism in flight when the sexes were fed senescent foliage as adults. Although age significantly affected the flight time of both males and females, the reproductive status of females did not affect their flight times. The significance of these results are discussed with respect to the influence of the nutritional complexity of habitats on life history strategies and population dynamics.     

Similarity in flight activity rhythms in coexisting species of Aleyrodidae, Bemisia tabaci and Trialeurodes abutilonea

Experiments were conducted in Arizona, USA to examine the diel patterns of flight activity of two coexisting species of whiteflies, Bemisia tabaci (Gennadius) and Trialeurodes abutilonea (Haldeman) (Aleyrodidae). Aerial populations were monitored during parts of two growing seasons using sticky traps. It was found that on most days when more than 100 whiteflies were captured, the flight activity rhythms of the two species were remarkably similar. During 13 of 14 weeks if aerial populations of one species were used to predict populations of the other, coefficients of determination were highly significant. This is in part a function of the two species having parallel patterns of pupal eclosion and teneral periods of approximately the same duration. The two species both experience 90% eclosion within 1 h of the onset of photophase and both have a teneral period slightly in excess of 4 h at 27°C. As a result populations of the two whiteflies emerge together, become flight ready, and fly at the same time. Arizona populations of these two introduced species appear to have developed certain very similar behavioral and physiological processes under conditions of a rigorous desert climate.

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Zusammenfassung In Arizona (USA) wurden Experimente durchgeführt, um die Muster der täglichen Flugaktivität von zwei co-existierenden Aleurodidenarten, Bemisia tabaci und Trialeurodes abutilonea zu untersuchen. Mit Hilfe von Klebefallen wurden die Adult-Populationen während zweier Wachstumperioden beobachtet. Die Rhythmen der Flugaktivität während der meisten Tage, an denen mehr als 100 Weisse Fliegen gefangen wurden, waren bemerkenswert ähnlich. Die Bestimmungskoeffizienten waren deutlich signifikant in 13 von 14 Wochen, wenn die Populationen der einen Art benutzt wurde, um die Population der anderen Spezies vorherzusagen. Dies rührt zum Teil daher, dass sich beide Arten in ähnlicher Weise entwicklen. Beide schlüpfen zu 90% innerhalb von 3 Stunden nach Beginn der Photophase und beginnen bei 27°C im Mittel nach 4 Stunden und 12 Minuten zu fliegen. Daraus folgt, dass Populationen beider Arten zur selben Zeit schlüpfen, flugbereit werden und zu fliegen beginnen. Es scheint, dass die in Arizona vorhandenen Populationen dieser beiden eingeführten Arten unter dem Einfluss eines rauhen Wüstenklimas einige sehr ähnliche Verhaltensweisen und physiologische Prozesse entwickelt haben.

     

Influence of flight time and flight environment on distance communication by dancing honey bees

Forager honey bees communicate the distance of food sources to nest mates through waggle dances, but how do bees measure these distances? Recent work suggests that bees measure distance flown in terms of the extent of image motion (integrated optic flow) that is experienced during flight. However, it is known that optic flow also regulates the speed of flight. Therefore, the duration of the flight to a destination is likely to co-vary with the optic flow that is experienced en route. This makes it difficult to tease apart the potential roles of flight duration and optic flow as cues in estimating distance flown. Here we examine whether flight duration alone can serve as an indicator of distance. We trained bees to visit feeders at two sites located in optically different environments, but positioned such that the flight durations to the two sites were similar. The distance estimates for the two sites, as reported in the waggle dance, were compared. We found that dances differed significantly between the two sites, even though flight times were similar. Flight time perse was a poor predictor of waggle dance behaviour. We conclude that foraging bees do not simply signal flight time as their measure of distance in the waggle dance; the environment through which they fly plays a dominant role. Received 11 April 2005; revised 16 May 2005; accepted 3 June 2005.     

Does pirimicarb affect the voracity of the euriphagous predator, Coccinella undecimpunctata L. (Coleoptera: Coccinellidae)?

Pirimicarb is considered a selective and effective insecticide for the control of aphids and whiteflies. Coccinella undecimpunctata L. is a euriphagous predator autochthonous to the Azores, which feeds preferentially on aphids. The voracity of 4th instars and adults (males and females) of C. undecimpunctata using Aphis fabae Scopoli or Aleyrodes proletella L. as preys was evaluated in laboratory, as well as the impact of pirimicarb on the feeding performance using A. fabae as prey. In the absence of chemical treatment and when the prey was A. proletella, satiation lower limits were estimated on a density of 200 individuals in a 24-h period, for 4th instars, adult females and males of C. undecimpunctata. With A. fabae, satiation was attained when 200, 150 and 100 aphids were provided to 4th instars, adult females and males, respectively. C. undecimpunctata exhibited a type II functional response for both prey species. Fourth instars displayed a lower handling time than the adults; handling times of the adults where higher when A. fabae was the prey and attack rates were sex-dependent, that is, attack rate of females was higher on A. fabae while of males was higher on A. proletella. Voracity of C. undecimpunctata was not significantly affected by pirimicarb; therefore, the use of this insecticide can constitute a complementary component for the integrated management of A. fabae.