Times for recovery from cold-torpor in the Queensland fruit fly Dacus tryoni: the relation to temperature during and after chilling

Recovery time after experience of a given minimum temperature below torpor threshold is related to the value of that minimum, the length of time spent at that minimum, and the temperature prevailing during the recovery period above torpor threshold. A model can predict recovery time for flies experiencing a given temperature fluctuation if the length of time spent at the minimum is expressed as a proportion of LE₅₀ at that minimum.The model has applications in defining the optimal protocol for chilling insects for use in the Sterile Insect Release Method. The model was confirmed by experiments showing that it is likely that flies will recover from non-lethal frosts before ant predators become active.

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Résumé Le temps de récupération après avoir subi une température minimal située au-dessous du seuil d'engourdissement dépend de la valeur de ce minimum, du temps passé à ce minimum, et de la température au-dessus du seuil d'engourdissement pendant la période de récupération. Un modèle mathématique permet d'estimer le temps de récupération après avoir subi une chute de température déterminée, en fonction du temps passé au minimum thermique exprimé comme une fraction du LE₅₀ (temps nécessaire pour tuer 50% des mouches) à ce minimum.Ce modèle s'est trouvé étayé par des observations montrant qu'il est probable que les mouches se remettent des gelées sublétales avant la reprise d'activité des fourmis prédatrices. Ce modèle peut être utilisé pour définir les conditions optimales de refroidissement des insectes utilisés lors de la libération d'individus stériles.

     

Thermal constraints to successful development of the Queensland fruit fly in regimes of constant and fluctuating temperature

Temperature can affect the survival rate through each immature stage of life history and hence the rate of survival from egg to adult emergence. This phenomenon was investigated experimentally by using both regimes of constant temperature and ones in which temperatures fluctuated on a daily basis with rates of heating and cooling approximating to those found in the field. In fluctuating regimes, the highest temperatures tolerated for a few hours on a daily basis were higher than those tolerable on a constant basis. The highest tolerable daily maximum was influenced to some extent by the daily minimum. Regimes near the tolerable threshold that were experienced during one stage of the life history adversely affected the survival rate during the next stage, even if the latter experienced optimal conditions. The results in dicate that, in nature, survival from egg to adult is unlikely if daily maxima prevail in the region of 38–40°C for more than 7 days.

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Affectien de température sur le développement couronné de succès chez Dacus tryoni dans des régimes à des températures constantes et fluctuantes

Résumé La température peut affecter le taux de survie, pour chaque stade d'immaturité, dans l'histoire d'une vie et d'où le taux de survie de l'oeuf à son apparition adulte. Ce phénomène a été étudié à titre expérimental en utilisant les deux régimes à une température constante et l'un d'eux à des températures variées sur une base journalière avec un taux approximatif de chauffage et refroidissement comme ceux que l'on trouve dans ce domaine.Dans un régime de fluctuation, les températures les plus élevées pendant quelques heures sur une base journalière étaient plus fortes que celles tolérées sur une base constante.La maximum journalier de la température la plus élevée supportable était influencé, jusqu'à un certain point, par le minimum journalier.Les régimes qui ont fait l'expérience proche du seuil du supportable au cours d'un stade, dan l'histoire d'une vie, on affecté défavorablement le taux de survie du stade suivant, même si ce dernier a expérimenté les conditions optimal.Les résultats indiquent que, dans la nature, la survie d'oeuf à adulte est improbable si le maxima journalier de 38–40°C prédomine dans la région pendant plus de 7 jours.

     

The role of adult learning in the acceptance of host fruit for egglaying by the Queensland fruit fly, Dacus tryoni

Evidence presented indicates that exposure of wild Queensland fruit files, Dacus tryoni (Froggatt), to a given host fruit type (e.g. pear) for 3 days causes females to attempt oviposition to a greater degree in that fruit type than in other fruit types (e.g. tomato, grape). The effects of exposure to a particular fruit type proved reversible, suggesting that D. tryoni females were capable of learning. Females exposed to pear for 3 days appeared to retain the effect of such exposure on acceptance of tomato for up to 4 days but appeared to retain the effect on acceptance of grape for less than 2 days. The possible significance of prior experience of females with a particular fruit type on future ability to discriminate among varying-quality specimens of that type is discussed.

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Résumé Les éléments apportés montrent que l'exposition de D. tryoni Froggat à un type de fruit déterminé (par exemple, la poire) pendant 3 jours, conduit la femelle à tenter de pondre à une plus haute fréquence dans ce type de fruit que dans d'autres (par example; tomate ou raisin). Les effects de l'exposition à un type particulier de fruit étant réversibles, ceci suggère que les femelles de D. tryoni sont capables d'apprentissage. Des femelles exposées à des poires pendant 3 jours ont conservé l'effet d'une telle exposition pendant 4 jours en présence de tomates, mais moins de 2 jours en présence de raisin. La discussion porte sur la signification possible de la connaissance antérieure d'un type particulier de fruit sur l'aptitude ultérieure des femelles à distinguer parmi des spécimens de ce type, mais de qualités différentes.

     

Attractants for the gravid Queensland fruit fly Dacus tryoni

The vapours of certain pure chemicals, typical of ripe fruits, elicited characteristic components of ovipositional behaviour from gravid Dacus tryoni (Froggat) in an olfactometer: the flies walked and flew upwind to the source of the vapour and then probed with their ovipositors. A range of alcohols, acids, ketones and esters having 2–6 carbon atoms were effective (1 and 10% of iso-butyric acid, n-butyric acid, methyl butyrate, ethyl butyrate, 2-butanone, ethyl lactate and ethyl acetate; and 10% concentrations of ethanol and 2-propanone). The most effective were 4–6 carbon acids, esters and ketones. Behavioural threshold for n-butyric acid vapour at 26°C was obtained from a 5×10^–3% dilution in paraffin oil; maximum fly response occurred at about 200 times this concentration. Low concentrations of the 15-carbon sesquiterpene, -farnesene, were also very effective, despite its lower volatility. These results suggest that at least three different types of alfactory sensory neurones are involved in the identification of fruit attractants by gravid D. tryoni.     

Demographic analysis of insect reproductive levels, patterns and heterogeneity: case study of laboratory strains of three Hawaiian tephritids

Reproductive data were collected on individually-held adult oriental fruit flies, Dacus dorsalis, melon flies, Dacus cucurbitae, and Mediterranean fruit flies, Ceratitis capitata including age-by-parity relations, birth interval, frequency distribution of individual egg production levels and the concentration of reproduction among females in a cohort. Specific findings include: i) delay in reproductive peaks in a cohort after eclosion is due almost entirely to the variance in attainment of reproductive maturity among individuals; ii) low reproductive output of reproductively mature melon flies is due mostly to long birth intervals; iii) high egg production in both the medfly and the oriental fruit fly is due to their consistency of egg laying levels and frequency (short birth intervals). Discussion stresses the importance of viewing reproduction, not as a singular and discrete life history trait, but as consisting of subcomponents of daily parity, cumulative parity and birth interval.

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Résumé Les informations sur la reproduction ont été obtenues à partir d'adultes de Dacus dorsalis, D. cucurbitae, C. capitata, élevés individuellement. Elles portent sur les paramètres suivants: distribution par âge en fonction de la fécondité, échelonnement des pontes, distribution des niveaux quotidiens de ponte, fréquence des pondeuses par cohorte.Différents caractères spécifiques ont été mis en évidence: 1) La variabilité de la date d'apparition de la maturité reproductive est pour l'essentiel responsable du retard dans les dates de reproduction maximale; 2) De 30 à 50% des femelles de D. dorsalis âgées de 10 jours pondent plus de 50 oeufs/jour pendant les deux semaines qui suivent, tandis que seulement 10 à 20% des femelles des deux autres espèces parviennent à pondre cette quantité d'oeufs à n'importe quel âge; 3) D. cucurbitae ayant atteint sa maturité pond environ pendant 40% des jours (c.à.d. chaque 2,5 j), tandis que les deux autres espèces pondent au moins quelques oeufs pendant 80% des jours (c.à.d. chaque 1,25 j); 4) La production élevée d'oeufs de C. capitata et de D. dorsalis est due à la régularité de leur niveau de ponte et à la fréquence (faible espacement); 5) Les fractions des effectifs qui ont pondu au moins 600 oeufs en 30 jours étaient approximativement de 0,8, 0,7, et 0,4 pour D. dorsalis, C. capitata, D. cucurbitae; 6) 50% des femelles de chacune des trois espèces contribuent en gros pour 65% à la ponte.

     

Remating inhibition in female Queensland fruit flies: effects and correlates of sperm storage

Reproductive success of male insects commonly hinges both on their ability to secure copulations with many mates and also on their ability to inseminate and inhibit subsequent sexual receptivity of their mates to rival males. We here present the first investigation of sperm storage in Queensland fruit flies (Tephritidae: Bactrocera tryoni; a.k.a. 'Q-flies') and address the question of whether remating inhibition in females is directly influenced by or correlated with number of sperm stored from their first mates. We used irradiation to disrupt spermatogenesis and thereby experimentally reduce the number of sperm stored by some male's mates while leaving other aspects of male sexual performance (mating probability, latency until copulating, copula duration) unaffected. Females that mated with irradiated rather than normal males were less likely to store any sperm at all (50% vs. 89%) and, if some sperm were stored, the number was greatly reduced (median 11 vs. 120). Despite the considerable differences in sperm storage, females mated by normal males and irradiated males were similarly likely to remate at the next opportunity, indicating (1) number of sperm stored does not directly drive female remating inhibition and (2) factors actually responsible for remating inhibition are similarly expressed in normal and irradiated males. While overall levels of remating were similar for mates of normal and irradiated males, factors responsible for female remating inhibition were positively associated with presence and number of sperm stored by mates of normal but not irradiated males. We suggest seminal fluids as the most likely factor responsible for remating inhibition in female Q-flies, as these are likely to be transported in proportion to number of sperm in normal males, be uninfluenced by irradiation, and be transported without systematic relation to sperm number in irradiated males.     

Effect of the presence of olive fruit on ovarian maturation in the olive fruit fly, Dacus oleae, under laboratory conditions

Ovarian maturation was prevented in 7-, 22-, 23- and 28-day-old females of Dacus oleae (Gmelin) (Diptera: Tephritidae), developed in the pre-imaginal stages at LD 12:12, 19±1°C and kept as adults at LD 16:8, 26±1°C without access to olive fruits. In females of the above ages having continuous access to olive fruits and held under the same photoperiod and temperature conditions, 54, 87 and 100%, respectively, had mature oocytes. When the females had access to domes of paraffin wax, the percentages of females with mature oocytes were intermediate between those with and those without access to olive fruits. Under the above photoperiod and temperature conditions unfavorable for maturation, 50% of 4-week-old females had mature oocytes if exposed for one week to olive fruits during their first week and 91% if exposed during their 4th week of adult life. The respective percentages with wax domes in the cages were again intermediate between those with olives and those without olives or wax domes. The presence of olive fruits had also a strong positive effect on the ovarian maturation of females which developed from egg through the adult stage at LD 16:8, 26±1°C, a condition favoring ovarian maturation. Access to wax domes had again an intermediate effect on maturation. It is concluded therefore that the lack of ovarian maturation of D. oleae females which is observed under a short photophase during the pre-imaginal stages if followed by a long photophase and an increase of temperature during the adult stage, continues at least till the end of the 4th week of adult life in the absence of olive fruits but is averted when such fruits are offered to the adult flies.

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Résumé La maturation ovarienne des femelles adultes agées de 7, 22–23 et 28 jours de D. oleae ayant accompli leur développement embryonnaire, larvaire et nymphal en LD 12:12, 19±1°C et maintenues en LD 16:8, 26±1°C, sans accès à des olives, est inhibée. Dans les mêmes conditions, mais avec accès permanent à des olives, 54% des femelles ont des ovocytes mûrs à 7 jours, 87% à 22–23 jours et 100% à 28 jours. Avec des femelles ayant accès à des domes de paraffine, les pourcentages d'individus ayant des ovocytes mûrs sont intermédiaires entre ceux des deux situations précédentes. Dans les conditions cidessus défavorables à la maturation ovarienne, 50% des femelles de 28 jours ont des ovocytes mûrs si elles sont en présence d'olives durant leur première semaine de vie imaginale et 91% si elles sont en présence la 4éme semaine. Les pourcentages respectifs concernant les femelles pourvues de dômes de paraffine sont encore intermédiaires entre ceux des femelles avec olives et ceux de femelles privées de tout substrat. La présence d'olives a aussi un effet fortement positif sur la maturation ovarienne de femelles ayant accompli leur développement pre-imaginal et maintenues aussi à l'etat adulte en conditions LD 16:8, 26±1°C, favorisant la maturation ovarienne. L'accès à des dômes de paraffine a, là encore, un effet intermédiaire. On conclut par conséquent que la non maturation ovarienne des femelles de D. oleae qui est causée par une photopériode à jour court pendant la vie pre-imaginale accompagné par une photopériode à jour long et une augmentation de la température pendant la vie imaginale persiste au moins jusqu'à la fin de la quatrième semaine de la vie imaginale en absence d'olives, mais ne se produit pas si on met les femelles adultes en présence d'olives.

     

Comparative demography of a laboratory and a wild strain of the oriental fruit fly, Dacus dorsalis

Host-specific development and survival rates were measured and population parameters computed for both a wild and a laboratory strain of the oriental fruit fly (Dacus dorsalis Hendel) in Hawaii. Gross fecundities of the wild and laboratory strains were 241 and 1551 eggs per female, respectively. Egg to eclosion developmental rates were 27 days for the wild strain and 24 days for the laboratory strain. The preovipositional period of the wild strain was 19 days compared to 9 days in the laboratory strain.Differences of this magnitude in fecundity and developmental rates between laboratory and wild strains have not been observed in other recent demographic studies of tephritids. The results suggest that the laboratory strain of the oriental fruit fly may have undergone more intense selection than laboratory strains of the other species.

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Résumé Pour deux souches, l'une sauvage, l'autre de laboratoire, de D. dorsalis de Hawaï, les mesures ont porté sur la durée de développement et le taux de survie, les paramètres caractéristiques de la population ont été traités sur ordinateur. Pour les souches sauvage et de laboratoire, les fécondités brutes ont été respectivement de 241 et 1551 oeufs par femelle. Les durées de développement larvaire et nymphal ont été de même de 27 jours pour la souche sauvage et de 24 j pour celle de laboratoire; les périodes de latence avant la ponte ont été de 19 j pour la souche sauvage contre 9 j pour celle de laboratoire.Jamais de telles différences de fécondités et de durées de développement entre souches sauvages et de laboratoire n'avaient été observées lors des études récentes sur des téphritidae. Ces résultats suggèrent que la sélection subie par la souche de laboratoire de D. dorsalis été plus intense que celles subies par d'autres espèces.

     

Survival of step and ramp changes of temperature by the Queensland fruit fly, Dacus tryoni

ABSTRACT. Survival time at subzero temperatures is related to both long-term thermal history and the rate at which the insects are cooled. Insects cooled at one degree per hour survive for up to 3 times as long at a given test temperature than do insects cooled at 1C/min. Survival times are significantly shorter than times taken to freeze. Survival time at an extreme high temperature is related to long-term thermal history but the rate of heating makes no difference.     

Thermal responses in the citrus fruit fly,Dacus tsuneonis: evidence for a pupal diapause

Thermal responses controlling pupariation and adult eclosion in a citrus fruit fly,Dacus tsuneonis (Miyake), were studied to understand the winter biology of this species. When mature larvae were exposed to various temperature conditions, the highest percentage of pupariation was obtained at 15 °C, although the variance at this temperature was greater than at 20 °C or 25 °C. Pupariation occurred most rapidly at 20 °C and an alternating temperature with a mean of 15 °C. At constant 15 °C, pupae failed to emerge as adults. Pupae were characterized by a reduced respiration rate, which is typical of a diapausing pupa. When insects were stored at different temperatures for 45 days after pupariation, and then transferred to 25 °C, adult eclosion occurred earlier when the initial temperature was 10 °C than when it was 5 °C or 15 °C. Adult eclosion occurred most synchronously and pupal mortality was lowest when insects were stored at 15 °C for 90 days before incubation at 25 °C. These results strongly suggest thatD. tsuneonis enters a pupal diapause.     

Electroantennogram responses of the oriental fruit fly, Dacus dorsalis, to a spectrum of alcohol and aldehyde plant volatiles

Electroantennograms (EAGs) were recorded from unmated, laboratory-reared, male and female oriental fruit flies, Dacus dorsalis, in response to a range of between C₁ and C₁₂ carbon chain-length saturated and unaturated aliphatic alcohols and aldehydes, most all of which are known host-plant volatiles. Only two of the 35 compounds tested elicited significantly larger EAGs from female than male antennae. For the two functional-group series tested, aldehydes elicited responses greater than or equal to the responses to the alcohols. In general, the unsaturated alcohols did not elicit responses significantly different from the saturated alcohols. However, the unsaturated aldehydes, (E)-2-hexenal and 10-undecenal, elicited larger amplitude EAGs than their saturated analogs. EAGs were significantly greater for a particular carbon chain-length, with responsiveness to primary alcohols peaking at C₆ and aldehydes peaking at C₇. The (E)-2- monoenic alcohols peaked at C₆, while the (E)-3-alcohols plateaued between C₅ and C₈. The greatest EAG responses of all compounds tested were elicited by the saturated and unsaturated C₆ alcohols and aldehydes which are constitutents of the general green-leaf volatile complex that emanates from most plants. The potential adapative benefit of selective sensitivity to green-leaf volatiles is discussed in regards to foraging behaviors of oriental fruit flies.

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Résumé Des électroantennogrammes (EAG) ont enregistré les réponses, en élevages de femelles et mâles vierges de Dacus dorsalis, à une gamme de chaînes de carbones de C₁ à C₁₂ saturés et non-saturés d'alcools aliphatiques et d'aldéhydes, dont beaucoup sont connus comme substances volatiles des végétaux. Seulement 2 des 35 composés examinés ont provoqué des EAG significativement plus importants chez les femelles que chez les mâles. Pour les séries des deux groupes fonctionnels examinés, les aldéhydes ont provoqué des réponses supérieures ou égales aux alcools. En général, les réponses aux alcools nonsaturés n'étaient pas significativement différentes des réponses aux alcools saturés. Cependant, les aldéhydes non-saturés, (E)-2-hexénal et 10-undécénal, ont induit des EAG de plus grande ampleur que leurs analogues saturés. Les EAG étaient significativement les plus importants pour une chaîne de longueur particulière, la réponse aux alcools primaires culminant en C₆ et les aldéhydes en C₇. Les alcools monoéniques (E)-2- culminaient en C₆, tandis que les alcools (E)-3- étaient étales entre C₅ et C₈. Les EAG les plus importants ont été obtenus pour tous les composés examinés avec les alcools et aldéhydes en C₆ qui appartiennent à l'odeur verte complexe émise par beaucoup de plantes. Le bénéfice adaptatif potentiel de la sensibilité sélective à l'odeur verte des feuilles est examinée en fonction du comportement de prospection de D. dorsalis.

     

Microsatellite Analysis of Olive Fly Populations in the Mediterranean Indicates a Westward Expansion of the Species

Bactrocera oleae is the major insect pest of the olive fruit. Twelve microsatellite loci isolated from the genome of this insect were used in a Mediterranean-wide population analysis. These loci were highly polymorphic with a mean number of alleles per locus of 10.42 and a mean effective number of alleles of 2.76. The analysis was performed on a sample of 671 flies collected from nineteen locations around the European part of the Mediterranean basin. Despite the high level of gene flow across the Mediterranean, results support the notion of a differentiation of three subpopulations: one of the Iberian Peninsula, one of Greece and Italy and one of Cyprus. In addition, the gradual decrease of heterozygosity from the Eastern to the Western part of the Mediterranean indicates a westward expansion of the species.     

Cold hardiness and winter survival of the grape berry moth, Endopiza viteana, in New York State

Laboratory and field investigations were undertaken to evaluate the effect of winter mortality on subsequent infestation levels of the grape berry moth (GBM), Endopiza viteana (Clemens) (Lepidoptera: Tortricidae). Supercooling points (SCP) were used as a measure of the minimum survivable temperature for GBM pupae. The SCP of winter forms (diapausing) from a laboratory colony averaged –25.2 °C in December, –24.3 °C in March, and –24.0 °C in April. When diapausing pupae from a laboratory colony were placed in the field from December to March, the SCP averaged –23.3 °C. The SCP of summer forms from a laboratory colony averaged –21.6 °C in March. Significant levels of mortality (ca. 80%) of diapausing GBM pupae were observed after 24 h at –21 °C. Comparable mortality occurred after 1-week at –15 °C. Eighty-four percent of diapausing pupae survived for 8-months at 3 °C; non diapausing pupae suffered high levels of mortality (ca. 60%) after only 7-days at 3 °C. Field survival of diapausing pupae were significantly greater at soil level than 1-meter above the soil. Pupal survival was greater at 75% r.h. than at 0% or ambient r.h.. In 1986–1987 and 1987–1988, pupae covered with snow or leaf-litter had higher of survival than exposed pupae although these differences were only statistically significant in 1986–1987. The above findings are discussed within the context of potential implications to management strategies for GBM.

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Zusammenfassung Labor und Freilandversuche wurden unternommen um den potenziellen Einfluss von Wintersterben auf subsequenten Wurmbefall des nordamerikanischen Traubenwicklers Endopiza viteana (Clemens) (Lepidoptera: Tortricidae) auszuwerten. Die niedrigste Temperatur wobei Puppen ueberleben konnten ist durch Ueberkuehlungstemperaturen der Puppen gemessen worden. Fuer das ueberwinternde Stadium (in Diapause) einer Laborkolonie lag diese Temperatur durchschnittlich bei minus 25.2 °C in Dezember, minus 24.3 °C in Maerz, und minus 24.0 °C in April. Der Ueberkuehlungspunkt lag um minus 23.3 °C im Durchschnitt fuer Laborkolonie Puppen die waehrend der Diapause von Dezember bis Maerz im Freiland ausgesetzt wurden. Der Ueberkuehlungspunkt von Sommerstadien von der gleichen Kolonie lag im Vergleich um minus 21.6 °C im Maerz. Signifikante Sterblichkeit (um 80%) der Traubenwicklerpuppen wurde bemerkt nach 24 Stunden bei minus 21 °C. Vergleichbar war die Sterblichkeit nach einer Woche bei minus 15 °C. Nach 8 Monaten bei 3 °C ueberlebten 84% der Puppen in Diapause; 60% der Puppen nicht in Diapause starben nach 7 Tage bei 3 °C. Das Ueberlebensprozent diapausierender Puppen im Freien war signifikant hoeher auf der Erdoberflaeche als fuer die 1 m ueber der Oberflaeche. Mehr Puppen ueberlebten bei 75% relativer Luftfeuchtigkeit als bei 0% oder umgebender Luftfeuchtigkeit. In 1986–1987 und 1987–1988 Puppen die mit Schnee oder Laub bedeckt waren, ueberlebten prozentual mehr als die ohne jedes Bedeckungsmaterial. Die Ergebnisse werden im Kontext ihrer potenzieller Verwendung fuer Kontrolle des Traubenwicklers diskutiert.

     

Effects of the angle of inclination of traps on the numbers of large Diptera caught on sticky boards in certain vegetable crops

The angle of inclination of the surface on which flies prefer to land in vegetable crops was studied in field plots and in field-cages using one-sided sticky traps aligned in one plane but orientated in eight directions. The four Delia species studied, D. antiqua, D. floralis, D. platura and D. radicum, preferred to land on horizontal surfaces, indicating that they are likely to be trapped in largest numbers on traps with a horizontal trapping surface, such as water traps. This trend was even more pronounced with the Syrphidae. In contrast, greatest numbers of the carrot fly, Psila rosae, were caught on the lower surface of traps inclined at 45° to the vertical. The advantages of using traps inclined in this way for trapping P. rosae are that more flies are caught on such surfaces, the sticky trapping compound is protected from the adverse effects of rain, and the traps are highly selective.

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Résu,é L'angle d'inclinaison de la surface sur laquelle les mouches préfèrent atterrir dans les cultures de légumes a été examiné dans la nature, dans des parcelles et dans des cages, en utilisant des pièges englués sur un côté, alignés dans le même plan, mais orientés dans 8 directions. Les 4 espèces de Delia étudiées: D. antiqua, D. floralis, D. platura, D. radicum, ont préféré atterrir sur des surfaces horizontales, ce qui implique qu'elles sont probablement prises en plus grand nombre sur des pièges avec une surface de capture horizontale, comme des pièges liquides. Cette tendance est encore plus prononcée chez les Syrphidae. A l'opposé, de nombreuses mouches de la carotte, Psila rosae, ont été capturées sur la face inférieure de pièges inclinés de 45°. Il est avantageux d'utiliser des pièges inclinés de cette façon contre P. rosae parce que, d'une part ils sont très efficaces, d'autre part le produit actif est protégé de la pluie et enfin, le piège est très sélectif.

     

Natural establishment of a parasitoid complex on Bactrocera latifrons (Diptera: Tephritidae) in Hawaii

Bactrocera latifrons (Hendel) (Diptera: Tephritidae) is the most recent of four tephritid fruit fly species accidentally introduced into Hawaii. Although parasitoids have been released against other tephritid fruit fly species and have shown partial success in Hawaii, no parasitoids were released until 2004 to suppress populations of B. latifrons. The present study was conducted to document the parasitoid complex that has naturally established against B. latifrons in Hawaii and to assess whether there is a need for improving the biological control of this species. Based on ripe turkeyberry (Solanum torvum Sw) fruit collections over three consecutive years B. latifrons was the dominant tephritid fruit fly infestating turkeyberry at all four sites surveyed, across three major islands in Hawaii. The overall percentage parasitism of B. latifrons ranged from a low of 0.8% (Hana, Maui) to a high of 8.8% (Kahaluu, Oahu). Five primary parasitoid species were recovered from individually held B. latifrons puparia: Fopius arisanus (Sonan), Psyttalia incisi (Silvestri), Diachasmimorpha longicaudata (Ashmead), D. tryoni (Cameron), and Tetrastichus giffardianus Silvestri. F. arisanus was the predominant parasitoid at three of the four sites. Low levels of parasitism suggest that there is a need to improve biological control of B. latifrons, to minimize chances of this species causing economic impacts on crop production in Hawaii. We discuss the possibility of improving biological control of B. latifrons through augmentative releases of F. arisanus or introduction and release of specific and efficient new parasitoid species.     

Facilitation in Ovipositional Behavior of Bactrocera tryoni Flies

Mature female Queensland fruit flies, Bactrocera tryoni Froggatt, released into canopies of field-caged trees containing host fruit, did not discriminate between fruit having or lacking two resident conspecific females when selecting fruit on which to alight. When released individually onto a fruit, mature females showed no greater or lesser propensity to initiate boring with the ovipositor into fruit having or lacking a resident female engaged in pre-ovipositional or post-ovipositional behavior. However, boring propensity of introduced females was significantly enhanced or facilitated when released onto fruit on which a conspecific female was in the act of ovipositing. Introduced females were significantly more prone to initiate boring into high-ranking fruit (nectarines) than low-ranking fruit (lemons) and to do so when having a high rather than a low egg load. Neither fruit type nor egg load of introduced females had a significant effect on the occurrence of encounters between introduced and resident females, on the occurrence of contests, or on the propensity of introduced females to initiate boring in the presence of a resident female. Among introduced females, there was a consistent trend to initiate boring earlier in the presence than in the absence of a resident female. We discuss circumstances, likely to be narrow, under which boring propensity of an intruding female might be facilitated in the presence of a resident female.