Ceratitis capitata: Effect of host fruit size on the number of eggs per clutch

A laboratory strain of Ceratitis capitata (Wiedemann) was presented with grapes, plums, apples and peaches for oviposition. Fruit diameter was highly correlated with the number of eggs/oviposition. Clutch size was 3.9±0.3 for grapes (20 mm) compared with 14.0±0.7 for apples (70 mm). When Parafilm^®-enveloped whole peeled fruits and smaller spheres of fruit flesh were offered, fruit size proved more important than fruit type in determining egg clutch sizes. Ovipositions that required the puncture of fruit skin gave larger clutches than ovipositions through Parafilm or into punctured fruit.

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Zusammenfassung Einem Laboratoriumsstamm von Ceratitis capitata (Wiedemann) wurden Trauben, Pflaumen, Aepfel und Pfirsiche zur Eiablage vorgelegt. Der Fruchtdurchmesser war stark korreliert mit der Eizahl pro Eiablage. Die Grösse der Eihaufen war 3,9±0,3 bei Trauben (20 mm) und 14,0±0,7 bei Aepfeln (70 mm). Wenn geschälte und mit Parafilm^® eingehüllte ganze Früchte und Fruchtscheiben vorgelegt wurden, war die Fruchtgrösse wichtiger als der Fruchttyp für die Grösse der Eiablage. Eiablagen, bei denen die Fruchthaut durchbohrt werden musste, waren grösser als Eiablagen durch Parafilm oder in perforierte Früchte.

     

(Z)-3-nonenol, (Z,Z)-3,6-nonadienol and (S,S)-(-)-epianastrephin: male produced pheromones of the Mexican fruit fly

(Z)-3-nonenol, (Z,Z)-3,6-nonadienol and (S,S)-(-)-epianastrephin proved active as male-produced pheromones which elicited behavioral responses from virgin female Mexican fruit flies (Anastrepha ludens) (Diptera: Tephritidae) in laboratory bioassays. All three chemicals elicited attraction and/or locomotor arrest when tested individually. When tested together, (Z)-3-nonenol inhibited the behavioral effect of (Z,Z)-3,6-nonadienol but either of the alcohols synergized the effect of (S,S)-(-)-epianastrephin. Quantities of the pheromones per male abdomen were: (Z)-3-nonenol-100 ng; (Z,Z)-3,6-nonadienol-40 ng; and total epianastrephin (R,R and S,S enantiomers)-700 ng. Relative to the quantities in abdominal extract, males released these chemicals during sexual display in a blend containing a higher proportion of the alcohols.

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Résumé Le (Z)-3-nonènol, le (Z,Z)-3,6-nonadiènol et le (S,S)-(-)-épianastréphine produits par les mâles de la mouche mexicaine du fruit (Anastrepha ludens) (Diptera: Tephritidae) ont attirés les femelles lors de tests conduits en laboratoire. Le pouvoir attractif du (Z)-3-nonènol est faible comparé à celui des deux autres phéromones. Evalués ensemble, le (Z)-3-nonènol inhibe l'attractivité du (Z,Z)-3,6-nonadiènol mais chacun des deux alcools synergise l'effet attractif de la (S,S)-(-)-épianastréphine. Les quantités recouvrées par mâle dans un extrait abdominal étaient respectivement de 100, 40 et 700 ng pour le (Z)-3-nonènol, le (Z,Z)-3,6-nonadiènol, et l'épianastréphine totale (R,R et S,S) énantiomères. Comparées à ces valeurs, le mélange élange émis par les mâles lors de leur cour sexuelle est plus riche in alcools. Le rapport (Z)-3-nonènol (Z,Z)-3,6-nonadiènol est cependant identique dans l'extrait abdominal et dans le mélange émis par les mâles.

     

Effect of larval host food substrate on egg load dynamics, egg size and adult female size in four species of braconid fruit fly (Diptera: Tephritidae) parasitoids

Life history theory predicts that individuals will allocate resources to different traits so as to maximize overall fitness. Because conditions experienced during early development can have strong downstream effects on adult phenotype and fitness, we investigated how four species of synovigenic, larval-pupal parasitoids that vary sharply in their degree of specialization (niche breadth) and life history (Diachasmimorpha longicaudata, Doryctobracon crawfordi, Opius hirtus and Utetes anastrephae), allocate resources acquired during the larval stage towards adult reproduction. Parasitoid larvae developed in a single host species reared on four different substrates that differed in quality. We measured parasitoid egg load at the moment of emergence and at 24 h, egg numbers over time, egg size, and also adult size. We predicted that across species the most specialized would have a lower capacity to respond to changes in host substrate quality than wasps with a broad host range, and that within species, females that emerged from hosts that developed in better quality substrates would have the most resources to invest in reproduction. Consistent with our predictions, the more specialized parasitoids were less plastic in some responses to host diet than the more generalist. However, patterns of egg load and size were variable across species. In general, there was a remarkable degree of reproductive effort-allocation constancy within parasitoid species. This may reflect more “time-limited” rather than “egg-limited” foraging strategies where the most expensive component of reproductive success is to locate and handle patchily-distributed and fruit-sequestered hosts. If so, egg costs, independent of degree of specialization, are relatively trivial and sufficient resources are available in fly larvae stemming from all of the substrates tested.     

Effects of adult chill treatments on mate attracting potential for irradiated Mexican fruit fly males

Mexican fruit flies, Anastrepha ludens (Loew), that are reared, sterilized and released for maintenance of a fly free zone in south Texas and for population eradication in California are routinely chilled for 1 to 2 h to facilitate handling and dispersal. While a number of behavioral, physical and physiological characteristics are routinely monitored as part of a quality control program, the effect of the chilling process on the ability of these males to attract wild females has not been evaluated. Tests were performed to compare the mate attracting effectiveness of mass reared, sterilized, chilled males with sterile males that had not been chilled and with recently colonized males. Tests were performed with two recently colonized strains of females in a large cage and males of the three types in plastic cups set on top of the cage. Controls consisted of empty cups. Results showed no significant differences among the three types of males. In tests with the most recently collected (least laboratory adapted) wild strain of females, the chilled males attracted the most females. Fly age and time of day were both significantly related to total attractiveness of males. Number of females responding to males per day increased over the five-day test period. The time period when female response was greatest was variable among the tests.     

Clutch size in frugivorous insects as a function of host firmness: the case of the tephritid fly Anastrepha ludens

Abstract. 1. Optimal clutch size theory predicts that individuals will oviposit the number of eggs that increases their fitness. In Anastrepha ludens Loew (Diptera: Tephritidae), females oviposit larger clutches in unripe (firm) fruits than in ripe (soft) fruits. The following hypotheses were tested: (1) Using fruit firmness as an indicator of fruit quality, A. ludens females vary the number of eggs per clutch every time they reach an oviposition decision. (2) Maximising offspring survival with respect to either unripe or ripe fruit requires placing large clutches in firm fruit and smaller clutches in soft fruit. 2. Agar spheres were used as artificial hosts. Three agar concentrations resulted in three degrees of firmness. Mango fruits Mangifera indica L. served as natural hosts. Ripe and unripe fruits were used to test soft and firm host conditions respectively. Females laid significantly larger clutches in the firmer artificial hosts than in the softer hosts. They also laid significantly more eggs in artificial hosts without sugar than in hosts with sugar. Firm (unripe) mangoes also received significantly larger clutches than soft (ripe) mangoes. 3. When an individual female was first presented with a firm artificial host, it laid a large clutch. If subsequently offered a soft host, the female laid a significantly smaller clutch. Finally, if again offered a firm host, clutch size was increased significantly. 4. Possible trade‐offs in offspring fitness were explored in ripe and unripe mangoes by measuring offspring egg‐to‐adult survival, pupal weight, mean adult longevity, and fecundity. Despite the fact that larval survival was greater in soft fruit than in firm fruit, parameters such as pupal weight, mean longevity, and fecundity of adults stemming from both fruit types did not differ significantly. 5. A probable trade‐off between high offspring mortality caused by host unsuitability and low offspring and adult mortality caused by parasitism and predation is discussed as the reason for the exploitation of sub‐optimal hosts.     

Influence of Conspecific Presence, Experience, and Host Quality on Oviposition Behavior and Clutch Size Determination in Anastrepha ludens (Diptera: Tephritidae)

Females of some insect species adjust the number of ovipositions and clutch size adaptively depending on conspecific density and probably experience. In a series of three experiments, we examined the effect of the presence of conspecifics, host quality, and oviposition experience on oviposition behavior and clutch size determination by females of the polyphagous fruit fly Anastrepha ludens (Diptera: Tephritidae). In the first experiment, we determined that grouped (eight females per cage) A. ludens females tended to visit and oviposit in more hosts than did solitary females probably as a result of stimulation by the presence of conspecifics. We also determined that females with previous oviposition experience visited and oviposited in more hosts than inexperienced ones. Importantly, when females were grouped, we observed significantly more landings on unoccupied hosts (i.e., devoid of flies) than on occupied ones (i.e., with at least one fly on it). However, oviposition experience, and not female density, was the most important factor affecting clutch size. Naive females deposited larger egg clutches than experienced ones. In the second experiment, we found that oviposition experience and host quality (i.e., clean fruit or fruit covered with a host marking pheromone [HMP] extract), influenced clutch size and the decision of females to defend or not defend the host. Clutch size and number of fights were greater on clean than on HMP-marked hosts. In the third experiment, we observed that host quality (i.e., size) played a significant role with regard to the number of female fights, host marking behavior, and clutch size. Specifically, females fought and dragged their aculeus longer on small- and medium-sized hosts than on large ones. But this behavior varied according to whether females were kept alone or grouped. Clutch size was greatest in the largest hosts. Considering all the above, we believe that the observed increase in ovipositional activity by grouped A. ludens females can be attributed to competition through mutual interference and not social facilitation as has been reported in other tephritid species.     

Mating behavior and male mating success in wildAnastrepha Ludens (Diptera: Tephritidae) on a field-caged host tree

Mating behavior and factors affecting mating success of males were studied using wild Anastrepha ludens on a fieldcaged host tree. The most common courtship sequence had five components: (1) male calls from the underside of a leaf, (2) female arrives to the maleoccupied leaf, (3) male orients to female and stops calling, (4) one or both approach to a face-to-face position 1–3 cm apart, and (5) male mounts female after 1–2 s. Courtship behavior was almost identical to that of laboratoryculture flies observed previously under laboratory conditions. Most malefemale encounters occurred at a height of 1–2m, well inside the outer canopy of the tree. Differential mating success by males occurred. No male mated more than once per day, owing possibly to a very short sexual activity period. Factors favoring mating success of males were survival ability and tendency to join male aggregations and to fight other males. Thorax length and age (9–11 days difference) had no effects on male copulatory success. Overall win/loss percentage was not related to mating success because the males that were most successful at mating fought mostly among themselves, driving their win/loss percentage down. However, these successful males (at mating) won most of their fights against less successful males. Results confirmed a lek mating system: males aggregated, called, and defended territories; territories did not contain femalerequired resources; and females exercised mate choice, apparently through selection of sites within leks.     

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.

     

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.     

Size specific demography of three species of Anastrepha fruit flies

Individuals of three Anastrepha species: A. obliqua, A. ludens, and A. serpentina (Diptera: Tephritidae), were sorted according to pupal weight in cohorts of large and small flies. Demographic parameters and reproductive patterns and heterogeneity were determined for each cohort. Large flies of the three species presented greater expectation of life and gross fecundity rates. A. ludens was the species with the longest life span (expectation of life of large adults was 110 days) and the greatest gross fecundity rates (1597 eggs/female for the large flies). While, A. obliqua had the shortest mean age of reproduction (33 days), and the greatest daily egg production (14 eggs/female/day). Net fecundity was similar in these two. A. serpentina had lower fecundity rates.Reproductive information for each size and each species include: age-by-parity relations, fraction of sexually mature life in which females lay eggs, and frequency distribution of individual egg production. Results demonstrate that even under constant laboratory conditions and using standard artificial hosts, there is a great deal of life history variation among these Anastrepha species and among other tephritid fruit flies.     

Effect of larval host on life history traits of the mediterranean fruit fly,Ceratitis capitata

Summary Demographic parameters for the Mediterranean fruit fly reared on each of twenty four different hosts from sixteen different plant families are reported. These include cohort parameters of development, survival, pupal sizc, and fecundity as well as population parameters such as intrinsic rate of population increase (r) and mean generation time. Major findings include the following: i) no consistent quantitative relationships existed between r and its chief demographic determinants such as preadult developmental time and adult fecundity; and ii) few correlations existed among the cohort life history parameters themselves. The principle conclusion is that the medfly is a successful generalist frugivore because of its developmental ability to offset the effect of the value for a host-specific trait that tends to lower r with one that tends to increase r, the net result of which is to maintain a relatively high r.     

Lekking and the small-scale distribution of the sexes in the Caribbean fruit fly,Anastrepha suspensa (Loew)

Male and female Anastrepha suspensa(Loew) had a clumped distribution in the foliage of their guava host plants. Males were no closer to other males than they were to females or than females were to other females. Flies were often found in roughly the same locations over time. However, contemporaries (flies present at the same time) were closer to each other than subsequent flies were to their predecessors. Males were more likely to be found near spots previously occupied by males than they were to spots used previously by females. Some trees had more flies than others, but there was no regional (northwest, etc.) preference within trees. Females were no more likely to be found in the vicinity of clumped (lekking) males than they were by isolated males. About a third of the females taken from inside leks had sperm in their spermathecae, and it is not clear if their motive for being in these areas was sexual. In pairs of males (within 15 cm of each other), the larger fly tends to be in a position farther up the branch, suggesting that larger males may control preferred territories. It seems possible that males attempting to intercept females accumulate in favorable microhabitats where females are likely to be concentrated and that leks have evolved from such clumping.     

Electroantennagrams of Mexican fruit flies to chemicals produced by males

Male-produced chemicals were tested on antennae of the Mexican fruit fly (Anastrepha ludens) (Diptera: Tephritidae) using the electroantennagram technique. Male and female antennae responded equivalently to six chemicals and combinations of the six chemicals. (S,S)-(-)-epianastrephin elicited responses two-three times greater than any of the other chemicals, (S,S)-(-)-anastrephin gave greater responses than (R,R)-(+)-anastrephin, and Z,Z-3,6-nonadienol gave greater responses than Z-3-nonenol. The combination of Z,Z-3,6-nonadienol and Z-3-nonenol elicited a response which was slightly less than the response to Z,Z-3,6-nonadienol alone. The EAG data were highly correlated with behavioral data from earlier experiments.

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Résumé L'étude des substances émises par les mâles d'A. ludens (Diptera, Tephritidae) comprenant 2 paires énantiomériques de lactones épimériques et 2 alcools, a été réalisée à partir d'électroantennogrammes.Les antennes des mâles et des femelles ont répondu de la même façon aux 6 substances examinées séparément, ou combinées 2 à 2, ou toutes ensembles. La (S,S)-(-) épianastréphine, seule ou en combinaison, a induit une réponse significativement de 2 à 3 fois plus importante que n'importe qu'elle autre substance. La (S,S)-(-) anastréphine a induit des EAG deux fois plus importantes que ceux obtenus avec la (R,R)-(+) anastréphine.L'importance des réponses aux 4 lactones est liée à leurs relations structurales.Le (Z,Z)-3,6 nonadiénol a provoqué des réponses 2 fois plus importantes que celles du (Z)-3 nonénol, et la combinaison des 2 alcools a induit une réponse légèrement inférieure à celle obtenue avec le (Z,Z)-3,6-nonadiénol seul.Les résultats en EAG sont très conformes aux observations comportementales d'expériences précédentes.

     

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.

     

Oviposition response and development of the egg-pupal parasitoid Fopius arisanus on Bactrocera oleae, a tephritid fruit fly pest of olive in the Mediterranean basin

To date, information is wanting with regard to the use of new exotic parasitoids against olive fruit fly, Bactrocera (=Dacus) oleae (Gmelin) (Diptera: Tephritidae), a serious pest of olives Olea europaea L., in the Mediterranean basin. We investigated the oviposition response and developmental biology on B. oleae of Fopius (=Biosteres) arisanus (Sonan) (=Opius oophilus Fullaway) (Hymenoptera: Braconidae), an egg-pupal parasitoid of tephritid fruit flies, never tested before as a potential parasitoid of this host. Our results showed that olive fruits infested with B. oleae eggs exerted a relevant attraction to gravid F. arisanus and represented a stimulus for oviposition. Nevertheless they were not as attractive to female parasitoids as the Mediterranean fruit fly, Ceratitis capitata Wiedemann (Diptera: Tephritidae), eggs infested papaya fruits (Carica papaya L.). In our experimental conditions, F. arisanus completed development in B. oleae within 33 ± 1.7 days (males) and 35 ± 1.6 (females). Increases in host egg to female parasitoid ratios of 1:1, 5:1, 10:1 and 20:1 corresponded with decreases in the percentage of B. oleae parasitisation and host killing but corresponded also with increases in absolute parasitisation. Our findings are discussed in light of possibilities of utilising F. arisanus for biological control of olive fruit fly.     

Specificity of olfactory responses in the tephritid fruit fly, Rhagoletis pomonella

Electroantennograms (EAG) were recorded from, and behavior observed of female apple maggot flies, Rhagoletis pomonella (Walsh) (Diptera: Tephritidae), in response to over 60 individual esters. For acetates through decanoates, 2 methylbutyrates, and isobutyrates, we tested homologous series of systematically altered chain lengths. Most of the compounds had been isolated from behaviorally active fractions derived from extracts of volatiles produced by host fruits of R. pomonella. For the acetates through hexanoates, maximum EAG amplitudes were elicited by esters with chain lengths of 9 carbons and for the heptanoates through nonanoates, by 10 carbon esters. Recovery time, or the rate at which the EAG trace returned to the baseline following maximum depolarization, was slowest for straight chain esters that were 9–11 carbons long. Branching of the chain by addition of a methyl group to either side of the ester resulted in a decline in amplitude and a faster recovery time. Compared to EAG results, only 5 esters (butyl and pentyl hexanoate; propyl and butyl heptanoate; propyl octanoate) were highly active in wind tunnel bioassays, demonstrating (1) the hazard of assigning significance to EAG-active compounds without accompanying behavioral data, but more importantly; (2) a high degree of olfactory specificity. Maximum behavioral response was contingent upon the following rules regarding size and structure of the molecule. The ester must (1) be a straight chain; (2) be 10–11 carbons in length; (3) have an acid portion of 6–8 carbons and an alcohol portion of 3–5 carbons. One of the active esters, butyl hexanoate, appears in significant concentrations in the headspace of host fruit and, because this ester elicits such a pronounced behavioral response, our results suggest that R. pomonella is adapted to perception of a compound that is typical of its hosts.

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Résumé Les réactions de R. pomonella à plus de 60 esters différents ont été enregistreées par électroantennogrammes (EAG) et par ovservation du comportement. Pour les acétates, avec les décanoates, les 2-méthylbutyrates et les iso butyrates, nous avons examiné des séries homologues de chaînes aux longueurs systématiquement altérées. La plupart de ces composés ont été isolés à partir des fractions actives sur le comportement, issues des extraits des substances volatiles des fruits des plantes hôtes de cette téphritidae. Pour les acétates, avec les hexanoates, les EAG aux plus grandes amplitudes ont été obtenus avec des esters dont la longueur des chaînes est de 9 carbones, et avec les heptanoates et les nonanoates pour les esters à 10 carbones. Le temps de récupération ou temps mis par l'EAG pour revenir à l'ordonnée de départ après dépolarisation maximum, a été plus lent pour les esters à chaînes droites avec 9 à 11 carbones. La ramification de la chaîne par addition d'un groupe méthyl de chaque côté de l'ester a provoqué une réduction de l'amplitude et une accélération de la récupération. 5 esters seuls provoquent une forte réaction dans le tunnel à vent (hexanoates butilique et pentylique, heptanoates propylique et butylique, octanoate propylique). Ceci montre (1) le risque qu'il y a à attribuer une signification aux substances provoquant une réaction en EAG, lorsqu'il n'y a pas d'observations comportementales parallèles, et, surtout; (2) le degré élevé de spécificité olfactive.La résponse comportementale optimale obéit aux règles suivantes concernant la taille et la structure de la molécule. L'ester doit avoir: (1) une chaîne linéaire; (2) 10–11 carbone de longueur; (3) une portion acide de 6 à 8 C et une portion alcool de 3 à 5 C. Le butyl hexanoate, l'un des esters actifs, présent en concentration suffisante près de fruits utilisés, provoque pour cette raison une réponse comportementale tellement marquée, que nos résultats suggèrent que R. pomonella est adapté à la perception des substances caractéristiques de leurs hôtes.

     

Attraction of Mexican Fruit Flies (Diptera: Tephritidae) to Grapefruit: Enhancement by Mechanical Wounding of and Experience with Grapefruit

Wild strain, mated, female Mexican fruit flies, Anastrepha ludens (Loew), with no prior experience with fruit (naive), were not attracted to grapefruit, a preferred cultivated host, in wind tunnel experiments. Naive, mated laboratory strain females were attracted. Prior experience with grapefruit increased attraction of both laboratory and wild strains. More females were attracted to fruit with peel damage than to undamaged fruit, indicating that fruit odor mediated attraction. More naive than experienced females attempted to oviposit on the sides of the wind tunnel. Experienced laboratory males, but not wild males or naive males, were attracted to grapefruit. Attraction and oviposition behavior of laboratory flies was greater than that of wild flies.     

Fluctuations in numbers and the significance of the sex ratio of the Mexican fruit fly, Anastrepha ludens caught in McPhail traps

The seasonal fluctuations in numbers, sex ratios and the changes in the reproductive status of the Mexican fruit fly, Anastrepha ludens, caught in McPhail traps in citrus orchards and the effect of control measures on them, were examined in Belize, Central America. Evidence is presented that the seasonal increase in numbers was derived mainly from infestations in grapefruit and that harvesting played a significant part in controlling numbers by removing infested fruit. In orchards where sprays were not used to control the fruit fly, the sex ratio and the proportion of fecund females were very variable but there were always greater numbers of females — often two to four times as many. During spray programs the sex ratio approached unity and the proportion of fecund females decreased to zero. The sex ratio therefore gave an indication of the mean reproductive status of the female flies in the traps and thus the capacity of a local population to initiate infestations as well as the efficiency of control measures used.

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Résumé Effectifs, taux sexuel, périodes de reproduction, ainsi que leurs variations au cours de l'année et après application de mesures de lutte ont été étudiés chez la mouche des fruits mexicaine A. ludens dans des vergers d'agrumes de Belize (Amérique centrale), à l'aide de pièges McPhail.Les effectifs d'A. ludens sont caractérisées par une progression régulière à partir d'un minimum entre juin et septembre, jusqu'à un maximum en février ou mars. Ces variations saisonnières dépendent de la présence de fruits mûrs, de pamplemousses notamment. Le taux sexuel des adultes capturés dans des vergers non traités est très variable, mais les sont toujours plus nombreuses (souvent 2 à 4 fois plus) que les mâles. Pendant la saison des pamplemousses, les peuvent pondre dans les fruits mûrs qui abondent; si la proportion de augmente, celle des fécondes diminue. Après un traitement efficace à l'aide d'un attractif insecticide à base d'hydrolisat de protéines, le taux sexuel tend vers 1 : 1, les fécondes tendant à disparaître et la majorité des caputées étant fraîchement émergées et immatures.Pendant la saison des pamplemousses, le taux sexuel donne des indications sur le potentiel reproducteur des , sur leur aptitude à provoquer une infestation, ainsi que sur l'efficacité et la persistance des attractifs insecticides utilisés pour la lutte contre la mouche des fruits.

     

Mating senescence and male reproductive organ size in the Mexican fruit fly

Ageing can reduce the probability that individuals reproduce. The present study investigates whether ageing influences the mating frequency of mass‐reared fertile and sterile Mexican fruit flies Anastrepha ludens (Loew). The ability of males of different ages to inhibit female remating is also determined, and the growth of male reproductive organs is measured as they age. Young males (6 days old) have a lower mating frequency than older males, and also have a lower capacity to inhibit female remating than older males. However, 7‐day‐old males are as likely to inhibit female remating as older males. Young males also have smaller reproductive organs than middle‐aged (21‐day‐old) or senescent males (57‐day‐old). These results have implications for the sterile insect technique because sterilized males of A. ludens are released in the field 6 days after emergence. The highest mating frequency, the lowest mating latency and the largest size of testes are observed at 21 days of age. Older males (57 days old) have more sperm in their seminal vesicles than young males (6 and 9 days old). Accessory glands take longer to grow to their complete size compared with testes, and mating frequency is more closely associated with accessory gland size than testes size. Furthermore, there are more sperm in the seminal vesicles during the afternoon period of peak sexual activity than during the morning when sexual activity is absent. These results indicate that, even at the onset of reproductive senescence, mass‐reared males of A. ludens are still capable of mating, as well as inhibiting remating in females.