The roles of adult and larval specialisations in limiting the occurrence of five species of Dacus (Diptera: tephritidae) in cultivated fruits

Summary The relative importance of adult preferences or specialisations of larval physiology in restricting the host range of five species of Dacine fruit flies (Diptera: Tephritidae) was examined, with particular emphasis on their utilization of cultivated fruits. The species; D. tryoni, D. jarvisi, D. cucumis, D. musae and D. cacuminatus differ widely in host range with D. tryoni being highly polyphagous while D. cacuminatus is virtually monophagous. Laboratory experiments showed that larvae of all species survived and developed in many cultivated fruits in which the specialists never occur in the field. By contrast the oviposition preferences and specificity of adult females differed widely between species. Female D. tryoni oviposited in most species of fruit. The specialised species; D. cucumis, D. musae and D. cacuminatus strongly preferred their usual hosts and would not oviposit in novel fruits even in the absence of the preferred host. In contrast, D. jarvisi consistently preferred its main native host but when this was not offered readily accepted cultivated fruits. These differences in preference are consistent with the pattern of infestation displayed by each species in the field. The study indicate that, in general, the occurrence of these species of Dacus in cultivated fruits is constrained more by the behavioural preferences of adult females than by larval specialisations. A genetic change in some aspect of host recognition or acceptance would be necessary for the specialised species to regularly infest cultivated fruits though no change in larval characteristics may be needed. As the types and concentrations of defensive secondary compounds may differ between native and cultivated fruits this conclusion cannot be extended to host shifts among native fruits.     

Oviposition preference in the oligophagous tomato fruit fly, Neoceratitis cyanescens

We assessed the role of visual and olfactory cues on oviposition preference in the oligophagous tomato fruit fly, Neoceratitis cyanescens (Bezzi) (Diptera: Tephritidae). In a field survey, we evaluated the stage of susceptibility of field‐grown tomatoes by monitoring N. cyanescens infestations from fruit‐setting up to harvest, in relation to post‐flowering time, size, and visual properties of fruit. In two‐choice laboratory experiments, we tested the degree to which females use visual and olfactory cues to select their host plant for oviposition. In addition, we investigated the ability of flies to avoid fruit already infested by conspecific eggs or larvae, and the influence of natal host fruit on oviposition preference. Neoceratitis cyanescens females preferentially lay their eggs in small yellow‐green unripe fruit (2–3.5 cm diameter, 10–21 days post‐flowering). Damage to fruit was significantly affected by brightness and size properties. In laboratory experiments, females chose to lay their eggs in bright orange rather than yellow domes. On the sole basis of olfactory stimuli, females showed a significant preference for unripe vs. ripe host fruit, for unripe fruit vs. flowers or leaves, and for host vs. non‐host fruit (or control). However, colour interacted with odour as females dispatched their eggs equally between the yellow dome and the bright orange dome when unripe fruit of tomato was placed under the yellow dome vs. ripe fruit under the bright orange dome. When offered real ripe and unripe tomatoes, females preferred unripe tomatoes. Females significantly chose to lay eggs in non‐infested fruit when they were given the choice between these or fruit infested with larvae. In contrast, recent stings containing eggs did not deter females from laying eggs. Rather, they could have an attractive effect when deposited within <1 h. Regardless of their natal host plant, tomato or bugweed, N. cyanescens females laid significantly more eggs in a dome containing bugweed fruit. However, 15% of females originating from tomato laid eggs exclusively in the dome with tomato, against 3% of females originating from bugweed.     

Olive fruit fly [Bactrocera (Dacus) oleae (Rossi) (Diptera: Tephritidae)] adult rearing diet without antibiotic

The olive fruit fly [Bactrocera (Dacus) oleae (Rossi) (Diptera: Tephritidae)] adult diet since its development in the 1960’s regularly incorporates antibiotic. Considering recent findings on the importance and function of the indigenous microbial flora of insects, the effects of antibiotic removal were measured on the survival and egg laying of wild flies derived from McPhail trappings and from field infested olive fruits. In the first case wild flies fed no antibiotic laid significantly greater numbers of eggs for two generations (in 5 out of 10 and 2 out of 10 counting dates for G1 and G2 respectively), while there were no significant differences in survival in either test (P = 0.221 for P generation, P = 0.988 for G1 generation from McPhail traps, P = 0.056 for flies from infested fruits). Percent egg–pupa recovery and adult emergence were not significantly affected by lack of antibiotic. An antibiotic‐free strain has been maintained for eight generations, showing acceptable performance when compared to the long‐reared standard ‘Laboratory’ strain. Overall results suggest the feasibility of an adult diet free of antibiotic without negative effects on colony survival and performance.     

Effect of heat stress on survival and reproduction of the olive fruit fly Bactocera (Dacus) oleae

The olive fruit fly Bactrocera (Dacus) oleae Gmelin is a major olive pest in Greece and other Mediterranean countries. Its population density and respective olive infestation is usually low in many areas of northern Greece during summer months. To some extent, this may be due to the prevailing high temperature and low relative humidity conditions. In the present work the effects of short term exposure to high temperatures on the survival and egg production of B. oleae pre‐imaginal stages and adults were studied under laboratory conditions. Different larval instars within infested green olive fruits, adults and pupae and were exposed for 2 h to a series of different high constant temperatures ranging from 34 to 42°C. Subsequently, survival percentages of pre‐imaginal stages and adults as well as the number of eggs laid by females previously exposed to high temperatures were determined. At temperatures up to 38°C high survival percentages of larvae and adults were observed, whereas pupae displayed a relatively increased heat tolerance up to 40°C. Female longevity and egg production were substantially reduced after heat stress. Prior acclimation at 33°C for 1 and 3 days resulted in increased adult survival following heat stress. We discuss the results with respect to the ability of the fly to survive and reproduce under high summer temperatures.     

Influence of fruit traits on the infestation of Dacus persicus in two fruit morphs of Calotropis procera

The larvae of Dacus (Leptoxyda) persicus (aak fruit fly) are key predispersal seed predators in Calotropis procera (Asclepiadaceae). Based on fruit characteristics, two morphs are distinguishable in C. procera viz., the soft-fruited morph (SF morph) and the hard-fruited morph (HF morph). The work reported here examined whether the fruit characteristics influenced the infestation by the aak fruit fly and, if so, what mechanism(s) were operative. Fruits in the SF morph were significantly more acceptable to the aak fruit fly than those of the HF morph irrespective of their size class and availability or fly population density. A general ranking of fruit acceptability for oviposition by the aak fruit fly within the fruit size class was: size class III ≥ size class II > size class I and IV. The negative relationship between fruit infestation and pericarp toughness, which is suggestive of trade-offs between the fly’s oviposition obligation and energy/time (predation risk) constraint, was found to correlate with the requirement of greater force to puncture the pericarp in the hard fruits. Lower penetrability of the pericarp in the hard fruits appeared to be primarily due to the thickness of pericarp and secondarily on account of the thickened walls of endocarpic–mesocarpic cells in the inner pericarpic layer. The present data point to the existence of two fruit morphs in C. procera differing in the acceptability of fruits for oviposition by the aak fruit fly primarily on account of toughness and internal structure of the pericarp.     

Infestation of fruit by conspecific and heterospecific females deters oviposition in two Tephritidae fruit fly species

Tephritidae fruit fly larvae develop entirely in the host chosen by the females. To improve the fitness of their progeny, females would benefit from rejecting previously exploited hosts. Anastrepha fraterculus and Ceratitis capitata are two species of fruit flies having similar nutritional requirements and overlapping in their distribution. Previous studies found that competition between the larvae of these species might reach high levels, suggesting that cross-recognition would be an adaptive trait. In this work, we tested the ability of A. fraterculus and C. capitata females to recognize and avoid fruits previously infested by both conspecific and heterospecific females. In laboratory behavioural arenas, females were presented with fruits that had been previously exposed to either conspecific or heterospecific females. Then, we conducted choice and non-choice assays to compare the response of A. fraterculus and C. capitata females to infested and non-infested fruits. In non-choice tests, the females from both species rejected fruits previously infested by conspecific and heterospecific individuals. However, the rejection occurred at different steps of the sequence leading to oviposition: A. fraterculus showed a lower rate of visits to infested fruits, whereas C. capitata visited both infested and non-infested fruits, but the latency to visit a fruit and the rejection frequency were higher and the duration of the visit to infested fruit was lower. In choice assays, the rejection of heterospecific infested fruit was higher than that of conspecific infested fruits, for both species. Our results suggest that, regardless of the sensory mechanism used by females, the recognition of previous infestation is bidirectional and females of both species, belonging to different genera, recognize fruit infested by heterospecifics. These responses indicate that cross-recognition, supposedly a highly beneficial trait, could be occurring in nature, thus reducing interspecific competition and contributing to the coexistence of these species.     

Predation potential of the earwig Euborellia annulipes on fruit fly larvae and trophic interactions with the parasitoid Diachasmimorpha longicaudata

The earwig Euborellia annulipes (Lucas) (Dermaptera: Anisolabididae), a generalist predator, has been observed in fruits infested with fruit fly larvae, which are frequently parasitized by parasitoid wasps. Neither the capacity of earwigs to predate on fruit flies nor intraguild interactions between earwigs and fruit fly parasitoids have been investigated. Here, we studied in laboratory conditions the predation on the fruit fly Ceratitis capitata (Wiedemann) (Diptera: Tephritidae) by the earwig E. annulipes, and whether parasitism of fruit fly larvae by the parasitoid wasp Diachasmimorpha longicaudata (Ashmead) (Hymenoptera: Braconidae) influences predation by the earwig. We evaluated the predation capacity, functional response and prey preference of E. annulipes for parasitized and non-parasitized fruit fly larvae in choice and no-choice tests. We found that earwigs prey on second- and third-instar larvae and pupae of C. capitata and consumed larger numbers of second-instar larvae, followed by third-instar larvae and pupae. Females prey on larger numbers of fruit flies than did males, regardless of the prey developmental stage, but both sexes exhibited a type II functional response. Interestingly, males killed but did not consume fruit fly larvae more than did females. In no-choice tests, earwig females consumed equal numbers of parasitized and non-parasitized fruit fly larvae. However, in choice tests, the females avoided feeding on parasitized larvae. Subsequent tests with hexane-washed parasitized and non-parasitized larvae showed that putative chemical markings left on fruit flies by parasitoids did not drive the earwig preference towards non-parasitized larvae. These findings suggest that E. annulipes is a potential biological control agent for C. capitata, and that, because the earwig avoids consuming larvae parasitized by D. longicaudata, a combination of the two natural enemies could have an additive effect on pest mortality.     

Competitive interactions and partial displacement of Anastrepha obliqua by Ceratitis capitata in the occupation of host mangoes (Mangifera indica)

1. We examined the competitive interactions between a native fruit fly species (Anastrepha obliqua Macquart) and the invasive medfly (Ceratitis capitata Wiedemann) when these co-occur on a shared mango fruit host (Mangifera indica L.).
2. Using mango fruits of distinct levels of ripeness, we investigated both competition among larvae and among adult females for oviposition. We quantified competition by the numbers of eggs laid and the intensity of agonistic interactions between adult females.
3. Interactions between immature fruit flies led to reduced size and number of emerged adults of both species. These impacts were felt more acutely in the native species.
4. Interspecific competition between females led to fewer eggs laid on semi-ripe fruit by both species, which may be the result of niche overlap associated with oviposition.
5. Intraspecific interactions between A. obliqua individuals led to intense agonistic behaviour, with a concurrent decrease in number of landings on these host fruits.
6. These results suggest that the native species undergoes a partial niche displacement when facing the invasive species. A portion of the fundamental niche of A. obliqua remained unoccupied by the invading C. capitata, which may allow their coexistence under natural conditions.

     

Cuticular hydrocarbons from six species of tephritid fruit flies

Cuticular alkanes obtained from larvae and adults of six species of tephritid fruit flies, Anastrepha ludens, A. suspensa, Ceratitis capitata, C. rosa, Dacus cucurbitae, and D. dorsalis were analyzed by gas chromatography. The same four major alkanes were shown to be present by capillary GC-mass spectra in all Anastrepha and Ceratitis larvae. Profiles were obtained from individual larvae and adult specimens that showed statistical differences between species, whereas profiles of conspecific life forms including pupae of A. suspensa from different locations showed some similarities. Sexual dimorphism was not observed in alkanes extracted from adults. A novel series of alkadienes was found in all Anastrepha and Ceratitis but not in Dacus.     

Larval competition within and between insecticide resistant and susceptible individuals in the oriental fruit fly,Bactrocera dorsalis

Insecticide resistance is a serious issue in agriculture. Ecological interactions may be used to manage the spread of resistance, but little information is currently available. In particular, virtually none is known about interactions between resistant and susceptible individuals. This study investigated competition between resistant and susceptible oriental fruit fly larvae (Bactrocera dorsalis). Competition in the larval stage was examined with an explicit consideration of individual identity (resistant or susceptible). Guava fruits were inoculated with eggs of susceptible and/or resistant flies, and their development and survival were monitored. Egg density influenced the time that larvae stayed in fruits as well as their survival. In addition, susceptible flies survived better when interacting with resistant flies than with other susceptible flies, indicating that susceptible flies are competitively superior to resistant flies. The results suggest that artificially creating environments that induce competition between susceptible and resistant flies can be useful for the management of insecticide resistance.     

Host species and vegetable fruit suitability and preference by the parasitoid wasp Fopius arisanus

Parasitoids that oviposit in a concealed host inside a plant part need to be able to find both the plant and the host. Egg parasitoids of fruit‐infesting Tephritidae need to assess the oviposition site based both on the host egg and the infested fruit. Infestation by Tephritidae fruit flies threatens fruit and vegetable production. Management methods have been implemented including biological control, using Fopius arisanus Sonan (Hymenoptera: Braconidae). The parasitism by F. arisanus in three Tephritidae flies in vegetable fruits was investigated. Laboratory assays were conducted to assess the parasitoid's preference and survival. Zucchini, sweet pepper, and tomato were artificially infested with eggs of Bactrocera dorsalis Hendel, Ceratitis capitata Wiedemann, and Ceratitis cosyra Walker (all Diptera: Tephritidae), then exposed to mated naïve F. arisanus females in a 20:1 egg:parasitoid ratio. Parasitoid behavioral activities (resting, antennating, probing, ovipositing) were observed on the infested fruits. Parasitism rate was determined by dissection of fruit fly eggs under a stereomicroscope. Behavioral activities of F. arisanus differed between all the fruits when infested with B. dorsalis or C. cosyra eggs but differed only between some of the fruits when infested with C. capitata. Fopius arisanus preferred B. dorsalis over C. capitata and C. cosyra, with a parasitism rate 2× higher on B. dorsalis compared to the Ceratitis species. Preference for fruits was dependent on the infesting fruit fly. The emergence of F. arisanus was higher with B. dorsalis than with Ceratitis spp. Although B. dorsalis completed its development earlier than Ceratitis spp., host fly species did not affect the developmental time of F. arisanus. We discuss the significance of F. arisanus preference in relation to naturally occurring Tephritidae infestations. We also discuss whether some fruits might constitute a refuge for Tephritidae flies and whether this will affect the current biological control efforts against B. dorsalis.     

Fruit trap: A detection and collection tool for opiine parasitoids (Hym.: Braconidae) of the oriental fruit fly,Bactrocera dorsalis (Dipt.: Tephritidae)

A fruit trap was developed for detection and collection of the opiine parasitoids of the oriental fruit fly,Bactrocera (=Dacus)dorsalis (Hendel). Gravid females ofBiosteres arisanus (Sonan), an egg-larval parasitoid, orDiachasmimorpha longicaudata (Ashmead) andPsytallia incisi (Silvestri), both larval parasitoids, were lured to parasitize the eggs or larvae ofB. dorsalis inoculated in ripe papaya fruits,Carica papaya L. Progenies ofB. arisanus were consistently recovered from papaya fruits inoculated withB. dorsalis eggs (subsequently referred to as egg fruit traps). Except in Moloaa on Kauai (6%), higher percentage ofB. dorsalis parasitization (range=38–43%) was recorded in Hilo, island of Hawaii and Waimanalo and Poamoho, island of Oahu. Progenies ofD. longicaudata and a fewP. incisi were recovered from papaya fruits artificially infested withB. dorsalis larvae (subsequently referred to as larval fruit traps). The recovery of parasitoid progenies from larval fruit traps suspended from papaya trees did not differ significantly from larval fruit traps placed on the ground. In both methods of trap placement, percent parasitization ofB. dorsalis byD. longicaudata (predominant species) ranged from 58–60%. On the other hand, significantly moreB. arisanus thanD. longicaudata andP. incisi adults (larval parasitoids) were recovered from fully ripened to highly deteriorated papaya fruits collected from papaya trees or ground (fallen fruits).     

Bacteria associated with four species of Dacus (Diptera: Tephritidae) and their role in the nutrition of the larvae

Summary The bacteria associated with Dacus tryoni (Froggatt), Dacus jarvisi (Tryon), Dacus neohumeralis (Hardy) and Dacus cacuminatus (Hering) were examined. Bacteria were isolated from the surface of freshly-laid eggs, from within surface sterilised pupae, from heads and abdomens of wild and laboratory-maintained flies, and from decomposed fruits in which the wild larvae were feeding. A more diverse flora was associated with D. tryoni and D. jarvisi (15 and 14 species, respectively) than with D. neohumeralis and D. cacuminatus (9 and 6 species, respectively). Most of the bacteria belonged to the family Enterobacteriaceae and while there were similarities of bacterial associations between fly species there was no evidence of a strict symbiotic association of a particular bacterium or bacteria with each species of fly. The larvae of D. jarvisi were unable to develop normally in an artificial medium containing unhydrolysed protein and free of bacteria and on a medium containing casein and Serratia liquefaciens (isolated from the flies and shown to secrete protease) the larvae died. On the same casein medium containing Enterobacter cloacae (isolated from the flies and shown to be protease negative) the larvae developed normally. Larvae of D. tryoni and D. jarvisi were devoid of protease and cellulase activity, but contained some amylase activity. The significance of these results in terms of current hypotheses concerning symbioses between tephritids and bacteria is discussed.     

Host fruit chemical stimuli eliciting distinct ovipositional responses from sibling species of Rhagoletis fruit flies

Laboratory experiments tested whether two economically-important sibling species of tephritid fruit flies have evolved distinct egg-laying responses to chemical stimuli on the fruits of their respective hostplants. The egg-laying preferences displayed by apple maggot flies, R. pomonella, and blueberry maggot flies, R. mendax, on artificial fruits treated with apple and blueberry extract paralleled their egg-laying responses to whole apples and blueberries. R. pomonella flies laid more eggs than R. mendax flies in artificial fruits treated with extract from ripe McIntosh apples, and vice versa for artificial fruits treated with extract from ripe Bluehaven blueberries. Furthermore, both species laid more eggs in artificial fruits treated with extract from their respective host fruits than control artificial fruits which were not treated with fruit extract. Prior electroantennogram recordings from R. mendax and R. pomonella flies exposed to volatiles from pentane extracts of apples and blueberries indicate that the antennal sensitivity of both species is selectively tuned to their respective host fruit odors. This differentiation in their olfactory responses to fruit odors could be important in mediating their distinct ovipositional responses to blueberry and apple fruits. Extract from unripe McIntosh apples also elicited egg laying by R. pomonella flies, however, artificial fruits treated with unripe apple extract received 1.9 times fewer eggs than those treated with ripe apple extract. Moreover, the numbers of R. pomonella ovipositor punctures and eggs placed in wax artificial fruits were increased when the artificial fruits were treated with a blend of 7 identified apple esters. Black coloration on these artificial fruits and the presence of apple esters had a synergistic effect on the egg-laying behavior of R. pomonella flies, which caused them to lay substantially more eggs per black fruit than white fruit treated with the same concentration of apple esters. In summary, our results indicate that the egg-laying responses of R. pomonella flies are mediated by the integration of information from fruit chemical and visual cues, and that R. mendax and R. pomonella flies have evolved divergent egg-laying responses to chemical stimuli on the fruits of their respective hostplants. These findings are discussed in the context of other studies on plant compounds which influence the ovipositional behavior of phytophagous Diptera.

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Stimuli chimiques des pommes et des myrtilles induisant la ponte des espèces jumelles, Rhagoletis pomonella et R. mendax

Résumé Des fruits artificiels en cire traités avec des extraits de fruits ont provoqué chez les espèces jumelles de R. mendax (Curran) et R. pomonella (Walsh) des réactions de ponte différentes suivant les stimulations chimiques par les fruits. Le comportement de ponte sur des fruits artificiels traités avec des extraits au pentane des myrtilles mûres (Vaccinium corymbosum L.) et de pommes mûres (Malus pumila Miller = Pyrus malus L.), est le même que sur des fruits naturels, ce qui montre que la réponse aux stimulations chimiques provenant du fruit constitue un aspect important de la reconnaissance de l'hôte. R. pomonella pond plus d'ufs que R. mendax sur les fruits artificiels traités à l'extrait de pommes mûres; c'est l'inverse pour les fruits traités aux extraits de myrtille. Les fruits artificiels traités avec des pommes ou des myrtilles provoquent la ponte de R. pomonella, tandis que les myrtilles mûres seules provoquent la ponte de R. mendax. Les extraits de pommes vertes stimulent la ponte de R. pomonella mais elle est alors 2 fois plus faible qu'avec des extraits de pommes mûres. Un mélange de 7 esters identifiés dans l'extrait de pomme induit aussi la ponte de R. pomonella. Le nombre de piqûres de tarièresfli dans les fruits artificiels en cire et le nombre d'ufs par fruit ont été augmentés par addition d'esters de pommes à des fruits blancs ou noirs. La couleur des fruits artificiels influence aussi la réaction de ponte de R. pomonella; la fréquence des piqûres de tarière contenant un uf et le nombre d'ufs par fruit étaient significativement plus élevés sur les fruits noirs que sur les fruits blancs traités avec la même concentration d'esters de pomme. Les fruits artificiels noirs traités avec la concentration la plus stimulante d'esters de pommes ont reçu 2, 3 fois plus d'ufs que les fruits blancs avec les mêmes concentrations en esters. Ces résultats montrent que les esters de pomme et la couleur noire stimulent synergiquement la ponte de R. pomonella sur des fruits artificiels.

     

Host location by the fruit fly parasitoid Diachasmimorpha krausii: role of fruit fly species,life stage and host plant

• 1 Diachasmimorpha krausii is a braconid parasitoid of larval tephritid fruit flies, which feed cryptically within host fruit. At the ovipositor probing stage, the wasp cannot discriminate between hosts that are physiologically suitable or unsuitable for offspring development and must use other cues to locate suitable hosts.
• 2 To identify the cues used by the parasitoid to find suitable hosts, we offered, to free flying wasps, different combinations of three fruit fly species (Bactrocera tryoni, Bactrocera cacuminata, Bactrocera cucumis), different life stages of those flies (adults and larvae) and different host plants (Solanum lycopersicon, Solanum mauritianum, Cucurbita pepo). In the laboratory, the wasp will readily oviposit into larvae of all three flies but successfully develops only in B. tryoni. Bactrocera tryoni commonly infests S. lycopersicon (tomato), rarely S. mauritianum (wild tobacco) but never C. pepo (zucchini). The latter two plant species are common hosts for B. cacuminata and B. cucumis, respectively.
• 3 The parasitoid showed little or no response to uninfested plants of any of the test species. The presence of adult B. tryoni, however, increased parasitoid residency time on uninfested tomato.
• 4 When the three fruit types were all infested with larvae, parasitoid response was strongest to tomato, regardless of whether the larvae were physiologically suitable or unsuitable for offspring development. By contrast, zucchini was rarely visited by the wasp, even when infested with B. tryoni larvae.
• 5 Wild tobacco was infrequently visited when infested with B. cacuminata larvae but was more frequently visited, with greater parasitoid residency time and probing, when adult flies (either B. cacuminata or B. tryoni) were also present.
• 6 We conclude that herbivore‐induced, nonspecific host fruit wound volatiles were the major cue used by foraging D. krausii. Although positive orientation to infested host plants is well known from previous studies on opiine braconids, the failure of the wasp to orientate to some plants even when infested with physiologically suitable larvae, and the secondary role played by adult fruit flies in wasp host searching, are newly‐identified mechanisms that may aid parasitoid host location in environments where both physiologically suitable and unsuitable hosts occur.

     

Acceptability of Drosophila suzukii as prey for common predators occurring in cherries and berries

The invasive cherry vinegar fly, Drosophila suzukii, has been identified in Europe as a destructive fruit pest since its arrival in 2008. In the present laboratory study, three predatory insects (Orius majusculus, Chrysoperla carnea, and Forficula auricularia) naturally occurring on fruit crops in Europe were investigated for their ability to attack and feed on D. suzukii within and outside fruits. The predators were provided with various D. suzukii life stages (eggs, larvae, pupae or adults) exposed or within infested cherries. The anthocorid bug O. majusculus fed on eggs and larvae, but was not able to attack pupae. Larvae of the lacewing C. carnea preyed upon D. suzukii eggs, larvae and pupae and also captured adult flies. The European earwig F. auricularia was the most voracious predator of these three tested species. Although the earwigs were not able to catch adult flies, they readily preyed upon every other developmental stage. Adult O. majusculus or third instar larvae of C. carnea significantly reduced the offspring of D. suzukii from infested cherries, when these contained the egg stage of the pest. None of the predators were able to attack early larval stages inside the cherries. But pupae that protruded from the fruit epicarp or that had pupated outside the fruit were accessible to lacewing larvae and earwigs and significantly reduced by them. Orius bugs, lacewing larvae and earwigs were able, under laboratory conditions, to capture and prey upon various life stages of the invasive pest, if not completely concealed inside the fruit. Our findings suggest that these generalist predators may have some control capacity on infested fruit in cultivated fruit crops and also in non‐crop habitats.     

Olfactory response of three parasitoid species (Hymenoptera: Braconidae) to volatiles of guavas infested or not with fruit fly larvae (Diptera: Tephritidae)

The olfactory responses of the native parasitoids Doryctobracon areolatus (Szépligeti) and Asobara anastrephae (Muesebeck) and of the exotic parasitoid Diachasmimorpha longicaudata (Ashmead) to guava (Psidium guajava L.) infested or not with fruit fly larvae were evaluated. D. areolatus and D. longicaudata females responded to the odors of uninfested rotting guavas, although D. areolatus was also attracted to fruits at the initial maturation (turning) stage. The females of these species recognized the volatiles of guavas containing Ceratitis capitata (Wied.) larvae. However, in bioassays involving fruits with larvae of different instars, D. longicaudata females were not able to separate between fruits containing C. capitata larvae at the initial instars and larvae at the third instar. In the evaluations of volatiles released by guavas containing C. capitata and Anastrepha fraterculus (Wied.) larvae, the D. longicaudata females were oriented toward the volatiles of fruits containing both host species, but differed significantly from volatiles of guavas containing C. capitata larvae. The D. areolatus females also showed responses to both species, although with a preference for volatiles of fruits containing A. fraterculus larvae. The A. anastrephae females were oriented toward the odors of fruits infested with both fruit fly species. In the shade house, D. longicaudata females were oriented to volatiles of rotting fruits containing larvae or not, but could not significantly differentiate between hosts. D. areolatus females were not attracted toward fruits on the ground in the shade house, regardless of host, suggesting that this parasitoid does not forage on fallen fruits.     

Is fruit size important in the selection of oviposition sites by cranberry fruitworm,Acrobasis vaccinii?

Under laboratory conditions, females of Acrobasis vaccinii (Riley) (Lepidoptera: Pyralidae) oviposit significantly more often on larger than on smaller cranberry fruit. This behaviour ensures that neonate larvae have access to maximum resources and are larger when moving to the next fruit. However, while there is some evidence that on a large spatial scale females may lay eggs in patches of larger fruit, there was no evidence of such an oviposition preference within patches in natural bogs. These results may be explained by the fact that the oviposition period for A. vaccinii begins early in the cranberry season, before fructification is completed, leading to potential competition among females for the first fruit present in the environment. Laying eggs on the first fruit available may be advantageous as this behaviour increases the probability that females select unexploited fruit. This strategy would be particularly effective for maximizing female fitness in grazer frugivorous species (such as the cranberry fruitworm) that live in environments where severe climatic conditions induce limited flowering/fruit formation and where hosts thus are rare.     

Opiine parasitoids (Hymenoptera: Braconidae) and biological control of fruit flies (Diptera: Tephritidae) in Australia: Past,present and future

Opiine braconids are parasitoids of the immature stages of frugivorous tephritids. The female wasp lays her eggs into the eggs or larvae of the fruit fly host, where the immature wasp develops before emerging as a next-generation adult from the now dead host pupal case. In support of a new generation of Australian fruit fly parasitoid research, this paper comprehensively reviews what is known about the Australian fruit fly infesting opiines. Based on the most recent taxonomic revision 11 fruit fly infesting opiine species are documented to occur in Australia, but we consider as doubtful the record for Diachasmimorpha longicaudata and consider the record for Fopius illusorius to be tentative without further collections. We identify that the systematics and taxonomy of the Australian native fruit fly infesting opiines are in urgent need of further work. The history of fruit fly biological control in Australia is comprehensively reviewed, including the export of native Australian opiines for fruit fly control elsewhere in the world. Australia was actively involved in three major classical biological control programmes against fruit flies from the turn of the 1900s until the mid-1960s. Despite the introduction of 11 opiine species, plus numerous other natural enemies, only Fopius arisanus established in eastern Australia, where in South-east Queensland it can now cause between 30 and 40% mean parasitism. In addition to the exotic F. arisanus, the native species Diachasmimorpha kraussii and Diachasmimorpha tryoni also cause fruit fly parasitism in agriculturally important crops: both species have also been liberated widely outside of Australia for fruit fly control. Other Australian opiines have not been reared from flies infesting commercial crops and appear biologically restricted to the fruits and environs of Australian east-coast rainforests. The biology literature for D. tryoni and D. kraussii is comprehensively reviewed, while for F. arisanus, already reviewed elsewhere, key literature only is covered. Forward looking, we consider the potential for inoculative or inundative releases of opiines in areas where they do not currently occur to be good, while conservation biological control may help to increase the impacts of parasitoids in areas where they are already established.     

Acceptance and suitability of different host stages of Ceratitis capitata (Wiedemann) (Diptera: Tephritidae) and seven other tephritid fruit fly species to Tetrastichus giffardii Silvestri (Hymenoptera: Eulophidae)

Tetrastichus giffardii Silvestri is a gregarious eulophid endoparasitoid of several tephritid fruit fly species. Host stage suitability was studied using nine age groups of Ceratitis capitata (Wiedemann) (Diptera: Tephritidae), namely, eggs less than 24 h and between 24 and 48 h old, and 1- to 7-day-old larvae. Life table studies for T. giffardii using C. capitata as host were done at 26 ± 5 °C and 55–60% RH. Egg load in relation to age of the female parasitoid was also assessed as was the effect of host deprivation on adult longevity. Host acceptance and suitability were examined with respect to eight species of tephritids. Potential hosts so tested were five Ceratitis species, the Medfly, C. capitata, the mango fruit fly, Ceratitis cosyra (Walker), the Natal fruit fly, Ceratitis rosa Karsch, Ceratitis fasciventris (Bezzi), and Ceratitis anonae Graham; two Bactrocera species, the melon fruit fly, Bactrocera cucurbitae (Coquillett) and the newly invasive Bactrocera invadens Drew, Tsuruta, and White; and one Dacus species, the lesser pumpkin fly, Dacus ciliatus Loew. No parasitoids were obtained from eggs while all larval stages were suitable though at varying degrees. Parasitism and number of progeny was related to host age in a curvilinear manner with maxima at 4- to 5-day-old larvae. By contrast, development time decreased with age of host larvae while sex ratio was not affected. The intrinsic rate of increase was 0.17 ± 0.01; gross and net reproductive rates were 64.9 ± 4.3 and 44.9 ± 3.8, respectively. Non-ovipositing females lived significantly longer than ovipositing ones. The females accepted all host species tested, but only C. capitata, D. ciliatus and, to a much lesser extent, C. cosyra were suitable. In the remaining host species, most eggs were encapsulated. In C. capitata and D. ciliatus, percent parasitism was similar, but number of progeny was lower and the sex ratio, as the proportion of females, was higher when the parasitoid was reared on D. ciliatus. Progeny per puparium were also similar for the two hosts. In the light of these results it can be concluded that T. giffardii has a narrow host range, but it attacks and successfully develops in larvae representing a wide range of ages.