Citrus Fruits and the Mediterranean Fruit Fly

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1 Citrus Fruits and the Mediterranean Fruit Fly Nikos T. Papadopoulos 1,*, Dimitrios P. Papachristos 2 and Charalambos Ioannou 1 1 Laboratory of Entomology and Agricultural Zoology, University of Thessaly, N. Ionia Magnisias, Greece 2 Benaki Phytopathological Institute, Kifisia, Atiki, Greece *Corresponding author: nikopap@uth.gr Abstract The Mediterranean fruit fly (medfly), Ceratitis capitata (Diptera: Tephritidae) is considered one of the most important pests for citrus fruits. Recent and older studies demonstrate a variable degree of sensitivity of citrus species to medfly infestations. It seems that the chemical properties of the citrus fruit rind are the most important barrier prohibiting survival and development of medfly immature stages. The toxic properties of rind vary a lot among different citrus species as a result of quantitative and qualitative (composition) aspects of citrus essential oils. Effects of fruit flesh on biological traits of larvae do not vary much among different citrus species. On the other hand, citrus essential oils affect, in a variable manner among different fruit species, a range of adult behavioral traits. For example, male medflies are attracted to citrus essential oils while exposure to them increases mating competitiveness over non-exposed males. Likewise, citrus oils regulate female ovipositional decisions. The current paper provides a comprehensive account on the complex interactions between medfly and citrus plants. Practical and theoretical implications are discussed. Keywords: host finding, citrus essential oils, plant resistance, sexual behavior INTRODUCTION The Mediterranean fruit fly (medfly), Ceratitis capitata (Wiedemann) (Diptera: Tephritidae) is one of the most destructive pests of fresh fruit and vegetables worldwide (Papadopoulos et al., 2001b). Females lay eggs in ripe or ripening fruits and larvae feed by destroying the fruit mesocarp (pulp, flesh). Saprophytic bacteria and fungi intensify the direct damage caused by larvae activity. Fruit and vegetable losses at a local level can reach high proportions resulting in devastating economic damage for farmers. However, the economic importance of medfly is magnified at regional and global level, since it is considered a major quarantine pest for many tropical and temperate countries, and specific, strict regulations restrict trading of fresh fruits and vegetable among regions and continents as well as well as among countries and counties. Indigenous to the west sub- Saharan Africa, it has dispersed throughout Africa, and either via the Nile valley or the coastal areas of west Africa to the shores of the Mediterranean sea, and from there to New Word, west Australia, and specific islands of the Indian, Atlantic and Pacific ocean (Malacrida et al., 2007). C. capitata is an extremely polyphagous, multivoltine species expressing high levels of adaptation and plasticity that enables it to thrive and persist in a multitude of diverse habitats (Diamantidis et al., 2008, 2009, 2011; Nyamukondiwa and Terblanche, 2009; Nyamukondiwa et al., 2010; Terblanche et al., 2010). Because of its enormous economic importance, the biology, ecology and behavior of the Mediterranean fruit fly have been extensively studied over almost a century. There are many studies addressing issues regarding the relationship between medfly and its host trees. The list of medfly hosts encompass more than 300 plant species, belonging to more than 50 plant families; however, 40% of its hosts belong to 5 families (Myrtaceae, 6%; Rosaceae, 10%; Rutaceae, 9%; Sapotaceae, 9%; and Solanaceae, 6%) (Liquido et al., 1991). Apparently, this list includes favorable and non-favorable hosts for immature and adult performance. It seems that there is a strong affinity between C. capitata and some of its hosts that goes well beyond oviposition and larvae survival and development. It is well documented that almost all activities of adults, including sexual interaction, resting, and Proc. XII th Intl. Citrus Congress Eds.: B. Sabater-Muñoz et al. Acta Hort. 1065, ISHS

2 feeding take place on specific host trees (Hendrichs and Hendrichs, 1990; Hendrichs et al., 1991; Shelly and Kennelly, 2007). Adult dispersion, on the other hand, is limited when suitable for oviposition host fruit are available in an area or even within farm (Papadopoulos et al., 2003). Biological traits such as the ability of (a) larvae to survive and conclude development in diverse sources of food (fruit and vegetable fruits), and (b) adult females to respond, discriminate, and deposit eggs in phylogenetically distant fruits account for the extremely long list of medfly hosts and its evolutionary success. There are many studies dealing with the host finding behavior of tephritids (true flies, Diptera: Tephritidae), and the influence of plant compounds on their reproductive success. Adults of the Mediterranean fruit fly, use both visual and chemical cues to locate hosts and oviposition sites, as well as mating resources. On the other hand, certain physical and chemical properties of host fruits may either deter female oviposition or provoke immature mortality contributing to fruit resistance to medfly infestation. The sexual behavior of the Mediterranean fruit fly has been the subject of intense research over many decades in both an applied and basic framework. Male medflies are polygynous, while females rather oligoandrous since only a small proportion of females has been found to mate more than once (Bonizzoni et al., 2006). Both males and females require proteinaceous food to attain sexual maturity and realize the full potential of reproductive performance. Sexually mature males gather on specific parts of selected host trees and release the sex pheromone forming a lek (Prokopy and Hendrichs, 1979; Hendrichs and Hendrichs, 1990). Females are attracted to lek and it is believed to select the best of males to mate with. Mating usually takes place in a hidden spot of the tree foliage located in close distance from the lek. Although medfly is considered one of the most important pests for citrus fruits there is a variable degree of sensitivity among different species and cultivars to medfly infestation that ranges from immunity no infestation (lemons) to high sensitivity (mandarins, bitter oranges). Apparently, the different citrus fruit species and cultivars demonstrate various degrees of resistance to medfly infestation. Indeed, this has been appreciated since long time ago (Back and Pemberton, 1915; Bodenheimer, 1951). On the other hand, citrus species have been demonstrated to comprise and important resource for medfly sexual and reproductive behavior (Hendrichs and Hendrichs, 1990; Hendrichs et al., 1991). Therefore, there is a dynamic association between medfly and citrus fruits that includes several practical and theoretical aspects that need to be understood. The current paper reviews recent and older studies reporting on the diverse interactions between medfly and citrus fruits. We examine aspects of citrus fruit resistance to medfly infestation, as well as positive effects of citrus fruit properties on the sexual and reproductive behavior of the fly. Finally, we attempt to resolve these paradoxical interactions and list possible practical and theoretical implications. RESISTANCE OF CITRUS FRUITS TO MEDFLY INFESTATION Citrus fruits exhibit a number of resistance mechanisms that affect adult and immatures performance (Papachristos et al., 2008; Staub et al., 2008; Papachristos and Papadopoulos, 2009). Physicochemical characteristics of citrus peels such as the quality and quantity of essential oils of the flavedo layer (the outer part of citrus fruit rind, bearing oil glands and pigments), peel thickness, elasticity, and mechanical resistance seem to constitute a strong barrier against infestation of C. capitata and that of other tephritid fruit flies (Back and Pemberton, 1915; Bodenheimer, 1951; Greany et al., 1983; Spitler et al., 1984; Aluja et al., 2003; Birke et al., 2006; Papachristos et al., 2008; Staub et al., 2008, Aluja and Mangan, 2008; Muthuthantri and Clarke, 2012; Lloyd et al., 2013). Females force their ovipositor into citrus fruit peel, forming oviposition cavities where eggs are deposited (Papaj et al., 1989). Larvae, penetrating the citrus peel to the most nutritious fruit pulp, have to overcome the lethal defensive mechanisms of the citrus fruit peel such gum secretion, the formation of hardened calluses around egg cavities that drown eggs and larvae and the toxic action of peel essential oils (Back and Pemberton, 1010

3 1915; Bodenheimer, 1951; Spitler et al., 1984; Papachristos et al., 2008; Staub et al., 2008). Toxic properties of the citrus peel oils seem to be one of the most crucial parameter determining larval survival for medfly (Salvatore et al., 2004; Papachristos at al., 2008, 2009) and other tephritids such as Anastrepha suspensa (Loew) (Styer and Greany, 1983; Greany et al., 1984). The toxicity of citrus oils against medfly larvae as well as among fruit species (even cultivars) variation is related to quantitative and qualitative aspects of their principal components (monoterpenes and sesquiterpenes) (Papachristos et al., 2009). Citrus essential oils contain mainly limonene (in proportion >90% in some species), which possess moderate toxicity against medfly larvae compared to other components of citrus oils (Papachristos et al., 2009). The oxygenated components (i.e citral, linalool, linalyl acetate, geranyl acetate, α-terpineol) were found to be more toxic than hydrocarbons (i.e. limonene, α- and β-pinenes, myrcene, γ-terpinene and sesquiterpenes like valencene), and their amount into citrus oils determines its toxicity (Papachristos et al., 2009). It worthies noting that in recent studies we demonstrated that orange and bitter orange oils were more toxic to C. capitata larvae than lemon oils. High concentration of α and β-pinene compared to other citrus species oils seems to account for the lower toxicity of lemon oil (Papachristos et al., 2009). Survival rates of medfly larvae into flavedo layer of citrus fruits depends, apart of oil toxicity, on concentration (Papachristos et al., 2008, 2009). In the aforementioned example, although lemon oil was less toxic than orange and bitter orange oils, none of the larvae hatched into lemon or orange flavedo managed to survive contrary to bitter orange flavedo where a low survival rate was reported (Papachristos et al., 2008). This could easily be explained taken into consideration the concentration of oils in lemon and sweet oranges flavedo (well above that required to kill 99% of larvae) compared to that of bitter orange (much lower than that required to kill 99%) (Papachristos et al., 2009). Besides its lethal effect on newly hatched larvae, citrus peels also interfere with female oviposition determining in a direct or an indirect manner citrus fruit resistance to C. capitata infestations (Levinson et al., 2003; Papachristos et al., 2008; Staub et al., 2008; Papachristos and Papadopoulos, 2009; Ioannou et al., 2012). Female oviposition decisions are considered crucial in governing larvae survival in medfly and other endophytic fruit flies (Birke et al., 2006; Papachristos et al., 2008; Papachristos and Papadopoulos, 2009). The physical characteristics of citrus fruits, such as peel thickness and resistance to pressure, prevent females from laying eggs directly into flesh of citrus fruit (Greany, 1989; Birke et al., 2006). The short and pointed ovipositor (Jones, 1989) consists the main phylogenetic constraint limiting female medflies of avoiding the toxic properties of citrus fruit peel (Birke et al., 2006). The tendency of females to oviposit in or near fruit wounds in order to direct egg-laying away from the toxic flavedo area has been described as an adaptive syndrome (Papaj et al., 1989). On the other hand, C. capitata females using intact citrus fruits for oviposition exhibit a remarkable ability to avoid the toxic flavedo area by placing a proportion of eggs into the albedo depending on the citrus fruit (Papachristos et al., 2008). Indeed, in a recent study we demonstrated that females of the Mediterranean fruit fly were unable to lay eggs into fruit flesh of sweet orange, bitter orange and lemon cultivar but deposited all eggs in variable proportions in flavedo and albedo. In sweet orange varieties, females tended to deposit more eggs into the albedo than flavedo, whereas in lemon and bitter orange, they deposited equal numbers of eggs in the two peel regions (Papachristos and Papadopoulos, 2009). Citrus oils and other fruit chemical properties (see below) as well as physical properties of citrus fruits such as shape, color and structure of the surface may regulate female ovipositional decisions (Bodenheimer, 1951; Eskafi, 1988; Levinson et al., 2003; Staub et al., 2008; Papachristos and Papadopoulos, 2009; Ioannou et al., 2012). Boring into fruit peel female ovipositor may come into contact with large amounts of citrus oils that may either deter egg laying or being toxic for females (Papachristos and Papadopoulos, 2009). Hence, the density of oil glands and concentration of citrus oil into flavedo may negatively affect female fecundity rates. Physical characteristics of citrus 1011

4 fruits such as resistance of fruit peel to pressure and thickness of the flavedo were found to be rather neutral for female oviposition into citrus fruits (Papachristos and Papadopoulos, 2009). Besides fruit rind, properties of citrus fruits flesh may also affect immature development and the performance of resulting adults (Carey, 1984; Krainacker et al., 1987; Papachristos et al., 2008; Papachristos and Papadopoulos, 2009). As it was recently demonstrated the pulp of different citrus species and varieties differently affect larval performance and pupae size of C. capitata, as well as the life history traits of obtained adults (Papachristos et al., 2008; Papachristos and Papadopoulos, 2009). Pulp chemical properties, such as soluble solid contents, acidity, and ph had rather small effects on larval and pupal survival and developmental times but they significant affected pupal weight (Papachristos et al., 2008), and the performance of resulting adults (Papachristos and Papadopoulos, 2009). Differential effects of citrus fruits on both immatures developmental times and survival and adult demographic properties results in big differences in the population increase parameters of medfly in different fruit species and cultivars (Papachristos et al., 2008; Papachristos and Papadopoulos, 2009). The intrinsic rate of population increase (r) in bitter orange was estimated to be approximately 2-6 times higher than that on three sweet orange cultivars. A negative r was estimated for lemons, indicating that the population cannot sustain itself in this host. Interestingly, these findings are in agreement with field infestation data (Katsoyannos et al., 1998). STIMULATORY EFFECTS OF CITRUS COMPOUNDS ON MEDFLY OVIPOSITION In several tephritid species females tend to exploit fruit wounds including preexisting oviposition punctures as oviposition sites (Díaz-Fleischer et al., 2000). Papaj et al. (1989) showed that deep wounds that pierced the fruit pulp of sweet oranges attract gravid medfly females and elicit oviposition attempts directly into or very near the wounds. In contrast, shallow wounds that pierced only the flavedo area failed to trigger similar behaviors. Likewise Katsoyannos et al. (1997) reported response of female medflies to fruit pulp but not to flavedo chemicals. Attraction to pulp chemical and stimulatory for oviposition effects elicited by deep citrus fruit wounds may facilitate female oviposition and enhance offspring survival. Conversely, oviposition into shallow wounds may increase exposure of immatures to toxic oils resulting in enhanced mortality of young imatures, and suppression of larval growth (Katsoyannos et al., 1997; Papachristos and Papadopoulos, 2009). Although several studies suggest that odors of host fruit juice stimulate oviposition in fruit flies (Tanaka, 1965; McInnis, 1989; Vargas and Chang, 1991) the behavioral and demographic aspects have only recently determined. Females that were allowed to oviposit into pre-punctured hollow hemispheres (domes) provided with orange juice started laying eggs at a younger age, remained ovipositionactive for a longer segment of their adult life and deposited two to three times more eggs than females ovipositing in stimuli free domes (water only) (Ioannou, 2005). The chemical basis of this phenomenon remains largely unknown. Sweet orange juice is a rich mixture of several components belonging to different chemical classes such as esters, aldehydes, ketones, alcohols and terpenes (Selli et al., 2004; Gómez-Ariza et al., 2004). Three esters (ethyl hexanote and methyl and ethyl octanoate) commonly occurring in many ripe fruits including orange juice (Selli et al., 2004) enhanced synergistically the effects of natural nectarine odors with respect to the attraction and oviposition rates of gravid medflies (Light and Jang, 1996). Despite the great diversity of unrelated host species that C. capitata infests, the olfactory sensilla of female antennae are extremely capable of detecting both gradual doses of citrus peel essential oils as well as individual compounds of their composition (Light et al., 1988; Levinson et al., 1990; Hernández et al., 1996). Notwithstanding, both the extent and the manner that citrus peel volatiles regulate female oviposition decisions remained largely unknown until recently (Ioannou et al., 2012). It worthies noting that 1012

5 Levinson et al. (2003) found neutral or deterrent effects of sweet orange oil on oviposition of laboratory adapted medflies. On the other hand, Kaspi et al. (2001) suggest the use of small amounts of orange peel oils in fruit surrogates as an agent to stimulate oviposition in wild captured females. In recent experiments, it was demonstrated that small quantities of citrus oils from various species such as sweet orange, satsuma mandarin, bitter orange, grapefruit and lemon stimulate oviposition in female medflies (Ioannou et al., 2012). Within citrus species comparison reveal an inferior ability of lemon oils to increase oviposition rates resulting from the substantially different chemical composition relative to other citrus oils. Furthermore, evaluation of gradually increasing doses of sweet orange oil showed that low amounts increase oviposition while higher ones inhibit eggs laying (Ioannou et al., 2012). Given that citrus peel essential oils are considered to constitute the most important mortality factor of citrus fruits against immature stages of C. capitata (Papachristos et al., 2009), the ability of females to evaluate different doses of citrus essential oils seems to be connected with offspring fitness. Under natural conditions there might be a selective preference of females to oviposit into citrus fruits or citrus fruits sites that contain low amounts of essential peel oils thus increasing chances of immature stages survival (Papachristos and Papadopoulos, 2009). Examining the role of individual compounds (major components of the citrus oils), stimulatory, neutral and inhibitory effects on female oviposition decisions have been found (Ioannou et al., 2012). In particular, limonene, the most abundant chemical in all citrus oils, was found to stimulate oviposition, myrcene and a-pinene had a rather neutral effect, while linalool, a representative compound of immature citrus fruits associated with high toxicity against immature stages of fruit flies, elicit strong deterrent effects. Interestingly, high linalool concentrations mask and/or disrupt the stimulatory effects of limonene. The apparent tendency of females to avoid oviposition sites loaded with high linalool amounts should be interpreted as a form of maternal care. A recent study revealed that linalool was among the most toxic constituents against C. capitata larvae (Papachristos et al., 2009). Furthermore, high linalool concentrations are representative of unripe citrus fruits, and, therefore, may provide additional information for a poor larval food environment. Thus, it appears to be beneficially adaptive for females that are assessing the suitability of citrus fruits to perceive the high amounts of this chemical as indicator of both allelochemically protected and sub-nutritious oviposition sites and react to its presence as deterrent. Despite the deleterious properties of citrus essential oils against its young larvae, medfly exhibit a remarkable adaptation to citrus chemicals that at relatively low concentrations play an important stimulatory effect regarding host finding and oviposition decisions (Ioannou et al., 2012). CITRUS OILS AND MALE BEHAVIOR As it is stated above, the reproductive success of polygynous medfly males rely on establishing, in a nonrandom though within orchard pattern, leks in selected host trees (Prokopy and Hendrichs, 1979; Hendrichs et al., 1991). Lek sites require sufficient foliage density, illumination, temperature and other microhabitat properties coupled with host tree odor that may serve as the initial stimulus to attract males (Hendrichs et al., 1991; Kaspi and Yuval, 1999). Citrus trees seem to bare all these properties, as it has been found following field observations, to serve as a primary lekking site for medfly males (Hendrichs and Hendrichs, 1990; Hendrichs et al., 1991). Although the ways that leks are established remain largely unknown, it is hypothesized that odor from citrus (or other appropriate host trees) attracts founders, and then subsequent males may join because of the produced pheromone plum (Hendrichs and Hendrichs, 1990; Shelly and Villalobos, 2004). Attraction of medfly males to specific plant derived or even synthetic compound such as trimedlure, a strong male specific attractant has been reported several decades ago (Beroza et al., 1961; Shelly et al., 1993; Katsoyannos et al., 1997). Strong attraction of male, but not female, medflies to odor emanated from citrus fruits wounded on the flavedo area, especially that of sweet oranges, has been demonstrated by Katsoyannos et al. (1997). In the same study, Katsoyannos and co-workers found also strong attraction of 1013

6 males to citrus essential oils. Specific compounds such as α-copaene, a common element in the blend of many essential oils (though minor element in citrus oils, elicit strong attraction to males and contribute to lek establishment (Nishida et al., 2000). Regardless of the importance of α-copaene, it seems that citrus essential oils serve as an important resource for lek establishment. Following the first study of Katsoyannos et al. (1997) the same group demonstrated few years later that citrus oils have an additional function since it increases the mating success of males medflies (Papadopoulos et al., 2001a). Indeed males exposed to citrus peel compounds and commercial citrus oils acquire a mating advantage over non-exposed males. At almost the same time another group working independently showed similar effects of the ginger root oil (Shelly, 2001). Exposure of males to the odor emanated from fruitless citrus trees and leaves confer similar effects on male medflies (Shelly et al., 2004). Although, initially it was hypothesized that α-copaene was the responsible chemical increasing male mating success in both citrus and ginger root oils (though detected in minor quantities in citrus oils) it is recently demonstrated that compounds other than α-copaene, either alone or in combination can also triger the same phenomenon (Kouloussis et al., 2010). Males exposed to mixture of limonene, linalool, geraniol, α-pinene, and b-myrcene (1:1:1:1:1) obtained 3 out of 4 possible matings when competing against non-exposed males. Although additional work is required in the respective field current evidences suggest that linalool significantly increases the mating performance of expose males while limonene not the major component of orange oil alone or in combination with other compounds seem to be the compound responsible for enhancing medfly the mating performance of exposed males (Juan-Blasco et al., 2011). Despite some recent attempts the physiological and behavioral mechanisms underlying the increased mating performance of males exposed to orange oil remains largely unknown. Ingestion of the responsible chemicals and use into sexual pheromone synthesis has been suggested as well as interaction of citrus oils volatiles with cuticular odor has been proposed (Papadopoulos et al., 2006; Shelly et al., 2007). Males exposed to citrus oils exhibit sexual signaling at higher rates compared to non-exposed males. And, virgin females tend to arrest longer in objects emanating pheromone of exposed males giving males some extra time to complete sexual courting in a proper way (Papadopoulos et al., 2006). CONCLUSIONS Although originated in different continents, and seem to lack long co-evolutionary history, there is an intimate link between the Mediterranean fruit fly and citrus trees. There is substantial progress over the last few decades towards understanding these contradictory and complex associations, however, there are still several open questions to ask and research. Resistance of citrus fruit to medfly infestation relies largely on the outer most region of fruit tissue, the oily flavedo area. Quantitative and qualitative aspects of citrus oils in the flavedo area determine the toxic defensive properties of the different citrus fruit species and cultivars. Citrus oils affect also female ovipositional decisions in a dual function. High concentrations have deterrent and probably toxic effect for ovipositing females, while lower doses trigger and regulate oviposition in a positive way. Seasonal changes in the composition of orange oils, especially the limonene to linalool ratio seems to consist a major element that female medflies perceive to accept or reject a fruit for oviposition. Interestingly, limonene the most common and abundant component of citrus oil is listed among the most toxic compounds for larvae and it is the stimulatoriest one for oviposition. Effects of pulp chemical on development and survival of medfly larvae are less variable among citrus species and cultivars. Pulp chemicals attract both males and females and stimulate female oviposition. Whether there are common chemicals in fruit pulp and peel that elicit similar stimulatory effects needs to be determined. To understand the complexity of citrus species and medfly interaction effects of citrus oils on male reproduction behavior should be considered as well. As it is mentioned 1014

7 earlier, citrus fruits provide leking sites and also citrus oil volatiles enhance the mating performance of males. Therefore, citrus fruits provide precious resources for medfly males, and it seems that medfly has adapted to citrus fruits over few centuries of coexistence. Regardless of the substantial progress that has been done over the last few decades in understand the interactions between medfly and citrus trees there several ultimate and proximate question yet to be answered. Practical Implications Citrus breeding programs towards developing medfly resistant cultivars should focus on properties of citrus fruit rind and explore the limonene:linalool ratio. Genetic engineering could be adopted in order to modify the content of linalool into citrus fruit peel as well the ratio between linalool and limonene. Limonene alone or citrus oils in general should be used as oviposition stimuli for wild medflies at least at the first steps of domestication. Response to citrus chemicals could be included into standard quality control tests that mass reared males are regularly subjected. Large scale massive exposure of sterile medfly males to citrus oils or specific mixtures of major components should be developed with an ultimate aim to incorporate this methodology into action area wide medfly control programs. Literature Cited Aluja, M. and Mangan, R.L Fruit fly (Diptera: Tephritidae) host status determination: critical conceptual, methodological, and regulatory considerations. Annu. Rev. Entomol. 53: Aluja, M., Perez-Staples, D., Macias-Ordóñez, R., Piñeiro, J., McPheron, B. and Hernández-Ortız, V Nonhost status of Citrus sinensis cultivar Valencia and C. paradise cultivar Ruby Red to Mexican Anastrepha fraterculus (Diptera: Tephritidae). J. Econ. Entomol. 96: Back, E.A. and Pemberton, C.E Susceptibility of citrus fruits to the attack of the Mediterranean fruit fly. J. Agric. Res. 3: Beroza, M., Green, N., Gertler, S.I., Steiner, L.F. and Miyashita, D.H Insect Attractants, New Attractants for the Mediterranean Fruit Fly. J. Agric. Food Chem. 9: Birke, A., Aluja, M., Greany, P., Bigurra, E., Perez-Staples, D. and McDonald, R Long aculeus and behavior of Anastrepha ludens render gibberellic acid ineffective as an agent to reduce Ruby Red grapefruit susceptibility to the attack of pestiferous fruit flίy in commercial groves. J. Econ. Entomol. 99: Bodenheimer, F.S Citrus Entomology in the Middle East. W. Junk, The Hague, The Netherlands. Bonizzoni, M., Gomulski, L.M., Mossinson, S., Guglielmino, C.R., Malacrida, A.R., Yuval, B. and Gasperi, G Is polyandry a common event among wild populations of the pest Ceratitis capitata? Journal of Economic Entomology 99: Carey, Jr Host-specific demographic studies of the Mediterranean fruit ίy, Ceratitis capitata. Ecol. Entomol. 9: Diamantidis, A.D., Carey, Jr. and Papadopoulos, N.T Life-history evolution of an invasive tephritid. Journal of Applied Entomology 132: Diamantidis, A.D., Carey, Jr., Nakas, C.T. and Papadopoulos, N.T Populationspecific demography and invasion potential in medfly. Ecology and Evolution 1: Diamantidis, A.D., Papadopoulos, N.T., Nakas, C.T., Wu, S., Muller, H.G. and Carey, J.R Life history evolution in a globally invading tephritid: patterns of survival and reproduction in medflies from six world regions. Biological Journal of the Linnean Society 97: Díaz-Fleischer, F., Papaj, D.R., Prokopy, R.J., Norrbom, A.L. and Aluja, M

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