Nikos T. Papadopoulos

Effect of adult age, food, and time of day on sexual calling incidence of wild and mass-reared Ceratitis capitata males

The sexual calling incidence of wild and mass‐reared Mediterranean fruit fly males, Ceratitis capitata (Wiedemann) (Diptera: Tephritidae), was studied at 25 °C and a photophase of 14 h starting at 0600 h. Wild males fed on yeast hydrolysate and sugar attained sexual maturity earlier and exhibited higher calling activity than males fed on sugar alone. In both sugar and yeast hydrolysate‐fed wild males, calling levels were high during the first hours of the photophase, declined at 0900–1000 h, then increased again reaching high levels between 1200 and 1500 h, and finally declined and ceased after 1600 h. Food deprivation for 8 h or more caused a significantly lower frequency of calling. Irradiated (sterile) and unirradiated mass‐reared males fed on either sugar and yeast or sugar alone did not differ in the age of attaining sexual maturity (maximum levels of calling occurred about 8 days earlier than in the wild males). However, irradiated males fed on sugar called less frequently than males in the other treatments of mass‐reared males. The daily rhythm of calling in protein and sugar‐fed irradiated males differed somewhat from that of wild males. Calling was recorded at high levels from the beginning of the photophase until 1300 h without any decrease at 0900–1000 h. It then decreased to very low levels from 1500–1800 h and increased slightly at 1900 h. These findings are discussed in relation to the mating behavior of the fly and to the effectiveness of released sterile males in Sterile Insect Technique programs.

Seasonal and Annual Occurrence of the Mediterranean Fruit Fly (Diptera: Tephritidae) in Northern Greece

Abstract The phenology and population dynamics of the Mediterranean fruit fly, Ceratitis capitata (Wiedemann), were studied from 1991 to 1995 using Jackson traps baited with trimedlure and periodic fruit sampling in two orchards in Thessaloniki northern Greece (40.3° north latitude, 22.5° longitude). This area is located within the northernmost zone of establishment of the fly in Europe. No adults were captured from December to the end of June. The first captures were recorded from the end of June to August, depending on the year and orchard, and captures rates peaked in the autumn of each year. Significant differences were observed in adult population density and in the initiation of fly activity between two neighboring orchards (≈500 m apart) that differed in host fruit abundance and availability. The results of fruit sampling showed that apricots were the first fruits infested every year in the area of Thessaloniki. Though infested at low rates, they were very important for breeding the first summer generation, and also for the increase in C. capitata population later in the summer. Peaches and figs were important hosts for breeding the late summer and early autumn generations. Apples and other pome fruits were important hosts later in autumn (October–November), and also served as overwintering refuges for the larvae. Among 17 fruit species collected in the area 11 were found infested. Pecan [ Carya illinoensis (Wang) k. Koch] and Malus floribunda Sieb. (an ornamental tree) are reported here for the first time as hosts of C. capitata. Our findings suggest that C. capitata completes four to five generations per year in the area of Thessaloniki. Practical and theoretical implications concerning the population dynamics and the control of this fly are discussed.

Effect of orange peel substances on mating competitiveness of male Ceratitis capitata

The response of wild Ceratitis capitata (Wiedemann) (Diptera: Tephritidae) males to orange peel chemicals and their effect in mating competitiveness of males exposed to these chemicals was studied in the laboratory (25±2 °C, 65±5%, r.h.). Males were attracted, landed, and arrested on ripe oranges that were superficially wounded in the flavedo region of the peel, and fed on the wounds. Exposure to wounded oranges conferred to males a mating advantage over unexposed males. In flies of 1 to 10 days of age, this advantage was independent of the age of the flies during exposure and lasted at least 10 days following exposure. Twenty‐four hours of exposure ensured this effect. Exposure to intact oranges, or to wounded oranges covered with a wire‐screen, which allowed olfactory response and landing on the screen but not direct contact with the fruit, did not confer any mating advantage. Apparently, males required direct contact with wounded oranges in order to increase their mating competitiveness. It is suggested that the acquisition of certain substances of the flavedo, most probably through their ingestion, is responsible for the observed phenomenon. Our findings are discussed in relation to the sexual behaviour of this fly. Implications of these findings for the enhancement of the mating competitiveness of released sterile males and of the effectiveness of the Sterile Insect Technique programs are discussed as well.

Demographic window to aging in the wild: constructing life tables and estimating survival functions from marked individuals of unknown age

We address the problem of establishing a survival schedule for wild populations. A demographic key identity is established, leading to a method whereby age‐specific survival and mortality can be deduced from a marked cohort life table established for individuals that are randomly sampled at unknown age and marked, with subsequent recording of time‐to‐death. This identity permits the construction of life tables from data where the birth date of subjects is unknown. An analogous key identity is established for the continuous case in which the survival schedule of the wild population is related to the density of the survival distribution in the marked cohort. These identities are explored for both life tables and continuous lifetime data. For the continuous case, they are implemented with statistical methods using non‐parametric density estimation methods to obtain flexible estimates for the unknown survival distribution of the wild population. The analytical model provided here serves as a starting point to develop more complex models for residual demography, i.e. models for estimating survival of wild populations in which age‐at‐entry is unknown and using remaining information in randomly encountered individuals. This is a first step towards a broad new concept of ‘expressed demographic information content of marked or captured individuals’.

Spatial Autocorrelation Analysis of a Ceratitis capitata (Diptera: Tephritidae) Adult Population in a Mixed Deciduous Fruit Orchard in Northern Greece

Abstract We studied the spatio-temporal dispersion patterns of Mediterranean fruit fly, Ceratitis capitata (Wiedemann), in a mixed, deciduous, fruit orchard in Thessaloniki (northern Greece), using spatial autocorrelation methods to analyze adult trapping data. Each trapping station consisted of a Jackson trap (baited with trimedlure) and a McPhail trap (baited with ammonium acetate, putrescine, and trimethylamine). More males than females were captured throughout the season. Males and females exhibited different spatial dispersion patterns. Females were first detected during the summer (June–July) in apricot and peach trees bearing ripe fruits and significantly aggregated there toward the end of July. In the autumn, females significantly aggregated in apple orchards bearing mature fruits. Early aggregations of males were first detected in August in cherries and plums. In September, males significantly clustered in pears at the edges of the orchard, and by October, after an increase in population density, their spatial dispersion pattern became random (no significant spatial autocorrelation). At the end of the season (November), the dispersion of both sexes became random. Our results show that spatial autocorrelation statistics can provide an important tool in studying the spatial dynamics of this fly even in small orchards. Results also suggest that the incorporation of knowledge on spatial patterns into area-wide control projects may improve monitoring efforts and reduce program costs.

From trickle to flood: the large-scale, cryptic invasion of California by tropical fruit flies

Since 1954, when the first tropical tephritid fruit fly was detected in California, a total of 17 species in four genera and 11 386 individuals (adults/larvae) have been detected in the state at more than 3348 locations in 330 cities. We conclude from spatial mapping analyses of historical capture patterns and modelling that, despite the 250+ emergency eradication projects that have been directed against these pests by state and federal agencies, a minimum of five and as many as nine or more tephritid species are established and widespread, including the Mediterranean, Mexican and oriental fruit flies, and possibly the peach, guava and melon fruit flies. We outline and discuss the evidence for our conclusions, with particular attention to the incremental, chronic and insidious nature of the invasion, which involves ultra-small, barely detectable populations. We finish by considering the implications of our results for invasion biology and for science-based invasion policy.

Use of engineering geophysics to investigate a site for a building foundation

The combination of geophysical data and geotechnical measurements may greatly improve the quality of buildings under construction in civil engineering. A case study is presented here at a vacant building site. Initially, boreholes indicated a complex geology. A dipole–dipole configuration was selected for electrical resistivity tomography (ERT) implementation and the data were processed and interpreted by applying 2D and 3D inversions. An electromagnetic survey was also carried out at a different time periods and successfully used to verify the results of the resistivity measurements. It is demonstrated that engineering geophysics is able to provide solutions for determining subsurface properties and that different prospection techniques are necessary for developing a reasonable model of the subsurface structure.

Age-specific and lifetime behavior patterns in Drosophila melanogaster and the Mediterranean fruit fly, Ceratitis capitata.

Patterns of behavior were recorded every 10 min during a 2-h period each day from eclosion to death for individual Drosophila melanogaster (both sexes) and Ceratitis capitata (males-only) including walking, preening, feeding, flying, and resting for the former species, and walking, calling (signaling), supine (upside-down), and resting in the latter. Results reveal that, with the exception of preening in D. melanogaster, behavioral patterns are age-specific and the frequency of several behaviors (e.g. supine in medfly; walking and resting in D. melanogaster) are correlated with time-to-death. This is the first set of studies to report the age patterns over a range of behavioral categories throughout the lives of individuals and thus the first that systematically documents the behavior of individuals at advanced ages. We suggest that the new and unique behaviors (e.g. supine) that emerge from the aging process be referred to as degenerative behaviors, not only to distinguish them from the conventional behavioral classifications (innate, learned), but also to reflect their emergent nature.

Early Detection and Population Monitoring of Ceratitis capitata (Diptera: Tephritidae) in a Mixed-Fruit Orchard in Northern Greece

Abstract Population monitoring of the Mediterranean fruit fly, Ceratitis capitata (Wiedemann), was studied in 1998 in a mixed-fruit orchard in northern Greece, using International Pheromone McPhail traps (IPMT) baited with the female targeted attractants ammonium acetate, putrescine, and trimethylamine, and Jackson traps baited with the male specific parapheromone trimedlure. Special emphasis was placed on detecting the low initial adult population resulting from surviving overwintering larvae as early as possible in the spring and early summer. Traps were suspended on various host trees, using trap grid densities of either 15 or 1.5 traps per hectare. The first adults detected were females captured on 24 June in IPMT traps suspended on apricot trees, which are among the earliest maturing hosts in the area. From the end of July, the most effective trap was the IPMT trap placed on peaches, which followed apricots in the fruit ripening sequence. IPMT traps captured predominately females (≈80% of the total captures) and by far outperformed Jackson traps in early detection (the first males in Jackson traps were captured in August) as well as in total captures until mid-October. After mid-October, however, more flies were captured in Jackson traps. Comparing the performance of two trap grid densities on apple trees (the common host in the two grids), we found that in the high-density trap grid the first adults were detected 1 wk earlier than in the low-density trap grid. Our findings for this locality suggest that trap type and plant species on which traps are suspended are of key importance in early detection and population monitoring of C. capitata.

Response of Ceratitis capitata to citrus chemicals under semi-natural conditions

Responses of Mediterranean fruit fly Ceratitis capitata (Wiedemann) (Diptera: Tephritidae) adults to chemicals from citrus fruits were quantified in choice tests conducted in large field cages housing naturally planted orange trees, on the Greek island of Chios. Both sexes responded strongly to chemicals released from artificial cuts made in the pulp of peeled oranges and also to natural or commercial orange juice applied to the surface of yellow 7.0 cm diameter spheres. Males also responded strongly to chemicals released from cuts made in the oily region of the orange peel, or flavedo and less to sour orange and lemon. In contrast, females did not respond to flavedo chemicals. Male response to peel chemicals occurred throughout the day and increased as the number of cuts per fruit increased from 2 to 8. Contact of male mouthparts with sap from cuts, and mating attempts between males on or near the cuts were frequently observed. The males also responded to commercial essential orange oils applied to yellow spheres, but less to essential mandarin oils. The role of citrus chemicals in host finding behaviour of C. capitata and their potential use for the development of effective traps for monitoring and controlling the fly are discussed. The experimental method followed in this study can be used as a standard technique for evaluation of the quality of flies to be used in sterile insect technique programmes.