Nikos A. Kouloussis

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.

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.

Remating in wild females of the Mediterranean fruit fly, Ceratitis capitata

Female remating is widespread among animal taxa, and shows high interspecific diversity in frequency. While there is no consensus on general explanations for why females mate multiply, it is clear that remating rate has important implications for many evolutionary processes such as sperm competition, cryptic female choice and sexual conflict. We investigated the refractory period and the effect of sex ratio on remating in wild-derived individuals of the Mediterranean fruit fly (medfly) Ceratitis capitata (Wiedemann) (Diptera, Tephritidae), an insect pest species of major worldwide economic importance. In addition, we determined the remating rates of wild females throughout the flying season. Experiments with medflies that were the offspring of wild flies showed that remating was frequent and was observed in 3.3–13.3% of females on each of the 4 days after the first mating. Many matings thus induce only a short refractory period. Again using the offspring of wild flies, we found that female remating increased significantly under a highly male-biased sex ratio. Microsatellite analysis of offspring from wild-collected females showed that remating is common (4–28% of offspring arrays showed multiple paternity) and occurred throughout the flying season of these insects. These results have important implications for insect pest management using the sterile insect technique.

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.

Captures of the olive fruit fly Bactrocera oleae on spheres of different colours

Alighting and capture of wild olive fruit flies, Bactrocera oleae (Rossi) (Diptera, Tephritidae), on spheres of seven different colours was studied on Chios island, Greece. The 70‐mm‐diam plastic spheres, coated with adhesive, were suspended on olive trees. Yellow and orange spheres trapped the greatest number of males while red and black spheres trapped the greatest number of females. White and blue spheres were the least effective for both sexes. Peak captures occurred in the late afternoon and especially around sunset. Since mating takes place in the last hours of the photophase, the increased captures during that period may be related to the sexual behaviour of the fly. When red spheres were assessed against glass McPhail traps baited with 2% ammonium sulphate, which consist a standard tool for monitoring the olive fruit fly in Greece, there were no significant differences in male captures. However, spheres trapped almost three times as many females as McPhail traps. The possible mechanisms underlying colour discrimination, the motivation of alighting flies and the possible use of red spheres for monitoring and controlling B. oleae are discussed.

Age structure changes and extraordinary lifespan in wild medfly populations

The main purpose of this study was to test the hypotheses that major changes in age structure occur in wild populations of the Mediterranean fruit fly (medfly) and that a substantial fraction of individuals survive to middle age and beyond (> 3–4 weeks). We thus brought reference life tables and deconvolution models to bear on medfly mortality data gathered from a 3‐year study of field‐captured individuals that were monitored in the laboratory. The average time‐to‐death of captured females differed between sampling dates by 23.9, 22.7, and 37.0 days in the 2003, 2004, and 2005 field seasons, respectively. These shifts in average times‐to‐death provided evidence of changes in population age structure. Estimates indicated that middle‐aged medflies (> 30 days) were common in the population. A surprise in the study was the extraordinary longevity observed in field‐captured medflies. For example, 19 captured females but no reference females survived in the laboratory for 140 days or more, and 6 captured but no reference males survived in the laboratory for 170 days or more. This paper advances the study of aging in the wild by introducing a new method for estimating age structure in insect populations, demonstrating that major changes in age structure occur in field populations of insects, showing that middle‐aged individuals are common in the wild, and revealing the extraordinary lifespans of wild‐caught individuals due to their early life experience in the field.

Supine behaviour predicts the time to death in male Mediterranean fruitflies ( Ceratitis capitata )

Over 97% of the 203 male medflies monitored in a lifetime study of their behaviour exhibited what we term supine behaviour (temporary upside–down orientation) starting an average of 16.1 days prior to their death (mean lifespan of 61.7 days). Supine onset increased the mortality risk by 39.5–fold and a unit increase in supine level increased mortality by 26.3%. The discovery that behavioural traits in insects can be used as biomarkers of their health and to predict their time to death has important implications regarding research on morbidity dynamics, behavioural neuroethology and gerontology, and the interpretation of longevity extension in model organisms.