## 6 Tephritid Sexual Chemoecology: Real-World Applications and Challenges
### Population Monitoring and Early Detection of Tephritid Outbreaks  
Given the influence semiochemicals play on insect behaviour, a better understanding of their identity, specificity and biological role(s) may benefit tephritid research by developing novel specific and environmentally-friendly attractants. Effective attractants are essential for adult trapping, which is a key tool used to (a) monitor density and seasonal patterns of established tephritid pest populations, (b) detect new infestations of exotic species, (c) delimit the detected populations, and (d) confirm the results of eradication campaigns. Early detection of small populations is particularly important to delimit the outbreak and thus implement control and eradication measures while the pest population is still present at low densities [449; 450].  
The list of odour attractants for tephritid fruit flies is quite long including food-based (protein-based, ammonia releasing compounds) and mating-related chemicals. The later can either be purely synthetic or derived from plants. The history of their discovery and development goes beyond the purposes of this review, and their identity, efficacy, and the related practical aspects of their use in monitoring and detection are widely reviewed in [171]. Attractants that are related to the mating behaviour or physiology of fruit flies have been more thoroughly studied in the case of _Bactrocera_ and _Ceratitis_ genera and they exclusively concern male lures. For example, both the plant derived \(\alpha\)-copaene and the synthetic trimedure and Ceraluare are highly attractive to male but not female medflies [171; 451; 452]. Interestingly, both plant-derived and synthetic attractants are related to male reproductive success and may enhance lekking behaviour and mating competitiveness [453; 454; 455; 456; 457; 458]. It should be stressed here that trimedure is rather the most commonly used attractant for medfly regular population monitoring, control programs and in detection and eradication campaigns [459; 460].  
Some _Bactrocera_ species respond to Cue Lure (CL)/RK, others to ME, the most powerful attractant so far identified, others appear to be non-responsive to both. Eugenol analogues (isoeugenol, methyl-isoeugenol and dihydroenenol) are also proving successful in attracting _Bactrocera_ species [461; 462]. Similar to species of the genus _Ceratitis_, the above compounds attract only males of the _Bactrocera_ species and again are related to their mating success [463; 464; 465; 466; 467; 468]. Methyl eugenol is considered one of the most powerful attractants for male fruit flies and it is extensively used in detection, population monitoring, delimitation and eradication campaigns worldwide [170; 469; 470].  
Conversely, no male lures are currently available for _Anustrepha_ and _Rlugoletis_ spp. [171]. Exploring the potential of tephritid pheromones to develop novel specific attractants is thus important, not only for _Anustrepha_ and _Rlugoletis_, but also for non-responsive species belonging to the _Bactrocera_ and _Ceratitis_ genera. Moreover, ME has been suggested to be carcinogenic [471] and alternatives are required that also do not exert effects on non-target species. Finally, the available lures are generally effective in attracting one sex, and do not have a species-specific action.  
Although food-based attractants [472] are still dominant in population monitoring of the olive fruit fly, the use of the female pheromone can provide additional information on both the population density of wild populations and the age structure of wild populations.  
More recently, Sarles and colleagues identified two lactones released exclusively by males of _R. completea_ and used lactone-bailed traps in walnut orchards [473]. These traps have been found particularly effective for _R. completea_ monitoring and allowed its earlier detection in the season, supporting the idea that the analysis of pheromone components may be particularly promising for trapping rephritids in the field.