## 3 Volatile Pheromones
### Composition of Volatile Pheromones
Venn diagrams ([[http://bioinformatics.psb.ugent.be/webtools/Venn/](http://bioinformatics.psb.ugent.be/webtools/Venn/)]([http://bioinformatics.psb.ugent.be/webtools/Venn/](http://bioinformatics.psb.ugent.be/webtools/Venn/))) (accessed on 10 March 2021) illustrating the number of common and unique chemicals found among the compared species in the (**A**) _Ceratitis_, (**B**) _Anastrepha_, and (**C**) _Bactrocera_ genera. (**D**) For the genus _Zeugodacus_, the number of compounds emitted by _Z. cucurbitate_ are reported. Pie charts represent the proportion in chemical classes of the total number of compounds (in parenthesis) isolated for each species. In _Anastrepha_, (Z)-non-3-en-1-ol (a member of the fatty acyl compound class) is the unique compound shared among _A. fracterulus_, _A. ludens_, _A. obliqua_, and _A. suspensa_. This compound is a typical host plant component and has been shown to elicit an active behavioural response in all four species [175; 188; 193; 242; 243]. For example, _A. fracterulus_ females are attracted to (_Z_)-non-3-en-1-ol [175]. These behaviours may be interpreted as a first step in the complex mating process of this species, i.e., attracting females to the mating site. Since mating is strongly associated with host plants, the use of plant typical compounds (e.g., limonene and pinene, among others) would help females to find simultaneously mating and oviposition sites [244]. _N_-(3-methylbutyl)acetamide (carboxylic acids and derivatives class) and the three organooxygen compounds (_E,E_)-8-ethyl-2-methyl-1,7-dioxaspiro[5.5]undecane, (_E,E_)-8-methyl-2-propyl-l,7-dioxaspiro[5.5]undecane, and (_E,E_)-2,8-dimethyl-1,7-dioxaspiro[5.5] undecane are shared among _B. dorsalis s.s., B. oleae, B. zonata_ (Saunders) and _B. tryoni_. Interestingly, _N_-(3-methylbutyl)acetamide elicits female attraction in _B. dorsalis_ and _B. carambolae_, but also in _Z. cucurbiate_[72; 204; 229]. The spiroacetal (_E,E_)-2,8-dimethyl-1,7-dioxaspiro[5.5]undecane elicits an antennal response in _B. musae_ males, suggesting a biological role for this compound [76]. It is noteworthy that research efforts in investigating pheromone composition have been particularly intense in certain species such as the medfly, and this may reflect in the number of identified compounds. Future studies integrating multiple analytical approaches in all species will enable a more extensive description of the shared and unique chemical signatures of tephritid volatile pheromones. The differences in the male pheromone composition that have been reported may be partially linked to technical aspects (e.g., different sampling techniques, experimental variables such as airflow, sampling duration, and column features), as well as to several factors affecting pheromone production and release, such as the time of the day [149; 200], social context [149], food availability [199], and diet [220; 245]. Larval diet (i.e., the different host fruits utilised) and adult age affect both the total amount of pheromone emitted by males, the relative quantity of major components, and the presence of specific minor compounds in the medfly [220]. Similarly, in _A. ludens_, the profile of the male pheromone blend and the relative abundance of the chemical components change in response to different host fruits used for larval development [245]. Moreover, qualitative and quantitative differences in the composition of male-emitted volatile pheromone have been detected among laboratory strains and different populations in _A. fracterulus_[176; 177], and among laboratory strains and wild populations in _C. capitata_[221]. In addition, emission of male pheromone increases in _Anastrepha_ species in response to treatments with methoprene (a synthetic analogue of the juvenile hormone), with important implications in gaining deeper insights into tephritid reproductive physiology and in enhancing the application of management methods such as the release of sterilised males [246; 247]. The components of male pheromone also display different volatilities [248].