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It is well-known that Bactrocera oleae (olive fruit fly) females attract conspecific males by using 1,7-dioxaspiro[5,5]undecane (1) as the main component of their sex pheromone, and that 1 is produced in the female rectal gland. Although some authors have claimed that B. oleae males also attract females, to date no male-produced female attractants have been found in this species. In this paper, we report the first identification of a substance unique to males and able to attract females. The findings of the study include the following: (1) females responded in a bioassay to hexane extracts obtained from rectal glands of 15-day-old B. oleae males, (2) the presence of (Z)-9-tricosene (2) was consistently and unambiguously identified in these extracts using gas chromatography (GC) and GC-mass spectrometry methods, (3) in preliminary bioactivity tests, low doses (equivalent to a few males) of chemically and stereoisomerically pure synthetic (Z)-9-tricosene (2) attracted olive fruit fly females. Interestingly, compound 2, commonly called muscalure, is also a well-known component of the house fly (Musca domestica) sex pheromone.

The olive fruit fly, Bactrocera oleae, has a peculiar sexual chemoecology, guided by both male- and female-borne olfactory cues, mostly produced in rectal glands. Despite the research on B. oleae female pheromones has a long history, only few components (mainly 1,7-dioxaspiro[5.5]undecane) have been deeply investigated. Detailed evidences about the chemical identity and bioactivity of several others C10–C18 molecules produced in female rectal glands are lacking. We conducted GC and GC/EI–MS, identifying nine sex-specific chemicals and an additional compound [ethyl(Z)-9-octadecenoate], less abundant in females over males. Age-related production of all compounds raised over time. In 21-day-old females, it reached amounts from a minimum of 8.08 ng/fly (n-butyl dodecanoate) to a maximum of 87.19 ng/fly (ethyl hexadecanoate). In EAG experiments, all chemicals were perceived by both sexes. Methyl hexadecanoate and ethyl decanoate attracted males and females, respectively. This is the first report on a female-borne compound attracting conspecific females in Tephritidae. Our study sheds light on the bioactivity of female-borne pheromones involved in the B. oleae chemoecology. Further research is ongoing to test methyl hexadecanoate and ethyl decanoate as lures to enhance sex pheromone blends used in IPM programmes\ud against B. oleae, thus improving control tools against this key pest

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Dimethyl disulfide (DMDS) and dimethyl trisulfide (DMTS) are used by saprophilous insects to locate breeding sites (decaying organic matter), and by brood-site deceptive flowers to attract such insects. However, little is known about the relative importance of these two compounds in eliciting electrophysiological and behavioural responses in the insects. Here, we compared the relative attractiveness of DMDS and DMTS to saprophilous flies in field choice experiments and tested whether potential differences in field responses can be explained by differences in electrophysiological antennal responses to these compounds. Field experiments revealed that the attractiveness of a mixture of these compounds is due to DMTS alone. This result was confirmed by electroantennographic recordings in which flies of four tested species of Calliphoridae (Lucilia sericata, L. caesar, Calliphora vicina, Protocalliphora azurea) and one Muscidae (Musca domestica) respond clearly to DMTS, but not to DMDS. In house flies, however, DMTS elicited electrophysiological responses only, not reflected in behavioural assays. Despite the fact that DMTS and DMDS exhibit similar chemical structures, both the electroantennographic and field responses from saprophilous flies to these two compounds strongly differed. Our study suggests that oligosulfide-responsive saprophilous flies rely on DMTS and not DMDS for finding appropriate breeding sites and that DMTS and not DMDS could act as a key mediator for pollinator attraction in brood-site deceptive plants

Mature fruits of Olea europaea L. ‘Frantoio’ with different degrees of damage [from 0% to 100% of fruits with exit holes (EHs)] caused by the olive fruit fly (Bactrocera oleae), the key pest in Mediterranean olive orchards, were sampled to quantify the effects on free acidity, peroxide value (PV), and concentrations of secoiridoids and lignans of virgin olive oil (VOO). The total concentration of phenolic compounds and that of individual secoiridoids were negatively related to the degree of fruit damage, whereas the concentration of lignans, namely (+)-pinoresinol and (+)-1-acetoxypinoresinol, was unaffected. Free acidity was similar for the 0% and 10% EH treatments, increased sharply between 10% and 30% EH, and was similar again for the 60% and 100% EH treatments. Free acidity values were low and well within the limit for VOO classification even after 6 months of oil storage. Peroxide value responded to both B. oleae damage and storage conditions. Peroxide values increased between 10% and 30% EH treatments but changed little between the 30% and 100% EH treatments regardless of oil storage conditions. Secoiridoid concentrations closely reflected the degree of B. oleae damage when sources of variability such as cultivar and cultural practices were kept under control and conditions of processing and oil storage were optimal.

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