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Simple Summary: We demonstrate that male potato aphids respond more to a combination of volatiles from the host plant on which the species overwinters and the female sex pheromone than to the host plant alone. In both cases, the level of response declines as wind speed increases, but the higher attraction to the combined odour sources is maintained. These findings are discussed within the context of mate location by male aphids, which are insects that have little control over flight direction. In fall, alate males of the potato aphid, Macrosiphum euphorbiae (Thomas), migrate from their summer (secondary) host plants, such as potatoes, to primary host plants, such as roses, where they mate with wingless oviparae who produce the overwintering egg stage. Males are weak fliers and generally walk towards a pheromone source under windy conditions, so we tested the hypothesis that upwind walking behaviour in response to wind velocity would be affected by the volatile cues present. We compared male responses to the odour of a rugosa rose cutting alone and to the combination of host plant volatiles and the female sex pheromone under a range of wind speeds in a laboratory walking bioassay. The proportion of males responding decreased as the wind speed increased, but at all wind velocities, the responses to the combined odours were higher than to the host plant alone. However, at any given wind velocity, the speed at which responding aphids moved was not influenced by the odour source. These findings support the idea that host plant volatiles serve as long-distance cues for males and that the female sex pheromone is used once on the host plant. [ABSTRACT FROM AUTHOR]

The circadian rhythm of behavior has interested many researchers in the past decades, yet amazingly little is known on the evolution of natural variation in circadian rhythms of behavior. Most research has been focused on identifying the circadian clock genes that form an intricate clock network, which turns out to be more complex with every discovery. To understand the importance of circadian rhythms of behavior in speciation, genetic analyses should be conducted on intra- and interspecific allochronic differentiation of behaviors. Many moth species show specific daily activity rhythms in their sexual activities, some species being sexually active early at night, while others are sexually active late at night. This differentiation has been suggested to have arisen to minimize communication interference between closely related species, as co-occurring and closely related species with overlapping sex pheromone blends show a temporal differentiation in their daily sexual activities. However, the genetic differentiation of this allochronic separation has barely been examined in any species so far. In this review I summarize studies conducted on timing of sexual activities in moths, and which factors have been found to influence this timing, with the aim to identify the gaps and challenges, to unravel the possible contribution of allochronic differentiation of sexual activities in moth speciation.

Males of certain species belonging to the Bactrocera dorsalis complex are strongly attracted to, and readily feed on methyl eugenol (ME), a plant secondary compound that is found in over 480 plant species worldwide. Amongst those species is one of the world's most severe fruit pests the Oriental fruit fly, B. dorsalis s.s., and the former taxonomic species B. invadens, B. papayae and B. philippinensis. The latter species have been recently synonymised with B. dorsalis based on their very similar morphology, mating compatibility, molecular genetics and identical sex pheromones following consumption of ME. Previous studies have shown that male fruit fly responsiveness to lures is a unique phenomenon that is dose species-specific, besides showing a close correlation to sexual maturity attainment. This led us to use ME sensitivity as a behavioural parameter to test if B. dorsalis and the three former taxonomic species had similar sensitivity towards odours of ME. Using Probit analysis, we estimated the median dose of ME required to elicit species' positive response in 50% of each population tested (ED50). ED50 values were compared between B. dorsalis and the former species. Our results showed no significant differences between B. dorsalis s.s., and the former B. invadens, B. papayae and B. philippinensis in their response to ME. We consider that the Bactrocera males' sensitivity to ME may be a useful behavioural parameter for species delimitation and, in addition to other integrative taxonomic tools used, provides further supportive evidence that the four taxa belong to one and the same biological species, B. dorsalis. [ABSTRACT FROM AUTHOR]

In moth pheromone communication signals, both quantitative and qualitative intraspecific differences have been found across geographic regions. Such variation has generally been hypothesized to be due to selection, but evidence of genetic control of these differences is largely lacking. To explore the patterns of variation in pheromone signals, we quantified variation in the female sex pheromone blend and male responses of two closely related noctuid moth species in five different geographic regions for 2–3 consecutive years. We found significant variation in the ratios of sex pheromone blend components as well as in male response, not only between geographic regions but also within a region between consecutive years. The temporal variation was of a similar magnitude as the geographic variation. As far as we know, this is the first study reporting such temporal variation in moth chemical communication systems. The geographic variation seems to at least partly be controlled by genetic factors, and to be correlated with the quality of the local chemical environment. However, the pattern of temporal variation within populations suggests that optimization of the pheromonal signal also may be driven by within-generation physiological adjustments by the moths in response to their experience of the local chemical environment. [ABSTRACT FROM AUTHOR]

Periodical and age-related changes in sex pheromone signaling and response were studied in the black cutworm moth, Agrotis ipsilon. Females began to call on the first night after eclosion and called mainly during the second half of the scotophase. The percentage of females calling increased from 1- to 3-day-old females and decreased from 3- to 6-day-old females ( P < 0.001). One-day-old females called later in the scotophase than 2- and 3-day-old females ( P = 0.016). The quantity of Z7–12:Ac, Z9–14:Ac, and Z11–16:Ac in pheromone gland extracts of 1- to 6-day-old females varied with time of the photoregime, increasing during scotophase and decreasing during photophase ( P ≤ 0.001). These oscillations were described by using equations containing angular terms with a period of 24 hr. The quantities of Z7–12:Ac and Z9–14:Ac, but not of Z11–16:Ac, varied with female age during the calling period ( P < 0.001, P = 0.021, and P = 0.529, respectively). The ratios of Z9–14:Ac and Z11–16:Ac to Z7–12:Ac did not change with age or time during calling period. Male response to female pheromone in a wind tunnel increased with age and time of the scotophase. The type of response exhibited by the males (taking flight, oriented flight, and pheromone source contact) was affected by both age and time of the scotophase ( P < 0.001). [ABSTRACT FROM AUTHOR]