Responsiveness of Pseudaletia unipuncta males to the female sex pheromone

ABSTRACT. In wind tunnel experiments male response to different concentrations of synthetic pheromone varied with age. At 25°C responsiveness increased up to day 5 and then declined slightly on day 7. For any given age the level of response generally increased with an increase in pheromone concentration. Males held at 15°C (since emergence) showed a continual increase in responsiveness with age; however, overall response levels were less than at 25°C. At 25°C male response to low concentrations of pheromone (10 and 30 μg) varied markedly over a 24 h period but no differences were observed at higher concentrations (100 and 300 μg).     

Oviposition Marking Behavior of <Emphasis Type="Italic">Diachasma alloeum</Emphasis>, (Hymenoptera: Braconidae), Parasitizing <Emphasis Type="Italic">Rhagoletis pomonella</Emphasis>, (Diptera: Tephritidae)

Diachasma alloeum (Muesebeck) (Hymenoptera: Braconidae) is a solitary larval endoparasitoid attacking Rhagoletis (Diptera: Tephritidae) species. Rhagoletis pomonella (Walsh) mark the surface of fruit after oviposition with an oviposition marking pheromone (OMP) which deters conspecific female flies. Herein we demonstrate that female D. alloeum wasps reared from either apple or hawthorn race R. pomenella larvae also deposit an OMP that reduces oviposition by conspecific female wasps. Significantly fewer wasps accepted fruit that had received prior wasp oviposition and OMP or OMP alone without oviposition compared with control fruit for a minimum of 7 days on both fruit types. Rinsing fruit with a 50% ethanol solution appeared to remove the OMP rendering fruit more acceptable for oviposition than marked fruit that was not rinsed. Wasps of each host race were able to detect and avoid the OMP of the sister race and fruit substrate type did not affect wasp response to the pheromone. The possibility of an internal marker deposited during oviposition is also discussed.     

蛾类昆虫雄性信息素及其功能

昆虫性信息素是两性通讯系统的基础,其中雄性信息素的研究相对较少。本文综述了蛾类昆虫雄性信息素的研究进展。迄今已鉴定出40余种蛾类昆虫的雄性信息素,其行为学功能主要有对雌性的引诱和激欲、对同种雄性的抑制及种间隔离等。     

Response of the fruit fly parasitoid Diachasmimorpha longicaudata to host and host‐habitat volatile cues

Chemical information is crucial to insect parasitoids for successful host location. Here, we evaluated the innate response of Diachasmimorpha longicaudata (Ashmead) (Hymenoptera: Braconidae), a fruit fly larval parasitoid, to cues from host and host habitat (i.e., fruit infested with host larvae). We first assessed the preference of female parasitoids between oranges infested with Ceratitis capitata (Wiedemann) (Diptera: Tephritidae) and non‐infested fruit. Females were highly attracted towards infested oranges on the basis of volatile chemical cues. After this initial experiment, we aimed at revealing the potential sources of volatile cues present in an infested fruit. To this end, we considered five potential sources: (1) punctured fruit; (2) fly feeding, frass, or host‐marking pheromone deposited on the orange surface; (3) larval activity inside the fruit; (4) the larvae themselves; and (5) fungi associated with infestation of oranges. Habitat cues associated with host activity and those produced by rotten oranges or oranges colonized by fungi were highly attractive for female wasps, whereas odours associated with the activity of the adults on the surface of the fruit, and those released by the fruit after being damaged (as happens during fruit fly egg‐laying) were not used as cues by female parasitoids. Once the female had landed on the fruit, direct cues associated with larval activity became important although some indirect signals (e.g., products derived from larval activity inside the fruit) also increased host searching activity. Our findings indicate that naïve D. longicaudata uses chemical cues during host habitat searching and that these cues are produced both by the habitat and by the host larvae.     

Effect of synthetic and plant‐extracted aphid pheromones on the behaviour of Aphidius colemani

Parasitoid females use several chemical cues to locate hosts. A better knowledge of how they respond to a complex of these cues in a small range may help us to understand how to manipulate the parasitoids in the field. Here, the response of the aphid parasitoid Aphidius colemani to a mixture of odours of synthetic and plant‐extracted nepetalactone (a component of aphid sex pheromone) and to (E)‐β‐farnesene (aphid alarm pheromone) was investigated. The behavioural responses of A. colemani to three semiochemical groups with different concentrations were studied in a square arena. Parasitoid females were significantly attracted by the semiochemicals, when their concentrations were high, in which case the females spent more time in squares with semiochemicals. The majority of females preferred plant‐extracted nepetalactone, when it was in high concentration, but they consistently did not respond to (E)‐β‐farnesene.     

Population dynamics and economic losses caused by Zeuzera pyrina,a cryptic wood‐borer moth,in an olive orchard in Egypt

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Male Sexual Behavior and Pheromone Emission Is Enhanced by Exposure to Guava Fruit Volatiles in Anastrepha fraterculus

Background

Plant chemicals can affect reproductive strategies of tephritid fruit flies by influencing sex pheromone communication and increasing male mating competitiveness.

Objective and Methodology

We explored whether exposure of Anastrepha fraterculus males to guava fruit volatiles and to a synthetic blend of volatile compounds released by this fruit affects the sexual performance of wild and laboratory flies. By means of bioassays and pheromone collection we investigated the mechanism underlying this phenomenon.

Results

Guava volatile exposure enhanced male mating success and positively affected male calling behavior and pheromone release in laboratory and wild males. Changes in male behavior appear to be particularly important during the initial phase of the sexual activity period, when most of the mating pairs are formed. Exposure of laboratory males to a subset of guava fruit volatiles enhanced mating success, showing that the response to the fruit might be mimicked artificially.

Conclusions

Volatiles of guava seem to influence male mating success through an enhancement of chemical and physical signals related to the communication between sexes. This finding has important implications for the management of this pest species through the Sterile Insect Technique. We discuss the possibility of using artificial blends to improve the sexual competitiveness of sterile males.     

Allyl‐2,6‐dimethoxyphenol,a female‐biased compound,is robustly attractive to conspecific males of Bactrocera dorsalis at close range

Insect cuticular hydrocarbons (CHCs) play important roles in mate recognition and chemical communication. To explore the cues regulating courtship and mating behaviour in the oriental fruit fly, Bactrocera dorsalis (Hendel) (Diptera: Tephritidae), CHCs were extracted from mature virgin female and male oriental fruit flies using n‐hexane. Nine compounds – i.e., 4‐allyl‐2,6‐dimethoxyphenol (designated ‘compound 3’) and eight ester compounds – had significantly greater abundance in female samples than in males. Of these nine compounds, six (1, 2, 4, 5, 6, and 8) elicited electrophysiological responses from the antennae of male flies. Compound 3 did not elicit a detectable male antennal response, but in Y‐tube olfactometer bioassays, it exhibited robust attractiveness to conspecific males at close range. We speculate that compound 3 is a close‐range sex pheromone in B. dorsalis. A mating competition experiment revealed that compound 3 significantly increased the competitiveness of males, which implied that compound 3 might be used in control programs of B. dorsalis.     

Effect of varying monoterpene concentrations on the response of Ips pini (Coleoptera: Scolytidae) to its aggregation pheromone: implications for pest management and ecology of bark beetles

Abstract 1 Host plant terpenes can influence attraction of conifer bark beetles to their aggregation pheromones: both synergistic and inhibitory compounds have been reported. However, we know little about how varying concentrations of individual monoterpenes affect responses. 2 We tested a gradient of ratios of α‐pinene, the predominant monoterpene in host pines in the Great Lakes region of North America, to Ips pini's pheromone, racemic ipsdienol plus lanierone. 3 Ips pini demonstrated a parabolic response, in which low concentrations of α‐pinene had no effect on attraction to its pheromone, intermediate concentrations were synergistic and high concentrations were inhibitory. These results suggest optimal release rates for population monitoring and suppression programmes. 4 Inhibition of bark beetle attraction to pheromones may be an important component of conifer defences. At terpene to pheromone ratios emulating emissions from trees actively responding to a first attack, arrival of flying beetles was low. This may constitute an additional defensive role of terpenes, which are also toxic to bark beetles at high concentrations. 5 Reduced attraction to a low ratio of α‐pinene to pheromone, as occurs when colonization densities become high and the tree's resin is largely depleted, might reflect a mechanism for preventing excessive crowding. 6 Thanasimus dubius, the predominant predator of I. pini, was also attracted to ipsdienol plus lanierone, but its response differed from that of its prey. Attraction increased across all concentrations of α‐pinene. This indicates that separate lures are needed to sample both predators and bark beetles effectively. It also provides an opportunity for maximizing pest removal while reducing adverse effects on beneficial species. This disparity further illustrates the complexity confronting natural enemies that track chemical signals to locate herbivores.     

Long‐term rearing affects pheromone‐mediated flight behaviour of the Indian meal moth,Plodia interpunctella

The pest Plodia interpunctella (Hübner) is reared in many research laboratories. In a culture established in 1996, attraction of males to the female‐produced sex pheromone in flight tunnel assays gradually decreased after ≈15 years of rearing. A new culture was established to enable comparison with the old culture regarding traits associated with mate finding. Female calling activity, pheromone titre and male antennal response to pheromone components did not differ between cultures. In contrast, very few males from the old culture reached the pheromone source in flight tunnel assays compared with 61%–81% of males from the other culture. Our results highlight the importance of maintaining viable insect cultures for research purposes and suggest frequent evaluation of traits involved in chemical communication in such cultures to ensure reliable results in experiments.     

Two‐tier morpho‐chemical defence tactic in Aethionema via fruit morph plasticity and glucosinolates allocation in diaspores

Fruit dimorphism and the production of glucosinolates (GSLs) are two specific life history traits found in the members of Brassicales, which aid to optimize seed dispersal and defence against antagonists, respectively. We hypothesized that the bipartite dispersal strategy demands a tight control over the production of fruit morphs with expectedly differential allocation of defensive anticipins (GSLs). In dimorphic Aethionema, herbivory by Plutella xylostella at a young stage triggered the production of more dehiscent (seeds released from fruit) than indehiscent fruit morphs (seeds enclosed within persistent pericarp) on the same plant upon maturity. Total GSL concentrations were highest in the mature seeds of dehiscent fruits from Aethionema arabicum and Aethionema saxatile among the different ontogenetic stages of the diaspores. Multivariate analyses of GSL profiles indicated significantly higher concentrations of specific indole GSLs in the diaspores, which require optimal defence after dispersal (i.e., seeds of dehiscent and fruit/pericarp of indehiscent fruit). Bioassays with a potentially coinhabitant fungus, Aspergillus quadrilineatus, support the distinct defensive potential of the diaspores corresponding to their GSL allocation. These findings indicate a two‐tier morpho‐chemical defence tactic of Aethionema via better protected fruit morphs and strategic provision of GSLs that optimize protection to the progeny for survival in nature.     

Coordination of Raiding and Emigration in the Ponerine Army Ant Leptogenys distinguenda (Hymenoptera: Formicidae: Ponerinae): A Signal Analysis

Several glandular sources of trail pheromones have been discovered in army ants in general. Nevertheless, at present the understanding of the highly coordinated behavior of these ants is far from complete. The importance of trail pheromone communication for the coordination of raids and emigrations in the ponerine army ant Leptogenys distinguenda was examined, and its ecological function is discussed. The secretions of at least two glands organize the swarming activities of L. distinguenda. The pygidial gland is the source of an orientation pheromone holding the group of raiding workers together. The same pheromone guides emigrations to new nest sites. In addition, the poison sac contains two further components: one with a weak orientation effect and another which produces strong, but short-term attraction and excitement. The latter component is important in prey recruitment and characterizes raid trails. This highly volatile recruitment pheromone allows the extreme swarm dynamic characteristic of this species. Emigration trails lack the poison gland secretion. Due to their different chemical compositions, the ants are thus able to distinguish between raid and emigration trails. Nest emigration is not induced chemically, but mechanically, by the jerking movements of stimulating workers.     

Orientation of male gypsy moths,Lymantria Dispar (L.), to pheromone sources: The role of olfactory and visual cues

The role of olfaction and vision in the close-ranging flying and walking orientation of male gypsy moths, Lymantria dispar(L.), to females was studied in the forest and in the laboratory. In the forest, feral males found an isolated pheromone source as readily as one supplemented with female visual cues; dead, acetonerinsed females deployed without pheromone received virtually no visitations. In flight tunnel choice experiments using cylinders as surrogate trees and pheromone in different spatial configurations, visual attributes of the female did not influence either the males' choice of landing site or the efficiency with which they located the female. Rather, the presence of pheromone on the cylinder was necessary to elicit orientation as well as landing and walking on the cylinder. When a female visual model was placed in various positions around a pheromone source, walking males oriented primarily to the chemical stimulus. There were, however, indications that males would alter their walking paths in response to female visual cues over short distances (<5 cm), but only if they continued to receive pheromone stimulation. When visual and chemical cues were abruptly uncoupled by altering the trajectory of the pheromone plume, most males responded to the loss of the odor cue rather than to visual cues from the female. Temporal pheromone stimulation patterns affected male walking orientation. When stimulated by pheromone, males oriented toward the source; loss of the odor cue prompted an arearestricted local search characterized by primarily vertical and oblique movements with frequent reversals in direction. Presumably these maneuvers enhance the likelihood of recontacting the plume or serendipitously encountering the female. The apparent lack of visual response to the female is discussed in light of morphological and behavioral evidence suggesting that gypsy moths were formerly nocturnal.     

Sexual selection in a tropical fruit fly: role of a plant derived chemical in mate choice

The specific mechanisms by which selective pressures affect individuals are often difficult to resolve. In tephritid fruit flies, males respond strongly and positively to certain plant derived chemicals. Sexual selection by female choice has been hypothesized as the mechanism driving this behaviour in certain species, as females preferentially mate with males that have fed on these chemicals. This hypothesis is, to date, based on studies of only very few species and its generality is largely untested. We tested the hypothesis on different spatial scales (small cage and seminatural field‐cage) using the monophagous fruit fly, Bactrocera cacuminata. This species is known to respond to methyl eugenol (ME), a chemical found in many plant species and one upon which previous studies have focused. Contrary to expectation, no obvious female choice was apparent in selecting ME‐fed males over unfed males as measured by the number of matings achieved over time, copulation duration, or time of copulation initiation. However, the number of matings achieved by ME‐fed males was significantly greater than unfed males 16 and 32 days after exposure to ME in small cages (but not in a field‐cage). This delayed advantage suggests that ME may not influence the pheromone system of B. cacuminata but may have other consequences, acting on some other fitness consequence (e.g., enhancement of physiology or survival) of male exposure to these chemicals. We discuss the ecological and evolutionary implications of our findings to explore alternate hypotheses to explain the patterns of response of dacine fruit flies to specific plant‐derived chemicals.     

Engineering d‐limonene synthase down‐regulation in orange fruit induces resistance against the fungus Phyllosticta citricarpa through enhanced accumulation of monoterpene alcohols and activation of defence

Terpene volatiles play an important role in the interactions between specialized pathogens and fruits. Citrus black spot (CBS), caused by the fungus Phyllosticta citricarpa, is associated with crop losses in different citrus‐growing areas worldwide. The pathogen may infect the fruit for 20–24 weeks after petal fall, but the typical hard spot symptoms appear when the fruit have almost reached maturity, caused by fungal colonization and the induction of cell lysis around essential oil cavities. d ‐Limonene represents approximately 95% of the total oil gland content in mature orange fruit. Herein, we investigated whether orange fruit with reduced d ‐limonene content in peel oil glands via an antisense (AS) approach may affect fruit interaction with P. citricarpa relative to empty vector (EV) controls. AS fruit showed enhanced resistance to the fungus relative to EV fruit. Because of the reduced d ‐limonene content, an over‐accumulation of linalool and other monoterpene alcohols was found in AS relative to EV fruit. A global gene expression analysis at 2 h and 8 days after inoculation with P. citricarpa revealed the activation of defence responses in AS fruit via the up‐regulation of different pathogenesis‐related (PR) protein genes, probably as a result of enhanced constitutive accumulation of linalool and other alcohols. When assayed in vitro and in vivo, monoterpene alcohols at the concentrations present in AS fruit showed strong antifungal activity. We show here that terpene engineering in fruit peels could be a promising method for the development of new strategies to obtain resistance to fruit diseases.     

Euschistus conspersus female morphology and attraction to methyl (2E,4Z)-decadienoate pheromone–baited traps in processing tomatoes

Previous work documented seasonal field response dynamics of Euschistus conspersus Uhler (Heteroptera: Pentatomidae) to Euschistus spp. pheromone [methyl (2E,4Z)‐decadienoate]‐baited traps in California processing tomatoes, Lycopersicon esculentum (Miller) (Solanaceae). A laboratory phenology model has been reported for E. conspersus egg incubation to adult emergence. In the present work, reproductive and thoracic dissections were performed on female E. conspersus collected year‐round from seasonal habitats in California's Central Valley. We used these dissection data to establish relationships between the morphology of E. conspersus and time of year, habitat, sample recovery method, and female attraction to pheromone traps in commercial tomato fields. All ovariole categories, sexually immature through postreproductive, were recorded for females collected from tomatoes by plant‐beating sample throughout the growing season. Conversely, pheromone trap captures in tomatoes over the same period revealed that females entering the traps were exclusively reproductively active with matured eggs. We conclude that early season female‐biased E. conspersus pheromone trap catch can be used to establish a ‘biofix’ from which to accumulate degree days and forecast nymphal development in the field. Focusing control efforts on the more susceptible nymph stages may improve efficacy of reduced‐risk insecticides such as the neonicotinoids. Thoracic dissection results, with no significant difference in flight muscle size or color by ovariole condition, failed to support our hypothesis of a life history trade‐off between female reproductive activity and flight capability to explain a decline in female pheromone trap response during the mid‐summer tomato‐fruiting stages. The adaptive value of the observed retention of E. conspersus flight capability over the calendar year, and across reproductive stages, is discussed.     

江苏无锡梨小食心虫发生动态及性诱剂防治

利用性诱剂调查江苏无锡地区三个水蜜桃Prunus persica种植区梨小食心虫Gtapholitha molesta成虫的年发生动态,并比较不同时间挂放诱芯的诱集效果。结果表明,在无锡地区,梨小食心虫年发生5代,部分发育较快的五代幼虫在越冬前发育为成虫,但因无法找到合适的产卵场所而成为无效虫口。越冬代成虫和一代成虫发生较为整齐,可以使用性诱剂集中诱杀,但从二代成虫开始,发生呈现多个高峰,田间世代重叠明显。对梨小食心虫的性诱剂防治试验表明,在无锡地区,需高密度放置诱芯并2周更换1次诱芯方能达到防治效果。     

Environmental conditions terminate reproductive diapause and influence pheromone perception in the long‐lived moth Caloptilia fraxinella

Reproductive diapause enables long‐lived insects to time mating with environmental conditions suitable for offspring development. Plasticity in the perception of pheromones used in sexual communication may enable mate‐finding at the appropriate time of year. The moth Caloptilia fraxinella (Ely) (Lepidoptera: Gracillariidae) undergoes a 9‐month reproductive diapause, during which the male response to pheromone is plastic and is highest during the period of reproductive activity. The mechanisms controlling this pheromone response plasticity are not well‐understood, and the aim of the present study is to determine the main factors involved. In the present study, the impact of temperature, photoperiod, juvenile hormone analogue (JHA) and adult nutrition on diapause termination are tested using electroantennogram (EAG) and behavioural response to pheromone in male C. fraxinella. Eclosion in a state of reproductive diapause occurs in most males; diapause is maintained under short‐day or cool conditions indoors, or under natural conditions outdoors. Exposure to long‐day, warm conditions over a period of 4 weeks causes a small number of males to become behaviourally responsive to pheromone; a larger number of males become behaviourally responsive over a period of 3 months of post‐eclosion. Treatment with a JHA impacts male EAG and the behavioural response to pheromone during the period of reproductive diapause. A carbohydrate food source is not required by reproductively active adult male C. fraxinella to respond to pheromone and express mate location behaviours. The main factors involved in controlling male pheromone response plasticity and the implications of these factors for the C. fraxinella population in its expanded range are discussed.     

Vertebrate responses to fruit production in Amazonian flooded and unflooded forests

We document patterns of fruit and vertebrate abundance within an extensive, virtually undisturbed mosaic of seasonally flooded (várzea and igapó) and unflooded (terra firme) forests of central Amazonia. Using phenological surveys and a standardised series of line-transect censuses we investigate the spatial and temporal patterns of immature and mature fruit availability and how this may affect patterns of habitat use by vertebrates in the landscape. All habitats showed marked peaks in fruiting activity, and vertebrate detection rates varied over time for most species both within and between forest types. Many arboreal and terrestrial vertebrates used both types of flooded forest on a seasonal basis, and fluctuations in the abundance of terrestrial species in várzea forest were correlated with fruit availability. Similarly, the abundance of arboreal seed predators such as buffy saki monkeys (Pithecia albicans) and macaws (Ara spp.) were closely linked with immature fruit availability in terra firme forest. We conclude that highly heterogeneous landscapes consisting of terra firme, várzea and igapó forest appear to play an important role in the dynamics of many vertebrate species in lowland Amazonia, but the extent to which different forest types are used is highly variable in both space and time.