Percentage Of Mating Research Articles

Response of Reproductive Traits and Longevity of Beet Webworm to Temperature, and Implications for Migration

Beet webworm, Loxostege sticticalis (L.) is a facultative long-distance migratory insect pest in many regions between 36° and 55° N latitude. The outbreaks of larvae are closely related to temperatures encountered by the immigrant adult. But mechanisms linking population outbreaks and migration are not well understood. We investigated the effect of exposing adults to constant temperatures from 14 to 34°C on mating, oviposition, and longevity. Our results showed that both mating percentage and frequency were highest at 22–26°C and decreased at temperatures outside this optimal range. Time of night when mating began was delayed at higher temperatures, while mating duration progressively decreased with increasing temperature. Both preoviposition period (POP) and oviposition period decreased linearly with increasing temperature. Peak daily and lifetime fecundity were highest at 22–26°C and declined at temperatures outside this range, suggesting that 22–26°C is the optimal thermal range for oviposition. Adult longevity was negatively correlated with temperature. Males lived longer than females at lower temperatures, but females lived longer than males in the 30–34°C treatments. Together, our findings suggest that reproduction occurs when the prevailing temperature is around 22–26°C, and that migratory flight is favored outside this range via increases in POP and proportion of virgins. We predict that larval damage or outbreaks of L. sticticalis will occur only in areas where the prevailing temperature is around 22–26°C, which provides a key basis for the prediction of population outbreaks in areas of immigration.

Effect of increased male and female age at mating on the reproductive performance of Cnaphalocrocis medinalis (Crambidae: Lepidoptera).

The success of mating disruption using synthetic sex pheromones depends not only on preventing mating, but also on delayed mating in the target insect. Using the rice leaffolder moth, Cnaphalocrocis medinalis (Guenée), we determined the effect of increased age at mating imposed on males only (male treatment), females only (female treatment),or on both sexes simultaneously (both sexes treatment). These increased age treatments had a negative effect on the percentage of mating, the total number of eggs, and the hatchability. The female reproductive performance in C. medinalis was decreased with increased moths' age. The both sexes treatment had the most potent negative effect on reproductive performance. Longevity of mated moths and duration of the preoviposition period in C. medinalis were not significantly different among these increased age treatments. The underlying mechanisms causing a decline in female reproductive performance of C. medinalis when increased age was imposed on males versus females and the potential of using mating disruption strategies to control the populations in paddy fields are discussed.

Mating disruption of the carpenter moth, Cossus insularis (Staudinger) (Lepidoptera: Cossidae) with synthetic sex pheromone in Japanese pear orchards

Mating disruption of the carpenter moth, Cossus insularis Staudinger (Lepidoptera: Cossidae), with a synthetic version of its sex pheromone, a mixture of (E)-3-tetradecenyl acetate and (Z)-3-tetradecenyl acetate, was tested for three successive years in Japanese pear (Pyrus pyrifolia var. culta) orchards. Pheromone trap catches, percentage mating of tethered females, and tree damage were measured in both the pheromone-treated and untreated control orchards. The attraction of male adults to pheromone traps was completely disrupted, and the mating of the tethered females was completely inhibited by the treatment of synthetic pheromones. The percentage of damaged trees in the pheromone-treated orchard decreased over the course of the experiment, while the damage percentage did not decrease in the untreated orchard. These results show that mating disruption with the synthetic sex pheromone is promising for the reduction of damage caused by C. insularis in apple and Japanese pear orchards.

Molecular tools for sterile sperm detection to monitor Ceratitis capitata populations under SIT programmes

The success of an area-wide sterile insect technique (SIT) programme against Ceratitis capitata (Wiedemann) (Diptera: Tephritidae) relies on the mating success of sterile males in the field. Limited information is available about the effectiveness of sterile males in achieving mates with wild females and how these matings contribute to reducing wild populations. To this end, firstly a mating competition test was performed in the laboratory with different release ratios (1:1:0, 1:1:1, 1:1:5, 1:1:10 and 1:1:20 for wild females:wild males:sterile VIENNA-8 males respectively) and different host fruit. Secondly, the same release ratios were evaluated under semi-natural conditions on caged trees and on sentinel host. By means of molecular markers, VIENNA-8 male sperm was positively detected in those females exposed to the male ratios 1:5, 1:10 and 1:20 in the laboratory. In the field test, sterile VIENNA-8 male matings and the C. capitata progeny on apples were positively correlated with the ratio of sterile males released and with the percentage of sterile matings respectively. These results confirm the validity of using the molecular detection of VIENNA-8 male sperm to predict the C. capitata population under semi-natural conditions. Implications of these results in measuring the efficacy of an SIT programme are discussed.

Modelling female mating success during mass trapping and natural competitive attraction of searching males or females

AbstractSimulation models of insects encountering sex pheromone with or without mass trapping in which the searching sex is either male (moths and many insect species) or female (some true bugs, beetles, and flies) were developed. The searching sex moved as a correlated random walk, while the opposite sex remained stationary (calling) and released an attractive sex pheromone. The searching sex was caught when encountering a pheromone‐baited trap, and females mated when encountering a male. An encounter with pheromone was defined by the searcher's interception of a circle termed the effective attraction radius (EARc). Parameters of movement (speed and duration), initial numbers of calling sex and searching sex, number of traps, area, and EARc of traps and calling sex were varied individually to evaluate effects on the percentage of females mating. In the natural condition without traps, female mating success in both models was identical. Increasing the EARc of the calling sex caused diminishing increases in female mating success, suggesting that evolution of larger pheromone release and EARc is limited by increasing costs (production/sensitivity) relative to diminishing increases and benefits of mating encounters. With mass trapping, increasing the EARc of traps or density of traps caused similar declines in female mating in both models, but the female‐searching model predicted slightly lower mating success than the male‐searching model. Increasing the EARc of calling insects or the initial density of insects caused similar increases in female mating in both models, but again the female‐searching model had slightly lower mating success than the male‐searching model. The models have implications for mating lek formation and for understanding the variables affecting the success of mass trapping programs for insect pests with either male or female sex pheromones.

Enhancing efficacy of Mexican fruit fly SIT programmes by large‐scale incorporation of methoprene into pre‐release diet

AbstractThe juvenile hormone analogue, methoprene, has been documented to accelerate the development of reproductive competence and sexual signalling of Caribbean (Anastrepha suspensa), the Mexican (Anastrepha ludens), the South American (Anastrepha fraterculus) and West Indian (Anastrepha obliqua) tephritid fruit flies. The incorporation of methoprene into sterile fly release protocols at fly emergence and handling facilities is a key step required for large‐scale application of the technology to field release strategies. The goal of our study was to develop a method to supply, in large scale, methoprene to sterile Mexican fruit flies for release in the current Sterile Insect Technique (SIT) programme in Mexico. In field cage tests, the isolation index of sterile males after treatment with methoprene was reduced, increasing the percentage of mating between laboratory sterile males and wild females. In laboratory trials, males fed a diet containing 0.05% or 0.1% methoprene mated 4‐day earlier than untreated control males. In a pilot area tested in 3500 ha to measure the impact of the sterile releases when methoprene was supplied, no adult wild flies were detected and no larvae were found after sampling more than 330 kg of fruit both in the treated and untreated blocks. Based on the results obtained in this study, we recommend the incorporation of the methoprene on adult diet to improve the Mexican fruit fly male sexual performance when release in the field, contributing to the increase in the cost‐effectiveness of the SIT programme.

Interspecific Hybridization of the Imported Bumblebee B. terrestris and the Korean Native Bumblebee Bombus hypocrita sapporoensis

The large bumblebee, Bombus terrestris, indigenous to Europe and adjacent area, and used extensively for high‐value crop pollination, has been artificially introduced to several parts of the world. Here we show the interspecific hybridization between the bumblebee species, B. hypocrita sapporoensis and B. terrestris, under laboratory conditions. The mating and oviposition percentages resulting from the interspecific hybridization of a B. terrestris queen with a B. h. sapporoensis male were higher than those resulting from the intraspecific mating of B. h. sapporoensis. Furthermore, a competitive copulation experiment indicated that the mating of B. h. sapporoensis males with B. terrestris queens was 1.2‐fold more frequent than the mating of these males with B. h. sapporoensis queens. The interspecific hybridization of a B. terrestris queen with a B. h. sapporoensis male produced either B. terrestris workers or the B. terrestris male phenotype, and the hybridization of a B. h. sapporoensis queen with a B. terrestris male produced B. h. sapporoensis males. Our results indicated that interspecific hybridization occurred between B. h. sapporoensis and B. terrestris. The results suggest that such hybridization will have a negative competitive impact and will cause genetic contamination of native bumblebees.

Interspecific Hybridization of the Korean Native Bumblebee Bombus hypocrita sapporoensia and the European Bumblebee B. terrestris

The large bumblebee <TEX>$Bombus$</TEX> <TEX>$terrestris$</TEX>, indigenous to Europe and adjacent areas and used extensively for high-value crop pollination, has been artificially introduced to several parts of the world. Here we show the occurrence of interspecific hybridization between the bumblebee species <TEX>$B.$</TEX> <TEX>$hypocrita$</TEX> <TEX>$sapporoensia$</TEX> and <TEX>$B.$</TEX> <TEX>$terrestris$</TEX> under laboratory conditions. The mating and oviposition percentages resulting from the interspecific hybridization of a <TEX>$B.$</TEX> <TEX>$terrestris$</TEX> queen with a <TEX>$B.$</TEX> <TEX>$h.$</TEX> <TEX>$sapporoensis$</TEX> male were higher than those resulting from the intraspecific mating of <TEX>$B.$</TEX> <TEX>$h.$</TEX> <TEX>$sapporoensis$</TEX>. Furthermore, a competitive copulation experiment indicated that the mating of <TEX>$B.$</TEX> <TEX>$h.$</TEX> <TEX>$sapporoensis$</TEX> males with <TEX>$B.$</TEX> <TEX>$terrestris$</TEX> queens was 1.2-fold more frequent than the mating of these males with <TEX>$B.$</TEX> <TEX>$h.$</TEX> <TEX>$sapporoensis$</TEX> queens. The interspecific hybridization of a <TEX>$B.$</TEX> <TEX>$terrestris$</TEX> queen with a <TEX>$B.$</TEX> <TEX>$h.$</TEX> <TEX>$sapporoensis$</TEX> male produced either <TEX>$B.$</TEX> <TEX>$terrestris$</TEX> workers or the <TEX>$B.$</TEX> <TEX>$terrestris$</TEX> male phenotype, and the hybridization of a <TEX>$B.$</TEX> <TEX>$h.$</TEX> <TEX>$sapporoensis$</TEX> queen with a <TEX>$B.$</TEX> <TEX>$terrestris$</TEX> male produced <TEX>$B.$</TEX> <TEX>$h.$</TEX> <TEX>$sapporoensis$</TEX> males. Our results indicated that interspecific hybridization occurred between <TEX>$B.$</TEX> <TEX>$h.$</TEX> <TEX>$sapporoensis$</TEX> and <TEX>$B.$</TEX> <TEX>$terrestris$</TEX>. These results suggest that such hybridization will have a negative competitive impact and will cause genetic contamination of native bumblebees.

Ginger root oil increases mating competitiveness of sterile Mediterranean fruit fly (Diptera:Tephritidae) in Western Australia

AbstractThe exposure of sterile male Mediterranean fruit fly, Ceratitis capitata (Wiedemann) to the aroma of essential oil derived from ginger root Zingiber officinale Roscoe (GRO) has been shown in field cage trials to increase their mating success. This field cage study compared the mating performance of mass reared sterile Mediterranean fruit fly males prepared for ground release programmes under four different post‐irradiation systems, two of which involved exposure of the flies to GRO aroma. In the first system, irradiated pupae were placed into non‐vented 5‐L paper tubs, individually aromatized by 20 μl of GRO (4 ml/m3) for 96–120 h until the adults were 2–3 days old. In the second system, irradiated pupae were placed in vented 5‐L paper tubs, exposed for 24 h in a GRO aromatized room (0.5 ml/m3) when the adults were 3 days old and contained until required for mating tests at 5 days old. The third and fourth systems were the same as the first two systems respectively, except that the flies were not exposed to GRO aroma. Significant differences in mating success were found among treatments. The exposure of 2 to 3‐day old flies to GRO aroma improved mating performance slightly compared with equivalent non‐exposed flies, but it was still below the minimum value accepted under international standards, while 27% of unexposed 5‐day‐old sterile males mated and had competitiveness (Fried value 0.38) slightly above this minimum level. GRO exposed 5‐day‐old flies had the highest mating percentage (67%) and a level of competitiveness (Fried value 1.81) based on induced sterility above that of wild flies (Fried value 1). The results indicate that the effectiveness of sterile male ground release programmes can be increased significantly by releasing 5‐day‐old sterile males that have been exposed to GRO in an entirely aromatized adult fly holding room.

Synergistic effects of olfactory and tactile cues in short-range mate finding of Ophraella communa

Sensory signals between individuals are important in short-range mate finding. The purpose of our experiments was to verify the roles of different sensory cues in mate orientation and discrimination in Ophraella communa LeSage (Coleoptera: Chrysomelidae) adults. Sex discrimination and sensory deprivation tests (i.e., depriving the olfactory and/or visual senses of either or both sexes by coating with paint) were conducted in the laboratory. Male O. communa were able to locate and recognize conspecifics using olfactory cues prior to physical contact, but could not discriminate the opposite sex prior to physical contact. When the olfaction of male O. communa was deprived by painting antennae, males spent significantly longer times seeking mates in the arena. Copulation duration did not differ significantly among treatments. Thus, the mating process of O. communa adults was mediated by contact cues, but not by olfactory cues. The percentages of successful mating, searching duration, and copulation duration were all unaffected by visual deprivation, i.e., when the eyes of either or both sexes were covered by black paint. The function of visual cues was thus negligible in the mate-finding process of O. communa adults. Overall, these results suggested that orientation and discrimination of the opposite sex by O. communa is dependent on the synergy between olfactory and tactile cues.

Nymphs of the common bed bug (Cimex lectularius) produce anti-aphrodisiac defence against conspecific males

BackgroundAbdominal wounding by traumatic insemination and the lack of a long distance attraction pheromone set the scene for unusual sexual signalling systems. Male bed bugs (Cimex lectularius) mount any large, newly fed individual in an attempt to mate. Last instar nymphs overlap in size with mature females, which make them a potential target for interested males. However, nymphs lack the female's specific mating adaptations and may be severely injured by the abdominal wounding. We, therefore, hypothesized that nymphs emit chemical deterrents that act as an honest status signal, which prevents nymph sexual harassment and indirectly reduces energy costs for males.ResultsBehavioural mating assays showed that males mount nymphs significantly shorter time compared to females, although initial mounting preference was the same. In support of our hypothesis, nymphs experienced the same percentage of mating with sperm transfer as females if they were unable to emit (E)-2-hexenal, (E)-2-octenal 4-oxo-(E)-2-hexenal and 4-oxo-(E)-2-octenal, from their dorsal abdominal glands. We report that the aldehydes and 4-oxo-(E)-2-hexenal are detected by olfactory receptor neurons housed in smooth and grooved peg sensilla, respectively, on the adult antennae, at biologically relevant concentrations. Behavioural experiments showed that application of 4-oxo-(E)-2-hexenal or the two aldehydes at a nymph-emitted ratio, to a male/female pair during mounting initiation, decreased mating frequency to a rate comparable to that of a male/nymph pair.ConclusionsBy combining behavioural and sensory studies, we show that the nymph-specific alarm pheromone plays an important role in intra-specific communication in the common bed bug. Alarm pheromones are commonly looked upon as a system in predator/prey communication, but here we show that alarm pheromones may be used as multipurpose signals such as decreasing the risk of nymphal mating by males.See commentary: http://www.biomedcentral.com/1741-7007/8/117

IMPACT D'UN CENTRE CUNICOLE DE RECHERCHE ET D'INFORMATION SUR LA RECHERCHE ET LE DÉVELOPPEMENT DE LA CUNICULTURE AU BENIN

lnvestigation results published in 1988 showed that despite of favourable conditions for a quick development of the rabbit rearing in Republic of Benin, many actions were still needed to be led in this domain for research, formation and information. To satisfy these obligations, CECURI (Rabbit Research and lnformation Center) was created. lts vocation is the increasing of the knowledge about rabbit as animal production species, the way of its breeding and all its pathology, in order to inprove local production and to extend a rational method for rearing this herbivore, by a very large information. Despite dithering before starting and poor exploitation results, linked to the lake of experience during the first year, CECURI was quickly qualified for the economic and technical management of its demonstration breeding unit. In 1988 the percentage of fertile mating was only 45 % ; it was increase upto 80 % in 1991. During the sama period, the number of youngs per litter at weaning and mortality from weaning to the slaughter age were also improved : 2.8 and 40 % respectively in 1988 and 5.1 and 5 % in 1991. Another way, in spite of short means since the creation, its impacts on research and rabbitries development are fully positiva obvious increasing of the researchers number, intensification of their activities, introduction of the rabbit breeding programme into agricultura! secondary school and university, retrain and advanced training for technicians and rabbit breeders, spray of results oustanding breeders, increasing of the number of small rabbitries around towns and village countries, creation of a Rabbit Breeders Association in Bénin, sensibilization of the financia! partners, holding on March 1992 an african rabbit congress ... etc. However, for a quicker and lasting development of this section, the activities of such a center must be helped by even regional programme timming.

Changes of Sex Pheromone Communication Systems Associated with Tebufenozide and Abamectin Resistance in Diamondback Moth, Plutella xylostella (L.)

Many insect pests have evolved resistance to insecticides. Along with this evolution, the sex pheromone communication system of insects also may change, and subsequently reproductive isolation may occur between resistant and susceptible populations. In this study of the diamondback moth, we found that resistant females (especially Abamectin resistant females) produced less sex pheromone and displayed a lower level of calling behavior. Resistant males showed higher EAG responsiveness to the sex pheromone mixture of females, and responded to a broader range of ratios between the two major components compared to the responses of susceptible moths. In addition, wind tunnel experiments indicated that changes associated with insecticide resistance in the Abamectin resistant strain (Aba-R) significantly reduced female attractiveness to susceptible males. Furthermore, mating choice experiments confirmed that non-random mating occurred between the two different strains. Aba-R females with an abnormal pheromone production and blend ratio exhibited significantly lower mating percentages with males from either their own strain or other strains, which corroborates the results obtained by the wind tunnel experiments. The implications of this non-random mating for insect speciation and insecticide resistance management are discussed.

Effect of γ-irradiation on the biology and ultrastructure of haemocytes of greater wax moth, Galleria mellonella (L.) (Lepidoptera: Galleridae)

This study was carried out on fully grown pupae of greater wax moth, Galleria mellonella L., gamma-irradiated to 100, 150, 300 and 400Gy. The four doses given to male parents in the F(1) generation decreased the average number of eggs per mated female, the percentage of egg hatching and the percentage of mating in both the male and female lines; the effects increased with the dose. Dose dependence of the reduction in the fecundity and the percentage of egg hatching among the female line pairings (female descendants of irradiated parental male pupae) was more significant than among the male line pairings (male descendants of irradiated parental male pupae). We also examined morphological changes in the irradiated blood cells using transmission electron microscopy (TEM). Vacuolization of the cytoplasm, disorganization and swelling of mitochondria were found.

Mating status of bumblebees, Bombus terrestris (Hymenoptera: Apidae) with notes on ambient temperature, age and virginity

The mating status of Bombus terrestris in relation to ambient temperature, queen to male ratio in the mating cage, age and virginity of sexuals were studied in the laboratory. Results showed that ambient temperature ranging from 17 to 29°C had a significant effect on the mating percentage of individuals, with queen to male ratios of 1 : 1.5 and 1 : 2. The highest mating percentage (76.9±1.9%) was found at 23°C, with a queen to male ratio of 1 : 1.5, and the lowest percentage (67.3±2.1%) was observed at 29°C with a queen to male ratio of 1 : 2. Both virgin and previously mated males preferred young and virgin queens, and showed a statistically higher mating success, indicating that male virginity and experience had identical effects on male mating fitness. Virgin queens that failed to mate at 7 days old showed a lower percentage of mating success with increasing age, indicating that female copulation fitness depended on their age.

Effect of Metarhizium anisopliae inoculation on the mating behavior of three species of African Tephritid fruit flies, Ceratitis capitata, Ceratitis cosyra and Ceratitis fasciventris

Bioassays were carried out in the laboratory to investigate the effect of inoculation by Metarhizium anisopliae on mating behavior of three species of fruit flies, Ceratitis cosyra, C. fasciventris and C. capitata. In all three species, inoculation by the fungus resulted in significant delay in the commencement of calling and mating of treated males as they spent substantial amount of time in grooming activity. In fungus-treated male flies, calling and mating started at 70.0–80.0 min after exposing them to untreated females. However, when females were treated, calling and mating started from 15.0 to 16.0 min. Fungus-treated males competed equally with untreated males for virgin female flies from day 0 to day 2 post-inoculation. There were, however, significant differences on day 3, with untreated males of the three fruit fly species having higher percentage of paring than fungus-treated males. There was no significant difference in the duration of pairing of fungus-treated males and untreated male of the three fruit fly species at day 0, 1 and 2 post-inoculation. However, on day 3 post-inoculation, there was a significant difference in the duration of mating with fungus-treated males having the lowest duration of mating. No significant differences in the percentage of mating between fungus-treated male and female flies; and the untreated flies at day 0, 1 and 2 days post-inoculation, except on day 3. The results are discussed with regard to application in autodissemination, baiting and the sterile insect techniques.

Altered mating behaviour in a Cry1Ac‐resistant strain of Helicoverpa armigera (Lepidoptera: Noctuidae)

AbstractRandomness of mating between susceptible and resistant individuals is a major factor that closely relates to the refuge strategy of resistance management for Helicoverpa armigera (Hübner) to Bacillus thuringiensis cotton. The mating behaviour of Cry1Ac‐susceptible and Cry1Ac‐resistant strains of H. armigera was compared to investigate the randomness of their mating. The percentage of mating was lower for Cry1Ac‐resistant H. armigera compared with that of the susceptible strain under both no‐choice and multiple‐choice conditions. The low percentage of mating in the resistant strain indicates a reduced incidence of successful mating. The percentage of spermatophore‐containing mated female H. armigera in the crossing of susceptible females × resistant males was significantly lower than in the crossing of resistant females × susceptible males, but the observed mating frequencies of these two types of cross were similar to each other. This indicates that resistant males reduce the incidence of mating paternity more than they do their mating frequency. The percentages of heterogametic matings (susceptible females × resistant males, resistant females × susceptible males) in the multiple‐choice experiment were lower than those of homogametic matings (susceptible × susceptible, resistant × resistant) on peak mating nights. However, the difference between heterogametic and homogametic mating was not significant, indicating that there was a random mating between susceptible and resistant strains. The results presented here do not reflect reality in mating associated with Cry1Ac resistance but can provide insight into variable expression.

Copulation behaviour of Neptunea arthritica: baseline considerations on broodstocks as the first step for seed production technology development

Copulation trials under three different scenarios were performed aiming to study the copulation behaviour of Neptunea arthritica and determine whether broodstock maintenance is required for artificial seed production. Neptunea arthritica showed polygamy, copulating at least three times with different partners. From all males and females used in this study, 43% of them copulated at least once. Female whelks showed rejection behaviour, which generated significant difference in copulation time between rejected (13.7±10.7 min) and non-rejected (49.7±44.7 min) males. The effect of body size on copula duration appeared to be superficial, while its effect on accumulative copulas played an important role as an indicator of copulation capacity because whelks varied in size. After first copula, males showed a contrasting tendency to mate copulated females over non-copulated females (χ2=6.23, d.f.=1, P=0.01). Broodstock maintenance as the first step in seed production is possible but considering low mating percentage and female rejection, it would be not economically reasonable due to the considerable number of whelks required and related logistical factors.

Simulation of Mating Disruption and Mass Trapping with Competitive Attraction and Camouflage

Simulation models of mass trapping and mating disruption were developed based on correlated random walks (CRW) of flying male moths searching for females. Males encountered pheromone plumes, transformed into a circular probability surface represented as an effective attraction radius (EAR), from females and from dispensers with or without traps. In simulations, parameters of dispenser EAR and density, female EAR and density, female stationary periods, male density, and male orienting times in EAR of dispensers or females were varied, whereas the male CRW parameters (speed, turning angle, and step size) remained constant to evaluate effects on the percentages of females mating. When male orienting time was constant regardless of EAR, the models indicated no difference in mating disruption efficacy between either a higher density of dispensers with smaller EAR or a lower density of dispensers with a compensating larger EAR. However, when the orienting time was increased in proportion to dispenser EAR, fewer dispensers with larger EAR were more effective in reducing female mating than were more numerous ones with smaller EAR. When costs of pheromone are substantial, however, more numerous dispensers of smaller EAR would be more economical because dose-response curves in previous studies indicate release rate must increase exponentially to achieve a linear increase in EAR. The models are useful in understanding the variables affecting the success of insect control programs. More precise measurements of the above parameters in the field are needed before the models can precisely predict outcomes of mating disruption and mass trapping.

Pheromone titer and mating frequency of E-and Z-strains of the european corn borer,Ostrinia nubilalis: Fluctuation during scotophase and age dependence

Periodicity of pheromone titer in female moths, modulated by various factors (age, photoperiod, temperature), has been reported for a number species, however, comparative studies on pheromone strains of those species where pheromone polymorphism is known to occur has so far scarcely been studied.In this study, the rhythm and age dependence of calling behavior as well as of the titer of the respective main sex pheromone components, and timing and frequency of mating within E-and Z-strains of European corn borer (ECB), Ostrinia nubilalis Hbn. (Lepidoptera: Pyraustidae) were compared during scotophase, under laboratory conditions (18/6 hours photoregime, 26 °C).Very similar trends were fund in both strains in the diel fluctuation of both calling behavior and pheromone titer within the scotophase, as well as its age dependence, and also in timing and mating frequency. The titer of the respective main pheromone component gradually increased during the scotophase. Highest titers were found in freshly emerged females, however even 6-day-old females produced roughly half amounts. Freshly emerged females of both strains were ready to mate with males of their own strain, however, the percentage of matings were higher in 1–3-day-old age cohorts. Differences between strains was found in the total amount of the respective main pheromone components in the gland. The average amount of ( Z )11-tetradecenyl acetate extracted from the ovipositor of Z-strain females 10 min. before the end of the scotophase was 2.17 ng / female equivalent, whereas the corresponding value of ( E )11-tetradecenyl acetate for E-strain females was 8.25 ng / female equivalent. Moreover, E-strain females tended to start calling somewhat earlier, and the percentages of calling females was higher during the peak calling period than that of the Z-strain. Significance of these findings in characterizing the strains are discussed.