Bactrocera dorsalis Zeugodacus cucurbitae Evaluation of grease, an industrial machinery lubricant... more Bactrocera dorsalis Zeugodacus cucurbitae Evaluation of grease, an industrial machinery lubricant, as an alternative to ant repellants for invasive fruit flies surveillance traps.
Quarantine pests in plants can be a serious agricultural problem; many eradication programs using... more Quarantine pests in plants can be a serious agricultural problem; many eradication programs using area-wide control measures have been implemented worldwide to combat this threat. Surveillance measures using sex pheromone (in general, male-attractant) traps are also widely implemented for rapid control and eradication of invasive pests. If initial pest colonization can be determined based on temporal count data of trapped insects (i.e., males), and countermeasures are applied only during colonization, costs incurred by these countermeasures would be dramatically reduced, especially in areas with frequent invasions. In this study, we developed a system to detect initial pest colonization, and to narrow down colonized regions using estimated temporal count data of the sweet potato weevil, Cylas formicarius Fabricius (Coleoptera: Curculionidae), in Tsuken Island, Okinawa, Japan. We verified the system by comparing our estimates to actual colonization data obtained via regular host plant surveys. Results indicated that our system was able to successfully detect pest colonization and estimate colonized regions. In this study, we discuss the conditions (i.e., pest biology, environment, etc.) that are optimal for application of our system.
Of the several exotic insect species in Japan, five quarantine plant pest taxa: the oriental frui... more Of the several exotic insect species in Japan, five quarantine plant pest taxa: the oriental fruit fly, Bactrocera dorsalis complex, the melon fly, Zeugodacus cucurbitae, the solanaceous fruit fly, Bactrocera latifrons, the sweet potato weevil, Cylas formicarius, and the West Indian sweet potato weevil, Euscepes postfasciatus, have been targeted in eradication programs using the male annihilation technique (MAT) and/or the sterile insect technique (SIT). Although all targeted fruit flies have successfully been eradicated, the incidences of re-invasion by Bactrocera dorsalis complex have been increasing in recent years, indicating the necessity for reinforcement and improvement of countermeasures for fruit fly re-invasion and/or recolonization. The program targeted at C. formicarius achieved the goal of complete eradication in Kume Island. The program for E. postfasciatus has yet to achieve eradication, even though it was initiated at the same time as that for C. formicarius. Major t...
This paper presents the first case of the successful eradication of a Coleoptera pest species ove... more This paper presents the first case of the successful eradication of a Coleoptera pest species over a wide area using a combination of male annihilation technique (MAT) and sterile insect technique (SIT) application. The sweet potato weevil, Cylas formicarius, is one of the most destructive and widely distributed pests of sweet potato, Ipomoea batatas. A project to eradicate it was launched in 1994 on Kume Island, Okinawa Prefecture, Japan. The MAT application was first used from November 1994 to January 1999 to reduce the density of wild populations. The distribution and densities of weevils were assessed by trapping them and surveying infestation rates in wild hosts and sweet potatoes in the field. The C. formicarius populations were suppressed by approximately 90% and plant infestations were reduced from 9.5% to less than 0.1% by using the MAT. Then, hundreds of thousands to millions of sterile weevils were released each week (ca. 460 million in total from 1999 to 2012). As a resu...
Larval diet significantly affects adult traits, although less is known about how they affect repr... more Larval diet significantly affects adult traits, although less is known about how they affect reproductive traits. Males of West Indian sweet potato weevil Euscepes postfasciatus deliver a remating inhibitor along with sperm to their mates during mating, leading to a refractory period (the period before females mate again). Crossing experiments were conducted using lines reared on artificial diets, including sweet potato powder (AD) or sweet potato tubers (SP) during the larval stage, and the refractory period was examined. We also examined whether the larval diet qualitatively or quantitatively altered male ejaculate. The results showed that the refractory period was significantly longer in the SP treatment than in the AD treatment for males and females. There was no significant difference in ejaculate volume. However, the number of sperm in the testes-seminal vesicles complex was significantly higher in the SP treatment. Additionally, SDS-PAGE revealed that the ejaculate was qualit...
Group predation promotes foraging efficiency because it increases the size of prey that can be ki... more Group predation promotes foraging efficiency because it increases the size of prey that can be killed and improves hunting success compared to solitary predation. However, group predation may increase competition among group members during feeding. Earlier studies have focused on the advantages of group predation, but little is known about the costs and benefits of group predation for individual members of the group. Here, we show that the costs and benefits of group predation for individuals of the predatory stink bug Andrallus spinidens vary with prey size in laboratory experiments. We found that when A. spinidens fed on small prey, group predation did not significantly increase foraging efficiency but did increase competition for food among group members. In contrast, when prey was large, group predation promoted foraging efficiency, and competition over food was not detected. Our results suggest that group predation by A. spinidens nymphs is advantageous for individual members b...
Sexual size dimorphisms (SSDs) in body size are expected to evolve when selection on female and m... more Sexual size dimorphisms (SSDs) in body size are expected to evolve when selection on female and male sizes favors different optima. Many insects show female-biased SSD that is usually explained by the strong fecundity advantage of larger females. However, in some insects, males are as large as or even larger than females. The seed bug Togo hemipterus (Scott) also exhibits a male-biased SSD in body size. Many studies that have clarified the evolutionary causes of male-biased SSD have focused only on male advantages due to male–male competition. To clarify the evolutionary causes of male-biased SSD in body size, we should examine the degree of not only the sexual selection that favors larger males but also natural selection that is acting on female fecundity. The obtained results, which showed higher mating acceptance rates to larger males, implies that females prefer larger males. No significant relationship was detected between female body size and fecundity; body size effects on female fecundity were weak or undetectable. We conclude that male-biased SSD in T. hemipterus can be accounted for by a combination of sexual selection through male–male competition and female choice favoring large males, plus weak or undetectable natural selection that favors large females due to a fecundity advantage.
Males of the seed bug Togo hemipterus are larger in size and have considerably larger front legs ... more Males of the seed bug Togo hemipterus are larger in size and have considerably larger front legs compared to females. This size discrepancy is likely related to the fact that males fight for food using their enlarged forelegs. A "hungry" bug, i.e. one previously without food, is expected to behave in a certain way when food is present. Here, we demonstrate that aggressive "fighting and chasing" behavior was frequently observed only between males under starvation conditions and became especially severe when food was present. Togo hemipterus males may adopt a resource-defense mating system that is beneficial for males because females aggregate near food when it is scarce. This strategy strongly suggests that the aggressive behavior acts as male-male competition. In a second set of experiments, aggressive behavior occurred between two small males, two large males, or one large and one small male. Fighting ensued mainly when large males were involved, and larger males won fights. Consequently, the male-biased sexual size dimorphism in T. hemipterus appears to be partially attributable to sexual selection favoring larger males.
Mitochondrial sequences of the Cytochrome oxidase 1 marker for the invasive ant species Brachypon... more Mitochondrial sequences of the Cytochrome oxidase 1 marker for the invasive ant species Brachyponera chinensis in its native and introduced ranges
Invasions are ecologically destructive and can threaten biodiversity. Trophic flexibility has bee... more Invasions are ecologically destructive and can threaten biodiversity. Trophic flexibility has been proposed as a mechanism facilitating invasion, with more flexible species better able to invade. The termite hunting needle ant Brachyponera chinensis was introduced from East Asia to the United States where it disrupts native ecosystems. We show that B. chinensis has expanded dietary breadth without shifting trophic position in its introduced range. Transect sampling of ants and termites revealed a negative correlation between the abundance of B. chinensis and the abundance of other ants in introduced populations, but this pattern was not as strong in the native range. Both termite and B. chinensis abundance were higher in the introduced range than in native range. Radiocarbon (14C) analysis revealed that B. chinensis has significantly younger 'diet age', the time lag between carbon fixation by photosynthesis and its use by the consumer, in the introduced range than in the nat...
Bactrocera dorsalis Zeugodacus cucurbitae Evaluation of grease, an industrial machinery lubricant... more Bactrocera dorsalis Zeugodacus cucurbitae Evaluation of grease, an industrial machinery lubricant, as an alternative to ant repellants for invasive fruit flies surveillance traps.
Quarantine pests in plants can be a serious agricultural problem; many eradication programs using... more Quarantine pests in plants can be a serious agricultural problem; many eradication programs using area-wide control measures have been implemented worldwide to combat this threat. Surveillance measures using sex pheromone (in general, male-attractant) traps are also widely implemented for rapid control and eradication of invasive pests. If initial pest colonization can be determined based on temporal count data of trapped insects (i.e., males), and countermeasures are applied only during colonization, costs incurred by these countermeasures would be dramatically reduced, especially in areas with frequent invasions. In this study, we developed a system to detect initial pest colonization, and to narrow down colonized regions using estimated temporal count data of the sweet potato weevil, Cylas formicarius Fabricius (Coleoptera: Curculionidae), in Tsuken Island, Okinawa, Japan. We verified the system by comparing our estimates to actual colonization data obtained via regular host plant surveys. Results indicated that our system was able to successfully detect pest colonization and estimate colonized regions. In this study, we discuss the conditions (i.e., pest biology, environment, etc.) that are optimal for application of our system.
Of the several exotic insect species in Japan, five quarantine plant pest taxa: the oriental frui... more Of the several exotic insect species in Japan, five quarantine plant pest taxa: the oriental fruit fly, Bactrocera dorsalis complex, the melon fly, Zeugodacus cucurbitae, the solanaceous fruit fly, Bactrocera latifrons, the sweet potato weevil, Cylas formicarius, and the West Indian sweet potato weevil, Euscepes postfasciatus, have been targeted in eradication programs using the male annihilation technique (MAT) and/or the sterile insect technique (SIT). Although all targeted fruit flies have successfully been eradicated, the incidences of re-invasion by Bactrocera dorsalis complex have been increasing in recent years, indicating the necessity for reinforcement and improvement of countermeasures for fruit fly re-invasion and/or recolonization. The program targeted at C. formicarius achieved the goal of complete eradication in Kume Island. The program for E. postfasciatus has yet to achieve eradication, even though it was initiated at the same time as that for C. formicarius. Major t...
This paper presents the first case of the successful eradication of a Coleoptera pest species ove... more This paper presents the first case of the successful eradication of a Coleoptera pest species over a wide area using a combination of male annihilation technique (MAT) and sterile insect technique (SIT) application. The sweet potato weevil, Cylas formicarius, is one of the most destructive and widely distributed pests of sweet potato, Ipomoea batatas. A project to eradicate it was launched in 1994 on Kume Island, Okinawa Prefecture, Japan. The MAT application was first used from November 1994 to January 1999 to reduce the density of wild populations. The distribution and densities of weevils were assessed by trapping them and surveying infestation rates in wild hosts and sweet potatoes in the field. The C. formicarius populations were suppressed by approximately 90% and plant infestations were reduced from 9.5% to less than 0.1% by using the MAT. Then, hundreds of thousands to millions of sterile weevils were released each week (ca. 460 million in total from 1999 to 2012). As a resu...
Larval diet significantly affects adult traits, although less is known about how they affect repr... more Larval diet significantly affects adult traits, although less is known about how they affect reproductive traits. Males of West Indian sweet potato weevil Euscepes postfasciatus deliver a remating inhibitor along with sperm to their mates during mating, leading to a refractory period (the period before females mate again). Crossing experiments were conducted using lines reared on artificial diets, including sweet potato powder (AD) or sweet potato tubers (SP) during the larval stage, and the refractory period was examined. We also examined whether the larval diet qualitatively or quantitatively altered male ejaculate. The results showed that the refractory period was significantly longer in the SP treatment than in the AD treatment for males and females. There was no significant difference in ejaculate volume. However, the number of sperm in the testes-seminal vesicles complex was significantly higher in the SP treatment. Additionally, SDS-PAGE revealed that the ejaculate was qualit...
Group predation promotes foraging efficiency because it increases the size of prey that can be ki... more Group predation promotes foraging efficiency because it increases the size of prey that can be killed and improves hunting success compared to solitary predation. However, group predation may increase competition among group members during feeding. Earlier studies have focused on the advantages of group predation, but little is known about the costs and benefits of group predation for individual members of the group. Here, we show that the costs and benefits of group predation for individuals of the predatory stink bug Andrallus spinidens vary with prey size in laboratory experiments. We found that when A. spinidens fed on small prey, group predation did not significantly increase foraging efficiency but did increase competition for food among group members. In contrast, when prey was large, group predation promoted foraging efficiency, and competition over food was not detected. Our results suggest that group predation by A. spinidens nymphs is advantageous for individual members b...
Sexual size dimorphisms (SSDs) in body size are expected to evolve when selection on female and m... more Sexual size dimorphisms (SSDs) in body size are expected to evolve when selection on female and male sizes favors different optima. Many insects show female-biased SSD that is usually explained by the strong fecundity advantage of larger females. However, in some insects, males are as large as or even larger than females. The seed bug Togo hemipterus (Scott) also exhibits a male-biased SSD in body size. Many studies that have clarified the evolutionary causes of male-biased SSD have focused only on male advantages due to male–male competition. To clarify the evolutionary causes of male-biased SSD in body size, we should examine the degree of not only the sexual selection that favors larger males but also natural selection that is acting on female fecundity. The obtained results, which showed higher mating acceptance rates to larger males, implies that females prefer larger males. No significant relationship was detected between female body size and fecundity; body size effects on female fecundity were weak or undetectable. We conclude that male-biased SSD in T. hemipterus can be accounted for by a combination of sexual selection through male–male competition and female choice favoring large males, plus weak or undetectable natural selection that favors large females due to a fecundity advantage.
Males of the seed bug Togo hemipterus are larger in size and have considerably larger front legs ... more Males of the seed bug Togo hemipterus are larger in size and have considerably larger front legs compared to females. This size discrepancy is likely related to the fact that males fight for food using their enlarged forelegs. A "hungry" bug, i.e. one previously without food, is expected to behave in a certain way when food is present. Here, we demonstrate that aggressive "fighting and chasing" behavior was frequently observed only between males under starvation conditions and became especially severe when food was present. Togo hemipterus males may adopt a resource-defense mating system that is beneficial for males because females aggregate near food when it is scarce. This strategy strongly suggests that the aggressive behavior acts as male-male competition. In a second set of experiments, aggressive behavior occurred between two small males, two large males, or one large and one small male. Fighting ensued mainly when large males were involved, and larger males won fights. Consequently, the male-biased sexual size dimorphism in T. hemipterus appears to be partially attributable to sexual selection favoring larger males.
Mitochondrial sequences of the Cytochrome oxidase 1 marker for the invasive ant species Brachypon... more Mitochondrial sequences of the Cytochrome oxidase 1 marker for the invasive ant species Brachyponera chinensis in its native and introduced ranges
Invasions are ecologically destructive and can threaten biodiversity. Trophic flexibility has bee... more Invasions are ecologically destructive and can threaten biodiversity. Trophic flexibility has been proposed as a mechanism facilitating invasion, with more flexible species better able to invade. The termite hunting needle ant Brachyponera chinensis was introduced from East Asia to the United States where it disrupts native ecosystems. We show that B. chinensis has expanded dietary breadth without shifting trophic position in its introduced range. Transect sampling of ants and termites revealed a negative correlation between the abundance of B. chinensis and the abundance of other ants in introduced populations, but this pattern was not as strong in the native range. Both termite and B. chinensis abundance were higher in the introduced range than in native range. Radiocarbon (14C) analysis revealed that B. chinensis has significantly younger 'diet age', the time lag between carbon fixation by photosynthesis and its use by the consumer, in the introduced range than in the nat...
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Papers by Chihiro Himuro