Biogeography and phenology of oviposition preference and larval performance of <Emphasis Type="Italic">Pieris virginiensis</Emphasis> butterflies on native and invasive host plants

In invaded environments, formerly reliable cues might no longer be associated with adaptive outcomes and organisms can become trapped by their evolved responses. The invasion of Alliaria petiolata (garlic mustard) into the native habitat of Pieris virginiensis (West Virginia White) is one such example. Female butterflies oviposit on the invasive plant because it is related to their preferred native host plant Cardamine diphylla (toothwort), but larvae are unable to complete development. We have studied the impact of the A. petiolata invasion on P. virginiensis butterflies in the Southeastern USA by comparing oviposition preference and larval survival on both plants in North Carolina (NC) populations without A. petiolata and West Virginia (WV) populations where A. petiolata is present. Larval survival to the 3rd instar was equally low in both populations when raised on A. petiolata. Mean oviposition preference on the two plants also did not differ between populations. However, we found a seasonal effect on preference between early and late season flights within WV populations. Late season females laid 99% of total eggs on A. petiolata while early season females utilized both host plants. Late season females were also less likely to lay eggs than early season females. This change in preference toward A. petiolata could be driven by the early senescence of C. diphylla and suggests a seasonal component to the impact of A. petiolata. Therefore, the already short flight season of P. virginiensis could become further constrained in invaded populations.     

Reproductive Behavior of the Bug <Emphasis Type="Italic">Molipteryx fuliginosa</Emphasis> Uhler (Heteroptera,Coreidae) in the South of the Russian Far East

Reproductive behavior of Molipteryx fuliginosa (Uhler) was investigated in Primorskii Territory of Russia. From 4 to 18 repeated copulations of one female lasting from 2 to 48 hours were recorded in cages. The behavior of ovipositing females and the stages of oviposition are described for the first time. The number of eggs laid between copulations varied from 1 to 13, the number of oviposition acts, from 4 to 11, and the total female fecundity, from 21 to 38 eggs. Caged females laid eggs on plants and also on dead substrates unsuitable for nymphal feeding, such as cloth, dry branches, and a wooden pole. Copulation of M. fuliginosa was also observed under natural conditions. The preferred mating places of M. fuliginosa in anthropogenically modified habitats and in small-leaved riparian forests were plants of Rubus idaeus L., R. caesius L., and Rubus sp. After mating, females migrated in search of places for oviposition. Single eggs were found on the following plants not known previously as hosts of this bug: Solanum lycopersicum L., Carex sp., Elytrigia repens (L.) Nevski, and Taraxacum officinale Wigg. The females seemed to lack selectivity in the choice of place for oviposition, which was not always associated with host plants, despite their abundance and availability.     

Trail Chemicals of the Convergens Ladybird Beetle, <Emphasis Type="Italic">Hippodamia convergens</Emphasis>, Reduce Feeding and Oviposition by <Emphasis Type="Italic">Diaphorina citri</Emphasis> (Hemiptera: Psyllidae) on Citrus Plants

We investigated feeding and oviposition behavior of the Asian citrus psyllid, Diaphorina citri, when exposed to the foraging trails of the convergens ladybird beetle, Hippodamia convergens. Diaphorina citri females feeding on citrus leaves directly exposed to the ladybird adults or treated with trail extract excreted significantly less honeydew droplets than controls. The trail chemicals of the ladybird beetle also decreased oviposition by D. citri females on citrus. In a no-choice experiment, D. citri females preferred to oviposit on control flush and plants than those with ladybird trail-extract treatments. In two-choice experiments, 68.0% of D. citri released into cages exhibited strong selection preference for settling and eventual oviposition on control plants than plants treated with ladybird trail extract. Diaphorina citri eggs were found on all new leaf flush of control plants, whereas only 29.5% of flush on treatment plants were selected for oviposition. The trail chemical deposited by the convergens ladybird beetle elicits repellency of D. citri feeding and oviposition. Therefore, the trail chemicals my contain components that could be useful for behavior-based management of D. citri and HLB disease by reducing psyllid feeding and oviposition.     

Oviposition Preferences of <Emphasis Type="Italic">Plutella xylostella</Emphasis> are Influenced by the Type of Plant Induction and Glucosinolate Hydrolysis Profiles

Effects of inducing plants by exposing them to insect herbivory, mechanical damage or damaged neighboring plants were evaluated on the oviposition preferences of Plutella xylostella. The role of plant genotypes differing in their glucosinolate hydrolysis profiles was also evaluated using a wild ecotype (Col-0) and a genetically modified line (tgg1tgg2) of Arabidopsis thaliana. While the Col-0 line has normal production of glucosinolate hydrolysis products, the double myrosinase knockout (tgg1tgg2) is defective in the production of these volatiles. Dual choice oviposition assays were performed using naïve P. xylostella females, and the two A. thaliana lines, which were exposed to the three types of induction treatments. Female oviposition preferences were significantly influenced by both the type of plant induction and the plant genotypes differing in their volatile profiles. Plutella xylostella females significantly preferred to oviposit on herbivore-damaged plants (versus undamaged controls) when Col-0 plants were used, but chose control plants over the double myrosinase knockout tgg1tgg2. However, plant genotype did not influence oviposition choices between plant-plant primed or mechanically damaged plants and paired undamaged controls. Given the prevalent use of genetically modified plants and the potential differences in their responses to different types of induction, these factors may be important to consider in the management of specialist pests such as the diamondback moth P. xylostella.     

Host plant quantitative trait loci affect specific behavioral sequences in oviposition by a stem-mining insect

Key message

Genetic diversity in quantitative loci associated with plant traits used by insects as cues for host selection can influence oviposition behavior and maternal choice.

Abstract

Host plant selection for oviposition is an important determinant of progeny performance and survival for phytophagous insects. Specific cues from the plant influence insect oviposition behavior; but, to date, no set of host plant quantitative trait loci (QTLs) have been shown to have an effect on behavioral sequences leading to oviposition. Three QTLs in wheat (Triticum aestivum L.) have been identified as influencing resistance to the wheat stem sawfly (WSS) (Cephus cinctus Norton). Wheat near-isogenic lines (NILs) for each of the three QTLs were used to test whether foraging WSS were able to discriminate variation in plant cues resulting from allelic changes. A QTL on chromosome 3B (Qss-msub-3BL) previously associated with stem solidness and larval antibiosis was shown to affect WSS oviposition behavior, host preference, and field infestation. Decreased preference for oviposition was also related to a QTL allele on chromosome 2D (Qwss.msub-2D). A QTL on chromosome 4A (Qwss.msub-4A.1) affected host plant attractiveness to foraging females, but did not change oviposition preference after females landed on the stem. These findings show that oviposition decisions regarding potential plant hosts require WSS females to discriminate signals from the plant associated with allelic variation at host plant quantitative loci. Allele types in a host plant QTL associated with differential survival of immature progeny can affect maternal choices for oviposition. The multidisciplinary approach used here may lead to the identification of plant genes with important community consequences, and may complement the use of antibiosis due to solid stems to control the wheat stem sawfly in agroecosystems.

     

Pathogen invasion triggers an evolutionary trap for an endangered checkerspot butterfly dependent on an exotic host plant

Exotic pathogen invasions can change host eco-evolutionary interactions and possibly create an evolutionary trap when the pathogen generates mismatches between developmental phenology and reproductive cues. Taylor’s checkerspot butterfly (Euphydryas editha taylori), is an endangered species of western North America with 80 % of the extant populations dependent on an exotic host, Plantago lanceolata. Survey of occupied, recently extinct, and unsuccessful butterfly reintroduction sites spanning 4° of latitude revealed widespread disease on P. lanceolata caused by Pyrenopeziza plantaginis. This fungal pathogen, new to North America, reduces the standing crop of P. lanceolata foliage throughout the winter post-diapause larval feeding period. However, disease is absent when adult butterflies and pre-diapause larvae are active. Diseased plants were frequent in Taylor’s checkerspot populations with a history of persistence, but >90 % of the host plants in these populations had initiated new leaves within the first few weeks of post-diapause larval feeding. Conversely, host plants in recently extinct and unsuccessfully reintroduced populations were severely diseased, >66 % mean foliage necrosis/plant, and <23 % had initiated new leaves. Feeding choice trials with 25 larvae indicated that new leaves were strongly and consistently preferred by post-diapause larvae over all other available leaf types, both diseased and non-diseased. Because the influence of disease on post-diapause larval food resources is developmentally disassociated from oviposition, P. plantaginis invasion appears to have triggered an evolutionary trap for Plantago-dependent populations of Taylor’s checkerspot.     

Predation of <Emphasis Type="Italic">Halyomorpha halys</Emphasis> (Hemiptera: Pentatomidae) from Web-Building Spiders Associated with Anthropogenic Dwellings

The brown marmorated stink bug, or Halyomorpha halys, is an invasive pest in North America and Europe that causes severe agricultural damage and nuisance problems for homeowners; and it is originally from China, Taiwan, and the Republic of Korea. While the natural enemy community of H. halys has been evaluated in several agroecosystems, it has not been examined where H. halys overwinters in anthropogenic structures. The aims of the current study were to evaluate 1) whether spider webs commonly found in the home and yard can successfully ensnare H. halys, 2) whether entanglement resulted in consumption by spiders inhabiting the webs, and 3) how frequently H. halys becomes entangled in webs under ambient conditions. To accomplish this, adult H. halys were introduced into webs in and near anthropogenic structures in West Virginia and Maryland, United States, and the behavior of spiders was observed for 5-min intervals at 0, 1, 2, and 24 h after introduction. In addition, a survey of webs was performed to determine the frequency with which spiders naturally capture H. halys inside buildings and in the landscape. Overall, the study found seven spider families in anthropogenic structures. Adult H. halys that were introduced into the webs of Theridiidae, Pholcidae, or Agelenidae had a greater than 50% chance of being ensnared and consumed. Adult H. halys were found naturally most often in webs of Theridiidae. Webs with a funnel or cob web architecture had the greatest probability of ensnaring H. halys, while those with orb structures resulted in the fewest caught. In the wild, 13–20% of spider webs contained dead H. halys. Our results suggest that spiders may be an important contributing factor for mortality of H. halys at overwintering sites, and spiders in or outside homes may help reduce nuisance problems caused by H. halys.     

Response of the predatory mite <Emphasis Type="Italic">Cydnoseius negevi</Emphasis> (Acari: Phytoseiidae) to webbing of the date palm mite, <Emphasis Type="Italic">Oligonychus afrasiaticus</Emphasis> (Acari: Tetranychidae), on date palm fruits and leaves

The behavioral response of a generalist phytoseiid predator, Cydnoseius negevi (Swirskii & Amitai) (Acari: Phytoseiidae) to the complicated webbing of the date palm mite (DPM) Oligonychus afrasiaticus (McGregor) (Acari: Tetranychidae) was evaluated for the first time on date palm leaves and fruits, both in the laboratory and on field-collected samples. Cydnoseius negevi used its first pair of legs in a swimming-like to-and-fro movement to penetrate the complicated webbing of DPM and demonstrated three attack behaviors, i.e., patrolling (PG), web invasion (WI), and web penetration (WP), against the webbing of DPM on date fruits and leaves. The time spent by the predator on attack behaviors was significantly longer in the laboratory for treatments where either more prey females or immature stages along with females were present. The time spent by C. negevi on response behaviors such as searching, grooming, and resting increased with increased number of DPM females and with the addition of immature stages along with DPM females. Cydnoseius negevi, even though being a generalist phytoseiid predator, showed its potential towards penetrating the complex dense webs of DPM on date palm fruits and leaves. If released in suitable numbers prior to establishment of DPM colonies, C. negevi may prove to be an effective biological control agent.     

Contribution of olfactory and gustatory sensations of octanoic acid in the oviposition behavior of <Emphasis Type="Italic">Drosophila melanogaster</Emphasis> (Diptera: Drosophilidae)

Selection of oviposition sites in insects represents an important part of their ecological adaptation. In Drosophila fruit flies, adult preference for a particular oviposition site determines larval food, affecting fitness throughout the entire life cycle. Two odorant-binding proteins (OBPs) OBP57d and OBP57e were identified to be involved in the evolution of specific preference for the toxic plant Morinda citrifolia L. in D. sechellia Tsacas &; Bächli. D. melanogaster Meigen mutants for Obp57d and Obp57e showed enhanced preference for octanoic acid, but still not as much as D. sechellia does, indicating that other genes are also involved in the behavioral evolution of D. sechellia. Here, by using an improved method for behavioral assay, we found that the ablation of antenna enhanced the preference for octanoic acid in the Obp57d and Obp57e mutants to a level comparable with D. sechellia, suggesting that both olfactory and gustatory sensations are involved in oviposition site selection in response to octanoic acid. Behavioral analysis of gene-knockout strains revealed that Odorant receptor co-receptor (Orco) has little contribution compared with the effect of antennal ablation. These data suggest that in addition to Obp57d and Obp57e, the evolution of D. sechellia involves genetic changes in olfactory genes that function independently from Orco.     

Heterologous expression of a novel <Emphasis Type="Italic">Poa pratensis</Emphasis> gibberellin 2-oxidase gene, <Emphasis Type="Italic">PpGA2ox</Emphasis>, caused dwarfism,late flowering,and increased chlorophyll accumulation in <Emphasis Type="Italic">Arabidopsis</Emphasis>

Gibberellin 2-oxidases (GA2oxs) irreversibly convert bioactive gibberellins (GAs) and their immediate precursors into inactive GAs via 2-β hydroxylation and so regulate gibberellin content in plants. However, to the best of our knowledge, little has been known about the GA2oxs and its function in cool season turfgrass Poa pratensis. In this study, rapid amplification of cDNA end (RACE) was employed to isolate PpGA2ox from P. pratensis. The open reading frame of PpGA2ox was 1 047 bp in length, corresponding to 348 amino acids. PpGA2ox was localized in both nucleus and cytoplasm. The expression of PpGA2ox could be up-regulated by 10 μM gibberellic acid, 5 μM methyl jasmonate, or 10 μM indole-3-acetic acid. In addition, its native promoter could drive GUS expression in both leaf apex and shoot apical region. Moreover, overexpression of PpGA2ox in Arabidopsis led to GA-deficiency leading to dwarf phenotype, delayed flowering time, and increased chlorophyll content. Our study suggests that PpGA2ox could be a candidate gene for breeding new cultivars of P. pratensis.     

The endosymbiotic bacterium <Emphasis Type="Italic">Wolbachia</Emphasis> enhances the nonspecific resistance to insect pathogens and alters behavior of <Emphasis Type="Italic">Drosophila melanogaster</Emphasis>

To determine biologically important effects of the cytoplasmic endosymbiont Wolbachia, two substrains of the same Drosophila melanogaster strain have been studied, one of them infected with Wolbachia and the other treated with tetracycline to eliminate the bacterium. Females of D. melanogaster infected with Wolbachia are more resistant to the fungus Blauveria bassiana (an insect pathogen) than uninfected females; infected females also exhibited changes in oviposition substrate preference. Males infected with the bacterium are more competitive than uninfected males. The possible role of Wolbachia in the formation of alternative ecological strategies of D. melanogaster is discussed.     

Optimization of Methodology for Rearing <Emphasis Type="Italic">Spodoptera albula</Emphasis> on Artificial Diet

Advances in techniques for rearing insects on artificial diets are fundamental to solving issues of basic and applied entomology. In this study, we evaluated the development of Spodoptera albula (Walker) (Lepidoptera: Noctuidae) on three artificial diets used for other species of Lepidoptera, at three larval densities, and two densities of adult couples housed in oviposition cages of two sizes, with the aim of optimizing methodology for rearing S. albula in the laboratory. Biological parameters were recorded from S. albula, and a fitness index was calculated based on the larval survival and duration and weight of pupae. The total and daily oviposition was recorded using 5 or 10 adult couples of S. albula housed in two cage sizes. Concentrations of total nitrogen and protein in the tested diets were determined. Development of S. albula was completed in all artificial diets; however, the diet used for rearing Anticarsia gemmatalis (Hübner) larvae was the most suitable for S. albula, yielding intermediate development time and higher survival relative to the other diets. Individualization of larvae favored S. albula development by producing overall greater weights of larvae and pupae, higher survival rates, and longer adult longevity. Cage size and number of couples per cage did not influence S. albula fecundity in the experiment conditions. Spodoptera albula can be satisfactorily reared on the artificial diet used for A. gemmatalis, using one larva per tube, and either density of adults at any cage size. Additional amendments are needed in the rearing methodology to achieve optimal conditions for larval development to adulthood.     

The Role of Males in Host-Fruit Selection by Females of a Walnut Infesting Tephritid (Diptera) <Emphasis Type="Italic">Rhagoletis zoqui</Emphasis>

Rhagoletis zoqui Bush flies have a mating system in which males guard and defend walnut fruit-hosts from other males and mate, apparently without courtship, with females as they arrive to oviposit. Hypothetically, female selection of a particular fruit may be due to the quality of fruit for larval development (previously determined by guarding males), the quality of the male upon the fruit as a mate, or both, but this is not clear. We performed an experiment to determine if R. zoqui females or males select the fruit to oviposit or guard based on its quality for larval development (i.e., size, sugar-content [brix] or hardness), or following male-mediated cues such as chemical residues, related to prior fruit occupation by the male during guarding. Fruit choice by R. zoqui females and males were examined under semi-natural conditions on caged branches of English walnut trees, Juglans regia L., growing in the highlands of south-central Mexico. A single male or female was allowed to select a fruit and was then removed. An individual of the opposite sex was then introduced to the same branch and presented with the opportunity to choose among the same array of hosts. The pattern of fruit choice was consistent, with female choice on the basis of male presence, suggesting that males left a chemical cue that persisted in their absence. No fruit quality differences were detected between selected and non-selected fruit. Fruit features selected by females and males matched almost exactly, although males rarely select the same fruit as females. We conclude that females preferentially selected fruit previously occupied by males although additional studies are required to determine the cues used by R. zoqui for oviposition resource selection by both females and resource guarding males.     

On oviposition in weevils of the genus <Emphasis Type="Italic">Larinus</Emphasis> Dej. (Coleoptera,Curculionidae)

The following actions performed by females of several Larinus Dej. species during egg laying are described: search of an appropriate place on the plant, making the hole for the egg, oviposition proper, and sealing the hole. The hole preparation takes the longest time and the greatest effort. Only one individual usually completes development in one flower head. Females of Larinus vulpes Ol. prefer larger flower heads for oviposition and occasionally lay eggs into stems. The ability of females to distinguish the flower heads with already laid eggs is discussed. Species of Larinus may be divided into two groups with “early” and “late” oviposition. The evolution of egg laying in the genus Larinus is discussed.     

Spraying pyrethroid and neonicotinoid insecticides can induce outbreaks of <Emphasis Type="Italic">Panonychus citri</Emphasis> (Trombidiformes: Tetranychidae) in citrus groves

Panonychus citri (McGregor) (Trombidiformes: Tetranychidae) is one of the main defoliator mites in citrus groves. In Brazil, P. citri was formerly considered a secondary pest, but in recent years, the population levels of this mite have increased in many groves, requiring additional acaricide applications for its control. The population growth of P. citri is associated with the increase in the number of applications of pyrethroid and neonicotinoid insecticides to control insect citrus pests. This study assessed the effects of pyrethroid (deltamethrin, esfenvalerate, λ-cyhalothrin) and neonicotinoid (imidacloprid and thiamethoxam) insecticides on biological, behavioral and demographic parameters of P. citri. None of the insecticides tested affected larval hatching, but deltamethrin, esfenvalerate, and λ-cyhalothrin reduced the survival of larvae and protonymphs. Deltamethrin, esfenvalerate, and λ-cyhalothrin induced a significant increase in the fecundity of surviving females. Pyrethroids also caused repellency and changed feeding and oviposition preferences. In contrast, imidacloprid and thiamethoxam did not affect the survival of immature stages, but imidacloprid significantly increased fecundity. Imidacloprid and thiamethoxam did not cause any repellent effect or changes in the feeding and oviposition preferences. Based on the demographic parameters, deltamethrin, λ-cyhalothrin, and imidacloprid increased R_o, r, and λ, whereas esfenvalerate and thiamethoxam were similar to the control. Therefore, the use of these insecticides (especially deltamethrin, λ-cyhalothrin, and imidacloprid) requires caution, such as avoiding repeated use of these compounds during the periods of P. citri incidence in citrus groves.     

Patterns of microhabitat and larval host-plant use by an imperiled butterfly in northern Florida

The quality of habitat for a given species is fundamental to its persistence in that habitat space. Herbivorous insects often require a specific combination of host plants, floral resources, and physical features such as shelter. Identifying these different habitat features is a focus of ecology and conservation, particularly for managing rare or imperiled taxa. We investigated the patterns of microhabitat and host plant use of the rare frosted elfin butterfly, Callophrys irus, a larval host-plant specialist found in frequently disturbed sand plains, barrens, and sandhill pine-oak forests of the eastern United States. Previous studies have been conducted on populations in the Northeastern and Midwestern US, but the southern part of its range remains unstudied. Our efforts focused on a persistent C. irus colony in northeastern Florida, resulting in a geographically referenced census of larval host-plant Lupinus perennis, along with a multiple year survey of microhabitat features relevant to both C. irus adults and immatures. Results of the larval host-plant census revealed that the highest densities of host plants were located distant to the highest densities of C. irus. Hot-spot analysis confirmed the significance of this pattern, suggesting different habitat requirements for larval host-plant L. perennis and C. irus individuals in order to achieve maximum potential densities. Our survey of C. irus immatures showed a similar pattern of microhabitat affinity that was previously recorded in the Northeast and Midwestern US, including large larval host-plants, low amounts of ground cover vegetation, and the presence of some shade. Unique to our study we found that the presence of other herbivores of L. perennis such as larvae of the crambid moth Uresiphita reversalis had a negative effect on encountering C. irus immatures. Our results suggest that management that aims to conserve these species needs to include habitat factors that favor the overlap of these species and to consider where their densities are the highest.     

Suitability of edaphic arthropods as prey for <Emphasis Type="Italic">Proctolaelaps bickleyi</Emphasis> and <Emphasis Type="Italic">Cosmolaelaps brevistilis</Emphasis> (Acari: Mesostigmata: Melicharidae,Laelapidae) under laboratory conditions

Soils are often complex habitats inhabited by a wide range of organisms, some harmful to plants and others beneficial, for example by attacking harmful organisms. Beneficial organisms include predatory mites, some of which have been commercialized for biological control of pest insects and mites. The objective of this work was to evaluate under laboratory condition the suitability of representative soil insect and mite pests, especially Aceria tulipae (Keifer), as prey to the soil-inhabiting predatory mites Proctolaelaps bickleyi (Bram) and Cosmolaelaps brevistilis (Karg). Predation, oviposition and survivorship of recently molted adult females of the predators were assessed in the dark in rearing chambers at 25 ± 1 °C and 75 ± 3% RH. Predation rate by P. bickleyi on A. tulipae was significantly higher than that by C. brevistilis (196.3 vs. 71.0 specimens/day). About 482 A. tulipae were preyed by each P. bickleyi at each day, when 500 A. tulipae were made available daily to the predator. Oviposition rate on that prey was also higher for P. bickleyi (4.2 eggs/day). For C. brevistilis, the highest level of oviposition was on Caliothrips phaseoli (Hood) (1.2 eggs/day). Survivorship was always higher for C. brevistilis (≥ 70%), given its ability to remain alive relatively long even in the absence of prey. High rates of survivorship of P. bickleyi were observed on A. tulipae, Bradysia matogrossensis (Lane) and Protorhabditis sp. Promising results were obtained for P. bickleyi on A. tulipae and even on other prey, justifying the conduction of complementary studies under field condition.     

On distribution and ecology of some species of cleonines (Coleoptera,Curculionidae): IV. Genus <Emphasis Type="Italic">Lixus</Emphasis> F., subgenus <Emphasis Type="Italic">Eulixus</Emphasis> Reitt.

Data on habitats, food plants of larvae and adults, feeding, mating, oviposition, larval and pupal development, natural enemies, and distribution of seven weevil species (Lixus canescens F.-W., L. iridis Ol., L. myagri Ol., L. punctirostris Boh., L. subtilis Boh., L. incanescens Boh., and L. brevipes Bris.) are given. New host plants of L. canescens and L. iridis are revealed. Gall induction by L. brevipes is reported for the first time. Distribution of all the species in Ukraine and Russia (the latter based on the literature) are given in more detail. Information on the known and potential economic importance of every species is provided.     

An Experimental Test of Trade-Offs Associated with the Adaptation to Alternate Host Plants in the Introduced Herbivorous Beetle, <Emphasis Type="Italic">Ophraella communa</Emphasis>

The adaptation to alternate host plants of introduced herbivorous insects can be vital to agriculture due to the emergence of crop pests. Historically, it is assumed that there are trade-offs associated with the adaptation to new host plants; a generalist genotype that adapts to an alternate host is expected to have a relatively lower fitness on the ancestral host than a specialist genotype (physiological cost) or a relatively lower host-searching ability for the ancestral host plant (behavioral cost). In this study, we tested the costs of adaptation to a new host plant in the introduced herbivorous insect, Ophraella communa LeSage (Coleoptera: Chrysomelidae). In its native range (United States), O. communa feeds mostly on Ambrosia artemisiifolia L. (Asterales: Asteraceae) and cannot utilize the related species, Ambrosia trifida L. (Asterales: Asteraceae), as a host plant. On the other hand, the introduced O. communa population in Japan utilizes A. trifida extensively, and is adapting to it, both physiologically and behaviorally. We compared larval performance on the ancestral and alternate plants and adult host-searching ability between the native and introduced beetle populations. The introduced O. communa showed higher larval survival and adult feeding preference for the alternate host plant A. trifida than did the native O. communa, indicating that the introduced O. communa has rapidly adapted to the alternate host plant. However, there are no differences in either larval performance on the ancestral host A. artemisiifolia or host-searching accuracy between the native and introduced O. communa.     

Reproductive interference between two serious pests,oriental fruit flies <Emphasis Type="Italic">Bactrocera carambolae</Emphasis> and <Emphasis Type="Italic">B. dorsalis</Emphasis> (Diptera: Tephritidae), with very wide but partially overlapping host ranges

Bactrocera carambolae and B. dorsalis (Diptera: Tephritidae) are extremely destructive pests of fruits and vegetables in the Asia-Pacific region. Earlier reports have described that B. carambolae and B. dorsalis, respectively, use mainly star fruit and mango, suggesting a certain level of host partitioning which can be ascribed neither to differences in larval food qualities nor host-specific parasitoid mortality. This study specifically examined reproductive interference (antagonistic sexual interaction) between B. carambolae and B. dorsalis as a potential factor strongly affecting their host partitioning. We observed mating behaviors, especially interspecific courtships and mating, by cohabiting the conspecific and heterospecific pairs together. Consequently, we quantified their effects on the reproductive success of females. Males of both species frequently courted their own females, but they also courted females of other species. Courtship refusal by females was not selective in males of either species. This incomplete discrimination of both sexes led to frequent occurrences of interspecific sexual interactions in both species, but only B. carambolae females showed reduced reproductive success. These results suggest that B. dorsalis, superior in reproductive interference, can occupy high-quality mango, whereas B. carambolae, inferior in reproductive interference, must use low-quality star fruit.