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Soil-dwelling animals are at risk of pathogen infection in soils. When choosing nesting sites, animals could reduce this risk by avoiding contact with pathogens, yet there is currently little evidence. We tested this hypothesis using Solenopsis invicta as a model system. Newly mated queens of S. invicta were found to nest preferentially in soil containing more actinobacteria of Streptomyces and Nocardiopsis and to be attracted to two volatiles produced by these bacteria, geosmin and 2-methylisoborneol. Actinobacteria-rich soil was favored by S. invicta and this soil contained fewer putative entomopathogenic fungi than adjacent areas. Queens in such soil benefited from a higher survival rate. In culture, isolated actinobacteria inhibited entomopathogenic fungi, suggested that their presence may reduce the risk of fungal infection. These results indicated a soil-dwelling ant may choose nest sites presenting relatively low pathogen risk by detecting the odors produced by bacteria with anti-fungal properties., Author summary Insect pathogens are widely distributed in soil. Soil-dwelling insects must overcome challenges arising from pathogens in soil. Here we report that a soil-dwelling ant may choose nest sites with lower pathogen infection risk, specifically the ant can sense the cues of some actinobacteria that can inhibit the growth of the pathogens. By choosing the sites with higher abundance of some actinobacteria, the ant can get a higher survival rate. The ant and some actinobacteria thus coordinate a specialized adaptive strategy of infection risk management, enabling the ant population to grow.

Increase in atmospheric CO2 directly affects the insect physiology and behavior, and indirectly affects the herbivorous insects by affecting their hosts. The increase in atmospheric CO2 is accompanied by an increase in temperature and heat waves. Ophraella communa LeSage is a natural enemy of Ambrosia artemisiifolia (common ragweed). The development and reproduction of this beetle is weakened upon eating common ragweed grown under stress conditions. As female behavior and physiology alter after mating, the reproductive tract of males is likely to modulate reproduction and development in this species. Herein, the transcriptional profiles of testes and accessory glands from male O. communa individuals feeding on common ragweed under conditions of high CO2 concentration and heat waves and that grown under ambient CO2 concentration were compared. Differentially expressed genes (DEGs) were identified between the same tissues from beetles fed on common ragweed grown under different stress conditions. There were 3, 2, 3, 1and 5 genes related to decomposition and transport of macromolecular substances, host location, stress response, reproduction, and poisonous food-utilization. No expected response was observed in the male reproductive tract, but some of the identified DEGs might control the development of the population. The results presented here should be helpful in guiding future studies on deciphering the indirect response of other organs to high CO2 concentration and heat waves, as well as the functions of seminal fluid proteins in O. communa.

Summary Finding a suitable oviposition site is a challenging task for a gravid female fly, because the hatched maggots have limited mobility, making it difficult to find an alternative host. The oriental fruit fly, Bactrocera dorsalis, oviposits on many types of fruits. Maggots hatching in a fruit that is already occupied by conspecific worms will face food competition. Here, we showed that maggot-occupied fruits deter B. dorsalis oviposition and that this deterrence is based on the increased β-caryophyllene concentration in fruits. Using a combination of bacterial identification, volatile content quantification, and behavioral analyses, we demonstrated that the egg-surface bacteria of B. dorsalis, including Providencia sp. and Klebsiella sp., are responsible for this increase in the β-caryophyllene contents of host fruits. Our research shows a type of tritrophic interaction between micro-organisms, insects, and insect hosts, which will provide considerable insight into the evolution of insect behavioral responses to volatile compounds.

Red imported fire ant, Solenopsis invicta, was first found in Taiwan province of China in 2003. To prevent transboundary expansion, the Chinese government has formulated various control strategies in the last 15 years to slow down the spread of S. invicta. Despite all efforts, S. invicta invasion has reached more than 390 counties of 13 provinces and two special administrative regions in China; at present, S. invicta remains at the stage of rapid expansion. The transnational entry of S. invicta is linked to imported logs and wastepaper coming mostly from the United States. In domestic settings, long-distance expansion of S. invicta relied on potted plant and turf transportation. Both monogyne and polygyne social forms of S. invicta were present in China with polygyne colonies as the dominant one. Data on population and breeding dynamics of S. invicta reveal the presence of two peaks annually with nuptial flights occurring throughout the year. Arthropods, plant seeds, and honeydew are important food sources of S. invicta, thereby causing negative impacts on the abundance, diversity, and richness of native arthropod communities. Fire ants are threats not only to agriculture and power facilities, but also to human health, with more than 30% of people having suffered from the sting and 10% having experienced an allergic reaction. To address the expansion of S. invicta, the National Fire Ant Detection and Management Union was established and the formulation and implementation of management policies were drawn. Plant quarantine becomes an essential step in fire ant management, whereas the two-step method of combing toxic baits and contact dust emerges as the forefront method crucial in managing S. invicta. The experience and lessons learned from fire ant management in China could benefit other countries when facing similar challenges.

Muscarinic acetylcholine receptors (mAChRs) play important roles in the insect nervous system. These receptors are G protein-coupled receptors, which are potential targets for insecticide development. While the investigation of pharmacological properties of insect mAChRs is growing, the physiological roles of the receptor subtype remain largely indeterminate. Here, we identified three mAChR genes in an important agricultural pest Bactrocera dorsalis . Phylogenetic analysis defined these genes as mAChR-A, -B, and -C. Transcripts of the three mAChRs are most prevalent in 1-d-old larvae and are more abundant in the brain than other body parts in adults. Functional assay of Bdor-mAChR-B transiently expressed in Chinese hamster ovary cells showed that it was activated by acetylcholine (EC 50, 205.11 nM) and the mAChR agonist oxotremorine M (EC50, 2.39 μM) in a dose-dependent manner. Using the CRISPR/Cas9 technique, we successfully obtained a Bdor-mAChR-B knockout strain based on wild-type (WT) strain. When compared with WT, the hatching and eclosion rate of Bdor-mAChR-B mutants are significantly lower. Moreover, the crawl speed of Bdor-mAChR-B knockout larvae was lower than that of WT, while climbing performance was enhanced in the mutant adults. Adults with loss of function of Bdor-mAChR-B showed declined copulation rates and egg numbers (by mated females). Our results indicate that Bdor-mAChR-B plays a key role in the development, locomotion, and mating behavior of B. dorsalis.

Exotic invasive species can influence the behavior and ecology of native and resident species, but these changes are often overlooked. Here we hypothesize that the ghost ant, Tapinoma melanocephalum, living in areas that have been invaded by the red imported fire ant, Solenopsis invicta, displays behavioral differences to interspecific competition that are reflected in both its trophic position and symbiotic microbiota. We demonstrate that T. melanocephalum workers from S. invicta invaded areas are less aggressive towards workers of S. invicta than those inhabiting non-invaded areas. Nitrogen isotope analyses reveal that colonies of T. melanocephalum have protein-rich diets in S. invicta invaded areas compared with the carbohydrate-rich diets of colonies living in non-invaded areas. Analysis of microbiota isolated from gut tissue shows that T. melanocephalum workers from S. invicta invaded areas also have different bacterial communities, including a higher abundance of Wolbachia that may play a role in vitamin B provisioning. In contrast, the microbiota of workers of T. melanocephalum from S. invicta-free areas are dominated by bacteria from the orders Bacillales, Lactobacillales and Enterobacteriales that may be involved in sugar metabolism. We further demonstrate experimentally that the composition and structure of the bacterial symbiont communities as well as the prevalence of vitamin B in T. melanocephalum workers from S. invicta invaded and non-invaded areas can be altered if T. melanocephalum workers are supplied with either protein-rich or carbohydrate-rich food. Our results support the hypothesis that bacterial symbiont communities can help hosts by buffering behavioral changes caused by interspecies competition as a consequence of biological invasions., Author summary Insects display a wide range of dependence on symbiotic bacteria for basic functions. Responses by resident species to selective pressures imposed by invasive species, as well as specific underlying mechanisms that give rise to these responses are still poorly understood. Here we investigate the role of the symbiotic bacteria of the ghost ant, Tapinoma melanocephalum, to changes in host behavior associated with interspecies competition in areas invaded by fire ants, Solenopsis invicta. We show that Wolbachia is significantly enriched in workers of T. melanocephalum from S. invicta infested areas, and that these bacteria also increase in abundance in colonies that have been supplied with protein-rich food. Our results suggest that bacterial symbiont communities can play an important role in enabling ants to tolerate changes in behavior and diet as a result of biological invasions.

The oriental fruit fly Bactrocera dorsalis (Hendel) is a worldwide pest leading to crop production. The management of B. dorsalis is becoming more and more difficult because of the emerging insecticide resistance. Searching for new and effective methods in managing this pest has become an urgent task. Here, we explored the relationship between pigmentation and insecticide resistance through conducting studies on 5 strains of B. dorsalis (CK, CZ, CB, LC and LX) with various traits of pigmentation and insecticide resistance. Strain CK was a wild strain with brown pupae coloration while strain CZ was a beta-cypermethrin-resistant strain with pupae coloration was brown. Strain CB was a pigmentation mutation strain with white pupae coloration. Strain LC was the female of pigmentation sex genetic strain whose pupae coloration was white. Strain LX was the male of pigmentation sex genetic strain whose pupae coloration was brown. Efficacy tests were employed to evaluate the resistance performance of the 5 trains, transcriptome sequencing and gene quantifications were used to explore the potential genes in both pigmentation and detoxification pathway. The brief of results were as follow: Results of efficacy tests of the 5 strains with beta-cypermethrin, abamectin and trichlorfon respectively showed that resistances to these three insecticide of strains LX and LC were very low. The corrective mortalities of strains LX and LC in 128 ug/ml of abamectin were 49.48±3.01%, 59.06±1.89% respectively while that of strain CK was 11.80%±1.37. The corrective mortality of strain CZ were lowest in all concentrations level of all test reagent. The resistance of strain CK was similar to CB. Transcriptomic analysis showed that 24 genes and 165 genes were associated with pigmentation and detoxification. Gene expression pattern of strain CK was similar to strain CB while these two strains were different to strains LC and LX, and the gene expression pattern of strain CZ was more similar to strains LC and LX. Results of gene quantifications in B. dorsalis pupae showed that the relative expressions of yellow gene MK529913, DDC gene MK515141, laccase2 gene MK515143 and PO gene MK515140 in brown pupae (CK, CZ, LX) were significantly higher than those in white pupae (CB, LC) while the relative expressions of AANAT gene MK515144 in white pupae were significantly higher than those in yellow pupae. In summary, analyses of gene quantifications and efficacy tests indicated that high expressions of P450 gene, AANAT gene might contribute to resistances of adults of B. dorsalis to beta-cypermethrin and a bamectin; high expression of yellow gene might contribute to resistances of adults which emergenced from brown pupae to beta-cypermethrin and abamectin; high expressions of yellow genes, laccase2 gene, PO gene and DDC gene might contribute to the resistance of B. dorsalis to trichlorfon.

Background Bactrocera dorsalis (Hendel) is the main fruit fly pest of tropical and subtropical countries. The application of insecticides to manage this pest has led to serious resistance problems; therefore, new ways to control B. dorsalis are required. Pathogenic bacteria are sources of biocontrol agents for pest management. Results We determined that a pathogenic bacterial strain, Serratia marcescens PS-1, isolated from a moribund striped flea beetle (Phyllotreta striolata), was lethal to B. dorsalis adults following ingestion. Histological analyses revealed that PS-1 damaged the intestinal epithelium, resulting in cell death within 24 h. We then generated a gut transcriptomic data set using RNA-Seq at two time points (6 and 24 h) after PS-1 infection. We found that genes encoding the peritrophic matrix constituent were down-regulated, whereas genes involved in lipid and glycan metabolism, and renewal of the gut epithelium, along with genes encoding digestive enzymes and stress response factors, were up-regulated. In addition, 14 cecropin genes were identified and cloned from B. dorsalis. To our knowledge, the number of cecropins identified in the present study is greater than that reported in the insects of earlier studies. Moreover, some of the cecropins identified were significantly down-regulated after PS-1 treatment. Conclusion Our findings provide new insights into the insect gut response to pathogenic bacterial invasion and may aid the development of new strategies for the biological control of B. dorsalis. © 2019 Society of Chemical Industry.

The green lacewing, Mallada basalis (Walker) (Neuroptera: Chrysopidae), has a broad prey range and effective searching abilities. Because rearing procedures based on natural or factitious foods for the larvae of this economically important predator are often time consuming and/or expensive, the main objective of our study was to develop an artificial diet suitable for mass rearing. We analyzed the development, survival, longevity, and reproduction of M. basalis (F1 generation) fed 3 artificial diets. These diets were formulated based on those of Chrysoperla sinica Tjeder and Chrysopa pallens (Rambur) (Neuroptera: Chrysopidae). All 3 of the diets contained chicken egg, beer yeast powder, sucrose, trehalose, vitamin C, and potassium sorbate. The first artificial diet (AD1) also contained honey and distilled water. AD2 also included pupal hemolymph of the Chinese oak silk moth (Antheraea pernyi Guerin-Meneville; Lepidoptera: Saturniidae), and AD3 also included whole A. pernyi pupae, which had been b...

Eco-evolutionary dynamics of microbiotas at the macroscale level are largely driven by ecological variables. The diet and living environment of the oriental fruit fly, Bactrocera dorsalis, diversify during development, providing a natural system to explore convergence, divergence and repeatability in patterns of microbiota dynamics as a function of the host diet, phylogeny and environment. Here, we characterized the microbiotas of 47 Bactrocera dorsalis individuals from three distinct populations by 16S rRNA amplicon sequencing. A significant deviation was found within the larvae, pupae and adults of each population. Pupae were characterized by an increased bacterial taxonomic and functional diversity. Principal components analysis showed that the microbiotas of larvae, pupae and adults clearly separated into three clusters. Acetobacteraceae, Lactobacillaceae and Enterobacteriaceae were the predominant families in larval and adult samples, and PICRUSt analysis indicated that phosphoglycerate mutases and transketolases were significantly enriched in larvae, while phosphoglycerate mutases, transketolases and proteases were significantly enriched in adults, which may support the digestive function of the microbiotas in larvae and adults. The abundances of Intrasporangiaceae, Dermabacteraceae (mainly Brachybacterium) and Brevibacteriaceae (mainly Brevibacterium) were significantly higher in pupae, and the antibiotic transport system ATP-binding protein and antibiotic transport system permease protein pathways were significantly enriched there as well, indicating the defensive function of microbiotas in pupae. Overall, differences in the microbiotas of the larvae, pupae and adults are likely to contribute to differences in nutrient assimilation and living environments.

The bean flower thrips, Megalurothrips usitatus (Thysanoptera: Thripidae), is an important pest of leguminous crops (Fabales: Fabaceae) in south China. In this study, life history parameters of M. usitatus were investigated on 4 leguminous crops: snap bean (Phaseolus vulgaris L.), cowpea (Vigna unguiculata (L.) Walp.), pea (Pisum sativum L.), and lima bean (Phaseolus limensis Macf.). The development times (mean ± SE) from egg to adult on snap bean, cowpea, pea, and lima bean pods were 9.53 ± 0.06, 10.62 ± 0.14, 11.20 ± 0.11 and 11.55 ± 1.13 days, respectively. Survivorship of immatures was high on snap bean (80%) but low on lima bean (48%). The total number of first instars produced was highest on snap bean (sexual reproduction: 112.15 ± 11.98; parthenogenesis: 195.89 ± 19.24), and lowest on lima bean (sexual reproduction: 42.17 ± 2.99; parthenogenesis: 49.50 ± 3.90). Megalurothrips usitatus had the highest intrinsic rate of increase (rm) on snap bean (0.205), followed by cowpea (0.181), pea (0.1...

The cotton mealybug Phenacoccus solenopsis Tinsley is an emerging invasive insect pest. Since its first report as a pest in the United States in 1991, it has invaded and colonized more than 23 countries over the past century. It was first recorded from Pakistan in 2006 and from China in 2008. In this study, we performed field surveys from 2010 to 2012 and obtained mtCOI sequences from specimens across China and Pakistan, then compared them with already available mtCOI sequences from additional Asian and North American countries. Our genetic analysis provides evidence that P. solenopsis should be classified into two groups, one of which is found only in the United States, and the other found only in Asia. The Asian group contains nine unique haplotypes, two of which have invaded and spread across China, Pakistan, India, and Vietnam over the last 4-6 yr. Our genetic analysis also indicates that P. solenopsis has a close relationship with the parasitoid wasp Aenasius bambawalei Hayat, providing preliminary evidence of a congruent spread of this mealybug and its parasitoids across China.

Mutualistic interactions between ants and hemipterans are mediated by the honeydew produced by the hemipterans. Previous works have demonstrated that the invasive mealybug Phenacoccus solenopsis produces abundant honeydew and attracts a large number of workers of the fire ant Solenopsis invicta. Mealybugs exhibit higher fecundity when tended by fire ants. The honeydew produced by P. solenopsis plays an important role in interactions between these two species. However, relatively few studies have focused on whether there is a cost to P. solenopsis mealybugs of being tended by S. invicta through changes in their excretion behavior and the quantity of honeydew produced. Our results indicated that the honeydew of P. solenopsis contains xylose, fructose, sucrose, trehalose, melezitose, and raffinose. The sugar concentration in the mealybug honeydew changed in an ant-tended treatment. When tended by fire ants, the mealybugs generated honeydew with a significantly decreased xylose concentration. In contrast, the droplets showed a considerable increase in the melezitose concentration. P. solenopsis excreted honeydew more frequently when tended by S. invicta, but the weights of the droplets excreted by the ant-tended mealybugs were significantly lower. In addition, S. invicta exhibited a significant preference for different sugars. Melezitose was visited more intensively than the other sugars in two choice tests. These results may suggest that, to attract more tending ants, mealybugs adjust their carbohydrate metabolism.

Mutualism between ants and honeydew-producing hemipterans is a common phenomenon in ecosystems, and interactions between ants and hemipterans have been extensively studied. The invasive solenopsis mealybug, Phenacoccus solenopsis Tinsley (Hemiptera: Pseudococcidae), and the ghost ant, Tapinoma melanocephalum (F.) (Hymenoptera: Formicidae), are widely distributed in China. Previous studies showed that the ghost ant can promote the fitness of the invasive mealybug when natural enemies of the mealybug are excluded. In this study, we investigated the interactions between the ghost ant and the invasive solenopsis mealybug when the mealybug's natural enemies were included. Our results indicated that the honeydew produced by mealybugs facilitated colony growth of the ghost ant significantly more than by allowing them to feed on the mealworm, Tenebrio molitor L. (Coleoptera: Tenebrionidae). Tending by the ghost ant increased mealybug survival on the plants when six-spotted zigzag lady beetle larvae, Chei...

Bactrocera dorsalis (Hendel) is a fruit-eating pest that causes substantial economic damage to the fresh produce industry in tropical and sub-tropical countries. Methyl eugenol (ME) is a powerful attractant for mature males of B. dorsalis, and has been widely used for detecting, luring and eradicating B. dorsalis populations worldwide. However, the molecular mechanism underlying the olfactory perception of ME remains largely unknown. Here, we analyzed the differential proteomics profiling of the antennae between ME-responsive and ME-non-responsive males by using isobaric tags for relative and absolute quantitation (iTRAQ). In total, 4622 proteins were identified, of which 277 proteins were significant differentially expressed, with 192 up-regulated and 85 down-regulated in responsive male antennae. Quantitative real-time PCR (qRT-PCR) analysis confirmed the authenticity and accuracy of the proteomic analysis. Based on the iTRAQ and qRT-PCR results, we found that the odorant-binding protein 2 (BdorOBP2) was abundantly expressed in responsive male antennae. Moreover, BdorOBP2 was significantly up-regulated by ME in male antennae. Mature males showed significantly greater taxis toward ME than did mature females. Silencing BdorOBP2 reduced mature males’ responsiveness to ME. These results indicate that BdorOBP2 may play an essential role in the molecular mechanism underlying B. dorsalis olfactory perception of ME.

Since it was found in Taiwan and mainland, the spread of red imported fire ant Solenopsis invicta Buren into China has been continuous. In order to achieve better control of this pest, science and technology research on fire ants has advanced from many aspects. This paper presents the history of fire ant invasion and spread, estimated origins and social forms, present distribution, and potential expansion in China. Also the invasion biology and ecology is discussed in view of ecological impacts of the invasion. Management of S. invicta in China was implemented as soon as it was detected. Besides biological and physical control, monitoring, quarantine, and chemical control were widely studied and employed. Although a lot of work was done, the fire ant spread in China remains and will proceed rapidly in the future, mainly due to poor quarantine.

Although many reports suggested the economic importance of the red imported fire ant, Solenopsis invicta Buren, few attempts to test the hypothesis that the red imported fire ant-aphid mutualism enhances the occurrence of red imported fire ant on crops, thereby interfering with their flowering and fruiting and affecting their output. To address this problem, we compare the effects of red imported fire ant on the flowering and fruiting of self-pollinating and cross-pollinating crops by field investigations and indoor experiments. In the field, our results revealed that regardless of the aphid interaction, red imported fire ant preferred flowering mungbean plants, and their activities decreased the yields of single plants, total pod number, kernel number, and kernel weight. The interaction of red imported fire ant and aphids generated unfavorable effects on rapeseed yields per plant, total pod number, grain number, grain weight, and thousand-kernel weight and stimulated an elevated proportion of malformed seeds. However, the differences were not significant if only red imported fire ant was present. In the laboratory, although red imported fire ant display no apparent preference toward the seedlings of mungbean or rapeseed, the ants clearly favor the flowering plants of mungbeans. Therefore, this study indicated that one of the main mechanisms whereby red imported fire ants affect the crop yield is by compromising the reproduction processes.

In natural as in agricultural ecosystems, interactions between ants and honeydew-producing hemipterans are commonly observed. Mutualisms between invasive ants and hemipterans have been extensively studied in recent years. However, native ant species can equally exploit the honeydew excreted by hemipterans, and establish close relationships with them. Up till present, little is known about the competition between exotic ants (such as Solenopsis invicta) and its co-occurring species (e.g., Tapinoma melanocephalum) for this food resource. In this study, we compared the competitive ability of the invasive ant S. invicta and its co-occurring species T. melanocephalum in the laboratory. We also determined whether the two ant species could coexist and share honeydew resource. Our results indicate that the foraging activity of T. melanocephalum was restrained by S. invicta. Mortality of S. invicta and T. melanocephalum was significantly higher in T. melanocephalum colony case than that in other cases. The invasive ability between the two ant species was significantly different. These results suggest that S. invicta suppresses exploitation of honeydew-producing hemipterans by native ants and occupies most of honeydew resource. S. invicta could not completely drive T. melanocephalum out of honeydew competition, with small numbers of T. melanocephalum workers coexisting and sharing the honeydew with S. invicta. This finding permits a better understanding of the invasion success of S. invicta, and its ability to occupy new habitats.

To understand whether sulfoxaflor, a novel neonicotinoid, poses unacceptable risks to the environment, it is important to assess its effects on nontarget insects. Therefore, the effects of short-term exposure (28 days) of free-feeding sublethal concentrations (1-2μg/ml) of sulfoxaflor to the red imported fire ant, Solenopsis invicta, were investigated. The following parameters were evaluated to determine the impact of exposure: colony growth, food consumption (sugar water and locusts), and interspecific interactions. Sulfoxaflor exposure produced significant negative effects on S. invicta colony growth, with cumulative colony weight losses of 83.36% and 100.00% after treatment with 1μg/ml and 2μg/ml, respectively. The consumption of sugar water (containing sulfoxaflor) of surviving colonies decreased with increasing sulfoxaflor concentration. Moreover, the consumption of locusts decreased after treatment with 2μg/ml, but not 1μg/ml, sulfoxaflor. Sulfoxaflor treatment for 14 days led to reduced aggressiveness of S. invicta workers in interspecific confrontations (S. invicta vs. unexposed Pheidole fervida), and their probability of survival of aggressive encounters was reduced significantly to 48% of that of control ants. Our results indicate that sublethal concentrations of sulfoxaflor are likely to have a negative impact on ants.

Biological control using an ectoparasitic idiobiont (e.g., Pachycrepoideus vindemmiae Rondani) (Hymenoptera: Pteromalidae) can be an effective approach to reduce the economic losses caused by the melon fly, Bactrocera cucurbitae (Coquillett) (Diptera: Tephritidae). In this study, we determined the parasitism of P. vindemmiae on B. cucurbitae pupae of different ages. The results showed that B. cucurbitae pupae at all ages could be successfully parasitized by P. vindemmiae. The higher numbers of pupae parasitized (10.12 to 9.32 pupae/day for no-choice tests and 8.0 to 7.82 pupae/day for choice tests) were achieved when 3 or 4-day old pupae were used as hosts. The selection coefficient revealed that P. vindemmiae preferred 3 or 4-day old pupae as the host. Pachycrepoideus vindemmiae females developed more quickly on 3 or 4-day old hosts than on pupae of other ages. Longevity of parasitoid offspring obtained from 2 and 7-day old melon fly pupae varied from 9.45 to 10.37 days and from 8.97 to 9.45 day...

Solenopsis invicta is an aggressive, destructive and invasive ant. It has a profound impact on the native species in its environment. In this paper, we studied the effect of S. invicta on the invasive weed Ageratum conyzoides in the field. Using grid sampling and geostatistical analysis, we found that the density of A. conyzoides increased significantly in the presence of S. invicta. Furthermore, the spatial distribution of A. conyzoides was affected by S. invicta. The spatial structure of A. conyzoides emergence was aggregated. Sites where S. invicta was present were described by a Gaussian model, whereas a spatial model was used to describe the sites in the absence of S. invicta. The range of spatial dependence was 7.07 m for sites with a high density of S. invicta, whereas the spatial dependence was 1.46 m for sites with a low density of S. invicta and 3.14 m for control sites. Semivariogram models based on grid sampling of actual emerging A. conyzoides densities were used to produce contour maps of A. conyzoides densities in the field.

BACKGROUND: In order to investigate the extent of resistance of oriental fruit fly, Bactrocera dorsalis (Hendel), which is a widespread pest throughout tropical, subtropical and temperate fruit crops, 25 populations of this insect were collected from 13 sites in mainland China in 2007 and 2008. In addition, resistant strains were established that showed increasing development of resistance. RESULTS: Compared with the susceptible strain, one population of B. dorsalis expressed high resistance (RR = 70.4-fold), 16 populations expressed medium resistance (11.5-fold < RR < 25.8-fold) and eight populations had low resistance or remained susceptible (1.4-fold < RR < 8.9-fold) to trichlorphon. As regards β-cypermethrin, one population showed high resistance (RR = 44.0-fold), nine populations expressed medium resistance (12.2-fold < RR < 28.4-fold), 14 populations expressed low or minor resistance (3.0-fold < RR < 9.7-fold) and one population remained susceptible (RR = 1.1-fold). As regards avermectin, five populations had developed high resistance (44.3-fold < RR < 104-fold), seven populations expressed medium resistance (11.4-fold < RR < 38.6-fold) and three populations expressed low or minor resistance (3.5-fold < RR < 5.6-fold). A continuous resistance selection in the laboratory strain showed that the resistance ratios to trichlorphon, β-cypermethrin and avermectin were 71.6-fold, 333-fold and 70.4-fold respectively. CONCLUSION: The data provided a comprehensive survey of insecticide resistance in Bactrocera dorsalis in mainland China. All results suggested that early resistance management programmes should be established for restoring the efficacy of pesticide-based control measures. Copyright © 2010 Society of Chemical Industry

A sex-ratio bias was studied in alates of natural polygyne colonies of Solenopsis invicta Buren in southern China. The results showed that at the population level, the numbers of male and female alates were nearly equal, even though there was a strong bias toward producing one particular sex at the nest level. For example, 88.89% of the nests sampled were strongly biased toward males or females. In particular, three bias types were observed: extreme female bias, extreme male bias, and a moderate bias. Future studies should address the factors that lead queens to produce strongly biased sex ratios.

Laboratory bioassays were carried out to determine the efficacy of garlic, Allium sativum L. (Amaryllidaceae), essential oil applied alone or with diatomaceous earth (DE) against adult rice weevils, Sitophilus oryzae (L.) (Coleoptera: Curculionidae) and red flour beetles, Tribolium castaneum (Herbst) (Coleoptera: Tenebrionidae). The results showed that the combination treatment was significantly more effective than either treatment alone. In addition, the results also showed that the simultaneous application of essential oil plus DE significantly reduced the concentration of essential oil alone required for an effective treatment and the application rate of DE can be reduced when combined with essential oil. Moreover, the activity of the combination treatment lasted longer than that of essential oil alone and the survival of eggs or larvae to adult stage was significantly inhibited in the combined treatments against both species, compared with the use of essential oil alone. Our results suggested that garlic essential oil combined with DE has a strong additive effect, and therefore may have potential as an alternative to synthetic insecticides for the control of insect pests of stored products.

Insect resistance to the pyrethroid toxins has been examined previously using a number of traditional biochemical and molecular techniques. In this study, a proteomic approach involving two-dimensional polyacrylamide gel electrophoresis (2D-PAGE), matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) and tandem mass spectrometry (MS/MS) were applied to examine changes in resistant stains larvae of Bactracera dorsalis Hendel induced by pyrethroid treatment over a 3 h, 6 h and 12 h time period, and a number of proteins changes were observed to change in the level of regulation. Out of total 15 proteins, 9 proteins were observed only after pyrethroid treatment; 6 proteins showed different expression. After MALDI-TOF analyses and peptide mapping method, the data was compared with those of the known proteins available in public databases. Sequence analyses revealed that resistance response correlates with up-regulation (glycerol-3-phosphate dehydrogenase) and down-regulation (ATP–ADP antiporter) of energy-related proteins. It indicated that increased metabolism and energy-indeed as a resistance response to pyrethroid toxins. The regulation of cytoskeleton proteins were possibly a B. dorsalis tissue repair response or in cell division. Up-regulation of protein synthesis would results in substantial bioenergetic enhancement, suggesting a trade-off insect resistance to pyrethroid. Down regulation of neural protein indicated that neural system was physically injured after pyrethroid stress. Some remaining proteins were not identifiable, suggesting these may be novel proteins. Oriental fruit fly proteomes of pesticide induced provide an integrative basis for consolidating our knowledge of insect resistance. The results pave the way for future investigation of the alteration of the insect resistance to chemical pesticides.

The thermo-sensitive genic male sterility (TGMS) lines play a crucial role in two-line hybrid rice production. For a practical TGMS line, the stability of male sterility is one of the most important technical indicators. In this study, XianS, a spontaneous mutant with stable male sterility from an indica rice cultivar Xianhuangzhan, was classified as a non-pollen type TGMS line. The critical non-pollen sterility point temperature of XianS was determined as 27 degrees C. Genetic analysis demonstrated that the non-pollen sterility in XianS was controlled by a single recessive gene. Using SSR markers and bulked segregant analysis, the TGMS gene in XianS was fine mapped to a 183 kb interval between RMAN81 and RMX21 on chromosome 2. Two markers, 4039-1 and RMX14 completely cosegregated with this gene. Allelism test indicated that the non-pollen phenotype in seven non-pollen type TGMS lines from different sources, XianS, AnnongS-1, Q523S, Q524S, N28S, G421S, and Q527S is caused by the same TGMS gene. Although the location of TGMS gene in XianS is close to the gene OsNAC6, a previously identified candidate gene of tms5 in AnnongS-1, the sequence of OsNAC6 and its promoter region was identical in TGMS line XianS, AnnongS-1, and wild-type Xianhuangzhan. These results suggest that the non-pollen type TGMS trait probably be controlled by the same TGMS gene in different TGMS rice lines, but its real candidate gene still need to be further studied and identified.

The effect of soil humidity on the survival of Solenopsis invicta (Buren) workers was evaluated in this study. The study showed that the relative soil water (RSW) content inside the mound contained less variation than the surrounding soil. At a depth of 5 cm underground, the RSW was 7.6% in the mound, while it was 29% in the surrounding soil. At a depth of 20 cm underground, the RSW was 99% in the surrounding soil, while in the mound, the RSW did not reach 98% until it was 45-cm deep. The soil humidity affected the survival rate of S. invicta. For workers, the survival rate decreased when they were exposed to a higher RSW. The spring population had a higher tolerance to a high RSW than the autumn population, while the drought tolerance was the opposite. In extreme RSW, the longer that S. invicta was exposed, the lower their survival rate. The drought tolerance of the fire ant workers could be improved if they were pre-exposed to a low non-lethal RSW for a short period of time. The water content of the workers changed after acclimation to humidity. After a low RSW treatment, the water content of the acclimated workers was higher than the control workers. This suggests that this species is able to maintain a certain water content after acclimation, and that the water content of workers increases in accordance with the RSW.

The reverse photoperiod-sensitive genic male sterility (PGMS) and thermo-sensitive genic male sterility (TGMS) lines have an opposite phenotype compared with normal PGMS and TGMS lines widely used by the two-line system in current hybrid rice seed production. Thus, the application of reverse PGMS and TGMS lines can compensate PGMS and TGMS lines in hybrid rice production. YiD1S is a reverse PGMS line, in which pollen fertility is mainly regulated by day-length, but also influenced by temperature. Genetic analysis indicated that male sterility of YiD1S was controlled by two recessive major genes. An F(2) population from a cross between YiD1S and 8528 was developed and used for molecular mapping of the two reverse PGMS genes which were first named rpms1 and rpms2. Both simple sequence repeat (SSR) markers and bulked segregant analysis (BSA) were used in this study. As a result, one reverse PGMS gene (rpms1) was mapped to the interval between SSR markers RM22980 (0.9 cM) and RM23017 (1.8 cM) on chromosome 8. Eight SSR markers, YDS818, RM22984, RM22986, RM22997, YDS816, RM23002, RM339 and YDS810 completely co-segregated with the rpms1 gene. Another reverse PGMS gene (rpms2) was mapped to the interval between SSR markers RM23898 (0.9 cM) and YDS926 (0.9 cM) on chromosome 9. The physical mapping information from publicly available resources shows that the rpms1 and rpms2 loci are located in a region of 998 and 68 kb, respectively. The analysis based on marker genotypes showed that the effect of rpms1 was slightly larger than that of rpms2 and that the two genes interacted in controlling male sterility.

Chemosensory proteins (CSPs) have been predicted to be involved in development; however, direct evidence for their involvement is lacking and genetic basis is largely unknown. To determine the function of the chemosensory protein 9 (Si-CSP9) gene in Solenopsis invicta, we used RNA interference to silence Si-CSP9 in 3rd-instar larvae. The 3rd-instar larvae failed to shed their cuticle after being fed Si-CSP9-directed siRNA and expression profiling of RNAi-treated and untreated control larvae showed that 375 genes were differentially expressed. Pathway enrichment analysis revealed that 4 pathways associated with larval development were significantly enriched. Blast analysis revealed that one fatty acid amide hydrolase (FAAH) gene was up-regulated and 4 fatty acid synthase (FAT) genes and one protein kinase DC2 gene (PKA) were down-regulated in the enriched pathways. Significantly higher expression of these genes was found in 4th-instar larvae and Pearson correlation analysis of the expression patterns revealed significant relationships among Si-CSP9, PKA, FAAH and FAT1-4. Moreover, we confirmed that expression levels of Si-CSP9, FAAH, and FAT1-4 were significantly reduced and that the development of 3rd-instar larvae was halted with PKA silencing. These results suggest that Si-CSP9 and PKA may be involved in the network that contributes to development of 3rd-instar larvae.

Spalangia endius (Walker) (Hymenoptera: Pteromalidae) is found to be one of the most important natural enemies of Bactrocera dorsalis Hendel (Diptera: Tephritidae) pupae in China. In this study, the influence of host pupal age on the preference for and suitability of the host by the parasitoid S. endius was determined using choice and nonchoice tests. S. endius females accepted the 1-7 d-old B. dorsalis pupae for oviposition, and their offspring developed successfully. However, the S. endius preferentially parasitized the 2-, 3-, and 4-d-old host pupae. The emergence rate of the adult progeny was not affected by the host pupal age, nor was the male body weight, male longevity, and sex ratio of the parasitoid offspring. However, the shortest development time of both male and female progeny and the greatest size and adult longevity of female progeny were observed in hosts that were ≤4 d old. Females emerged later and lived longer than males, and they weighed more than the males. Host mortality decreased as the age of the host increased for 1-7-d-old hosts. Our findings suggest that 2-, 3-, and 4-d-old B. dorsalis pupae would be the best host ages at which to rear S. endius for effective control in field releases.

This study compared the amount of food resource depletion and interference competition at the individual and colony levels between Solenopsis invicta and Tapinoma melanocephalum laboratory colonies. The consumption of sausage, honey water, and mealworm by S. invicta colonies of equal worker number was higher than that by T. melanocephalum colonies. The consumption of sausage and honey water by S. invicta colonies of equal worker number was significantly higher than that by T. melanocephalum colonies. However, the amounts of sausage, honey water, and mealworm depleted by S. invicta colonies of equal worker biomass were lower than those depleted by T. melanocephalum colonies. The consumption of sausage and mealworm by S. invicta colonies of equal worker biomass were also significantly lower than that by T. melanocephalum colonies. Individual-level interference competition between S. invicta and T. melanocephalum colonies in limited space was intense. Competition intensity and the death rate reached their maximum when the worker numbers of both colonies were equal. In any proportion, the death rate of T. melanocephalum reached over 80%, higher than that of S. invicta . S. invicta colonies of equal worker biomass and equal worker number recruited more workers for colony-level interference competition and used more resources. However, the death rates among S. invicta colonies were higher than those among T. melanocephalum colonies. The active resource plundering of S. invicta reflected their intense competitiveness and limited the range of activity of T. melanocephalum .

Mutualism is a common and important ecological phenomenon characterized by beneficial interaction between two species. Red imported fire ants, Solenopsis invicta Buren, tend honeydew-producing hemipteran insects and reduce the activity of these insects' enemies. Ant-hemipteran interactions frequently exert positive effects on the densities of hemipterans. We tested the hypothesis that ant tending can increase the densities of the mealybug, Phenacoccus solenopsis Tinsley (Hemiptera: Pseudococcidae), and reduce the densities of the mealybug's predatory and parasitic enemies, the lady beetle, Menochilus sexmaculata Fabricius (Coleoptera: Coccinellidae), and the parasitoid wasp, Aenasius bambawalei Hayat (Hymenoptera: Encyrtidae). We found that more ants foraged on mealybug-infested hibiscus plants than on mealybug-free plants. The number of foraging ants on plants infested with high densities of mealybugs (62.5 ants per plant) was nearly six times that on mealybug-free plants (10.2 ants per plant). Experiment results showed that ant tending significantly increased the survival of mealybugs: if predatory and parasitic enemies were present, the survival of mealybugs tended by fire ants was higher than that in the absence of tending ants. Furthermore, this tending by fire ants significantly decreased the survival of lady beetle larvae. However, no apparent effect was observed on the survival of parasitoid.

The importance of mutualism is receiving more attention in community ecology. In this study, the fire ant Solenopsis invicta was found to take advantage of the shelters constructed by the leaf roller Sylepta derogata to protect mealybugs (Phenacoccus solenopsis) against their natural enemies. This protective effect of fire ant tending on the survival of mealybugs in shelters was observed when enemies and leaf rollers were simultaneously present. Specifically, fire ants moved the mealybugs inside the shelters produced by S. derogata on enemy-infested plants. Compared with that in plants without ants, the survival of mealybugs in shelters in the presence of natural enemies in plants with ants markedly improved. Both the protection of ants and the shelters provided by leaf rollers did not affect the survival of mealybugs in the absence of enemies in plants. Ants and leaf rollers significantly improved the survival of mealybugs in predator-infested plants, whereas no such improvement was observed in parasitoid-infested ones.

Although mutualism between ants and honeydew-producing hemipterans has been extensively recognized in ecosystem biology, however few attempts to test the hypothesis that mutualism between two alien species leads to the facilitation of the invasion process. To address this problem, we focus on the conditional mutualism between S. invicta and P. solenopsis by field investigations and indoor experiments. In the laboratory, ant colony growth increased significantly when ants had access to P. solenopsis and animal-based food. Honeydew produced by P. solenopsis also improved the survival of ant workers. In the field, colony density of P. solenopsis was significantly greater on plots with ants than on plots without ants. The number of mealybug mummies on plants without fire ants was almost three times that of plants with fire ants, indicating a strong effect of fire ants on mealybug survival. In addition, the presence of S. invicta successfully contributed to the spread of P. solenopsis. The quantity of honeydew consumption by S. invicta was significantly greater than that of a presumptive native ant, Tapinoma melanocephalum. When compared with the case without ant tending, mealybugs tended by ants matured earlier and their lifespan and reproduction increased. T. melanocephalum workers arrived at honeydew more quickly than S. invicta workers, while the number of foraging S. invicta workers on plants steadily increased, eventually exceeding that number of T. melanocephalum foragers. Overall, these results suggest that the conditional mutualism between S. invicta and P. solenopsis facilitates population growth and fitness of both species. S. invicta tends to acquire much more honeydew and drive away native ants, promoting their predominance. These results suggest that the higher foraging tempo of S. invicta may provide more effective protection of P. solenopsis than native ants. Thus mutualism between these two alien species may facilitate the invasion success of both species.

An invasive mealybug Phenacoccus solenopsis Tinsley (Hemiptera: Pseudococcidae) has attacked cotton (Gossypium hirsutum L.) seriously in Pakistan and India, and caused great loss in the production of cotton in recent years. This kind of pests can probably spread rapidly and would threaten cotton and other crops in many infested and non-infested countries. P. solenopsis has first been reported to severely damage Chinese hibiscus (Hibiscus rosa-sinensis) in Guangzhou, in December, 2008. In order to understand the effects of temperature on the development of P.solenopsis, the developmental threshold temperature (Ct) and effective accumulated temperature (K) were calculated for each developmental stage. A total of 30 P. solenopsis individuals were divided into 6 groups and reared at six constant temperatures (18, 21, 24, 27, 30, and 33°C). Total developmental duration ranged from 81.3 days at 18°C to 24.06 days at 30°C for female mealybug, and from 44.21 days at 18°C to 12.95 days at 30°C for male mealybug. Degree-day values for each developmental stage for both male and female mealybugs were determined. Total degree-day values required for full development for female and males were 414.9 and 218 degree-days respectively. Estimated threshold temperatures for different life stages ranged from 12.8°C (pre-oviposition) to11.7°C (3rd instar) for female mealybugs, and 16.5°C (prepupa) to 11.5°C (2nd instar) for male mealybugs. Key words: Mealybug, Phenacoccus solenopsis, development, temperature.

By using pitfall and bait traps, an investigation was made on the diversity and similarity of ant communities in the areas infested and un-infested with Solenopsis invicta Buren in Shenzhen of Guangdong. The results showed that under the invasion of S. invicta, the ant species number in lawn and wasteland reduced obviously, with a decrease of 6 in lawn and 3 in wasteland, and the native dominant ant species in lichee orchard, especially in wasteland and lawn, were replaced by S. invicta. With the infestation of S. invicta, the diversity and evenness of ant communities in wasteland and lawn decreased but the predominance increased obviously, while it was in adverse in lichee orchard. The similarity coefficients of the ant communities between S. invicta infested and un-infested lichee orchard, wasteland and lawn were 0.6316, 0.5882 and 0.2941, respectively.