Number Of Wasps Research Articles

War of the wasps: is <em>Diadegma insulare</em> or <em>Microplitis plutellae</em> a more effective parasitoid of the Diamondback Moth, <em>Plutella xylostella</em>?

Parasitism levels by Diadegma insulare (Muesebeck) (Hymenoptera: Ichneumonidae) and Microplitis plutellae (Haliday) (Hymenoptera: Braconidae) at various densities of their host, Plutella xylostella (L.) (Lepidoptera: Plutellidae), were assessed. Cages with densities of 10 hosts, 20 hosts, and 40 hosts were set up, with the cage volume (40 500 cm3) and number of wasps (2 females) remaining constant. The host populations were also exposed to the wasps for two different exposure times: 1 day and 3 days. The study showed that D. insulare was a better parasitoid overall, achieving a level of parasitism equal to or higher than M. plutellae at all densities. Microplitis plutellae performed best at a lower host density (76% ± 9% of 10 hosts vs. 43% ± 3% of 40 hosts). Diadegma insulare performed similarly at all densities tested (75% ± 5% of 10 hosts, 83% ± 4% of 20 hosts, and 79% ± 6% of 40 hosts). This suggests that D. insulare may be the better parasitoid overall and should be applied in severe, large-scale infestations, while M. plutellae may be better for small-scale infestations.

Ants Visiting the Post-Floral Secretions of Pericarpial Nectaries in Palicourea rigida (Rubiaceae) Provide Protection Against Leaf Herbivores But Not Against Seed Parasites

Pericarpial nectaries (PNs) have frequently been treated in the literature as extrafloral nectaries (EFNs). This treatment is partly justified by their morphological and functional similarities in attracting bodyguard ants to protect the plant against herbivores. Palicourea rigida is a common Neotropical savanna treelet with tubular yellow flowers that are pollinated by hummingbirds. After pollination, the corolla falls, but the sepal ring remains and keeps the nectaries active over the ovarium throughout fruit development stages. Using a standard ant-exclusion experiment, we tested whether these PNs attract ants to protect the developing fruits against seed parasites and the leaves against chewing herbivores. We analyzed the differences between the initial and final leaf area. Before full fruits maturity, they were collected and taken to the laboratory for weighing and to observe wasp emergence. The number of wasps per fruit and per plant was recorded. The results showed that after pollination, the floral nectaries of P. rigida act as EFNs, attracting visiting ants. Ant-tended plants lost significantly less leaf area and had heavier fruits than untended plants. However, the ants did not protect the fruits against seed-parasitic wasps. In P. rigida, the post-floral secretions of PNs play the same role as EFNs, and the ant-plant mutualism is context-dependent based on the type of herbivore and the plant tissue consumed.

Reduced Densities of the Invasive Wasp,Vespula vulgaris(Hymenoptera: Vespidae), did not Alter the Invertebrate Community Composition ofNothofagusForests in New Zealand

Invasive common wasps (Vespula vulgaris L.) are predators of invertebrates in Nothofagus forests of New Zealand. We reduced wasp densities by poisoning in three sites over three y. We predicted an increase in the number of invertebrates and a change in the community composition in sites where wasps were poisoned (wasps removed) relative to nearby sites where wasps were not poisoned (wasps maintained). Wasp densities were significantly reduced by an average of 58.9% by poisoning. Despite this reduction in wasp densities, native bush ants (Prolasius advenus Forel) were the only taxa that was significantly influenced by wasp removal. However, contrary to our predictions there were more ants caught in pitfall traps where wasps were maintained. We believe that the higher abundance of these ants is probably because of the scarcity of honeydew in wasp-maintained sites and compensatory foraging by ants in these areas. Otherwise, our results indicated no significant effects of reduced wasp densities on the total number of invertebrates, or the number of invertebrate families, observed in pitfall or Malaise traps. An analysis of community composition (permutational multivariate analysis of variance) also indicated no significant difference between wasp-removed or wasp-maintained communities. The most parsimonious explanation for our results is that although we significantly reduced wasp numbers, we may not have reduced numbers sufficiently or for a sufficiently long period, to see a change or recovery in the community.

Jasmonate-Mediated Induced Volatiles in the American Cranberry, Vaccinium macrocarpon: From Gene Expression to Organismal Interactions

Jasmonates, i.e., jasmonic acid (JA) and methyl jasmonate (MeJA), are signaling hormones that regulate a large number of defense responses in plants which in turn affect the plants’ interactions with herbivores and their natural enemies. Here, we investigated the effect of jasmonates on the emission of volatiles in the American cranberry, Vaccinium macrocarpon, at different levels of biological organization from gene expression to organismal interactions. At the molecular level, four genes (BCS, LLS, NER1, and TPS21) responded significantly to gypsy moth larval feeding, MeJA, and mechanical wounding, but to different degrees. The most dramatic changes in expression of BCS and TPS21 (genes in the sesquiterpenoid pathway) were when treated with MeJA. Gypsy moth-damaged and MeJA-treated plants also had significantly elevated expression of LLS and NER1 (genes in the monoterpene and homoterpene biosynthesis pathways, respectively). At the biochemical level, MeJA induced a complex blend of monoterpene and sesquiterpene compounds that differed from gypsy moth and mechanical damage, and followed a diurnal pattern of emission. At the organismal level, numbers of Sparganothis sulfureana moths were lower while numbers of parasitic wasps were higher on sticky traps near MeJA-treated cranberry plants than those near untreated plants. Out of 11 leaf volatiles tested, (Z)-3-hexenyl acetate, linalool, and linalool oxide elicited strong antennal (EAG) responses from S. sulfureana, whereas sesquiterpenes elicited weak EAG responses. In addition, mortality of S. sulfureana larvae increased by about 43% in JA treated cranberry plants as compared with untreated plants, indicating a relationship among adult preference, antennal sensitivity to plant odors, and offspring performance. This study highlights the role of the jasmonate-dependent defensive pathway in the emissions of herbivore-induced volatiles in cranberries and its importance in multi-trophic level interactions.

A new species of Cerchysiella (Hymenoptera: Encyrtidae) parasitic in larva of chestnut trunk borer (Coleoptera: Cerambycidae) from China with notes on its biology

A new species of Cerchysiella Girault (Hymenoptera: Chalcidoidea, Encyrtidae), Cerchysiella raddeii Yang, sp. nov., is described from China. It is a gregarious koinobiont endoparasitoid in mature larvae of the chestnut trunk borer, Massicus raddei (Blessig) (Coleoptera: Cerambycidae), a serious pest which causes severe damage to many oak tree species, particularly Quercus mongolica and Quercus liaotungensis (Fagaceae) in forested areas of northeastern China. The new species is one of the principal natural enemies of the wood borer and it has high potential as a biological control agent with parasitism rates of 6.7%, large numbers of adult wasps were reared from a single host larva (average 1083.8), and there is a high female : male sex ratio (9.67 : 1).

The Hohenheimer Box – A new way to rear and release Lariophagus distinguendus to control stored product pest insects

To improve the biological control of stored product pests, the present paper reports on the development of a rearing box for parasitoids of pest insects. The box contains breeding substrate and populations of hosts and parasitoids and is placed in storage sites, where parasitoids are released continuously over several months. The box was developed to rear Lariophagus distinguendus (Förster) (Hymenoptera: Pteromalidae) to control the granary weevil Sitophilus granarius (L.) (Coleoptera: Curculionidae). Due to sanitary reasons, the bean weevil Acanthoscelides obtectus Say (Coleoptera: Bruchidae) was chosen as an alternative host. Rearing experiments revealed that the cowpea Vigna unguiculata unguiculata (L.) Walp. is most suitable as host substrate. For the outlet of the rearing device, a wire gauze mesh size of 0.8–1.0mm was found suitable to release wasps while holding back the bean weevils. The size of the starting populations of hosts and parasitoids was determined experimentally in a storage building. An amount of 5ml weevils plus 21–60 adult parasitoids on 2kg of cowpeas produced an average of 56 and 62 wasps per week respectively, from June to September. Wasps reared in the boxes had the same number of offspring on granary weevils as wasps from regular lab-cultures. This study demonstrates the feasibility of a rearing box for parasitoids of stored product pests that releases large numbers of wasps over several months. We consider our study as a guideline for the development of similar rearing boxes also for other parasitoid-pest systems in stored products protection throughout the world.

Of volcanoes and insects: the impact of the Puyehue–Cordon Caulle ash fall on populations of invasive social wasps, Vespula spp.

AbstractVolcanic eruptions have important effects on terrestrial ecosystems. The biotic effects of volcanic ash on insect populations vary from widespread and catastrophic to subtle and localized. Volcanic eruptions may increase insect mortality through the effects of the ash plume, and these vary by taxon or specific biological features. The Puyehue–Cordon Caulle Volcanic Complex is the most recent eruption in Patagonia. Here we explore and describe the effects of the eruption of this volcanic complex on invasive Vespula spp. populations. These wasps are very abundant social hymenoptera that have recently invaded Patagonia. We placed baited traps following the gradient of deposited ash, and revisited them once a week during February to April. No wasps were caught where ash deposition levels exceeded 3.0 cm. The number of wasps caught in sites with minimal ash deposits was similar to that of previous years. In locations where ash layers are intermediate, a few wasps were observed, but only during the peak of wasp abundance. We show that Vespula spp. populations were severely affected by the ash deposition and plume, caused by this eruption. These results show catastrophic effects of ash deposition over a large area, even at great distances from the eruption epicenter. We conclude that wasp mortality explained by the volcanic eruption may reach distant areas, and cause local extinction. In areas where active volcanoes are common, invasive insects may encounter an additional obstacle in their invasion success.

Dispersal of Aphytis melinus (Hymenoptera: Aphelinidae) after augmentative releases in citrus orchards

The efficacy of natural enemies in controlling pests under field conditions is largely correlated with their capacity to spread within infested crops. In this study the spatial dispersal of the California red scale parasitoid Aphytis melinus DeBach (Hymenoptera: Aphelinidae) was evaluated in the field after augmentative releases. The experiment was conducted in 2007 in six 1-ha plots in a Sicilian citrus orchard under integrated pest management. A total of 180,000 A. melinus adults was released in each of three plots and the other plots were left as untreated control. The flight range of the parasitoid was evaluated, for 35 days after the release, on 16 trees per each plot, located at 20 and 40 m from the central release point using yellow sticky traps activated with Aonidiella aurantii (Maskell) (Hemiptera: Diaspididae) sexual pheromone and by monitoring the percentage parasitism of the scale on fruits and twigs. The effects of the distance from the release point and density of susceptible stages of host on parasitoid dispersal were evaluated. The number of wasps captured during the whole trial was greater in the traps located 20 m from the release point than in those at 40 m and in the control plots. Aphytis melinus dispersed over distances less than 40 m based on both the lower per- centage parasitism and numbers captured recorded at distances of 40 m. The results are discussed in the context of the biological control of California red scale in citrus orchards by means of wasp releases. In particular, the release points should be no more than 40 m apart for a quick and homogeneous colonization of the area treated.

Mutualism from the inside: coordinated development of plant and insect in an active pollinating fig wasp

Recent studies on the obligate interaction between fig trees and their pollinating agaonid wasps have focused on population aspects and wasp–seed exploitation at the level of the inflorescence. Detailed studies on larval and gall development are required to more fully understand how resources are exploited and adaptations fine-tuned by each partner in nursery pollination mutualisms. We studied the larval development of the active pollinating fig wasp, Pegoscapus sp., and the galling process of individual flowers within the figs of its monoecious host, Ficus citrifolia, in Brazil. The pollinator development is strongly dependent on flower pollination. Figs entered by pollen-free wasps were in general more likely to abort. Retained, unpollinated figs had both higher larval mortality and a lower number of wasps. Pegoscapus sp. larvae are adapted to plant development, with two contrasting larval feeding strategies proceeding alongside gall development. The first two larval stages behave as ovary parasites. Later larval stages feed on hypertrophied endosperm. This indicates that a successful galling process relies on endosperm, and also reveals why pollination would be a prerequisite for the production of high-quality galls for this Pegoscapus species.

‘Push’ and ‘pull’ responses by fig wasps to volatiles released by their host figs

In the specific mutualism between fig trees (Ficus) and their obligate pollinating fig wasps (Agaonidae), it is crucial that fig wasps can recognize the developmental stages of their host figs. However, the responses of fig wasps to volatiles released from figs during their developmental phases are less clearly understood and are the focus of this study. We extracted and identified the volatiles released from the figs of Ficus curtipes throughout their development. Using Y-tube choice experiments, we also compared the behavioural responses of the tree’s pollinator (Eupristina sp.) to figs at different developmental stages, and compared these results to those obtained by trapping fig wasps as they arrived at a tree with a developing fig crop. The chemical composition of the fig volatiles changed during fig development with the blends exhibiting clear segregation among figs at different developmental phases. Male phase figs had the most distinct blend. Fig wasp females were preferentially attracted to receptive figs, but figs at most other developmental phases were also attractive. Conversely, male phase figs had a repellent effect. These results were supported by the behaviour of the wasps under natural conditions, with small numbers of fig wasps arriving at the tree before and after receptive figs were present. These results indicate a more complex relationship between fig volatiles and fig wasp behaviour than previously realized, with volatiles mediating both the initial meeting of the mutualists to achieve pollination and egg laying and the subsequent departure of the next generation of fig wasps. This offers an explanation for the specialization and long-term coexistence of figs and fig wasps.

Parasitoid wasp diversity in apple orchards along a pest-management gradient

This study examined the impact of pest-management practices on Hymenopteran parasitoid diversity and assemblage composition in six apple orchards in southeastern Michigan, USA. The orchards comprised a gradient of pest-management intensity from organic to IPM to conventional practices. We used a pesticide toxicity index to quantify monthly and seasonal pest-management intensity in each orchard and conducted monthly vacuum-sampling of wasps during summer of 2009.Monthly toxicity scores predicted wasp abundance, setting an upper bound on the number of wasps in the orchard, but did not predict species richness. Total species richness was significantly higher in the organic orchard than in all others, but in August a conventional orchard had the highest wasp abundance and species richness. These results suggest that a toxicity index could guide pesticide choices or application times so as to increase parasitoid wasp populations, which have untapped potential for pest management in apple orchards.

Endogenous RNA viruses of plants in insect genomes

Endogenous viral elements (EVEs) derived from RNA viruses with no DNA stage are rare, especially those where the parental viruses possess single-strand positive-sense (ssRNA+) genomes. Here we provide evidence that EVEs that share a sequence similarity to ssRNA+viruses of plants are integrated into the genomes of a number of insects, including mosquito, fruit flies, bees, ant, silkworm, pea aphid, Monarch butterfly, and wasps. A preliminary phylogenetic analysis places these EVEs as divergent relatives of the Virgaviridae and three currently unclassified plant viral species.

Changes in Oak Gall Wasps Species Diversity (Hymenoptera: Cynipidae) in Relation to the Presence of Oak Powdery Mildew (Erysiphe alphitoides)

Changes in oak gall wasps species diversity (Hymenoptera: Cynipidae) in relation to the presence of oak powdery mildew (Erysiphe alphitoides). Zoological Studies 51(2): 175-184. Plant-mediated interactions usually lead to multipartite interactions in a community of organisms. To evaluate the impact of oak powdery mildew Erysiphe alphitoides infestation on the distributions of cynipid oak gall wasps (Hymenoptera: Cynipidae), a field survey was conducted in West Azerbaijan Province, Iran, in 2 consecutive years of 2009-2010. Multiple samples were taken from both infected and uninfected trees (Quercus spp.) at 4 different sites where maximum activity of E. alphitoides occurred and cynipid galls exhibited complete development. The species diversity and richness of gall-forming wasps were estimated and also parameters such as Simpson's index, Shannon's H', and the Sorensen similarity quotient were calculated. Data were also analyzed by independent-samples t-test to compare the mean numbers of galls occurring on infected and uninfected trees. Results clearly indicated that the highest richness and diversity of oak gall-forming wasps were consistently found on uninfected trees at all study sites in the 2 consecutive years. Further, the number and diversity of gall-forming wasps were negatively correlated with the extent (percentage) of pathogen infection, and trees with the heaviest E. alphitoides infection had the lowest numbers of gall-forming wasps. In addition, E. alphitoides decreased the rate of Sorensen's coefficient between regions where oak trees infected with E. alphitoides were sampled. This study demonstrates plant-mediated interactions between a native pathogen and a community of gall-forming insects on oak trees.

福州大叶榕隐头果内的小蜂群落结构与多样性

对福州2个样地10株大叶榕果内小蜂群落组成和物种多样性进行研究。全年在两个样地267个隐头果内共收集到小蜂13458只。发现大叶榕隐头果内有7种小蜂,隶属小蜂总科Chalcidoidae中的榕小蜂科Agaonidae、金小蜂科Pteromalidae的隐针榕小蜂亚科Epichrysomallinae、锥尾榕小蜂亚科Otitesellinae和延腹榕小蜂亚科Sycoryctinae;广肩小蜂科Eurytomidae、刻腹小蜂科Ormyridae、姬小蜂科Eulophidae,其中榕小蜂科的<em>Platyscapa coronata</em>是大叶榕唯一的传粉者,传粉方式为主动传粉;非传粉榕小蜂的雄性多型现象普遍。传粉与非传粉小蜂的性比明显具有偏雌现象。传粉小蜂性比为0.19±0.07,非传粉小蜂中<em>Camarothorax bismasculinus</em>小蜂性比为0.36±0.10;<em>Walkerella </em>sp.小蜂性比为0.36±0.22,<em>Sycoscapter</em> sp.小蜂性比为0.31±0.22,<em>Sycophila</em> sp.小蜂性比为0.35±0.13。雄性多型现象可能是导致非传粉小蜂性比提高的原因之一。根据各种榕小蜂发生数量及连续性,可将大叶榕隐头果中的榕小蜂分为常见种和偶见种,<em>Platyscapa coronata</em>、<em>Camarothorax bismasculinus</em>、<em>Walkerella</em> sp.、<em>Sycoscapter</em> sp.和<em>Sycophila</em> sp.为常见种,<em>Omyrus</em> sp.和<em>Aprostocetus </em>sp.为偶见种。偶见种的存在对常见种的数量几乎没有影响,偶见种利用的是榕果内未饱和的一部分资源,也可能是榕果为偶见种的发生预留了空间和资源。首次发现姬小蜂科的昆虫寄生在榕果内,且有一定的种群数量,为姬小蜂科昆虫分类及其生物学、生态学特性研究提供了基础资料。在大叶榕小蜂群落结构中,传粉小蜂和非传粉小蜂的种类和数量呈现明显的季节性。冬-春季(12-翌年5月)榕果内小蜂的种类和数量较多,传粉榕小蜂是优势种,其重要值达到0.42,榕果种子结实率高;夏-秋季(6-11月间)小蜂种类和数量略少,<em>Camarothorax bismasculinus</em>和<em>Sycophila </em>sp.是优势种,其重要值分别为0.56和0.28,而传粉小蜂的重要值仅为0.025,此期大叶榕榕果中几乎找不到传粉小蜂,榕果结实率极低,对大叶榕的繁殖利益有较大的负面影响。雨水和高温等不良气候,可能是导致夏-秋季雄花期榕果内的传粉小蜂数量骤减的主要原因。两个实验样地的小蜂群落结构组成没有明显差异,年变化趋势相似。研究结果为城市绿化和热带雨林生物多样性保护提供科学依据。;<em>Ficus virens</em> Ait. var.<em> sublanceolata</em> is a common monoecious landscape trees in Fuzhou. In this study, the structure and biodiversity of fig wasp community inside syconia of <em>F. virens</em> Ait. var.<em> sublanceolata</em> were investigated based on 10 plants at two selected sites in Cangshan and Minhou town of Fuzhou. A total of 13458 fig wasps were collected from 267 syconia in different seasons. Seven fig wasp species were found, which belonged to Agaonidae, Epichrysomallinae, Otitesellinae, Sycoryctinae, Eurytomidae, Ormyridae and Eulophidae of Chalcidoidea, respectively. Among them, only<em> Platyscapa coronata</em> of Agaonidae served as a pollinating agent for<em> F. virens</em> Ait. var.<em> sublanceolata</em> through a way of active pollination. Male polymorphism was common in the non-pollinating fig wasps. Both pollinating and non-pollinating fig wasps showed female-biased sex ratios. The sex ratio of pollinating fig wasps was 0.19±0.07, and the sex ratios of non-pollinating fig wasps <em>Camarothorax bismasculinus</em>, <em>Walkerella </em>sp., <em>Sycoscapter</em> sp.<em> and Sycophila</em> sp. were 0.36±0.10, 0.36±0.22, 0.31±0.22 and<em> </em>0.35±0.13, respectively. Male polymorphism may be one of the reasons for the increase of sex ratio in the non-pollinating wasps. According to the number and continuity of occurrence, fig wasps could be classified into common species and occasional species.<em> Platyscapa coronata</em>, <em>Camarothorax bismasculinus</em>, <em>Walkerella</em> sp., <em>Sycoscapter</em> sp. and <em>Sycophila</em> sp. were common species, while <em>Omyrus</em> sp. and <em>Aprostocetus </em>sp. were occasional species. The presence of occasional species had little effect on the number of common species. Occasional species might use the unsaturated part of the resources in the fig fruit. It might also be that the fig fruit reserved space and resources for the occurrence of the occasional species. It was the first time that a certain number of Eulophidae parasitic insects were found in fig fruits. This provides the basic data for the taxonomy and the research of biological and ecological characteristics of Eulophidae insect. <br> The wasp community composition and structure differed greatly across seasons. In winter and spring (from December to May of next year), there were more species and higher numbers of fig wasps inside syconia, among which pollinating fig wasps were the dominant species with an importance index up to 0.42. This resulted in a high setting rate of fig seeds. In summer and autumn (from June to November), there were fewer species and lower numbers of fig wasps inside syconia, among which <em>Camarothorax bismasculinus </em>and <em>Sycophila </em>sp. were dominant species with importance indexes up to 0.56 and 0.28, respectively, whereas the importance indexes of pollinating wasps was only 0.025. During this period, it was difficult to find pollinating wasps in the fig. Therefore, the setting rate of fig seeds was lower. The large proportion of non-pollinating had a great negative impact on the reproduction of <em>Ficus virens </em>Ait. var. <em>sublanceolata.</em> Rain and high temperature might be the main causes of the dramatic decrease of the number of pollinating fig wasps inside syconia during the summer and autumn seasons. There were no significant differences in community structure and its annual change between the two sites. The results of this study provide a scientific basis for the urban greening and biodiversity conservation in tropical rain forests.

细叶榕榕小蜂群落结构及动态变化

Ficus microcarpa Linn.f.(Ficus,Moraceae) is a common monoecious tree,which is widely distributed in the fig center area of Asia-Australasia.It is both a main tree species in the tropical forest and a common tree species planted in the courtyard and street.In this study,we investigated the structure,biodiversity and dynamics of fig wasp community in syconia of 19 F.microcarpa plants at two selected sites by observation on and collection from the specific trees at specific time and season all year around.A total of 26,318 fig wasps were collected from 530 syconia in different seasons.Seventeen fig wasp species belonging to Agaonidae,Epichrysomallinae,Otitesellinae,Sycoryctinae,Eurytomidae and Ormyridae of Chalcidoidea were collected.Among them,only Eupristina verticillata of Agaonidae served as a pollinator for F.microcarpa through a way of active pollination.The sex ratio in this pollinating fig wasp species was 0.16,with a very strong female-bias phenomenon.In the non-pollinators,the sex ratio is higher(0.46—0.55) in the species with winged male wasps(Odontofroggatia galili,O.quinifuniculus,O.corneri,Sycophila sp.1,Sycophila sp.2 and Meselatus bicolor),lower(0.31—0.37) in the species with wingless male wasps(Philotrypesis taiwanensis,Sycoscapter gajimaru,Walkerella microcarpae),and medium(0.47) in the species with both winged and wingless male wasps(Philotrypesis okinavensis).The results suggested that the sex ratio of fig wasps may be related to the strategy of mating behavior. In the structure of fig wasp community in F.microcarpa,the importance index was dominant in the pollinating fig wasps,but was much smaller in non-pollinating species O.galili and Sycophila sp.2.According to the number and continuity of occurrence,fig wasps could be classified into common species and occasional species.E.verticillata,Odontofroggatia galili,Walkerella microcarpae,Sycophila sp.1,Sycophila sp.2 and Philotrypesis okinavensis were common species,while the remaining 11 were occasional species.The composition and structure of wasp community differed greatly across seasons.From February to June,there were fewer(only 3—4) species inside syconia,with 48.88 pollinating wasps and 13.64 non-pollinating wasps in a single fig on average,respectively.From July to January of next year,there were more(as many as 6—13) species inside syconia,with 24.38 pollinating wasps and 18.89 non-pollinating wasps in a single fig on average,respectively.The results suggested that the number of pollinating wasps in the latter period reduced greatly compared with that in the former period(P0.001);whereas for the non-pollinating wasps,both the number of species and that of wasps were significantly increased(P=0.001).The species and the number of fig wasps in the male-flower phase depended on the species and the number of spawning wasps in the female-flower phase.However,the rainfalls,temperature and the number of syconia in the female-flower phase may affect on the number of spawning wasps and the spawning behavior of wasps.The results of this study provide a scientific basis for urban greening and biodiversity conservation in tropical rain forests.

Flower-Visiting Social Wasps and Plants Interaction: Network Pattern and Environmental Complexity

Network analysis as a tool for ecological interactions studies has been widely used since last decade. However, there are few studies on the factors that shape network patterns in communities. In this sense, we compared the topological properties of the interaction network between flower-visiting social wasps and plants in two distinct phytophysiognomies in a Brazilian savanna (Riparian Forest and Rocky Grassland). Results showed that the landscapes differed in species richness and composition, and also the interaction networks between wasps and plants had different patterns. The network was more complex in the Riparian Forest, with a larger number of species and individuals and a greater amount of connections between them. The network specialization degree was more generalist in the Riparian Forest than in the Rocky Grassland. This result was corroborated by means of the nestedness index. In both networks was found asymmetry, with a large number of wasps per plant species. In general aspects, most wasps had low niche amplitude, visiting from one to three plant species. Our results suggest that differences in structural complexity of the environment directly influence the structure of the interaction network between flower-visiting social wasps and plants.

Relationships between beneficial invertebrates, field margin vegetation, and thrip damage in organic leek fields in eastern England

Beneficial invertebrate numbers in two organic leek fields in eastern England were assessed in relation to four field margin vegetation treatments (clover/grass, regeneration, two flower mixtures) using pitfall and pan traps. Damage caused by onion thrips in one field was also estimated. Clover/grass and regeneration margins generally had more beneficial invertebrates than either flower mixture margins and invertebrate numbers in the fields were least opposite flower mixture margins. Distance from field margins had a greater effect on invertebrate numbers, with most ladybirds (Coccinellidae), hoverflies (Syrphidae), lacewings (Neuroptera) and parasitic wasps (Hymenoptera) recorded from the middle of fields. High ladybird, hoverfly and parasitic wasp (Icheumonidae) numbers were associated with lowest onion thrip damage, but there was no evidence that field margin treatments were related to damage. Sown flower mixture margins did not positively affect beneficial invertebrate numbers in the leek crop. It appears that an approach in keeping with elements already in the landscape would be just as effective as the use of alien vegetation mixtures in generating invertebrate natural enemy activity in vegetable fields of eastern England.

Connectivity counts: disentangling effects of vegetation structure elements on the searching movement of a parasitoid

1. A heterogeneous habitat structure can have a profound impact on foraging carnivorous arthropods. In the present study, we examined which elements of complex vegetation structure influence the searching movement of a parasitoid model organism.2. Previous field work showed that tall and dense vegetation reduces the parasitism success of the eulophid egg parasitoid Oomyzus galerucivorus while the probability of host egg deposition increased close to plant tips.3. In laboratory bioassays, dried grass stems were arranged according to the natural situation in different setups. The wasps' walking time on stems increased with increasing stem height and density. High stem density decreased the walking time of the parasitoids on the ground and an increased stem height reduced the propensity to fly to the ground. Connectivity had a minor positive effect on the number of stem contacts, but considerably reduced the number of wasps reaching the upper part of grass stems by two‐thirds.4. Thus, although enhanced vegetation complexity enhances walking activity of the parasitoids in the vegetation, laying eggs at the tip of long grass stems in dense vegetation can be an adaptive strategy for the host, as it maximises the number of connections between plant parts to cross by parasitoids before reaching the host. The connection points disorient the wasps, which lose time, reverse their direction or fly away.

Nectar-Seeking and Host-Seeking byLarra bicolor(Hymenoptera: Crabronidae), a Parasitoid ofScapteriscusMole Crickets (Orthoptera: Gryllotalpidae)

Larra bicolor F. (Hymenoptera: Crabronidae) is a specialist parasitoid of Scapteriscus (Orthoptera: Gryllotalpidae) mole crickets, attacking adults and medium to large nymphs of the hosts. Adult wasps derive energy from plant nectars. In replicated trials in pastures in northern Florida, many more wasps fed on nectar of Spermacoce verticillata F. (Rubiaceae), a non-native plant, than on nectar of the native plants Spermacoce prostrata Aubl. or Spermacoce remota Lamarck. Few of them fed on the native plant Solidago fistulosa Michx. (Asteraceae). About as many fed on the native plant Chamaecrista fasciculata (Michx) Greene as on S. verticillata in the autumn months until the native plant ceased flowering by October. In contrast, S. verticillata continues flowering until the first hard freeze, which typically occurs in December, so overall, it is a more reliable nectar source in northern Florida and may be still more reliable in frost-free areas of southern Florida where it may flower year-round. The number of immature wasps (eggs and larvae) parasitizing mole crickets was positively related to host density but also declined with distance from a plot of S. verticillata out to 200 m, based on samples of pitfall trap-collected mole crickets. The occurrence of parasitized mole crickets at a 200-m distance suggests that female wasps recruited to a plot of S. verticillata forage for hosts out to at least 200 m. This in turn suggests that mole cricket populations might be diminished by planting plots of S. verticillata at least 400 m apart when L. bicolor wasps are present.

Pollinator and non-polinator fig wasp relationship in syconia of &lt;i&gt;Ficus exasperata&lt;/i&gt;

Ficus species are pollinated only by species specific wasps of the subfamily Agaoninae (Hymenoptera: Agaonidae). Hence, figs have an intimate relationship with its pollinating fig wasps that oviposit within fig ovaries and the resulting larvae feed on the developing seeds. Figs are also associated with non-pollinator wasps of the family Agaonidae that either oviposit within fig ovaries thereby resulting in galls, or parasitize the larvae of pollinator wasps thereby affecting the fig-pollinator relationship. The present study identifies the fig wasps associated with the dioecious fig, Ficus exasperata, a common fig in Sri Lanka and investigates the relationship between the pollinator and non-pollinator wasps. During the fig off season in December 2007, 50 syconia collected from a single hermaphroditic tree of F. exasperata located in the Peradeniya University Park were subjected to this study. From these figs emerged the pollinator wasp Karadibia gestroi and the non-pollinator parasitoid wasp Philotrypesis quadrisetosa. Emergent pollinator fig wasps were the most abundant with a mean of 213.50 wasps per fig in comparison to the non-pollinator parasitoid wasps that ranged from 0-67 per fig. There was no significant relationship (r = -0.168) between the numbers of pollinator and non-pollinator wasps that emerged from a fig. The sex ratio of the pollinator wasp, K. gestroi that emerged from figs was strongly female biased (0.20) inferring that the offsprings are from a single or few mothers. Keywords: dioecious fig; syconia; parasitoid; parasitism DOI: 10.4038/cjsbs.v38i2.1860 Cey. J. Sci. (Bio. Sci.) 38 (2): 67-73, 2009