Abundance Of Wasps Research Articles

Density-dependent effects of an invasive wasp on the morphology of an endemic New Zealand ant

Invasive species can cause extinction, but perhaps more commonly they compete for resources, resulting in subtle life history modification in native species. Changes in food quantity and quality as a result of biological invasions have the potential to influence the size and morphology of native species. The invasive wasp Vespula vulgaris reaches its highest known population densities in the honeydew beech forests of New Zealand, where it competes with native ants (Prolasius advenus) for food. We tested the hypothesis that this competition would reduce ant worker size in areas of high wasp density. A significant reduction in worker size was found with increasing invasive wasp density, after accounting for site and environmental covariate effects. However, this significant average reduction in size was small. For example, an increase of 10 wasp nests ha−1 was associated with an average decrease of only 1.2 % in the Weber’s length of native ant workers. We also examined scaling of morphological relationships in ants to test the hypothesis that scaling would vary between ant populations at differing wasp densities. Scaling relationships for six out of eight measured morphological characters significantly differed in ants when subject to high wasp densities, relative to areas of low wasp abundance. These results indicate that invasive wasps can potentially reduce native ant size, and alter scaling relationships, likely by limiting resource availability during ant development. Such subtle effects of an invasive species may be common in situations where invasive species exert strong competitive pressure.

Effects of Forest Type and Management on Native Wood Wasp Abundance (Hymenoptera: Siricidae) in Mississippi, United States

The United States has a rich fauna of native Siricidae (wood wasps), but they are rarely studied because they have limited economic impact. In 2004, a non-native wood-boring pest, Sirex noctilio F., was found established in North America. Because S. noctilio is an economically important pest in pine plantations throughout the Southern Hemisphere, interest in the ecology of American native wood wasp populations has increased. A study was conducted during fall 2011 to investigate the effects of forest stand type and characteristics on native wood wasp abundance, and to describe their flight phenology in northeastern Mississippi. In total, 609 native wood wasps were captured, consisting of 608 Sirex nigricornis F. and one Urocerus cressoni Norton. There were significant treatment and location effects that influenced wood wasp abundance. The flight period of wood wasps captured in our study (October-December) was similar to studies in the southeastern United States, but differed from results in Minnesota and the northeastern United States (June-October). Wood wasp abundance was significantly correlated with higher basal area, smaller tree diameter at breast height, and shorter trees, all indicators of forest stand stress. It appears proper silvicultural management of pine plantations may reduce native wood wasp population abundance in the southeastern United States, as it does to S. noctilio in the Southern Hemisphere. We propose implementing management models used for the southern pine beetle to reduce stand hazard of future infestations of native and invasive wood wasps.

Diversity of the Nests of Social Wasps (Hymenoptera: Vespidae: Polistinae) in the Northern Pantanal, Brazil

Some species of wasps demonstrate plasticity with diverse nesting habits according to the environmental conditions and substrates used for building the nests, while others are restricted to habitats with specific conditions and may exhibit some degree of fide-lity. The aim of this study was to estimate species richness and abundance of nests of Polistini and Epiponini wasps in four landscape units in the Pantanal of Poconé, Retiro Novo Farm, southwestern Mato Grosso state, Brazil. The nests of social wasps were sampled in four plant physiognomies locally known as cambarazal, landizal, pombeiral and campo limpo from August 25, 2011 to April 11, 2012, being recorded 308 nests of eight genera and 14 species of social wasps. The highest number of nests belongs to Polybia ruficeps xanthops (32.69%), Poly. sericea (24.27%) and Synoeca surinama (15.21%). The highest species richness was recorded in cambarazal and the highest abundance of nests in pombeiral, while campo limpo showed the lowest richness and abundance of nests. The nests of S. surinama were associated with cambarazal and landizal (IndVal = 93.3, P = 0.001), while the nests of Poly. ruficeps xanthops and Poly. chrysothorax were associated with cambarazal, landizal and pombeiral (IndVal = 97, P = 0.001). There was lower abundance and lower species richness of wasps in campo limpo. These results demonstrate that the maintenance of forest environments in the Pantanal is essential for the establishment and maintenance of social wasp nests.

Releases of Psyttalia fletcheri (Silvestri) (Braconidae : Opiinae) into cucurbit crops on Reunion Island

Three fruit flies (Diptera : Tephritidae) damage cucurbit crops on Reunion Island : Bactrocera cucurbitae (Coquillet), Dacus demmerezi (Bezzi) and D. ciliatus (Loew). Chemical control does not provide any satisfactory control of fly populations. The GAMOUR project aims at promoting agroecological management of these pests. The present work is aimed at studying the augmentative releases of the parasitoid Psyttalia fletcheri (Silvestri) (Hymenoptera : Braconidae) as a biological control agent. From 2010 to 2011, four trials were set up. We released between 1,600 to 3,000 parasitoid wasps according to the trial. The parasitism rate of P. fletcheri was then recorded using fruit samples collected in the field. Parasitism was almost null before the releases. After the releases, mean parasitism rates increased moderately with a maximum of 16.7%. The parasitism was moreover null on crops where no B. cucurbitae were caught. In light of a cost-benefit analysis, releases of P. fletcheri appear therefore irrelevant. On the other hand, inoculative releases of parasitoids in low altitude agrosystems (B. cucurbitae is present below 800 m) could locally increase the abundance of wasps and promote environmentally friendly methods to growers.

Landscape composition and configuration differently affect trap-nesting bees, wasps and their antagonists

Intensification of agriculture reduces heterogeneity at local and landscape levels and thereby impact biodiversity and ecosystem processes. We studied a host-antagonist system of cavity-nesting bees, wasps and their antagonists and hypothesised that hosts and antagonists show different responses to local land-use intensity, the diversity of landscape in terms of composition and the spatial structure of landscape in terms of configuration.In a highly replicated study, we established nesting resources on 95 grasslands in three geographic regions across Germany and measured species richness and abundance of hosts (bees and wasps) and their antagonists, and rates of parasitism. For each site, we quantified local land-use intensity as well as landscape heterogeneity in terms of composition and configuration at spatial scales ranging from 250m to 2000m.Increasing landscape heterogeneity enhanced species richness, abundance and parasitism rate, whereas local land-use intensity only marginally negatively affected total abundance. Bee and wasp abundance as well as wasp species richness were enhanced by landscape composition at 250m, whereas their antagonists were enhanced by landscape configuration at 1500m.In conclusion, landscape composition and configuration affect trophic levels differently and are more relevant than local land-use intensity. Solitary bees and wasps, which offer important pollination and pest control services, could be supported by enhancing landscape diversity, while their antagonists could benefit from measures that promote landscape connectivity. Hence, scale-dependent and trophic group specific conservation management schemes are required, that address different components of landscape heterogeneity to enhance functional diversity and trophic interactions in agricultural landscapes.

Plant diversity in a nutshell: testing for small‐scale effects on trap nesting wild bees and wasps

Declining plant species richness in agro‐ecosystems and thus reduced habitat quality can have cascading effects on ecosystem functioning, leading to reduced pollination and biological control. Here we test if plant diversity can affect arthropod diversity and abundance on a very small scale, manipulating plant species richness (2, 6, 12 and 20 sown species) in small adjacent subplots (6 × 9 m) in 10 wildflower strips in an agricultural landscape. We simultaneously analyzed the effect of plant species richness, vegetation structure, and plant composition on the species richness and abundance of cavity‐nesting wild bees, wasps, their prey and natural enemies, and on the structure of their food webs. By separating the trap‐nesting species into functional groups according to their prey, we aimed to understand the underlying patterns for the effects of plant diversity. Increasing plant species richness had a significant effect only on spider‐predating wasps, the group of wasps trophically most distant from plants. In contrast, bees and food‐web structure were unaffected by plant diversity. Spider‐predating wasp abundance negatively correlated with the abundance of spiders, suggesting top‐down control. Interestingly, the abundance of spiders was the only variable that was strongly affected by plant composition. The hypothesis that the effect of plant diversity decreases with increasing trophic level is not supported by our study, and the mobility of species appears to play a greater role at this small spatial scale.

Ecological and Forensic Implications of Social Wasps on Pig Carcass Degradation in Brazilian Savannah

Herein are recorded the composition and richness of 188 specimens of social wasps collected processing pig carcasses (Sus scrofa L.) in a Brazilian Savannah. Among the species collected Polybia (Myrapetra) fastidiosuscula de Saussure, 1854 (n = 178), Polybia (Trichotorax) ignobilis (Haliday, 1836) (n = 6), Apoica (Apoica) gelida Van der Vecth, 1972 (n = 3) and Polybia (Trichotorax) sericea (Olivier, 1791) (n = 1) were founded using fresh, bloated, decayed and skeletonized pig caracass. P. fastidiosuscula showed significant differences among decomposition stages, with preference for the bloated stage. The high abundance of social wasps in animal carcasses under decomposition, mainly those considered necrophagous, reveals the ecological importance of these wasps in carcass fragmentation by directly influencing the duration of the decomposition process. Moreover, the preference of P. fastidiosuscula for the bloated stage may be used as subsidy for forensic implications.

The invertebrate communities associated with a Chrysanthemum coronarium-invaded coastal sage scrub area in Southern California

The escape of ornamental plants is a main pathway of invasion into many ecosystems. Non-native plants can alter basal resources and abiotic factors leading to effects that ripple throughout an ecosystem. Invertebrates mediate these effects—responding quickly to abiotic and primary producer changes and, in turn, influencing other species. Invasions are of particular concern in the coastal sage scrub ecosystems of Southern California, where habitat loss and urban encroachment increase invasive species propagule sources and decrease native community resistance. The introduced annual Chrysanthemum coronarium (crown daisy) is a common invader with largely undocumented community-level effects. Our study tested the relationships between the invasive Chrysanthemum and a coastal scrub invertebrate community using a field study at the Tijuana River Estuary. We found similar or lower abundances and diversity of canopy fauna in the presence of Chrysanthemum. Community composition dramatically differed, however, in the presence Chrysanthemum, which was associated with higher abundances of dipterans, wasps and flower beetles, and lower abundances of hemipterans and thysanopterans than native shrubs. Differences in communities were consistent at the species- and order-levels, and were associated with the generally greater plant biomass and shadier conditions afforded by the natives. This study reveals that even a proportionally small amount of Chrysanthemum may shift the invertebrate community through alterations of abiotic properties and plant biomass. We recommend that Chrysanthemum be removed at the first sign of invasion or that spread is prevented since effects on the invertebrate community are dramatic and occur quickly.

The role of parasitoids in regulation of Polistes wasp population (Hymenoptera, Vespidae: Polistinae)

The study conducted in 2005–2010 analyzes the behavioral response of the parasitoids Latibulus argiolus (Rossi) (Hymenoptera, Ichneumonidae) and Elasmus schmitti Ruschka (Hymenoptera, Eulophidae) to the distribution of their host, Polistes wasps (Hymenoptera, Vespidae). Various conditions of the parasitoid-host system and conditions of regulation of the host abundance are discussed. The parasitoid females are more active in wasp colony clusters and tend to infest larger nests. If the parasitoids are abundant, infestation of host colonies starts earlier, sometimes before the worker emergence; therefore, density-dependent behavioral response of parasitoids is caused primarily by the impact of the aggregation component. Thus, the host population density factor appears to be mediated not only by the non-uniform development rates of colonies and their spatial distribution, but also by the seasonal (temporal) aspect of their development. Low density of the host population, at which the parasitoids regulate the wasp abundance, corresponds to a certain phase of the seasonal colony development, namely to the period before the emergence of workers. On the whole, we are dealing with a host-parasitoid system in which the spatial and temporal factors are closely interrelated.

OCORRENCE OF <i>MISCHOCYTTARUS ROTUNDICOLLIS</i> (VESPIDAE) IN MANGROVE SWAMPS ATTRACTED BY FISH IN DECOMPOSITION

Vespidae is an important insect family that is among the largest predators of other insects in natural environments. This study in mangrove swamps was carried out in order to know if social wasp, Mischocyttarus (Mischocyttarus) rotundicollis could be attracted by fish (sardine) in decomposition. The insects were collected in mangrove swamps in Itaborai, every two weeks, totaling 72 samples from August 2008 to July 2011. Over a 36 months period 69 individuals were caught. The abiotic factors (season and tidal variations) that could influence the occurrence of these wasps in mangrove swamps were recorded. The abundance of wasps was only affected by the spring season and the highest tides (spring-tides). The presence of the M. rotundicollis, in the mangrove swamps caught with fish in decomposition, may indicate that the studied forest area still represents a natural preserved refuge and reveals the importance of understanding of ecology these wasps and provides much information that will contribute greatly to environmental sciences.

Effects of Habitat Fragmentation on Abundance, Larval Food and Parasitism of a Spider-Hunting Wasp

Habitat fragmentation strongly affects species distribution and abundance. However, mechanisms underlying fragmentation effects often remain unresolved. Potential mechanisms are (1) reduced dispersal of a species or (2) altered species interactions in fragmented landscapes. We studied if abundance of the spider-hunting and cavity-nesting wasp Trypoxylon figulus Linnaeus (Hymenoptera: Crabronidae) is affected by fragmentation, and then tested for any effect of larval food (bottom up regulation) and parasitism (top down regulation). Trap nests of T. figulus were studied in 30 agricultural landscapes of the Swiss Plateau. The sites varied in the level of isolation from forest (adjacent, in the open landscape but connected, isolated) and in the amount of woody habitat (from 4 % to 74 %). We recorded wasp abundance (number of occupied reed tubes), determined parasitism of brood cells and analysed the diversity and abundance of spiders that were deposited as larval food. Abundances of T. figulus were negatively related to forest cover in the landscape. In addition, T. figulus abundances were highest at forest edges, reduced by 33.1% in connected sites and by 79.4% in isolated sites. The mean number of spiders per brood cell was lowest in isolated sites. Nevertheless, structural equation modelling revealed that this did not directly determine wasp abundance. Parasitism was neither related to the amount of woody habitat nor to isolation and did not change with host density. Therefore, our study showed that the abundance of T. figulus cannot be fully explained by the studied trophic interactions. Further factors, such as dispersal and habitat preference, seem to play a role in the population dynamics of this widespread secondary carnivore in agricultural landscapes.

FLIES - The Natural History and Diversity of Diptera

Human knowledge will be erased from the world’s archives before we possess the last word that a gnat has to say to us. -Henri Fabre- The new book, FLIES, tells us a lot about what gnats and their relatives have to tell us about nature, would we but listen attentively. The author, Stephen Marshall, began his biological interests in beetles and then somehow went to the dark side, FLIES. This reviewer began his career in beetles and stayed put; that is what qualifies him as a reviewer of this simply superb book Steve Marshall has produced both in text and images. Why? It’s in the subtitle: the Natural History and Diversity of Diptera, the key word being diversity by which Marshall means many different kinds. Beetles and parasitic wasps are universally touted as the hyper-diverse and divergent groups of insects, so why does Marshall claim that Flies also exhibit such diversity in the natural world? In doing so, he sets himself apart from what more focused Dipterists have usually done, that is stay the course, look at one genus, one family, one region at a time; not much diversity displayed on their watch, for sure. Marshall, on the other hand, took on the entire dipteran Order, globally, with hundreds of superb photos (adults and immatures) that he took in the field over years of searching out fly species richness. He added an up-to-date text covering all taxa of the entire Order at the subfamily and tribal levels with hundreds of examples and images named at the genus and/or species level. Marshall’s FLIES is written and imaged for both the academic and the enthusiastic layperson. It contains some 2000 color images of flies in their natural environment, nearly all taken by the author. He has selected (out of some 160,000 named species of flies), those that he finds especially fascinating and those essential for demonstrating global dipteran diversity in form and function. The latter, form and function, speak directly to the astounding diversity and divergence of dipterans and justify including them along with the celebrated richness and abundance of beetles and parasitic wasps. Marshall, in FLIES, has justified that leap with his broad coverage and excellent story telling about flies’ lives. Such dipteran diversity is a mixed blessing for the public and for scientists alike. Who wants to see a blow fly from your neighbor’s garbage bin walking around on your chocolate cake, or a dozen mosquitos landing on you when you are trying patiently to photograph a hummingbird at a tropical flower in an Amazonian Heliconia patch? On the other hand, colorful hover flies on a yellow flower (Marshall’s book cover jacket) are part of nature’s exquisite beauty. While many groups of flies are vectors of devastating human and animal diseases and pests of crops and forests, others are important pollinators, recyclers, and beneficial control agents of insect pests. Marshall’s text tells compelling stories about all these kinds of flies that are easily read by citizen naturalists and high-schoolers in science class, as well as professional biologists of all walks of study. While Marshall’s introduction claims that “flies rule!” and his book sets out to prove that claim, Coleopterists and Hymenopterists certainly will argue that point. However, this reviewer has to agree that in the Amazon Basin during the rainy season there is more fly abundance by far in the rain forest canopy than any other group of insects (except relatively species-poor but abundant ants). This is thanks to one family of dipterans, the fungus gnats, Mycetophilidae (see Marshall’s pages 139-140) that emerge by the multimillions, as fungi reach their fruiting peak. While flies might not truly “rule,” gnats do have a lot to say about temperate and tropical fly abundance, something that Henri Fabre would appreciate. Without a doubt, Marshall sets high standards with this and his previous book, Insects: Their Natural History and Diversity, (also, Firefly Books). These treatments offer a challenge to entomologists of other ordinal taxa to produce similar books. Should that come to pass, and considering that insect and their relatives constitute three-fourths of life on earth, we humans would have a far better understanding of the natural world and our place in it.

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.

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.

Forest fragments' contribution to the natural biological control of Spodoptera frugiperda Smith (Lepidoptera: Noctuidae) in Maize

The present work evaluated the influence of forest distance on predatory solitary wasps' abundance and richness and its relation to the natural biological control of the fall armyworm (Spodoptera frugiperda Smith - Lepidoptera: Noctuidae) in maize. The study consisted of two parallel lines of six experimental maize plots located at an increasing distance from a forest edge. Four trap-nests were placed in the vertices of each plot of the first line to evaluate the abundance and species richness of predatory solitary wasps. The larvae of the fall armyworm were sampled weekly by inspecting ten randomly chosen plants per plot. Predatory solitary wasp abundance (but not species richness) decreased whilst the fall armyworm abundance increased with the distance from the forest. Moreover, population densities of predatory solitary wasps and the fall armyworm were negatively correlated. Results suggested that the crop plantations located near forest fragments might benefit from the reduced pest problems as a result of increased natural biological control.

A comparative approach to understanding factors limiting abundance patterns and distributions in a fig tree–fig wasp mutualism

Numerous factors affect distribution and abundance. Due to their intimate host association, pollinating fig wasps are expected to occupy the entire distribution of their host fig. An understanding of the physiology of fig wasp species and the factors affecting adult survival are important for understanding and explaining wasp abundance and distribution patterns. We examine distribution and abundance patterns of a fig tree–fig wasp system in which the non‐pollinator (Ceratosolen galili) has been reported to be rarer than the pollinator (Ceratosolenarabicus) in drier areas due to lower desiccation tolerance. Both species are closely related and utilise the same oviposition sites onFicus sycomorus.We used ecological niche modelling to determine whetherC. galilicovers the range ofF. sycomorusand whether it is consistently rarer thanC. arabicus.We examined emergence times, critical thermal limits, desiccation and starvation tolerances of the wasps. The suggested rarity ofC. galilirelates to lower abundance in certain months and at certain localities but a similar number of occurrence records within the distributional range (except in arid regions, e.g. Namibia). In contrast toC. galili,C. arabicushas a wider thermal range, lives longer under hydrating and dehydrating conditions and is a nocturnal flier. The synergistic effect of physiological tolerances and flight time differences exacerbate the less favourable conditions available toC. galiliduring flight and location of receptive figs. These factors enableC. arabicusto survive for longer thanC. galili, meaning that they are more likely to disperse to trees that are flowering further away in space and time. Combining correlative and mechanistic approaches has aided us in understanding the ecological niches of these species.

The relationships between Apocrita wasp populations and flowering plants in Maine's wild lowbush blueberry agroecosystems

This was the first study to have surveyed the spatial and temporal structure of Apocrita wasps in lowbush blueberry fields, a unique native agricultural landscape in Maine and eastern Canada. The relative abundances of wasps associated with lowbush blueberry (Vaccinium angustifolium Ait.) were investigated in 33 blueberry fields throughout Washington County, Maine, USA. Native wasps were captured during the springs and summers of 1997 and 1998 in Malaise traps erected along a transect in each field. Vegetation sampling was also conducted along these transects to quantify available floral resources. Data indicate the abundance of the total wasp community was positively associated with the abundance of sheep laurel (Kalmia angustifolia L.). Relationships between trap capture of 13 wasp morphospecies and other flowering weeds were also investigated. Most taxa in 1998 were positively associated with one or more of the following flowering plants: bunchberry (Cornus canadensis L.), bush honeysuckle (Diervilla lonicera P. Mill.), dogbane (Apocynum androsaemifolium L.), sheep laurel, and witherod (Viburnum nudum var. cassinoides L.). Similar results were not evident in 1997 because the method used to sample vegetation was not as extensive as that used in 1998. However, sheep laurel was positively associated with the wasp genera Microplitis spp. and Phanerotoma spp. during both years.

Fluctuations in Richness and Abundance of Social Wasps During the Dry and Wet Seasons in Three Phyto-Physiognomies at the Tropical Dry Forest of Brazil

The social wasp nests were quantified in three different plant physiognomies (forested Caatinga, shrubby Caatinga, and agricultural systems) to analyze the effect of environmental seasonality and plant physiognomy on the richness, nest abundance, and species composition of social wasps in the region of tropical dry forest of Brazil. The forested Caatinga physiognomy had the greatest richness of species (S = 16), followed by shrubby Caatinga (S = 13) and by agricultural system (S = 12). The first axis of detrended correspondence analysis (DCA) explained 67.8% of the variability and shows a gradient of the fauna from agricultural system and shrubby Caatinga to forested Caatinga. In the first axis, wet season scores were much higher than those for the dry season in forested Caatinga. The second axis explained 18.7% of the variability and shows a separation of samples collected during the wet or the dry periods in shrubby Caatinga. This separation was less evident in the agricultural system. Variations in nest abundance were more intense in arbustive caatinga (45% decrease in number of active nests in the dry period), moderate in forested Caatinga (24% decrease in number of active nests in the dry period), and low in agricultural systems (8% decrease in the dry period).

Effects of the bittering agent denatonium benzoate on the success of toxic baiting of pestiferous German wasps (Vespula germanica)

Our aim was to study the effects of the addition of varying concentrations of the bittering agent, denatonium benzoate (DB), to toxic baits used for the control of German wasps (Vespula germanica). We tested the level of detection of different concentrations of DB by wasps, and measured the overall effectiveness of freeze-dried baits containing 0.1% fipronil and DB to control local wasp activity. The addition of DB concentrations higher than 10 ppm to fresh beef baits made them less attractive to wasps compared with controls. Lyophilized toxic baits containing DB 10 ppm and fipronil 0.1% were as attractive as control baits and reduced local wasp abundance by, on average, 74%. The results for lyophilized baits containing 0.1% fipronil but lacking DB were similar (average reduction: 80%). The addition of DB to toxic baits against Vespula spp. can bring about undesirable effects on toxic baiting efficacy. In the case of V. germanica, we suggest using the lowest concentration possible (i.e. 10 ppm or lower) that may still elicit an aversive response in humans and/or non-target species.

The reproductive success of Ficus altissima and its pollinator in a strongly seasonal environment: Xishuangbanna, Southwestern China

Fig trees (Ficus spp.) are of great ecological significance, producing fruits that are fed on by more birds and mammals than any other plants in the tropics. They are pollinated by host-specific pollinator fig wasps (Hymenoptera, Agaonidae), and their fruit phenology and reproductive success are, therefore, modulated by symbiotic fig wasps. However, there are few studies focusing on the variation of Ficus reproductive success in strongly seasonal environments. We examined the phenology and reproductive success of Ficus altissima growing in a highly seasonal climate towards the northern limit of the range of fig trees in Xishuangbanna, China. Leaf production occurred at irregular intervals throughout the year, with new leaves and syconia initiated together, producing between three and seven crops over a 3-year period. Syconia were produced in synchronous crops with asynchrony between trees. The syconia produced more seeds than pollinators, and those syconia with more seeds also produced more pollinators. Reproductive success (measured as the number of seeds and pollen-carrying agaonid females produced by each syconium) varied greatly between seasons. It was highest for crops that matured during the cooler, relatively dry periods from February to March and October to November, and was lowest during the summer months from April to August. This variation corresponded to small differences in the number of flowers in the syconia, but was mainly driven by large seasonal differences in the relative abundance of non-pollinating fig wasps.