Native Wasp Research Articles

No adverse effects of symbiotic control on the parasitism of Halyomorpha halys by egg parasitoids

The brown marmorated stink bug Halyomorpha halys is a polyphagous insect, which has a devastating impact on agricultural production in many countries. The alteration of symbiont vertical transmission, by removing symbionts from stink bug eggs (symbiotic control), has been recently introduced in control programmes against this insect. A major advantage of this strategy is the compatibility with natural enemies, since it allows an insecticide-free approach that is not harmful to other agroecosystem components. However, the effect of anti-symbiont products on parasitism by egg parasitoids is still unexplored. Here, we investigated the impact on parasitism by native (Anastatus bifasciatus, Ooencyrtus telenomicida and Trissolcus kozlovi) and exotic (Trissolcus japonicus and Trissolcus mitsukurii) parasitoids that attack H. halys eggs, after treatment with the micronutrient biocomplex Dentamet®, used for symbiotic control. The native wasp species were tested in no-choice bioassays, showing that treatment of the egg masses did not affect emergence percentages, but the non-reproductive effects were often reduced by the biocomplex. The exotic species T. japonicus and T. mitsukurii were used in no-choice and paired choice bioassays, showing an opposite influence of Dentamet® on emergence percentage and preference in the two species. No-choice tests indicated the highest successful parasitoid emergence on biocomplex-treated egg masses for T. japonicus, while no preference in the paired comparison with eggs treated with water or untreated. In contrast, T. mitsukurii displayed the lowest parasitism after Dentamet® treatment in no-choice tests, and preferred egg masses without Dentamet® in paired choice tests. We did not record any natural symbiont acquisition by the parasitoids emerged from H. halys egg masses, indicating that the wasp fitness is very unlikely to be altered by dysbiotic effects resulting from treatments. Therefore, our results support a further implementation of symbiotic control in different crops in combination with biological control, as sustainable options for H. halys integrated pest management.

Impacts of the invasive hornet Vespa velutina on native wasp species: a first effort to understand population-level effects in an invaded area of Europe

Invasive alien species could generate a multitude of impacts towards native species. The introduction and spread of Vespa velutina in Europe is raising concern for the conservation of insect’s biodiversity, including wasps due to predation, competition or a combination of these two mechanisms. Nevertheless, most evidence for negative effects on other wasps are based on laboratory experiments, direct observations, and on considerations about the biology and ecology of Vespidae. No field study in Europe explored how the abundance of V. velutina could affect the population of native Vespidae, as expected in case of competition and predation. We analysed how the abundance of V. velutina influenced that of Vespa crabro, 4 years after the arrival and establishment of V. velutina in our study area, in Italy. Moreover, we compared the abundances of three native Vespidae (V. crabro, Vespula vulgaris, Vespula germanica), between our study area and an adjacent uninvaded area with similar environmental conditions. Bayesian Generalized Linear Models revealed that the abundance of V. velutina and V. crabro was positively associated, where V. velutina was scarce. Covariation disappeared only at those trapping sites where V. velutina was extremely abundant. Moreover, abundances of native wasps were similar between the invaded and the uninvaded areas.Implications for insect conservationThe wide-scale monitoring activity performed to investigate the effects of V. velutina on native wasps has not detected any negative effects in relation to the presence of the invasive species. More effort is however requested for understanding if V. velutina could really affect native Vespidae at the population-level.

The effect of acidic pH on the adsorption and lytic activity of the peptides Polybia-MP1 and its histidine-containing analog in anionic lipid membrane: a biophysical study by molecular dynamics and spectroscopy.

Antimicrobial peptides (AMPs) are part of the innate immune system of many species. AMPs are short sequences rich in charged and non-polar residues. They act on the lipid phase of the plasma membrane without requiring membrane receptors. Polybia-MP1 (MP1), extracted from a native wasp, is a broad-spectrum bactericide, an inhibitor of cancer cell proliferation being non-hemolytic and non-cytotoxic. MP1 mechanism of action and its adsorption mode is not yet completely known. Its adsorption to lipid bilayer and lytic activity is most likely dependent on the ionization state of its two acidic and three basic residues and consequently on the bulk pH. Here we investigated the effect of bulk acidic (pH 5.5) and neutral pH (7.4) solution on the adsorption, insertion, and lytic activity of MP1 and its analog H-MP1 to anionic (7POPC:3POPG) model membrane. H-MP1 is a synthetic analog of MP1 with lysines replaced by histidines. Bulk pH changes could modulate this peptide efficiency. The combination of different experimental techniques and molecular dynamics (MD) simulations showed that the adsorption, insertion, and lytic activity of H-MP1 are highly sensitive to bulk pH in opposition to MP1. The atomistic details, provided by MD simulations, showed peptides contact their N-termini to the bilayer before the insertion and then lay parallel to the bilayer. Their hydrophobic faces inserted into the acyl chain phase disturb the lipid-packing.

Weather Variables Affecting the Behaviour of Insect Flower Visitors and Main Pollinators of Erythroxylum myrsinites Martius (Erythroxylaceae)

Basic research assessing environmental effects on entire pollinator communities are still uncommon, particularly for rare and commercially unattractive plant-pollinator partners. We investigated the community of flower visitors of Erythroxylum myrsinites to check for potential pollinators and to check the extent of weather influence of visitor behaviour, registered as the number of visitors attending flowers of E. myrsinites. We then calculated species’ dominance and constancy and assessed location of pollen attachment in each visitor’s body. We correlated weather variables with the composition and abundance of visits carried out by the entire community and by most constant and dominant species. The wasps Polybia sericea, P. ignobilis and P. fastidiosuscula showed the highest values of constancy, dominance and attached pollen. There was a community-level effect of atmospheric pressure, solar radiation and wind speed on the number of visits. Atmospheric pressure affected the number of visits of eudominant species P. fastidiosuscula and P. sericea, while solar radiation affected the number of visits of P. ignobilis. Our results demonstrate the influence of weather variables on flower visiting insects and suggest the importance of native wasps in pollen transport and pollination, a relationship that should be further studied under the worldwide bee pollination decline.

Color, odor, and species preferences of Copidosoma bakeri to prospective cover crops to enhance control of cutworms

AbstractCutworms (Lepidoptera: Noctuidae) are economically important pests of multiple field crops, but are difficult to control with insecticides. Biological control with native parasitoids may offer a sustainable alternative for pest management. Cover crops improve the availability of resources required by parasitoids to increase their effectiveness as biocontrol agents. Copidosoma spp. (Hymenoptera: Encyrtidae) have the potential to control several species of cutworms in the Canadian Prairies. However, their foraging preferences for non‐host food items are unknown. In this study, we tested flower color and odor preferences of Copidosoma bakeri (Howard) across nine potential cover crop species and investigated how these resources affect survival and longevity of the female wasps. Results indicated that the wasps were most attracted to plants with yellow flowers in the family Brassicaceae (i.e., camelina, mustard, and canola). In multiple‐choice tests, the wasps preferred camelina over all other flower species, and showed an intermediate preference for mustard and canola. In dual‐choice tests with color paper, the wasps preferred yellow over white, and the light yellow of camelina over the bright yellow of canola and mustard, whereas they showed a preference for the odors of mustard and canola. Life expectancy was increased when the wasps were provided floral resources compared to the absence of a food source. Later planting dates and mixed‐species plantings of cover crops resulted in flowering times that better coincided with native wasp emergence. Camelina is known to suppress weeds and may be used as a habitat management tool for enhancing parasitism of cutworms by C. bakeri in the Canadian Prairies. However, further testing is needed to achieve late flowering well into August and early September and to ensure planting additional Brassica spp. does not attract more late‐season pests to cash crops such as canola.

Invasive brown marmorated stink bug (Hemiptera: Pentatomidae) facilitates feeding of European wasps and ants (Hymenoptera: Vespidae, Formicidae) on plant exudates

The brown marmorated stink bug, Halyomorpha halys, is a polyphagous species from eastern Asia, which has spread to America and Europe where it damages many crops. In recently colonized areas, facilitative interactions between H. halys and native insects are poorly investigated. In this study, we report for the first time facilitation of native wasp and ant feeding by H. halys in Europe. The facilitation was related to the outflow of plant exudates caused by H. halys feeding on manna ash trees, where they have aggregated in response to an aggregation pheromone, which then attracted species of Hymenoptera to the infested trees. Trees other than manna ash were not involved in the facilitation between these two taxa. The species that frequently visited infested manna ash were Polistes dominula, Vespa crabro, Formica (Serviformica) cunicularia and Lasius emarginatus, while Polistes cf. nimpha, Vespula germanica, Crematogaster scutellaris and Tapinoma subboreale were occasional visitors. The numbers of wasps and ants feeding on plant exudates differed at different times in a day, with more Hymenoptera foraging in the afternoon, when more H. halys individuals were actively feeding. Facilitative interactions, such as those recorded in this study, are important for furthering our understanding of the ecology of invasive species in terms of creating sources of food for native organisms.

Non-target effects of the exotic generalist parasitoid wasp Fopius arisanus (Sonan) estimated via competition assays against Doryctobracon areolatus (Szepligeti) on both native and exotic fruit fly hosts

Biological control by the generalist egg parasitoid Fopius arisanus (Sonan) (Hymenoptera: Braconidae) has been proposed against Bactrocera carambolae (Drew & Hancock) (Diptera: Tephritidae) in northern Brazil. This study assessed possible effects of F. arisanus on native parasitoids by focusing on competition with the native wasp Doryctobracon areolatus (Szepligeti) (Hymenoptera: Braconidae) on two hosts, Anastrepha fraterculus (Wiedemann), a native tephritid, and Ceratitis capitata (Wiedemann), an introduced pest tephritid. Laboratory and greenhouse cage studies showed that F. arisanus parasitized < 3% of the native host in competition or alone compared to 41–65% for C. capitata, while D. areolatus parasitized 12–42% of the native host and < 4% on C. capitata. The host origin of F. arisanus did not affect subsequent parasitism rates on native or exotic hosts. However, when reared on C. capitata, F. arisanus had higher parasitism on C. capitata than on A. fraterculus. Lab and greenhouse competition studies showed that F. arisanus had no measurable detrimental effect on the native parasitoid in either the native or introduced host, suggesting that F. arisanus interfered minimally with the native parasitoid. Based on these results and other relevant studies showing non-preference of F. arisanus for the native fruit fly species, as well as the non-preference of native parasitoids for exotic fruit flies, we infer that the release of F. arisanus against exotic tephritids such as C. capitata and B. carambolae in Brazil would not cause major disruption of the native populations of A. fraterculus parasitoids.

Surveys in northern Utah for egg parasitoids of Halyomorpha halys (Stål) (Hemiptera: Pentatomidae) detect Trissolcus japonicus (Ashmead) (Hymenoptera: Scelionidae).

The highly polyphagous and invasive brown marmorated stink bug, Halyomorphahalys (Stål) (Hemiptera: Pentatomidae), has become a significant insect pest in North America since its detection in 1996. It was first documented in northern Utah in 2012 and reports of urban nuisance problems and plant damage have since increased. Biological control is the preferred solution to managing H.halys in North America and other invaded regions due to its alignment with integrated pest management and sustainable practices. Native and non-native biological control agents, namely parasitoid wasps, have been assessed for efficacy. Trissolcusjaponicus (Ashmead) (Hymenoptera: Scelionidae) is an effective egg parasitoid of H.halys in its native range of southeast Asia and has recently been documented parasitising H.halys eggs in North America and Europe. Field surveys for native and exotic egg parasitoids using wild (in situ) and lab-reared H.halys egg masses were conducted in suburban and agricultural sites in northern Utah from June to September 2017–2019. Seven native wasp species in the families Eupelmidae and Scelionidae were discovered guarding H.halys eggs and adult wasps from five of these species completed emergence. Native species had low mean rates of adult emergence from wild (0.5–3.7%) and lab-reared (0–0.4%) egg masses. In 2019, an adventive population of T.japonicus was discovered for the first time in Utah, emerging from 21 of the 106 wild H.halys egg masses found that year, and none from lab-reared eggs. All T.japonicus emerged from egg masses collected on Catalpaspeciosa (Warder). Our results support other studies that have observed biological control of H.halys from T.japonicus and improved parasitoid wasp detection with wild as compared to lab-reared H.halys egg masses.

Environments, spatial structures, and species competitions: determining the impact of yellow-legged hornets, Vespa velutina, on native wasps and bees on Tsushima Island, Japan

Invasive alien species (IAS) can have serious negative impacts on native species in invaded areas. Researchers attempting to measure the impacts of IAS on native species at a landscape level often face challenges though, because the effects of environmental gradients and spatial autocorrelation on population structures are difficult to separate. To evaluate the impacts of IAS, we used spatial filtering and variation partitioning to remove environmental and spatial autocorrelation effects from abundance data for seven native insect species and one IAS, Vespa velutina, on the island of Tsushima, Japan. Here we show that negative correlations among Vespa species persisted after removal of environmental and spatial autocorrelation effects. The fact that alien V. velutina and native Vespa mandarinia japonica showed the strongest negative correlations with other native Vespa species suggested that there were strong competition or/and predation among Vespa species. The ongoing expansion of V. velutina since its incursion indicates that this species may impose strong negative impacts on other Vespa species, but it is possible that the slow expansion of V. velutina to the southern part of Tsushima is due to the presence of other Vespa species that function as a biological barrier. Since most IAS showed spatially structured distributions, especially at the initial stage of the incursion, spatial filtering is a promising tool to evaluate IAS impacts on native species.

Vespa velutina: An Alien Driver of Honey Bee Colony Losses

Vespa velutina, or Asian yellow-legged hornet, was accidentally introduced from China to other parts of the world: South Korea in 2003, Europe in 2004, and Japan in 2012. V. velutina represents a serious threat to native pollinators. It is known to be a fierce predator of honey bees, but can also hunt wild bees, native wasps, and other flying insects. When V. velutina colonies are developed, many hornets capture foraging bees which are coming back to their hives, causing an increase in homing failure and paralysis of foraging thus leading to colony collapse. The hornets may enter weak beehives to prey on brood and pillage honey. Unlike Apis cerana, Apis mellifera is unable to cope with the predation pressure of V. velutina. Monitoring the spread of an invasive alien species is crucial to plan appropriate management actions and activities to limit the expansion of the species. In addition, an early detection of V. velutina in areas far away from the expansion front allows a rapid response aimed to remove these isolated populations before the settlement of the species. Where V. velutina is now established, control measures to prevent colony losses must be implemented with an integrated pest management approach.

Effects of floral resources on the longevity and parasitism of Cotesia vestalis Haliday (Hymenoptera: Braconidae) on Plutella xylostella (L.) (Lepidoptera: Plutellidae) in Vietnam

Parasitoids are important biological control of crop pests. In Vietnam, Cotesia vestalis is a native wasp species that has demonstrated its applicability as a natural insect pest enemy. Many adult parasitoids require food resources such as nectar and pollen to optimize their life cycles. Potential effects of yellow cosmos (Cosmos sulphureus), shrub verbena flower (Lantana camara), common zinnia (Zinnia elegans), and coriander flower (Coriandrum sativum L.) on the longevity and parasitism of C. vestalis were investigated. Results showed that nutrition resources from yellow cosmos (C. sulphureus) and shrub verbena flower (Lantana camara) significantly increased the longevity of C. vestalis in comparison with water (P < 0.001). Kaplan-Meier estimates of survival functions of female Cotesia vestalis exposed to different food sources indicated a significant difference in the treatments (P < 0.01). Male and female wasps feeding on Cosmos sulphureus, Lantana camara, and Coriandrum sativum survived significantly longer than wasps fed on water or Zinnia elegans. Parasitism efficiency of C. vestalis was tested on diamondback moth Plutella xylostella (L.) larvae for different food resources. Cosmos sulphureus, Lantana camara, Coriandrum sativum treatments gave the different mean number of emergence parasitoids per day compared to water treatment. Results implied that food resources from flowers benefitted the longevity of C. vestalis.

Recruitment of native parasitic wasps to populations of the invasive winter moth in the northeastern United States

Ecological communities may be resistant to invasive species through a combination of top-down and bottom-up mechanisms, including predation, competition, parasitism, and disease. In particular, natural enemies that cross over from native species to use newly introduced non-native species as hosts can influence invasive species population dynamics and may slow down invasions. However, research on parasitism in biological invasions is lagging behind research on biological invasions in general. We used the model species winter moth (Operophtera brumata) to study the effect of recruitment of native parasitoids on an invasive population of winter moth in the northeastern United States. We deployed sentinel pupae over 4 years across this population’s range, identified recovered parasitoids, and measured the rate of parasitism by native sources across years, seasons, invasion history, and host densities. Native Pimpla wasps inflicted 98% of the parasitism detected, resulting in an annual average of 15–40% mortality on pupae not depredated. Pimpla were present across all years, seasons, and sites. Where winter moth has invaded, parasitism was greatest when winter moth pupal density was high (i.e., positive density-dependent mortality) suggesting that Pimpla is helping to regulate the population. The wasps were morphologically identified as Pimpla aequalis Provancher; however, using a multilocus genetic comparison approach, they were determined to comprise two cryptic species. Overall, this study shows that recruitment of these native wasps to the invasive winter moth population is likely playing a significant role in regulating population outbreaks and is aiding in biological control of winter moth.

Parasitoid assemblage associated with a North American pine weevil in South Africa

Abstract The weevil Pissodes sp. was first reported as an introduced pest on exotic Pinus spp. in South Africa in 1942. It is only recently that the native wasp Pycnetron pix Prinsloo was described from South Africa as a parasitoid of this weevil. We estimated the frequency and distribution of the association between P. pix and Pissodes sp., as well as the occurrence of possible other natural enemies. Parasitoids were reared from Pissodes‐infested Pinus radiata D. Don and Pinus patula Schiede ex Schltdl. &amp; Cham logs collected from major Pinus‐growing regions. The identity of parasitoids was confirmed using morphological and molecular techniques. Parasitism was confirmed by analyzing gut content sequences of parasitoids. Pycnetron pix was found parasitizing Pissodes sp. throughout major Pinus‐growing provinces of the country. Another native parasitoid, Cratocnema sp., is reported for the first time as a parasitoid of Pissodes sp. Rhopalicus tutela (Walker), a known parasitoid of Pissodes spp. in their native range, was also detected and confirmed to be of European origin. Although characterized by an erratic distribution and a low parasitism rate, an accruing suite of natural enemies was documented, suggesting that there is potential for augmentative biological control of Pissodes sp. in South Africa.

'Bee hotels' as tools for native pollinator conservation: a premature verdict?

Society is increasingly concerned with declining wild bee populations. Although most bees nest in the ground, considerable effort has centered on installing ‘bee hotels’—also known as nest boxes or trap nests—which artificially aggregate nest sites of above ground nesting bees. Campaigns to ‘save the bees’ often promote these devices despite the absence of data indicating they have a positive effect. From a survey of almost 600 bee hotels set up over a period of three years in Toronto, Canada, introduced bees nested at 32.9% of sites and represented 24.6% of more than 27,000 total bees and wasps recorded (47.1% of all bees recorded). Native bees were parasitized more than introduced bees and females of introduced bee species provisioned nests with significantly more female larva each year. Native wasps were significantly more abundant than both native and introduced bees and occupied almost 3/4 of all bee hotels each year; further, introduced wasps were the only group to significantly increase in relative abundance year over year. More research is needed to elucidate the potential pitfalls and benefits of using bee hotels in the conservation and population dynamics of wild native bees.

Introduced and Native Parasitoid Wasps Associated With Larch Casebearer (Lepidoptera: Coleophoridae) in Western Larch.

The larch casebearer [Coleophora laricella (Hubner)], a non-native insect, continues to impact western larch (Larix occidentalis Nutt.) through defoliation events in the Pacific Northwest. Biological control programs starting in the 1960s released seven species of parasitoid wasps to control C. laricella outbreaks. However, information about current population dynamics of C. laricella and associated parasitoids remains lacking. Therefore, the goal of this study was to document the presence, current distributions, densities, and parasitism rates of introduced and native parasitoid wasps occurring on C. laricella throughout the Northwestern U.S. range of L. occidentalis. We sampled L. occidentalis trees at multiple sites in Oregon, Washington, Idaho, and Montana. C. laricella was present at all sites with average state densities ranging from 6.2 to 13.1 moths/100 buds. We recovered two introduced hymenopteran biological control agents; Agathis pumila (Ratzeburg: Braconidae) at 79% of the sites, and Chrysocharis laricinellae (Ratzeburg: Eulophidae) at 63% of the sites. Fourteen species of native parasitic wasps were also recovered. The most common species were: Bracon sp., Spilochalcis albifrons, and Mesopolobus sp. The average native species parasitism rate across the four states was 9.0%, which was higher than the introduced species Ch. laricinellae (2.9%), but not as high as A. pumila (19.3%). While survey results suggest that native species may be more important for the control of C. laricella than previously thought, A. pumila remains the major source of regional control. However, further research is needed to better understand how introduced and native parasitoids interact to control invasive pest populations.

Nest Parameters of Polistes and Mischocyttarus Species (Hymenoptera: Vespidae) Before and After Detection of the Invasive Wasp, Polistes dominula in Western South Dakota and Wyoming

Abstract In this paper I report first records for the invasive species, Polistes dominula (Christ), in Wyoming and western South Dakota, U.S.A. In addition, the early nesting success of this invasive species and the nest parameters in two native paper wasps, Polistes fuscatus (F.) and Mischocyttarus flavitarsis (de Saussure), are analyzed through a survey of nests, nesting locations, nest size and relative levels of parasitism in the northern Black Hills area and surrounding plains. Polistes dominula occurred predominantly in towns and at elevations below 4000 ft. Some collecting sites had high P. dominula population numbers, with heavy use of available nesting sites, water sources and other resources. This wasp attached its nests to horizontal, sloping and vertical surfaces and nested in unusual and exposed locations not observed in the native species. The distribution and successful nesting of M. flavitarsis was not impacted at this early stage of introduction, because it nests predominantly in forested...

A role for thermoregulation in the Polistes dominulus invasion: a comparison of the thermoregulatory abilities of the invasive wasp P. dominulus and the native wasp P. fuscatus

Social insects are excellent invaders that have had negative impacts on native species and humans. Many invasive species move from warmer to cooler climates. For these species, thermal adaptations may both be important for their ability to invade and to limit their invasion range. The invasion of Polistes dominulus into North America provides an example of a primitively eusocial invader from a warmer climate. We studied the differences in thermoregulation between P. dominulus and the native P. fuscatus. We found that, during flight, thorax temperature in P. fuscatus was less affected by ambient temperature than thorax temperature of P. dominulus. We also found that P. dominulus and P. fuscatus showed different patterns of warming after removal from a cold environment. Unlike P. dominulus, live P. fuscatus never fully cooled down in a cold environment. P. fuscatus also reached their relative minimum flight temperatures earlier than P. dominulus, but P. dominulus maintained higher elevated temperatures for longer. These differences in thermoregulatory ability suggest that the lower winter survival of P. dominulus could be offset by a greater thermal tolerance during flight, while the lower thermal tolerance of P. fuscatus in flight is offset somewhat by better thermoregulatory ability.

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.

Contrasting foraging patterns for Africanized honeybees, native bees and native wasps in a tropical agroforestry landscape

Abstract:Ecological and temporal factors can influence animal foraging patterns and may obscure our understanding of how native and exotic species interact. To understand how such factors affect foraging, the visitation of native and exotic bees and wasps was observed at nectar feeders within Mexican agroforestry systems, while documenting (1) vegetation management (low-shade vs. high-shade coffee), (2) light and floral resource levels and (3) recruiting ability, as measured by the change in visitation between two consecutive experimental days. On day one, Africanized honeybee visitation was significantly greater in low-shade habitats, and native solitary bee abundance was significantly greater in high-shade habitats, while native social bee and solitary wasp visitation were not significantly different between habitat types. After 24 h, Africanized honeybee visitation increased significantly in both habitat types, while native social bee visitation increased significantly only in high-shade coffee. In contrast, native solitary bee and native solitary wasp visitation decreased in both habitat types. Overall, this study reveals that Africanized honeybees exhibit only initial foraging preference for low-shade habitats, while native bees exhibit both initial and delayed recruitment-based foraging preferences for high-shade habitats.

Sampling Native Wasps Along Both Vertical and Horizontal Gradients in the Maine Lowbush Blueberry Landscape

Native wasps were sampled from 33 lowbush blueberry (Vaccinium angustifolium) fields and adjacent forests in eastern Maine during the summers of 1997 and 1998. Sampling was conducted along a horizontal transect that bisected the field/forest interface using two methods: window-pane traps suspended at varying heights (1, 7, and 14 m above the ground) and ground-level malaise traps. The objectives of this study were to assess (1) the spatial distributions of wasp species assemblages associated with the two distinct habitats and (2) the potential interactions of wasp species assemblages across the blueberry/forest landscape. Wasp samples from the two trap types collected different wasp species assemblages, each of which were consistent across the 2 yr. Both methods documented lower abundances of wasps in blueberry fields in comparison with adjacent forests. Window pane traps at varying heights identified statistically significant but remarkably minor differences in height even at the highest traps in the middle of blueberry fields in both years of the study. The malaise traps detected distinct species assemblages whose horizontal distributions differed substantially from each other. Distributions ranged from those that were trapped exclusively in the forest, through those that were evenly distributed across the landscape, to taxa that were almost exclusively found in the blueberry field centers. Our results suggest that forest and edge habitats may be important refugia for wasp species assemblages that contribute to regulation of blueberry insect pest populations. Detailed knowledge of specific taxa should assist in the management of the blueberry/forest landscape for the conservation and enhancement of beneficial insects.