Oviposition preference and larval performance of monarch butterflies (Danaus plexippus) on two invasive swallow-wort species

Abstract The potential of two invasive herbaceous vines Vincetoxicum nigrum (L.) Moench and Vincetoxicum rossicum (Kleopow) Barbar. (Asclepiadaceae) to reduce monarch butterfly ( Danaus plexippus L.) (Lepidoptera: Nymphalidae, Danainae) populations was investigated by evaluating oviposition selection in adult monarch butterflies and larval feeding preference in choice tests comparing the native host plant of monarch butterflies, Asclepias syriaca L. (Asclepiadaceae) and the two non-indigenous Vincetoxicum species. In both choice and no-choice tests, no eggs were oviposited on either of the two Vincetoxicum species whereas over 66 eggs per female were oviposited on A. syriaca plants. All first instar larvae allowed to feed on A. syriaca for 48 h survived while a significantly lower proportion survived on V. rossicum (44%) and V. nigrum (14%). Mean weight of larvae that did survive on the Vincetoxicum species was significantly lower than the mean weight of larvae that fed on A. syriaca . The mean weight of surviving larvae, however, did not differ between the two Vincetoxicum species. The mean proportion of leaves consumed by larvae feeding on A. syriaca was significantly greater than the mean proportion of leaves consumed by larvae feeding on either Vincetoxicum species. Findings from this research indicate that V. rossicum and V. nigrum are not viable hosts of monarch butterflies and are likely to pose little direct threat to their populations as oviposition sinks. The ability of these highly aggressive plants, however, to out-compete and displace the native host of monarchs, A. syriaca , may pose a more serious threat. The potential of monarch populations to adapt to the two Vincetoxicum species as host plants over the long-term is discussed

Habitat Persistence Underlies Intraspecific Variation in the Dispersal Strategies of Planthoppers

Dispersal is considered a vital life history characteristic for insects exploiting temporary habitats, and life history theorists have often hypothesized an inverse relationship between dispersal capability and habitat persistence. Most often, this hypothesis has been tested using interspecific comparisons of dispersal capability and qualitative estimates of habitat persistence. Consequently, most assessments have failed to control for possible phylogenetic nonindependence and they also lack quantitative rigor. We capitalized on existing intraspecific variation on the dispersal capability of Prokelisia planthoppers to examine the relationship between habitat persistence and dispersal, thereby minimizing possible phylogenetic effects. Two congeneric species (Prokelisia marginata and P. dolus) occur in the intertidal marshes of North America, where they feed exclusively on cordgrasses (Spartina). Because these planthoppers exhibit wing dimorphism, flight-capable adults (macropters with fully developed wings). Thus, dispersal capability can be readily estimated by the percentage of macropters in a population. At a regional spatial scale, we found a highly significant negative relationship between dispersal capability (present macroptery) and habitat persistence. In this system, habitat persistence is influenced by a combination of marsh elevation, winter severity, and tidal range, which interact to determine the ability of planthoppers to endure through winter in their primary habitat for development. P. marginata develops primarily in low-marsh habitats during summer, habitats that can be subjected to pronounced winter disturbance due to ice scouring and/or extensive tidal inundation. Levels of winter disturbance of the low marsh are extreme along the Atlantic coast, intermediate along the Pacific, and low along the Gulf. Both the failure of P. marginata populations to remain through winter in the habitat, and the dispersal ability of these populations (92%, 29%, and 17% macroptery, respectively), are correlated with levels of disturbance. Thus, in regions where winter disturbance is high, levels of dispersal are correspondingly high to allow for recolonization of extirpated habitats from overwintering sites on the high marsh. Unlike P. marginata, P. dolus develops primarily in high-marsh habitats, which are much less disturbed on all coasts during winter. Consequently, this species remains year-round in its primary habitat for development, and most populations exhibit relatively low levels of macroptery (\u3c10%). When raised under common garden conditions, many more macropters of both species were produced from Atlantic compared to Gulf populations. Thus the proportion of macropters produced from the populations used in this experiment paralleled the incidence of macroptery measured in the field, providing evidence that the geographic variation in dispersal capability in both species has in part a genetic basis. The results of this study provide strong intraspecific evidence for an inverse relationship between the dispersal capability of insects and the persistence of their habitats

An aluminum resist substrate for microfabrication by LIGA.

Resist substrates used in the LIGA process must provide high initial bond strength between the substrate and resist, little degradation of the bond strength during x-ray exposure, acceptable undercut rates during development, and a surface enabling good electrodeposition of metals. Additionally, they should produce little fluorescence radiation and give small secondary doses in bright regions of the resist at the substrate interface. To develop a new substrate satisfying all these requirements, we have investigated secondary resist doses due to electrons and fluorescence, resist adhesion before exposure, loss of fine features during extended development, and the nucleation and adhesion of electrodeposits for various substrate materials. The result of these studies is a new anodized aluminum substrate and accompanying methods for resist bonding and electrodeposition. We demonstrate successful use of this substrate through all process steps and establish its capabilities via the fabrication of isolated resist features down to 6 {micro}m, feature aspect ratios up to 280 and electroformed nickel structures at heights of 190 to 1400 {micro}m. The minimum mask absorber thickness required for this new substrate ranges from 7 to 15 {micro}m depending on the resist thickness

Crop pests and predators exhibit inconsistent responses to surrounding landscape composition

The idea that noncrop habitat enhances pest control and represents a win–win opportunity to conserve biodiversity and bolster yields has emerged as an agroecological paradigm. However, while noncrop habitat in landscapes surrounding farms sometimes benefits pest predators, natural enemy responses remain heterogeneous across studies and effects on pests are inconclusive. The observed heterogeneity in species responses to noncrop habitat may be biological in origin or could result from variation in how habitat and biocontrol are measured. Here, we use a pest-control database encompassing 132 studies and 6,759 sites worldwide to model natural enemy and pest abundances, predation rates, and crop damage as a function of landscape composition. Our results showed that although landscape composition explained significant variation within studies, pest and enemy abundances, predation rates, crop damage, and yields each exhibited different responses across studies, sometimes increasing and sometimes decreasing in landscapes with more noncrop habitat but overall showing no consistent trend. Thus, models that used landscape-composition variables to predict pest-control dynamics demonstrated little potential to explain variation across studies, though prediction did improve when comparing studies with similar crop and landscape features. Overall, our work shows that surrounding noncrop habitat does not consistently improve pest management, meaning habitat conservation may bolster production in some systems and depress yields in others. Future efforts to develop tools that inform farmers when habitat conservation truly represents a win–win would benefit from increased understanding of how landscape effects are modulated by local farm management and the biology of pests and their enemies

The harlequin ladybird, Harmonia axyridis: global perspectives on invasion history and ecology

The harlequin ladybird, Harmonia axyridis (Pallas) (Coleoptera: Coccinellidae), is native to Asia but has been intentionally introduced to many countries as a biological control agent of pest insects. In numerous countries, however, it has been introduced unintentionally. The dramatic spread of H. axyridis within many countries has been met with considerable trepidation. It is a generalist top predator, able to thrive in many habitats and across wide climatic conditions. It poses a threat to biodiversity, particularly aphidophagous insects, through competition and predation, and in many countries adverse effects have been reported on other species, particularly coccinellids. However, the patterns are not consistent around the world and seem to be affected by many factors including landscape and climate. Research on H. axyridis has provided detailed insights into invasion biology from broad patterns and processes to approaches in surveillance and monitoring. An impressive number of studies on this alien species have provided mechanistic evidence alongside models explaining large-scale patterns and processes. The involvement of citizens in monitoring this species in a number of countries around the world is inspiring and has provided data on scales that would be otherwise unachievable. Harmonia axyridis has successfully been used as a model invasive alien species and has been the inspiration for global collaborations at various scales. There is considerable scope to expand the research and associated collaborations, particularly to increase the breadth of parallel studies conducted in the native and invaded regions. Indeed a qualitative comparison of biological traits across the native and invaded range suggests that there are differences which ultimately could influence the population dynamics of this invader. Here we provide an overview of the invasion history and ecology of H. axyridis globally with consideration of future research perspectives. We reflect broadly on the contributions of such research to our understanding of invasion biology while also informing policy and people

Improved Transect Sampling to Enhance Efficiency of Corn Rootworm Monitoring

Crop monitoring for corn rootworm remains the best means to assess fields at risk from this pest if replanted to corn the following year. Use of sequential sampling reduced the minimum sampling time to about 20 minutes or less per field per visit to make a management decision. With previous funding from the NYSIPM program we developed a transect sampling protocol for sequential sampling that reduced sampling time by an additional 6 minutes per field. Our previous results were based on a relatively small number of fields (3) and simulations over a realistic but limited range of adult CRW spatial dispersion patterns. In this project we compared transect sampling to the commonly used systematic “W” system in 13 fields. Field trials using systematic, and transect sampling in each field were used to compare the categorization of adult corn rootworm densities into “above” or “below” threshold with a sequential sampling plan. Efficiency measured in time to reach a decision, number of corn plants evaluated, and time divided by plants observed were compared between sampling methods

Evaluating Soil Characteristics as a Potential Means to Minimize Soil Insecticide Usage to Control Corn Rootworm

NYS IPM Type: Project ReportPrevious research by Davis (1997), Allee (1998) and others has indicated a relationship between soil drainage, soil suitability for corn cropping and relative impacts of corn rootworm. Current research was an effort to explore this relationship as a means to enhance corn rootworm management decisions. In the second phase of this multiyear project, studies were conducted to determine root injury by larval populations of corn rootworm beetle (CRW), Diabrotica species, in corn fields grown for silage in well-drained and poorly drained soils and fields rated as “good”, “fair” or “poor” for corn cropping (Cline and Marshall 1988). Seventeen fields were identified in western NY which met the following criteria: fields with either “well-drained” or “poorly drained” soils, second or greater year corn fields, a range of planting dates, a documented range of known 1998 CRW beetle counts “low” (0-0.25 CRW / plant), “medium” (0.26 — 0.99 CRW / plant) and “high” (1.0+ CRW / plant), corn grown for silage, plant populations 32-34,000 plants / A, row spacing at least 30 inches, no Prowl herbicide used in 1999, and the field manured within past 3 years. Replicated experiments comparing insecticide and non-insecticide treated plots were established in each field identified. Fields were evaluated for rootworm larval feeding injury in early August and silage yields in late September. Rootworm injury ratings were very low regardless of insecticide use or soil drainage category. Most root systems evaluated were less than the 3.0 rating generally accepted as causing economic impacts. No overall significant differences between root ratings from either “well-drained” or “poorly” drained fields were found. Widespread drought conditions are thought to have caused corn rootworm larval mortality resulting in the low root injury ratings observed. Overall silage yields were also not significantly different between insecticide treatments in any soil drainage category. This study unfortunately did not yield the data that will allow us to modify recommendations for CRW management based on soil quality, however it did provide us with some very valuable information on the interactive effects of soil quality and climatic conditions on CRW damage. We can conclude from our results that the low moisture conditions experienced in 1999 drive CRW populations to a low enough level that other factors are relatively unimportant. Further research will be required to further our understanding on the efficient use of soil drainage and cropping suitability information as tools to help improve corn rootworm management decisions

Fig. 2 in Sexual Dimorphism in North American Coccinellids: Sexing Methods for Species of Coccinella L. (Coleoptera: Coccinellidae) and Implications for Conservation Research

Fig. 2. Pronotal pigment pattern on a female (top) and male (bottom) of Coccinella novemnotata. Two measurements were taken: the width at the widest anterior points (p-width) and the depth from the pigment edge at the midline to a line drawn to connect the two endpoints from the width measurement (p-depth). To control for size differences between males and females, p-depth was divided by p-width and this proportion was used for analysis (p-prop). Photographs by L. Stellwag.Published as part of <i>Stellwag, Leo & Losey, John E., 2014, Sexual Dimorphism in North American Coccinellids: Sexing Methods for Species of Coccinella L. (Coleoptera: Coccinellidae) and Implications for Conservation Research, pp. 271-281 in The Coleopterists Bulletin 68 (2)</i> on page 275, DOI: 10.1649/0010-065x-68.2.271, <a href="http://zenodo.org/record/10101705">http://zenodo.org/record/10101705</a&gt