Evidence of Pre-Imaginal Overwintering of Diamondback Moth, \u3ci\u3ePlutella Xylostella\u3c/i\u3e (Lepidoptera: Plutellidae) in Michigan

We investigated the possibility of overwintering of the diamondback moth, Plutella xylostella L., in central Michigan. In the spring of 1993, counts of immature stages on brassicaceous weeds in a field previously planted to broccoli revealed a small but significant number of late instars that could not be attributed to oviposition of immigrant moths from the southern United States. We suggest that crop debris and snow cover played an important role in sheltering the larvae, which are known to tolerate sub·freezing temperatures. There was no indication of adult survival

Movement of Adult Colorado Potato Beetles, \u3ci\u3eLeptinotarsa Decemlineata\u3c/i\u3e (Coleoptera: Chrysomelidae), in Response to Isolated Potato Plots

Mark recapture techniques were used to determine Colorado potato beetle movement in circular arenas with isolated plots of potatoes at each ordinal direction. Post-diapause beetles aggregated on one or a few of the plants in one of the plots for each release, but not on the same plants in different releases. Differences in plant attractiveness were therefore not likely responsible for the aggregatory behavior. Aggregations were probably a result of either coordinated movement from the release site to the plants or an aggregatory signal with a range of at least 15 m. Summer adults did not aggregate on plants. Correlations of summer beetle recapture distributions to wind direction showed that anemotactic behavior could not account for the major portion of variation in beetle orientation to the potato plots. Some positive attraction to the plots was indicated because more beetles were recaptured at the plots than would be expected from random motion. The number of beetles recaptured at plots covered by cheesecloth was not significantly different from recaptures on uncovered plots, indicating little reliance on visual cues specific to potatoes for location of the plants

Marking Adult Colorado Potato Beetles, \u3ci\u3eLeptinotarsa Decemlineata\u3c/i\u3e (Coleoptera: Chrysomelidae) Using Paper Labels

The smooth elytra of adult Colorado potato beetle, Leptinotarsa decemlineata, make this insect difficult to make efficiently for long-term field studies. Enamel paint marks fell off rapidly, and after 28 days, 25010 of marked beetles had lost all four original marks. Use of small paper labels glued to the elytra after an acetone wash and sanding pretreatment was the most effective method for long term marking of individual beetles. Mortality in labeled laboratory-reared and field-collected beetles did not increase when compared to unmarked beetles

The conversion of allochthonous material by stream detritivores

The role of detritivores in the conversion of allochthonous leaf material in two small streams in the Cascade Range of Oregon was studied. Their importance in relation to other consumers was estimated from emergence and benthic standing crop data. Ingestion rates and efficiencies of utilization of bigleaf maple (Acer macrophyllum) and red alder (Alnus rubra) leaves by several species of stream detritivores, one species of stonefly and several species of caddis lies, were measured under field or laboratory conditions. Mean consumption rates varied from 0. 04 mg/mg/day for Halesochila taylori larvae (Trichoptera:Limnephilidae) feeding on maple leaves to 0.60 mg /mg /day' for Lepidostoma sp. larvae (Trichoptera :Lepidostomatidae) feeding on alder and maple leaves. Ecclisomyia sp. larvae (Trichoptera:Limnephilidae) consumed 0.10 mg/mg/day of maple leaves in the field. All consumption rates were calculated assuming constant feeding rates by the insects and constant rates of leaf decomposition without insects, but a model is discussed that allows non-linear feeding and leaf decomposition rates. Efficiency of food utilization was measured either as assimilation efficiency, the ratio of assimilated food (ingestion minus egestion) to consumption; or as gross growth efficiency, the slope of the growth:consumption line calculated by linear regression analysis. Assimilation efficiencies ranged from 7.4% for Heteroplectron californicum larvae (Trichoptera:Calamoceratidae) fed on maple leaves to 12% for Lepidostoma sp. larvae fed on alder and maple leaves. In order to assess the role of microbial communities in leaf utilization by Pteronarcys princeps (Plecoptera:Pteronarcidae), nymphs were fed untreated maple leaves and maple leaves treated to reduce bacterial or fungal populations, for a period of 54 days. Gross growth efficiency when fed on untreated leaves was 4.94% compared with 1.03% for the insects fed antibacterial treated leaves. When fed fungicide treated leaves, the mean consumption rate was less than 10% of the consumption of untreated leaves and mortality was 85% compared with 15% for the insects fed untreated leaves. It was concluded that bacteria play a major role in the utilization of leaves by Pteronarcys princeps and that fungi are important as astimulus to feeding, although they may also aid in utilization of the leaves. To aid in classifying the emergence and benthos data into trophic categories, an extensive literature review of the foods of aquatic insects was compiled. The estimated yearly emergence of aquatic insects from Watershed 10 was 81 mg/m² /yr. of algivores, 253 mg/m²/yr. of detritivores, and 135 mg/m²/yr. of carnivores. The mean standing crop of aquatic insects in an old-growth location in Mack Creek was 0.85 g/m² of algivores, 3.10 g/m² of detritivores, and 2.31 g/m² of carnivores; and 0.83 g/m² of algivores, 1.57 g/m² of detritivores, and 4.04 g/m² of carnivores in a clear-cut location. A model is included describing the cycling of energy within the detrital component of the stream system, reflecting the importance of the fecal material and leaf fragments that return to the detrital pool

Bioenergetics and strategies of some trichoptera in processing and utilizing allochthonous materials

The purpose of the study was to provide quantitative information on the utilization and processing of leaves and needles by several species of caddisfly larvae. Field and laboratory studies were conducted on three species of Lepidostoma Rambur (Lepidostomatidae), from Willamette Valley and Cascade Mountain streams, and on Clistoronia magnifica (Banks) (Limnephilidae) from a Cascade lake. These species were selected to represent a wide range of habitats, food sources, and developmental patterms. Consumption, fecal production, growth, and assimilation efficiency were measured gravimetrically in the laboratory as influenced by food quality (food type and conditioning time), food quantity, larval size, and temperature. Respiration was measured with a Gilson respirometer as influenced by temperature and larval size. Consumption rates generally increased with temperature and conditioning of the food, and decreased with increased larval size. Mean assimilation efficiencies were 20 to 30% for L. quercina Ross and Douglas fir needles, and 57% for C. magnifica fed on wheat grains. Assimilation efficiency of alder leaves by L. quercina decreased with higher temperatures, while assimilation efficiency of alder by C. magnifica increased with temperature. This may reflect physiological adaptations to the species' respective temperature regimes. Maximum consumption rates by L. quercina were reached when food (alder) was only slightly in excess, in contrast to consumption rates by L. unicolor (Banks) which did not reach maximum until food (Douglas fir) was greatly in excess. Net growth efficiency of L. unicolor fed on Douglas fir needles (60%) was higher than for L. quercina fed on alder leaves (13%) or C. magnifica fed on alder plus wheat (33%). Increased food selectivity and high net growth efficiency are apparently adaptations by L. unicolor for utilizing poorly digestible food. Respiration rates were highest for smaller larvae. Temperature effects on respiration rates were largest for those species found in habitats with little temperature variation (e.g. Q₁₀ for L. unicolor was 1.99). C. magnifica larvae, normally experiencing a temperature range from 4 to 25°C, showed a respiratory Q₁₀ of 1.12, indicating almost complete compensation for changes in temperature. The ability to compensate for changes in temperature appeared to be most pronounced in the larval sizes most often exposed to temperature fluctuations (e.g. first- through fourth-instar L. quercina or late-final instar L. unicolor). In the field, L. cascadense and L. unicolor appeared to minimize competition for food, occurring in different microhabitats and growing most rapidly at different times of the year. Estimated annual production for the three species of Lepidostoma was nearly identical (0.23 to 0.26 gm⁻²), requiring approximately 3 gm⁻² of deciduous leaves for L. quercina and 9 to 10 gm⁻² of conifer needles each for L. cascadense and L. unicolor. Production of fine particulate material was thought to be the species' most important impact on the stream system and could support collector production of up to 5 gm⁻². Simulation modeling of L. quercina growth, based on laboratory data on feeding and respiration, suggested that food quality may be limiting factor for growth in the field. It was concluded that the species studies exhibited a wide variety of adaptive strategies for using allochthonous foods in their respective habitats and these strategies result in maximum utilization of food when it is most available and usable. Identification and characterization of different strategy-types could be valuable in understanding stream systems and predicting their behavior

Urban meadows as an alternative to short mown grassland: Effects of composition and height on biodiversity

There are increasing calls to provide greenspace in urban areas, yet the ecological quality, as well as quantity, of greenspace is important. Short mown grassland designed for recreational use is the dominant form of urban greenspace in temperate regions but requires considerable maintenance and typically provides limited habitat value for most taxa. Alternatives are increasingly proposed, but the biodiversity potential of these is not well understood. In a replicated experiment across six public urban greenspaces we used nine different perennial meadow plantings to quantify the relative roles of floristic diversity and height of sown meadows on the richness and composition of three taxonomic groups – plants, invertebrates and soil microbes. We found that all meadow treatments were colonised by plant species not sown in the plots, suggesting that establishing sown meadows does not preclude further locally determined grassland development if management is appropriate. Colonising species were rarer in taller and more diverse plots, indicating competition may limit invasion rates. Urban meadow treatments contained invertebrate and microbial communities that differed from mown grassland. Invertebrate taxa responded to changes in both height and richness of meadow vegetation, but most orders were more abundant where vegetation height was longer than mown grassland. Order richness also increased in longer vegetation and Coleoptera family richness increased with plant diversity in summer. Microbial community composition seems sensitive to plant species composition at the soil surface (0–10 cm), but in deeper soils (11–20 cm) community variation was most responsive to plant height, with bacteria and fungi responding differently. In addition to improving local residents’ satisfaction, native perennial meadow plantings can produce biologically diverse grasslands that support richer and more abundant invertebrate communities, and restructured plant, invertebrate and soil microbial communities compared with short mown grassland. Our results suggest that diversification of urban greenspace by planting urban meadows in place of some mown amenity grassland is likely to generate substantial biodiversity benefits, with a mosaic of meadow types likely to maximise such benefits

Urban meadows as an alternative to short mown grassland: effects of composition and height on biodiversity

There are increasing calls to provide greenspace in urban areas, yet the ecological quality, as well as quantity, of greenspace is important. Short mown grassland designed for recreational use is the dominant form of urban greenspace in temperate regions but requires considerable maintenance and typically provides limited habitat value for most taxa. Alternatives are increasingly proposed, but the biodiversity potential of these is not well understood. In a replicated experiment across six public urban greenspaces, we used nine different perennial meadow plantings to quantify the relative roles of floristic diversity and height of sown meadows on the richness and composition of three taxonomic groups: plants, invertebrates, and soil microbes. We found that all meadow treatments were colonized by plant species not sown in the plots, suggesting that establishing sown meadows does not preclude further locally determined grassland development if management is appropriate. Colonizing species were rarer in taller and more diverse plots, indicating competition may limit invasion rates. Urban meadow treatments contained invertebrate and microbial communities that differed from mown grassland. Invertebrate taxa responded to changes in both height and richness of meadow vegetation, but most orders were more abundant where vegetation height was longer than mown grassland. Order richness also increased in longer vegetation and Coleoptera family richness increased with plant diversity in summer. Microbial community composition seems sensitive to plant species composition at the soil surface (0–10 cm), but in deeper soils (11–20 cm) community variation was most responsive to plant height, with bacteria and fungi responding differently. In addition to improving local residents’ site satisfaction, native perennial meadow plantings can produce biologically diverse grasslands that support richer and more abundant invertebrate communities, and restructured plant, invertebrate, and soil microbial communities compared with short mown grassland. Our results suggest that diversification of urban greenspace by planting urban meadows in place of some mown amenity grassland is likely to generate substantial biodiversity benefits, with a mosaic of meadow types likely to maximize such benefits.N/