Showing papers in "Environmental Entomology in 1980"
TL;DR: The relationships between vegetation architecture and spider community attributes were examined in a big sage community and suggest that architectural properties of habitat may be an important determinant of the distribution and species diversity of predatory invertebrates.
Abstract: The relationships between vegetation architecture and spider community attributes were examined in a big sage ( Artemisia tridentata ) community. Spiders were separated into guilds using similarities of species' hunting behavior. Shrub architecture was experimentally manipulated in the field by either clipping 50% of a shrub's foliage to decrease foliage density or tying together a shrub's branches to increase foliage density.
Shrub perturbations resulted in changes in the number of spider species, spider guilds and guild importance values. The number on spider species and guilds in the tied shrubs were significantly higher than those in the clipped or control shrubs sampled. Spider species diversity and the number of species and guilds were positively correlated with indicators of shrub volume and shrub foliage diversity. This suggests that structurally more complex tied shrubs can support a higher number of spider Species and species diversity.
Temporal patterns of the number of spider species, and species diversity (H') showed midsummer peaks m both 1974 and 1975. Evenness (J') remained relatively constant through both seasons.
The data suggest that architectural properties of habitat may be an important determinant of the distribution and species diversity of predatory invertebrates.
258 citations
TL;DR: Reduction in the length of the nymphal stage and increased adult longevity resulting in a shortened life cycle and longer oviposition period respectively, were additional factors contributing to resurgence.
Abstract: Resurgence of the brown planthopper, Nilaparvata lugens (Stal) on rice was induced by applications of decamethrin, methyl parathion, and diazinon. Differential mortality of predators and hoppers did not appear to be the primary factor for resurgence. Hoppers appeared to be attracted to methyl parathion and decamethrin treated plants because of plant growth. Improved plant growth however did not compensate for the increased feeding of the insecticide-treated hopper population, and plants treated with resurgence-causing insecticides succumbed to feeding injury earlier than untreated plants.
Population increases were due in part to stimulation of reproduction of the hopper, either by contact action of the insecticides or through increased plant growth. Reduction in the length of the nymphal stage and increased adult longevity resulting in a shortened life cycle and longer oviposition period respectively, were additional factors contributing to resurgence.
140 citations
TL;DR: The pronounced response of N. carpocapsae to CO2 suggests that this compound aids host finding, and infective stage juveniles exhibited characteristic rearing and lateral motions in migrating up the CO2 gradient and aggregating at the source.
Abstract: The behavioral response of infective stage juveniles of Neoaplectana carpocapsae to carbon dioxide was studied on an agar substrate. Exposure elicited a strongly positive response. Juveniles exhibited characteristic rearing and lateral motions of the head in migrating up the CO2 gradient and aggregating at the source. The directed movement observed was attributed to klinotactic orientation. Maximum attraction was recorded at a flow rate of 4.1 ml/h; the range of attraction extended to 5 cm. Juvenile aggregations of approximately 60 and 90% were recorded within 30 and 50 mm, respectively, from a 2 cm distance. The pronounced response of N. carpocapsae to CO2 suggests that this compound aids host finding.
137 citations
TL;DR: During the summer sampling period, organic farms had significantly greater numbers of carabids captured in pitfall traps in 3 of 4 pairs, and organic farms also had approximately the same level of diversity as measured by the Shannon-Wiener index.
Abstract: The abundance of ground beetles (Coleoptera: Carabidae) was compared on 4 pairs of conventional and organic farms. All farms compared had identical locations, soil types, and cropping histories, but differed in that one farm in each pair was conventionally managed; the other, organically (no use of commercial fertilizers or pesticides). During the summer sampling period, organic farms had significantly greater numbers of carabids captured in pitfall traps in 3 of 4 pairs. Differences in abundance during this time ranged from 20 percent to almost 7-times greater on organic farms. Organic farms also had about twice the number of species found on conventional farms, but had approximately the same level of diversity as measured by the Shannon-Wiener index.
105 citations
TL;DR: A logistic model of population growth is presented which describes the effects of introducing sterile individuals into a wild population regulated by density-dependent factors and shows that for certain levels of sterile releases two steady states exist.
Abstract: A logistic model of population growth is presented which describes the effects of introducing sterile individuals into a wild population regulated by density-dependent factors. It is shown that for certain levels of sterile releases two steady states exist, of which the upper state is stable and the lower state is unstable. Once a population is driven to below the lower threshold, continued releases will cause (local) extinction. The 2 steady states exist for a wide variety of density-dependent growth functions. The release of sterile males alone is less effective than the release of sterile males and sterile females but not importantly so; however, the release of sterile females alone is not a satisfactory strategy for eradication.
105 citations
TL;DR: Despite the apparent commonness of parasitoid aggregation in areas of high host density, positive spatial correlations between host density and the intensity of parasitism appear to be uncommon in nature.
Abstract: Despite the apparent commonness of parasitoid aggregation in areas of high host density, positive spatial correlations between host density and the intensity of parasitism appear to be uncommon in nature. Negative correlations, and lack of any correlation, have been reported more frequently. Much remains to be learned of these important spatial relationships. They presently lack an unequivocal theoretical explanation, and empirical investigations designed to clarify relationships between searching behavior and spatial variations in the intensity of parasitism have not yet been carried out.
97 citations
TL;DR: Gas chromatographic analyses of pheromone component ratios from 381 individual female tip extracts from field and laboratory populations of redbanded leafroller moths revealed that a narrow-variance signal (coefficient of variance = 9.7%) was used by both populations.
Abstract: Gas chromatographic analyses of pheromone component ratios from 381 individual female tip extracts from field and laboratory populations of redbanded leafroller moths revealed that a narrow-variance signal (coefficient of variance = 9.7%) was used by both populations. Although all measured ratios of ( E )-/( Z )-11-tetradecenyl acetates for both populations fell within 4–15% for the E -component, the untransformed means and standard deviations for the field and lab insects were 9.1±1.8 and 7.0±1.4%, respectively (difference significant at P<0.01). The field Insects contained an average of 139±81 ng of pheromone/female compared to 107±58 ng/female for the laboratory insects. No significant relationships were found between insect body weights, quantity of pheromone, or component ratios.
85 citations
TL;DR: Preliminary field data indicate that attractancy of lures containing all four components present in a similar source ratio to a calling female is not significantly different from lure containing E11/Z11 unsaturated aldehydes alone.
Abstract: Chemical analyses of glands from virgin female eastern spruce bud worm by capillary GC show three major classes of compounds: 14-carbon aldehydes, acetates and alcohols Each class consists of an E11/Z11 unsaturated pair with an E/Z ratio of 95/5 The corresponding saturated compounds in each class are also present at 2–3% of the E11-components E11-14:Ac is the major component of the gland, 30–40 ng/insect with E11-14:Ald and E11-14:OH at 1–3 ng/insect
Analysis of female effluvia collected on Porapak Q® and pumping chamber washes show the presence of four compounds, E11-14:Ald, Z11-14:Ald, 14:Ald and E11-14:Ac (95:5:2:02) Rate of emission of E11-14:Ald from 2–3 day old virgin females maximized at 20–40 ng/insect/night Preliminary field data indicate that attractancy of lures containing all four components present in a similar source ratio to a calling female is not significantly different from lures containing E11/Z11 unsaturated aldehydes alone
79 citations
TL;DR: At least 120 species of Coleoptera were recovered from poultry manure in narrow, widespan, and high-rise types of caged-layer poultry houses in the Mountains, Piedmont, and Coastal Plain regions of North Carolina.
Abstract: At least 120 species of Coleoptera were recovered from poultry manure in narrow, widespan, and high-rise types of caged-layer poultry houses in the Mountains, Piedmont, and Coastal Plain regions of North Carolina. Carcinops pumilio (Erichson) and Alphitobius diaperinus (Panzer) were consistently the most abundant species in all 3 regions, followed by Gnathoncus nanus (Scriba) and the Aleocharinae (Staphylinidae). According to 5 indices of diversity, the Piedmont ranked 1st in overall diversity, species richness and equitability, followed by the Coastal Plain, and thirdly, by the Mountains.
Narrow and high/rise house types were compared for adult and larval C. pumilio and A. diaperinus . The larval population peak for A. diaperinus occurred significantly earlier in the high-rise than in the narrow houses, however, the narrow houses had significantly higher beetle diversity.
A qualitative examination of overwintering forms showed that most species overwintered primarily, but not exclusively, as adults.
79 citations
TL;DR: Under natural conditions, Geocoris bullatus, G. punctipes, and G. uliginosus fed on 67 species of small (0.25—8.7 mm long) prey from 3 classes of arthropods, and most prey were not physically capable of injuring the attacker, and in many cases prey capture was effected without triggering the prey's defensive behaviors.
Abstract: Under natural conditions, Geocoris bullatus (Say), G. punctipes (Say), and G. uliginosus (Say) fed on 67 species of small (0.25—8.7 mm long) prey from 3 classes of arthropods (Insecta, Arachnida, and Diplopoda). Sessile, ambulatory, saltatory, and winged forms (many representing pest species) were successfully attacked. Most prey were not physically capable of injuring the attacker, and in many cases prey capture was effected without triggering the prey's defensive behaviors. Vegetative structures and occasionally seeds of herbaceous angiosperms (monocots and dicots) of several families constituted a small part of their diet, as did dead insects. As opportunistic polyphagous predators, Geocoris spp. are probably of great importance in the prevention of pest outbreaks in many agricultural, turfgrass, and natural habitats.
65 citations
TL;DR: It is suggested that desert subterranean termites locate relatively large size surface foods such as cattle dung and Yucca sp.
Abstract: Chihuahuan desert subterranean termites, Gnathamitermes tubiformans (Buckley) and Amitermes wheeleri (Desneux) readily located surface foods but failed to utilize buried foods of the same type. The termites attacked both natural cowdung pats and artificial(polyurethane) cowdung pats at the same rate as estimated by holes chewed through plastic film barriers placed between the soil and both kinds of pats. There was smaller diel excursion of temperatures in the upper 20 cm of soil under dungpats than in the soil not under dung. We suggest that desert subterranean termites locate relatively large size surface foods such as cattle dung and Yucca sp. logs by sensing the thermal shadows cast by such items.
TL;DR: First-instar Trichoplusia ni larvae feeding on cabbage deterred oviposition by adult moths in laboratory assays, suggesting that larval frass can serve as a signal of occupancy to gravid females searching for Oviposition sites.
Abstract: First-instar Trichoplusia ni larvae feeding on cabbage deterred oviposition by adult moths in laboratory assays.The effect remained for at least 3 days after removal of larvae from plants.When cabbage plants were treated with a dispersion of larval frass in water, oviposition was also deterred. The results suggest that larval frass can serve as a signal of occupancy to gravid females searching for oviposition sites.
TL;DR: The NCR dispersed more readily from cornfields to weedy oat stubble and soybean fields, whereas the WCR for the most part moved from corn to other cornfields, which partially explain the displacement phenomenon and varying degrees of coexistence now observed between the NCR and WCR in different areas of Nebraska.
Abstract: Over the past 30 yr the western corn rootworm (WCR) Diabrotica virgifera LeConte, largely displaced the northern corn rootworm (NCR), D. longicornis (Say), as the dominant rootworm species in eastern Nebraska. Only in the northeast cropping district has the NCR exhibited significant persistency. Here a comparative study of the ecology and behavior of the 2 species disclosed specific distributional and behavioral differences. The avg no. and percentage of the 2 species varied according to whether the samples were from “upland” or “lowland” fields. The NCR was significantly more abundant in upland fields. The NCR dispersed more readily from cornfields to weedy oat stubble and soybean fields, whereas the WCR for the most part moved from corn to other cornfields. These behavioral differences, coupled with prevailing farming practices (continuous corn vs corn in short rotations), partially explain the displacement phenomenon and varying degrees of coexistence now observed between the NCR and WCR in different areas of Nebraska. The southern corn rootworm (SCR), D. undecimpunctata howardi Barber is of minor importance as a pest of corn in Nebraska.
TL;DR: The data suggested no apparent differences in the survival or persistence of endospores among the crops, and bioassay was the best indicator of total field persistence of B. thuringiensis.
Abstract: Persistence and survival of Bacillus thuringiensis were studied in order to evaluate statistically abiotic influences under field conditions. Viable and total endospores, and bioassay with the cabbage looper Trichoplusia ni , were monitored. Abiotic factors were measured on leaves of beans, broccoli and cabbage. The data suggested no apparent differences in the survival or persistence of endospores among the crops. Solar radiation, leaf temperature and vapor pressure deficit affected B. thuringiensis endospore viability and pathogenicity. Bioassay was the best indicator of total field persistence of B. thuringiensis .
TL;DR: Narcosis for 15 sec with CO2 and 3 min at −20°C did not affect survival or pollen foraging behavior, but CO2 treatments of 30, 60, and 120 sec reduced survival and pollen gathering behavior.
Abstract: Short exposure of less than 2 min to pure CO2 or 3 min to −20°C did not alter the orientation and successful return of released forager honey bees to colonies. Narcosis for 15 sec with CO2 and 3 min at −20°C did not affect survival or pollen foraging behavior, but CO2 treatments of 30, 60, and 120 sec reduced survival and pollen gathering behavior.
Narcosis with pure CO2 should not exceed 15 sec to reduce the risks of inducing abnormal physiological and behavioral changes in worker bees.
TL;DR: Consumption of small larvae was largest for the nabids T. capsiformis and H. deceptivus, the lygaeids G. punctipes and G. uliginosus, and the carabid beetle Calleida decora.
Abstract: Approximately 200 specimens of predators representing 16 species were evaluated in field cage tests to determine daily consumption levels of eggs and larvae of the soybean looper, Pseudoplusia includens (Walker). The highest predation rates were recorded for the nabids Reduviolus roseipennis (Reuter), Tropiconabis capsiformis (Germar), and Hoplistoscelis deceptivus (Harris); the green lacewing, Chrysopa rufilabris (Burmeister); and the lygaeids Geocoris punctipes (Say) and Geocoris uliginosus (Say). Consumption of small larvae was largest for the nabids T. capsiformis and H. deceptivus , the lygaeids G. punctipes and G. uliginosus , and the carabid beetle Calleida decora (F.). The pentatomid Stiretrus anchorago (F.) and the reduviid Arilus cristatus (L.) consumed the most medium-sized larvae.
TL;DR: In a uniform infestation with eggs of the western corn rootworm, the root damage rating was found to be a more sensitive measurement of root worm damage than vertical pulling weight, root lodging and goosenecking, plant stunting, or adult recovery.
Abstract: In a uniform infestation with eggs of the western corn rootworm, Diabrotica virgifera LeConte, the root damage rating was found to be a more sensitive measurement of root worm damage than vertical pulling weight, root lodging and goosenecking, plant stunting, or adult recovery. Also, root damage ratings, unlike vertical pulling weight, were independent of the size of the root system.
Adult insects began to emerge from the artificial infestation at the same time as from a nearby natural infestation. The maximum damage the test corn hybrids were able to sustain was reached at ca. 1200 eggs/30.5 cm of row (row-ft); any increase beyond this level resulted in a decrease in the number of adults recovered. The relationship established between yield reduction and a known number of corn rootworms showed that even with almost ideal growing conditions, as few as 100 eggs/30.5 cm of row caused a highly significant reduction.
TL;DR: Analysis of response curves revealed a 930-fold range in susceptibility between the most sensitive and the most resistent individuals in these larval populations of the velvetbean caterpillar to a nucleopolyhedrosis virus.
Abstract: The inter-instar susceptibility of the velvetbean caterpillar to a nucleopolyhedrosis virus was quantitated. Analysis of response curves revealed a 930-fold range in susceptibility between the most sensitive and the most resistent individuals in these larval populations. The LD50 values for 2nd, 3rd, 4th, and 5th instars were 103, 432, 682, and 4100 polyhedra/larva, respectively. At 26.7°C the virus replicated efficiently in all larval instars. Virus replication was slower at lower temperatures (15.6°C, 21.1°C) but the cumulative virus mortality at these these temperatures were similar fo that achieved at 26.7°C. Incubation at higher temperatures (32.2°C), however, caused a 30–50% less virus mortality than occurred at lower temperatures.
TL;DR: Soldier and reproductive proportions of Reticulitermes flavipes (Kollar) were determined in sampling baits from 89 colonies and 5 logs.
Abstract: Soldier and reproductive proportions of Reticulitermes flavipes (Kollar) were determined in sampling baits from 89 colonies and 5 logs. Soldiers averaged 2% of the colony and neotenics, when present accounted for up to 1.28%. The sex-ratio of R. flavipes neotenics was ca. 2 females for every male. Soldier proportions were always high in the vicinity of the neotenics.
TL;DR: An average of 3.9% of laboratory-reared, marked male gypsy moths released uniformly across a 0.64 km2 area were captured in pheromone-baited traps set out 800 m apart in a 64 km2 grid, a proportion that can be used to estimate the average density and the maximal density of a population of feral moths based on the numbers caught in a trapping grid of the same trap density.
Abstract: An average of 3.9% of laboratory-reared, marked male gypsy moths ( Lymantria dispar L.) released uniformly across a 0.64 km2 area were captured in pheromone-baited traps set out 800 m apart in a 64 km2 grid. In contrast, an average of 0.9% of males released simultaneously from a single point at the center of the grid (566 m from the nearest trap) were captured. The 4.0% recapture can be used to estimate the average density and the 0.9% recapture to estimate the maximal density of a population of feral moths, based on the numbers caught in a trapping grid of the same trap density, if we assume that the feral and laboratory-reared moths behave similarly. Approximately 97% of the recaptured males from the uniform release and 80% from the grid center release were captured within 800 m of the release site and no moths were recaptured beyond 1600 m. An average of 18% of males released from the center of a smaller (0.64 km2) grid of higher trap density (80 m spacing) were recaptured. Once again, recaptures occurred predominantly in traps near the center of the grid. The proportion recaptured was highest on the warmer days. Males were released 1, 2 and 3 days after eclosion to assess the effects of adult age, and mortality plus emigration upon trap catch. A higher proportion of older moths (2- and 3-days-old) were captured than one-day-old moths. The apparent average rate of mortality plus emigration between the first and second day after release was 96%, an estimate that may be influenced by individual differences in responsiveness of males to a pheromone source.
TL;DR: The effects of spatial differences in host density on parasitism of Heliothis zea (Boddie) eggs by Trichogramma spp.
Abstract: The effects of spatial differences in host density on parasitism of Heliothis zea (Boddie) eggs by Trichogramma spp. were investigated in cultivated soybean plots. H. zea egg density per leaf and the distance separating egg-bearing leaves within lots were experimentally manipulated. A kairomone-containing extract of H. zea scales was used to mimic natural oviposition sites. Spatial relationships between the probability of parasitism and egg density per leaf were the result of 2 opposing trends. The probability of at least one egg on an eggbearing leaf being encountered and parasitized by Trichogramma (here termed a “discovery” of that leaf by parasitoids) increased as the egg density per leaf increased; the conditional probability of parasitism for other eggs present, given an attack on one egg, decreased with increasing egg density. The net result of these opposing trends varied with separation distance and, statistically, percent parasitism varied from inversely density-dependent to density-independent as separation distance increased from 25 to 150 cm.
TL;DR: Results indicated that the younger larval and pupal stages of T. castaneum were more ozone sensitive than similar older stages; 28-d-old pupae were the most ozone resistant of the stages tested.
Abstract: Studies of 2 species of flour beetles, Tribolium confusum (du Val) and T castaneum (Herbst), were conducted to determine the toxicity of ozone given at specific life cycle stages Toxicity was measured in terms of adult survival one mo posteclosion Results indicated that the younger larval and pupal stages of T castaneum were more ozone sensitive than similar older stages; 28-d-old pupae were the most ozone resistant of the stages tested For a given stage, the younger forms of T confusum were more ozone sensitive than older ones Ozone resistance of T confusum progressively increased with age, except the resistance of 20-d-old larvae was comparable to that of adults: In general, all stages of T castaneum were more ozone sensitive than those of T confusum ; however, for both species the l5-d-old larvae were equally sensitive at each exposure, as were the 28 d pupal stages The hours of ozone exposure for 100% lethality of 15-, 20-, 23-, 28-d-old forms and adults ( T confusum : T castaneum ) were 3½:3½; 6½:5½; 5½:3½; 6:6; and 6½:5, respectively
TL;DR: Dispersal of Nezara viridula (L.) and Piezodorus guildinii (Westwood) nymphs, the 2 most abundant stink bugs in soybeans in Brazil, was studied and showed that they moved more along than across rows.
Abstract: Dispersal of Nezara viridula (L.) and Piezodorus guildinii (Westwood) nymphs, the 2 most abundant stink bugs in soybeans in Brazil, was studied. Results showed that they moved more along than across rows. Maximum distance recorded for both species along rows was 12 m, while across rows was 7.2 m for N. viridula and 4.8 m for P. guildinii .
The total number of nymphs recaptured was higher for P. guildinii than N. viridula , and the recovery rate decreased with increase in distance from the release point. Nymphs in the 2nd and 3rd stages showed strong gregarism and dispersal was more pronounced for 4th and 5th stages, which were the principal ages involved in colonization of the field. Dispersal patterns of the nymphs best fitted the equation Y = a + b Log x + c/x, where Y = density, x = distance from the release point, a = intercept, b = slope, and c = a proportionality constant.
TL;DR: A field trial on apples showed that pre-bloom “pink bud” sprays of 4 synthetic pyrethroids were all highly toxic to the predatory mite Typhlodromus pyri but had no appreciable toxicity to the dominant spider mite species, Panonychus ulmi.
Abstract: A field trial on apples in southeastern England showed that pre-bloom “pink bud” sprays of 4 synthetic pyrethroids—permethrin, cypermethrin, fenvalerate, and decamethrin, were all highly toxic to the predatory mite Typhlodromus pyri , but had no appreciable toxicity to the dominant spider mite species, Panonychus ulmi . The virtual elimination of the predatory mite at this growth stage of apples led to a marked population increase of P. ulmi later in the same season. The use of these pyrethroids for insect control is incompatible with integrated mite management on apples using T. pyri . Laboratory data supported the field results.
TL;DR: Male Heliothis virescens (Lepidoptera: Noctuidae) were shown to transfer 36% of a whole body 65Zn burden to the females at the time of mating, representing the conservation of an essential trace element that must be retained throughout the life cycle.
Abstract: Male Heliothis virescens (Lepidoptera: Noctuidae) were shown to transfer 36% of a whole body 65Zn burden to the females at the time of mating. Approximately 5% of the male's and 11% of the female's total 65Zn burdens were found in eggs oviposited during a 10-day period following mating. Transfer of zinc at mating by Heliothis males may represent the conservation of an essential trace element that must be retained throughout the life cycle.
TL;DR: Topical applications of sub-lethal doses of methyl parathion and decamethrin on 5th instar nymphs caused increases in reproduction in the resulting adults, and Perthane did not cause reproductive stimulation at any of the four dosages tested.
Abstract: LD5, 10, 25, and 50 values of the insecticides methyl parathion, decamethrin, and Perthane were estimated for the 5th instar nymphs of N. lugens . LD values were lowest for decamethrin, followed by Perthane and methyl parathion. Topical applications of sub-lethal doses of methyl parathion and decamethrin on 5th instar nymphs caused increases in reproduction in the resulting adults. Highest reproductive stimulation occurred at the LD dosage for methyl parathion and at LD 50 for decamethrin. Perthane did not cause reproductive stimulation at any of the four dosages tested.
TL;DR: The results suggest that distinctive blends of host plant volatiles, differing quantitatively or qualitatively, release varying degrees of female and male onion fly host-finding behavior.
Abstract: Decomposing onion seedlings and bulbing plants elicited a greater host-finding response by female (but not male) onion flies, Hylemya antiqua (Meigen), than did healthy plants. Clear acetate cone traps baited with the onion chemical, n-dipropyl disulfide, caught more female and male onion flies than traps baited with plants or propanethiol. Of variously damaged onions, only mechanically injured plants released a significant male response, whereas female onion flies were caught by traps baited with maggot infested, Fusarium inoculated, and mechanically injured hosts. Seed corn fly, H. platura (Meigen), females showed a slight, but statistically significant, preference for rotting onion plants, rotting seedlings and healthy seedlings. These results suggest that distinctive blends of host plant volatiles, differing quantitatively or qualitatively, release varying degrees of female and male onion fly host-finding behavior. The apparent advantage of female preference for the decomposing onion would be increased larval survival due to easier larval penetration of onion bulbs and faster larval development.
TL;DR: The results show that onion flies locate host plants as a result of positive taxes, of which anemotaxis plays a significant role.
Abstract: Host-finding behavior by the onion fly, Hylemya antiqua (Meigen), was observed in the field in response to sliced onions (the host plant), barnyard grass ( Echinochloa sp.), and a control treatment. More flies landed within 0.5 m of the onion bait than within 0.5 m of any of the other treatments. Flies which landed downwind of the onion bait flew directly or in a series of short flights toward the volatile source. These behaviors were not observed in the vicinity of the other treatments. Traps designed to assess flight direction with respect to the wind substantiated the observations of female and male upwind flight in response to distant host-plant odors. These results show that onion flies locate host plants as a result of positive taxes, of which anemotaxis plays a significant role.
TL;DR: Field cage experiments were conducted to identify predators which feed on eggs and early stage larvae of Heliothis spp.
Abstract: Field cage experiments were conducted to identify predators which feed on eggs and early stage larvae of Heliothis spp., Pseudoplusia includens (Walker) and Anticarcia gemmatalis Hubner. Isotope labeled (32p) eggs, 1st-, 2nd-, and early 3rd-stage larvae were exposed to possible predators. Predaceous arthropods which obtained the label were identified by autoradiography. A total of 349 individual arthropods from 25 species obtained radioactive labels when exposed to lepidopterous eggs or early stage larvae.
Major predators identified in this study were Nabis roseipennis Reuter, Geocoris punctipes (Say), and Oxyopes salticus Hentz. Nabis roseipennis was the most frequently labeled predator of eggs and larvae. Spider species encountered in this study were not labeled when eggs were provided as prey. A high percentage of the carabids found in the foliage such as Lebia analis Dejean, Callida decora (F.) and Colliuris pennsylvanicus (L.) was labeled. Other foliage dwelling beetles which contained the isotope were Coleomegilla maculata (DeGeer) adults and larvae and Notoxus monodon (F.). Several tettigoniids, Conocephalus fasciatus (Forster), also were labeled. Predation upon primary predators was demonstrated when labeled nymphs of G. punctipes and N. roseipennis were exposed to the indigenous predator complex.
TL;DR: Oribatid mites were sampled from deep soil, soil cores, litter bags, and woody litter on a clearcut and adjacent control hardwood watershed at Coweeta Hydrologic Laboratory, North Carolina to find a richer fauna than intensive sampling of a few habitat types.
Abstract: Oribatid mites were sampled from deep soil, soil cores, litter bags, and woody litter on a clearcut and adjacent control hardwood watershed at Coweeta Hydrologic Laboratory, North Carolina. The inclusion of woody litter and deep soil samples caused the total number of genera found to reach 72, as opposed to the 37–42 genera range reported in other studies. The more common genera were assigned to three habitat types based on stratification data. The fauna was similar to those of other holarctic study sites. Sampling a greater variety of habitat types yielded a richer fauna than intensive sampling of a few habitat types. Clearcutting caused a reduction in numbers and a shift in faunal dominance. This effect is attributed to temperature-humidity phenomena rather than to food availability.