摘要:

AdultBiprorulus bibax(Breddin) in southwestern New South Wales showed substantial variation in weight and lipid reserves associated with reproductive condition. Females were reproductive from September to March but contained the greatest number of eggs during spring (September–November). Females were larger and heavier than males. Highest body weights occurred in nonreproductive individuals overwintering on oranges or mandarins. Lowest body weights occurred during summer (December–February). Nonreproductive bugs overwintering on oranges or mandarins (but not lemons)contained substantial lipid reserves (0.040–0.048 g/0.1 g). Lipid levels of summer reproductive bugs were about half those of individuals overwintering on nonlemon citrus. Overwintering survival ofB. bibaxis facilitated by biochemical adjustments associated with reproductive dormancy. The accumulation and storage of energy reserves to enable survival during seasonal adversity are fundamental to the success of this citrus pest in southeastern Australia.

DOI:10.1093/ee/19.6.1710

出版商:Oxford University Press    

年代:1990

数据来源: OUP

摘要:

The roles of mating, grouping with conspecific individuals, and exposure to conspecific odors were investigated using the onset of calling behavior (pheromone release) and oocyte development as indirect measures of corpus allatum activity. For any given age in the first gonadotrophic cycle, oocyte size at the onset of calling in virgin females was smaller than that at the onset of mating receptivity. Isolation had no significant effect on either calling or oocyte growth in virgin females. However, females grouped with normal males (i.e., mated) exhibited accelerated gonadotrophic cycles compared with females grouped with phallomerectomized males (i.e., unmated). Thus, copulation accelerates corpus allatum activity and oocyte maturation. The onset of calling and its diel periodicity were advanced in females housed with other virgin females relative to females housed with either mated females or with phallomerectomized males. The importance of experimental design in studies of extrinsic factors that affect endocrine-mediated events is discussed.

DOI:10.1093/ee/19.6.1716

出版商:Oxford University Press    

年代:1990

数据来源: OUP

摘要:

Previously, we examined the effect of insecticides on four species of pteromalid parasitoids and their host, the house fly,Musca domesticaL. Generally, the parasitoids are more susceptible to insecticides than the flies. In this study we examined the effects of synergists that are known to block oxidative (piperonyl butoxide) (PBO) or hydrolytic (S,S,S-tributylphosphorotrithioate) (DEF) metabolism on the toxicity of five insecticides toM. domesticaand the pteromalid wasp,Muscidifurax raptorGirault&Sanders, to evaluate if metabolism was involved in the differential toxicity observed in the fly–parasitoid system. No consistent differences in PBO- or DEF-enhanced insecticide toxicity between species were seen. This suggests there is no general rule that can be made regarding increased levels of monooxygenase or hydrolase activities between host versus parasitoid species. Although the differential toxicity of certain insecticides toM. raptorandM. domesticais due in part to differential metabolism, it is clear that other processes must also be involved.

DOI:10.1093/ee/19.6.1722

出版商:Oxford University Press    

年代:1990

数据来源: OUP

摘要:

Bacteria isolated from the crop and stomach of laboratory-reared and wild oriental fruit flies,Dacus dorsalisHendel (Diptera: Tephritidae), were identified and tested for attractancy to adult flies in a laboratory olfactometer. Bacteria were identified primarily as belonging to the family Enterobacteriaceae and includedEnterobacter cloacae, E. agglomerans, Klebsiella oxytoca, Citrobacter freundii, andKluyverasp. Bacteria isolated from laboratory flies but found in wild flies includedProvidencia rettgeri, P. stuartii, andSerratiaandCedeceaspp. Attractancy of flies to samples of bacteria cultures, both broth-free (washed) and in broth (unwashed), indicated a relatively low response of flies to these substrates compared with a known attractant, PIB-7 (protein hydrolysate). However, when washed bacteria were tested in the presence or absence of PIB-7 as a treatment, there was a significantly higher response of the flies to the washed bacteria when PIB-7 was absent. Washed bacteria also attracted significantly more flies than water or saline controls. When bacteria were tested as broth cultures (unwashed), they were not significantly different from the broth media in which they were grown. In washed and unwashed bacteria experiments, females showed a greater response than males when treatments were combined for analysis, whereas there were no apparent differences in response among flies of different ages to the combined treatments. Differences in response by sex to the individual treatments revealed significantly greater attraction of females toC. freundiias washed bacteria and toE. cloacaeandK. pneumoniaeas unwashed bacteria.

DOI:10.1093/ee/19.6.1726

出版商:Oxford University Press    

年代:1990

数据来源: OUP

摘要:

The persistence and distribution ofEdovum puttleriGrissell, an egg parasitoid of Colorado potato beetle,Leptinotarsa decemlineata(Say), on potato (Solanum tuberosumL.) plants with different host resources were quantified.E. puttleriwere released into 1.5-m3field cages enclosing pairs of potato plants with different combinations of host eggs, aphids producing honeydew, or without these resources. Observations every 2 h throughout the day revealed that the parasitoids spent more time during peak foraging periods on plants with aphids or host eggs, or both. However, the percentage of parasitism and mortality of beetle egg masses was not significantly higher on plants with aphids. The relationship between parasitism and mortality of beetle eggs byE. puttleriand weather conditions were analyzed.

DOI:10.1093/ee/19.6.1732

出版商:Oxford University Press    

年代:1990

数据来源: OUP

摘要:

The means by which spiders arrive in newly cultivated fields were investigated in east Tennessee study plots through collections of cursorial and aerial immigrants into a garden system; through experimental manipulations of garden plots to distinguish between aerial and cursorial immigrants; and through censuses of the spider faunas of garden plots and of neighboring habitats in various stages of succession. The familial compositions of the aerial dispersers and cursorial dispersers differed significantly. Further, the majority of the spiders entering the garden plots arrived via ballooning (passive dispersal on air currents). Mark-recapture experiment results indicate that bordering habitats can contribute spiders if these are physiognomically similar. However, ≍50% of the spider species found in our garden plots were not found in nearby “natural habitats.” This represents a minimum estimate of the contribution of long-distance immigration. These data indicate that spider immigration into agricultural systems is not dependent on a neighboring reservoir (natural habitat).

DOI:10.1093/ee/19.6.1738

出版商:Oxford University Press    

年代:1990

数据来源: OUP

摘要:

A study was conducted in 1986 and 1987 to determine the effects of perturbation and habitat characteristics on the population dynamics and community structure of darkling beetles on mixed-grass rangeland. Two 1,400-ha blocks of rangeland in western South Dakota were treated aerially with malathion liquid spray or carbaryl-bran bait in early July 1986 to determine the immediate and second-year effect of treatments on darkling beetles, as well as grasshoppers and other nontarget arthropods. Populations of the dominant species (83% of total),Eleodes opacus(Say), were reduced significantly by 59.2 and 87.9% in the carbaryl-bran bait and malathion spray treatment plots, respectively, within 1 wk of treatment and remained at low levels throughout the rest of the summer. Populations did not change significantly in the control plots. Populations of the next three most abundant species (15.7% of total),E. tricostatus(Say),E. obsoleta(Say), andE. suturalis(Say), were negatively affected by one or both treatments. Populations increased to or above pretreatment levels in 1987 in treated and control plots. Analysis of covariance of the abundance of darkling beetles during July 1987, with pretreatment abundance as a covariable, indicated that treatment (treatment and block effects combined) had no significant effect on second-year populations ofE. opacus, E. obsoleta, orE. suturalis, but did explain a significant amount of variation of second-year populations ofE. tricostatus. However, the covariable, pretreatment abundance, was significantly correlated with July 1987 population levels ofE. opacus, E. tricostatus, andE. obsoleta. The multivariate technique, detrended correspondence analysis (DCA), was used to ordinate undisturbed communities along ecological gradients, and correlation analysis of DCA axes values with habitat variables was used to define specific gradients underlying the community structure of darkling beetles. Analysis of abundance and incidence data indicated that darkling beetle communities were ordinated along ecological gradients of percentage of grass coverage, particularlyBuchloe dactyloides(Nutt.) Engelm. andBromusspp., coverage of several forb species, and percentage of sand and clay in the soil. Numbers of total darkling beetles,E. opacus, andE. obsoleta, and species richness increased along a gradient defined by coverage of grass and percentage of sand.E. suturalisdecreased along the same gradient.

DOI:10.1093/ee/19.6.1746

出版商:Oxford University Press    

年代:1990

数据来源: OUP

摘要:

A study was conducted to determine if grazing history affected community composition of plants and grasshoppers by comparing communities in an undisturbed grassland that has not been grazed by livestock for approximately 60 yr (Badlands National Park, South Dakota) with communities on adjacent grasslands that are managed for grazing (Buffalo Gap National Grasslands). Grasshoppers were sampled with sweep nets in August 1986 at 29 sites within the Badlands National Park and Buffalo Gap National Grasslands. Concurrently, plant communities were sampled at the sites to determine species richness of grasses and percentage of coverage of all grass species, forbs, sedges, and bare ground. Detrended correspondence analysis and Spearman correlation analysis of insect abundance and incidence data were used to assess spatial changes in grasshopper community structure and to relate vegetation variables to grasshopper community composition. Results indicated that grasshopper communities changed along habitat gradients defined by grazing history and coverage and species richness of grasses. Sites within the undisturbed grassland habitat had similar community compositions of grasshoppers and were dominated by mixed forb- and grass-feeding species. Grazed sites supported higher populations of obligate grass-feeding grasshoppers. Differences in grasshopper communities between the grazed and undisturbed sites were, in part, due to differences in plant community composition; grazed sites were dominated by short grasses, whereas ungrazed sites were composed mainly of tallgrass species. In general, the mixed forb- and grass-feeding species of grasshoppers increased along vegetation gradients defined by increasing coverage ofAgropyron smithiiRydb.,Bromusspp.,Poaspp.,Stipa viridulaTrin., andCarexspp., and decreasing coverage of bare ground andBouteloua gracilis(H.B.K.) Lag. ex Steud. Communities dominated by obligate grass-feeding species were associated with high coverage of bare ground andB. gracilis. Grasshopper species richness was greatest at sites with high richness of grasses and total coverage of grasses and sedges.

DOI:10.1093/ee/19.6.1756

出版商:Oxford University Press    

年代:1990

数据来源: OUP

摘要:

Seasonally dense populations ofMononychellus tanajoa(Bondar), feeding on the leaves of cassava,Manihot esculentaCrantz, significantly reduced the leaf, stem, and storage-root dry matter of mite-infested plants. Stressed plants met metabolic demands by remobilizing the dry matter in stems and storage roots; however, the proportion of dry matter allocated between the stems and storage roots did not change. Damage byM. tanajoareduced the dry matter in storage roots by 10–30% by the end of the dry season and by 25–45% three months into the subsequent wet season, depending on the age of the plant. Renewed plant growth following the dry season compensated for drought effects, but mite-induced dry matter losses persisted or increased until harvest during the subsequent wet season. A multiple regression model for predicting yield shows that cassava planted early in the wet season and harvested following the period of maximum mite damage at the beginning of the dry and wet seasons, produces more than twice as much dry matter as cassava planted later, but harvested at the same time.

DOI:10.1093/ee/19.6.1767

出版商:Oxford University Press    

年代:1990

数据来源: OUP

摘要:

A rainout shelter was used to control soil moisture and rainfall conditions in soybean plots artificially infested with twospotted spider mites,Tetranychus urticaeKoch, in 1987 and 1988. Leaf disks were collected to determine the separate and interactive effects of plant water stress and impact energy of rainfall on spider mite population dynamics. In both seasons, spider mites initially colonized lower leaves and dispersed into the upper canopy as populations peaked 3–4 wk later. Precipitation applied with a rainfall simulator was not found to significantly affect mite intensity (mites per leaf area). Significantly greater mite intensities were found in stressed plots on two of six sampling dates in 1987 and in the pooled data of 1988. However, the differences in intensity were slight and may be accounted for, in part, by less total leaf area on the stressed plants. Results did not support the traditional belief that plant stress and the occurrence of heavy, driving rains are important factors in spider mite population dynamics. Rather, other factors associated with drought conditions require consideration to explain spider mite population dynamics in soybean.

DOI:10.1093/ee/19.6.1773

出版商:Oxford University Press    

年代:1990

数据来源: OUP