摘要:

Spatial aggregation patterns of flying southern pine beetles,Dendroctonus frontalisZimm., were studied using a systematic grid of sticky flight traps placed in 3 beetle infestations. Five methods of characterizing dispersion were compared: Lloyd's index of patchiness (IP), Morisita's index of dispersion (Iδ), the coefficient of dispersion (CD), the slope of Taylor's power function (b), and the slope (β) of Iwao's regression of mean crowding (m) on mean density (m*).All indices indicated a high degree of aggregation of flying southern pine beetles within the infestations. The indices varied, however, in their ranking of aggregation for the 3 study sites. IP and Iδgave the same relative results while CD showed a different pattern. The two regression techniques showed no significant differences between slopes for the various study sites.The m*-m regression provided more information for interpretation and more potential for evaluating influences of system manipulations. It is recommended, therefore, for characterization of southern pine beetle aggregation within infestations. IP (which serves as the theoretical basis of the regression), is suggested for comparisons between daily aggregation patterns.The m*-m pairs to the 95% prediction limits about the regression line; pairs falling outside these limits represent aggregation patterns significantly different from the norm.

ISSN:1754-5692    

DOI:10.1093/ee/8.3.381

出版商:Oxford University Press    

年代:1979

数据来源: OUP

摘要:

Prepupae and newly formed pupae of the bollwom,Heliothis zea(Boddie), and the tobacco budworm,Heliothis virescens(F.), were allowed to enter 3 types of soil or were manually buried in the soils and were then exposed to 3 simulated regimes of rainfall. Soil type did not affect emergence, but there were significant differences in emergence when the prepupae were allowed to form their own pupation cells or were manually buried. The depth at which the pupae were buried was insignificant, but the regime of rainfall affected emergence of moths of both species. In prepupal behavior tests, both species moved further from the release point on smooth and packed soils compared to rough, soft soil.

ISSN:1754-5692    

DOI:10.1093/ee/8.3.388

出版商:Oxford University Press    

年代:1979

数据来源: OUP

摘要:

A one-h light pulse, which occurred between 7 and 9 h after the beginning of a short-day scotophase, inhibited diapause in a laboratory colony of the mosquitoAedes atropalpus. Tests were conducted to see if induction of diapause in the field is also inhibited by nighttime light pulsing. It was determined that the natural light intensities at whichA. atropalpusexperiences the start of the scotophase occur shortly before sunset. Therefore, a one h pulse of light, at 8 h post sunset, was used to simulate the conditions which inhibited diapause in the laboratory. This prevented induction of diapause both in field cages and at a natural breeding site forA. atropalpus. The observation, made during this study, that the natural scotophase forA. atropalpusends at much lower light intensities than those at which it begins is discussed.

ISSN:1754-5692    

DOI:10.1093/ee/8.3.392

出版商:Oxford University Press    

年代:1979

数据来源: OUP

摘要:

The relative efficiency of the D-Vac® suction insect collector as a sampling method for collection of potato leafhopper adults on alfalfa was compared with that of an emergence trap, drop trap, and sweep net. The D-Vac and drop trap techniques were most efficient. Using the D-Vac insect collector, a sampling plan was developed to study the dynamics of potato leafhopper populations on alfalfa. The sample unit was a set of 10 (0.09 m2) sucks (a suck consisted of placing the suction orifice on the soil for ca. 2 sec). This sample unit showed the distribution of leafhoppers to be aggregated, following the negative binomial distribution. This distribution was used to calculate sample sizes required to estimate adult density within either a 10, 20, or 30% coefficient of variation. The densities of adult leafhoppers during most of the 1976 and 1977 seasons permitted population estimates within a 10–20% coefficient of variation.

ISSN:1754-5692    

DOI:10.1093/ee/8.3.397

出版商:Oxford University Press    

年代:1979

数据来源: OUP

摘要:

Dormancy is significant in determining the seasonal interactions between the thelyotokous braconid parasitePerilitus coccinellaeand its coccinellid host,Coleomegilla maculata. The parasite's autumnal diapause is maintained by short daylengths and it ends in 50% of the population by the winter solstice. Low temperatures are not required to terminate diapause. The autumnal-hibernal diapause of the host is maintained by short daylengths. By the end of Mar. the photoperiodic control of diapause ends in 50% of the beetles; subsequently temperature and availability of prey determine when oviposition begins.P. coccinellaeparasitizes the overwinteringC. maculatapopulation twice: during Sept., before the beetles form overwintering aggregations, and again in spring after the beetles disperse.

ISSN:1754-5692    

DOI:10.1093/ee/8.3.400

出版商:Oxford University Press    

年代:1979

数据来源: OUP

摘要:

Two population levels of western corn rootworm,Diabrotica virgiferaLeConte, were given a choice of 2 soil moisture levels for oviposition. In 1977, significantly more eggs were oviposited in subplots with high moisture levels. Population level did not affect the selection of moisture level or depth at which eggs were oviposited. In both years of the test, the majority of eggs was placed in the top 15 cm of soil.

ISSN:1754-5692    

DOI:10.1093/ee/8.3.406

出版商:Oxford University Press    

年代:1979

数据来源: OUP

摘要:

The mean number of frit fly,Oscinella frit(L.), infested stems in field plantings of reed canarygrass,Phalaris arundinaceaL., ranged from 11.1 to 39.9% for 16 clones at one site and from 9.7 to 31.2% for 25 clones at another site. The mean number of stems/9.3 dm2ranged from 31.0 to 101.1 at site 1 and from 56.7 to 148.2 at site 2. Alkaloid contents ranged from 0.075 to 0.617% (d.w.) at site 1 and 0.072 to 0.532% at site 2. Mean percentages of infested stems were negatively correlated with both mean number of stems/9.3 dm2(r = −0.865) and with total basic alkaloid concentration (r = −0.544). Alkaloid content was positively correlated (r = 0.661) with number of stems/clone. There was a weak negative correlation (r = −0.478) between number of immature frit fly (larvae + pupae)/stem and alkaloids.The mechanism of resistance to the frit fly in reed canarygrass could be nonpreference controlled by stem density or antibiosis controlled by toxic alkaloids, or a combination of both factors. The great variability in frit fly infestation among these clones suggests that selection for resistance to frit fly should be productive.

ISSN:1754-5692    

DOI:10.1093/ee/8.3.408

出版商:Oxford University Press    

年代:1979

数据来源: OUP

摘要:

A guild of 12 sap-feeding Homoptera and Hemiptera, mostly leafhoppers and planthoppers, was sampled on large and small patches of the salt marsh grassSpartina patens. Several species maintained consistently larger densities (individuals per kg of live grass) in large (∼20 ha) compared to small (∼1 ha) patches and the herbivore load (total individuals per kg of live grass) was also greater in large patches. The number of resident sap-feeder species supported by large and small patches was the same. Small patches supported lower densities of sap-feeders because immigration rates were probably lower and removal rates higher there.

ISSN:1754-5692    

DOI:10.1093/ee/8.3.412

出版商:Oxford University Press    

年代:1979

数据来源: OUP

摘要:

The Wardecker watering device was beneficial to colonies of honey bees,Apis melliferaL., stressed by confinement, heat, and lack of water in the desert southwest. The benefits included larger populations of adult bees, more sealed brood, less mortality of unsealed brood, and no mortality of queens or colonies. Colonies in the northern Rocky Mountain area where such stress did not occur did not benefit from the waterer, and those without it generally had more bees, brood, and honey.

ISSN:1754-5692    

DOI:10.1093/ee/8.3.418

出版商:Oxford University Press    

年代:1979

数据来源: OUP

摘要:

Herbicidal effect onRhinocyllus conicusFroet., a thistle head weevil, was studied by examining the mortality, emergence rates and weights of weevils developing from plants treated with 2,4-D (LVA). Infested heads, obtained by caging ovipositingR. conicuson primary heads of musk thistle (Carduus nutansL.) (resemblesC. thoermeriWeinmann), were treated with 2,4-D at 1.68 kg/ha 0–3 wk after oviposition. Mortalities of larvae developing from untreated plants and those plants sprayed 1–3 wk were significantly lower than mortality from plants sprayed within 48 h of oviposition. The latter failed to support larval development beyond the 2nd instar. Developmental times and weights of weevils that emerged from blooms sprayed at 1, 2, and 3 wk were not significantly different from controls. Plants sprayed up to 2 wk after oviposition (late-bud to early-bloom) did not produce viable seeds, but treatments at 3 wk after oviposition (full-bloom) allowed 10% germination of seeds not damaged byR. conicusin primary heads, and plants survived to produce additional heads. Treatment of musk thistles with 2,4-D at late-bud to early-bloom stage of the primary heads prevented formation of viable seeds without adversely affectingR. conicusdevelopment.

ISSN:1754-5692    

DOI:10.1093/ee/8.3.421

出版商:Oxford University Press    

年代:1979

数据来源: OUP