摘要:

The relationship between long-duration flight and the state of oogenesis in the migratory mothAgrotis ipsilon(Hufnagel) was examined in unmated females 1,2,3,4, and 5 d old by using computer-interfaced flight mills. Evidence presented suggests that such long-duration flights (i.e., continuous flights ≥1 h) are indices of migratory flight. There were no significant correlations between the number of chorionated eggs and flight duration, times of flight initiation and termination, or flight speed within age classes 1–4. In 5-d-old moths, however, there was a positive correlation with flight duration. Mated females began their long-duration flights ≍3 h later in the night and averaged 2 h of flight less than unmated females. Their propensity and capacity to engage in such flights, however, was still considerable. The long-duration flight behavior of 3-d-old mated males was similar to that of unmated males, as was their propensity to engage in such flights. Therefore, a delay in oogenesis and suppression of reproductive behavior are not prerequisites for the initiation of long-duration flight activity in A.ipsilon, as would be predicted if the oogenesis-flight syndrome was characteristic of this species. Our data are consistent with previous findings that suggest that most females arrive in the midwestern United States in the spring already mated. We argue that the concept of an oogenesis-flight syndrome in migratory insects has no inherent explanatory power and its only valid use is as a convenient descriptive term. Its most frequent misuse as an explanatory principle is seen in the common assumption that duration of the prereproductive period determines the maximum duration of the migratory period. Empirical evidence as well as theoretical considerations indicate that it is never safe to accept this assumption without testing. To do so risks impeding progress in understanding specific systems through unwarranted extrapolation of data or through building a house of cards.

ISSN:1754-5692    

DOI:10.1093/ee/21.4.677

出版商:Oxford University Press    

年代:1992

数据来源: OUP

摘要:

Published research concerning insect development rate or phenology models shows that the effect of fluctuating temperature and rate summation on nonlinear and linear model predictions is not well understood. Models of rates of development at constant temperatures of an example insect are compared graphically with predicted rates under artificial and naturally varying temperature regimes. Acceleration of insect development at low temperatures and retardation at high temperatures are shown to be implicit to the assumption of nonlinearity of development. The influence of the diurnal range of the temperature regime on the rate summation effect and the interaction between rate summation and the mathematical structure of a particular development rate model are clearly demonstrated. This study shows that the selection of a development rate function for prescriptive use, based on closeness of fit to developmental data from constant temperature experiments, is meaningless. Nor should selection be based on how well a model derived from constant temperature experiments predicts insect development measured under a narrow range of fluctuating temperatures. Reasons why a nonlinear model fitted directly to rates observed under variable temperature laboratory or field data is inappropriate for subsequent prediction (in theory at least), are clearly demonstrated. An appropriate technique that calculates instantaneous development rate functions from fluctuating temperature development time observations is tested with hypothetical data. This technique failed to give reasonable estimates of the parameters of the instantaneous development rate function that generated the hypothetical data.

ISSN:1754-5692    

DOI:10.1093/ee/21.4.689

出版商:Oxford University Press    

年代:1992

数据来源: OUP

摘要:

Measurements of trichome length and density were carried out on seedling and Hag leaves of 28 winter wheat genotypes over a 2-yr period. Also resistance of genotypes to the cereal leaf beetle,Oulema melanopus(L.), was estimated in 3-yr studies. The genotypes showed very significant differences in both leaf pubescence (≍ 19 times) and leaf-feeding damage of cereal leaf beetle (≍ 10 times). Close correlations were found between data for seedlings and Hag leaves (total trichome length,r= 0.80,P= 0.001; average trichome length,r= 0.69,P= 0.001), except for the trichome density, which did not show a significant correlation (r= 0.29). On a 1-mm2surface of the seedlings, many fewer trichomes were found (about one-sixth of those found on the Hag leaves). However, the average trichome length was ≍ 8 times longer than that of the Hag leaves. Ranks of the genotypes did not differ significantly in the 2 yr except for the average trichome length of seedlings. On Hag leaves only, the trichome length provides reliable information about the level of resistance to O.melanopus(r= -0.76,P= 0.001), but in seedlings, the trichome density is better suited for resistance estimation (r= -0.52,P= 0.01). These results have application in breeding. From the breeding point of view, the highly significant correlations between seedling and flag leaf pubescence are of utmost importance because it makes screening possible in the seedling stage for Hagleaf pubescence, the most important factor in cereal leaf beetle resistance.

ISSN:1754-5692    

DOI:10.1093/ee/21.4.700

出版商:Oxford University Press    

年代:1992

数据来源: OUP

摘要:

Cadavers of late instars of the gypsy moth,Lymantria dispar(L.), that were attached to tree boles were examined to determine cause of death. Cadavers of gypsy moth larvae killed by the fungal pathogenEntomophaga maimaigaHumber, Shimazu&Soper were predominantly oriented vertically with heads downward, all prolegs were frequently at a 900 angle to the axis of the body, and older cadavers were usually dry in appearance. By contrast, larvae killed by the L.disparnuclear polyhedrosis virus (NPV) were predominantly positioned with anterior prolegs attached to the bole, the anterior section of the body hanging unattached, and the body bending at an angle of<90°. Cadavers of NPV-killed larvae remained soft and moist when older, and all prolegs were seldom at a 90° angle to the body. In 4.4% of cadavers analyzed, mixed infections with both fungus and virus were evident. Individual samplers with little field experience with these pathogens averaged correct field diagnosis of 69.9% of cadavers of pathogen-killed larvae in the field using these criteria. Cadavers of larvae that had died only recently were more frequently incorrectly diagnosed. It is concluded that field diagnosis of the cause of death of gypsy moth larvae due to E.maimaigaor NPV leads to an unacceptably high level of error for quantitative ecological studies. Nevertheless, cadaver signs and symptoms can provide generalized information on the occurrence of these pathogens.

ISSN:1754-5692    

DOI:10.1093/ee/21.4.706

出版商:Oxford University Press    

年代:1992

数据来源: OUP

摘要:

Drift residues of naled and fenthion, which were applied for mosquito control, were sampled with α-cellulose pads in pineland and hammock ecosystems of the Florida Keys in 1989. These included habitats of state and federally protected insect and cactus species on wildlife refuges with no-spray zones. Naled residues were detected up to 750 m downwind in a no-spray zone in pinelands 6 h after application to adjacent target areas. Fenthion residues were detected up to 50 m downwind in hammock 15 min after application to adjacent target areas. In controlled residue degradation experiments, technical naled did not disappear significantly from pads suspended vertically from wires or laid flat on the substrate over a 240-min period. Fenthion did not disappear significantly from pads laid on the substrate but did disappear partly from pads suspended from wires. Estimated environmental concentrations of naled and fenthion in these habitats may be used to calculate ecological risk indexes for protected species.

ISSN:1754-5692    

DOI:10.1093/ee/21.4.714

出版商:Oxford University Press    

年代:1992

数据来源: OUP

摘要:

The spatial distribution of gypsy moth,Lymantria dispar(L.), egg masses was determined in 60 developed lots in a residential community in Greenbelt, Md. The community was divided into low and high gypsy moth density sections, with average densities of 393.3 and 2,656.3 egg masses per ha, respectively. In the high-density lots, the proportion of egg masses found on trees, man made objects, and houses was 73.9, 21.6, and 4.5%, respectively. The distribution in the low density lots was similar. Oaks,Quercusspp., received the highest proportion of egg masses out of all tree species subcategories at both low and high population densities. The cost effectiveness of a number of potential sampling units, including entire lots, back yards, fixed area plots, and individual trees, was evaluated. The entire lot sampling units required the fewest samples to achieve a predetermined level of precision. However, cost (= sampling time) for these sampling units was also the highest, resulting in relatively low cost effectiveness. Fixed-area plot samples (0.01 ha) were in general the most cost effective sampling units. A binomial (presence-absence) sampling approach, in which the percentage of trees in each lot with>5 egg masses is determined, was nearly as cost effective as fixed-area plots, but its usefulness is limited because it does not provide direct estimates of absolute gypsy moth population density.

ISSN:1754-5692    

DOI:10.1093/ee/21.4.722

出版商:Oxford University Press    

年代:1992

数据来源: OUP

摘要:

In conjunction with experiments to evaluate water drainage as a control method for the rice water weevil,Lissorhoptrus oryzophilusKuschel, studies were performed to compare the abundance and species composition of aquatic arthropods in two sets of continuously flooded and temporarily drained but reflooded rice,Oryza sativaL., paddies. A total of 1,736 individuals representing 22 arthropod taxa was collected. Few differences in abundance were detected; however,Notonectaspp. were significantly more abundant in reflooded paddies. Percentage similarity (PS) between paired treatments was>0.50 on all but one date; relatively high PS values on the first sampling dates suggest that the aquatic arthropod community is able to recover rapidly following reflooding. Several taxa appear to possess traits that enhance survival in a rice paddy subjected to temporary drainage. Implications are discussed for the wide-scale use of drainage on California rice acreage.

ISSN:1754-5692    

DOI:10.1093/ee/21.4.731

出版商:Oxford University Press    

年代:1992

数据来源: OUP

摘要:

Ovipositional preferences ofAedes taeniorhynchus(Wiedemann) in south Florida mangrove basin forests were measured by eggshell sampling and compared with several site characteristics. Mangrove basin forest geomorphology (elevation mean, standard deviation, range, and basin spillover elevation), soil (litter standing crop, soil bulk density, and percentage organic matter), and vegetation (total absolute dominance and vegetative association) were quantified and correlated with eggshell density at 34 sites. The only significant (P<0.05) variables (basin spillover elevation, elevation range) accounted for 58% of the variability of eggshell density using a piecewise regression model. These data indicated that any mangrove basin forest, regardless of vegetative association, Hooded by<14% of the highest daily tides, can potentially produce A.taeniorhynchus. Including data from operational surveys, nearly 50% of the sites sampled (n= 89) contained sufficient eggshells (0.05 per cubic centimeter) to produce significant larval broods. Sites flooded only by storm tides were especially productive, with high upland eggshell densities indicated oviposition even when mangrove plains were flooded.

ISSN:1754-5692    

DOI:10.1093/ee/21.4.737

出版商:Oxford University Press    

年代:1992

数据来源: OUP

摘要:

The effect of lindane on numbers and community structure of oribatid mites was studied in northern Montana. Trees on five O.4-haplots were sprayed with lindane at 5.5 kg/ha (AI) in a simulated operational program to protect lodgepole pine from bark beetles. Sprayed plots and paired control plots were sampled before spray application and five times after treatment over a 2-yr period. Numbers of immature specimens changed more than numbers of adults. Both were Significantly depressed 113 after treatment. Two superfamilies were significantly affected after spraying. Of five measures of community structure, none demonstrated an effect; however, the powers of the statistical tests were quite low. The importance of statistical power in studies of effect of pesticides on nontarget species is discussed. Because the observed effects were short-lived and of relatively small amplitude, we conclude it is unlikely there is a lasting effect on the oribatid community.

ISSN:1754-5692    

DOI:10.1093/ee/21.4.745

出版商:Oxford University Press    

年代:1992

数据来源: OUP

摘要:

This study investigated the influence of host plant availability and suitability to the abundance pattern ofNezara viridulaL. in soybean-growing areas of southeastern Queensland, Australia. In particular, the reasons why bug numbers are low during summer months and why the bugs concentrate and increase on fruiting soybean later in the season were investigated. Glasshouse experiments showed that the host plant species available to bugs during summer were inadequate for egg production by adult females and for nymphal survival and development. However, host plant species available to bugs in spring (the wild crucifersRapistrum rugosum(L.) All. andRaphanus raphanistrumL.) and in early autumn (fruiting soybean) were suitable. The number of nymphs produced per female was highest on these host plant species, and nymphal survival was also high. The concentration of bugs on fruiting soybean for feeding and oviposition was not caused by the attractiveness of the plant relative to other host species but may be attributed to the unavailability of other suitable hosts (species and plant growth stage) other than soybean in the area during this time of the season. The concept of host plant suitability is also reexamined specifically in relation toN. viridula-host plant interaction.

ISSN:1754-5692    

DOI:10.1093/ee/21.4.751

出版商:Oxford University Press    

年代:1992

数据来源: OUP