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  • 11
    Electronic Resource
    Electronic Resource
    Distribution and dispersal in populations capable of resource depletion (1976)
    Springer
    Oecologia 23 (1976), S. 255-269 
    Details
    ISSN: 1432-1939
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary A simulation model has been used to investigate the influence of animal (insect) distribution and dispersal among exhaustable resource units (food plants). Population size and stability were used as measures of success. The results showed that population size and stability are highest when egg batch size is as large as can be supported by the average food plant or slightly larger if larval dispersal occurs. Clumping of egg batches of food plants increases population stability when egg batches are small by insuring that some food plants will not be overcrowded. Increasing the proportion of larval dispersers or the success of dispersers can increase or decrease population size and stability depending on the original egg batch distribution, but individuals which produce offspring some of which disperse, generally have a selective advantage. Density dependent larval dispersal decreases population stability. Finally, individuals with lower reproductive capacities can have a selective advantage over those with higher reproductive capacities under certain conditions of egg batch size and larval dispersal.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00345956
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    Paper (German National Licenses)
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  • 12
    Electronic Resource
    Electronic Resource
    Changes in the fecundity of tent caterpillars: a correlated character of disease resistance or sublethal effect of disease? (1995)
    Springer
    Oecologia 103 (1995), S. 475-480 
    Details
    ISSN: 1432-1939
    Keywords: Population cycles ; Forest lepidoptera ; Nuclear polyhedral virus ; Fecundity ; Sublethal
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Over the fluctuation in population density of tent caterpillars, Malacosoma californicum pluviale and M. disstria, fecundity changes from being high at peak density to low for several years during the decline. During the increase phase, fecundity rapidly returns to moderately high levels with a further increase occurring to-ward the end of the increase phase. Two hypotheses which might explain these shifts are that (1) mortality from viral disease which is common during population declines selects for resistant individuals with low fecundity as an associated characteristic, and (2) sublethal viral disease reduces fecundity of moths during population decline. In this study we observed rapid shifts in the frequencies of large and small egg masses and in the mean fecundity between different phases of the population fluctuation. Viral disease was more common in caterpillars from small egg masses of the forest tent caterpillar. These observations are consistent with the hypothesis that sublethal effects of virus reduce the fecundity of moths during the population decline, but high fecundity is quickly restored when disease is rare during the population increase.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00328686
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  • 13
    Electronic Resource
    Electronic Resource
    Distribution and dispersal in populations capable of resource depletion (1976)
    Springer
    Oecologia 24 (1976), S. 7-20 
    Details
    ISSN: 1432-1939
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Theoretical predictions from a simulation model of insect distributions and dispersal among isolated food plants have been tested with data gathered from 13 Cinnabar moth populations. Agreement with the predictions was good. Egg batch size was equal to or slightly larger than the number which could be supported by the average food plant. Egg batch distribution was more clumped when density was high and when egg batch size was small relative to food plant size. The tendency for larval dispersal was lower in populations in areas where plants were widely spaced. These findings indicate that the Cinnabar moth has the genetic or phenotypic flexibility to adjust egg batch size, egg distribution, and larval dispersal to characteristics of the habitat. A hypothesized model is proposed to describe the interactions between larval dispersal, food plant response to defoliation, and population fluctuations for the Cinnabar moth and its food plant, tansy ragwort.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00545484
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  • 14
    Electronic Resource
    Electronic Resource
    Previous herbivore attack of red alder may improve food quality for fall webworm larvae (1984)
    Springer
    Oecologia 63 (1984), S. 166-170 
    Details
    ISSN: 1432-1939
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Three hypotheses of insect-plant interactions were tested by rearing fall webworm larvae in the laboratory on foliage from red alder trees with different histories of western tent caterpillar herbivory. Fall webworm larvae raised on foliage from trees which had been attacked previously for two summers by moderate densities of western tent caterpillars grew faster and attained heavier pupal weights than did those fed foliage from unattacked trees. This contradicts the hypothesis that moderate levels of previous herbivory induces the production of plant defensive chemicals in red alders. Growth of webworms, when fed foliage from unattacked trees adjacent to alders that were attacked by fall webworm larvae, was the same as when fed foliage from trees isolated by distance from attacked trees. This contradicts the hypothesis that attacked trees stimulate the production of defensive chemicals in neigh-boring trees. Young and mature alder foliage was equally good for fall webworm growth and survival, and foliage from trees heavily attacked by both fall webworm and western tent caterpillars for three years produced slow growth rates and small pupal sizes. This supports the hypothesis that continued heavy insect attack can cause the deterioration of the food quality of attacked trees.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00379873
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  • 15
    Electronic Resource
    Electronic Resource
    Does tent caterpillar attack reduce the food quality of red alder foliage? (1984)
    Springer
    Oecologia 62 (1984), S. 74-79 
    Details
    ISSN: 1432-1939
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary We assayed the quality of red alder trees for western tent caterpillar growth and survival to test the hypothesis that caterpillar feeding stimulates plant defenses in both attacked and adjacent trees. Three years of high tent caterpillar density were necessary before deterioration in foliage quality occurred, and even then only foliage from trees which were almost completely defoliated in the current year reduced the growth of caterpillars. Both tent size and mean egg mass size increased after the second year of high density which indicates that good conditions still existed for tent caterpillars after 2 to 3 years of heavy feeding. Egg masses which were moved to areas where trees had not recently supported a high caterpillar population produced significantly smaller tents than endemic controls in 1982. Therefore the small tent and egg mass size of the high density population in 1982 was inherent to the insects rather than modified by food source. In 1983 the tents from introduced egg masses were as large as naturally occurring tents. If lightly attacked trees within areas of high caterpillar density are better defended against insect attack, this does not show up in their ability to support caterpillar growth and survival. We found no evidence to support the hypothesis that trees communicate insect attack and stimulate chemical defenses in adjacent trees. Reduced foliage quality seems to be a result of extensive insect damage rather than a defense against insect damage.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00377376
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    Paper (German National Licenses)
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  • 16
    Electronic Resource
    Electronic Resource
    The development of larval resistance to a nucleopolyhedrovirus is not accompanied by an increased virulence in the virus (2000)
    Springer
    Evolutionary ecology 14 (2000), S. 645-664 
    Details
    ISSN: 1573-8477
    Keywords: biological control ; caterpillar ; coevolution ; geographic mosaic theory ; nucleopolyhedrovirus ; resistance ; Trichoplusia ni ; virulence
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Two laboratory experiments were conducted to examine the possible coevolution of cabbage loopers (Trichoplusia ni) and their S nucleopolyhedrovirus (TnSNPV). At the conclusion of Experiments 1 and 2, T. ni had respectively evolved 4.4 × and 22 × resistance to TnSNPV. The higher level of resistance achieved in Experiment 2 could be due to marginally stronger selection, possibly greater genetic variability in larval resistance to TnSNPV, or both. However, the evolution of resistance was not accompanied by an increased virulence of TnSNPV or a change in the restriction profile of the viral DNA when digested with BamHI, EcoRI, HindIII, PstI, SalI, SstI or XhoI. Little genetic variability for virulence in the initial TnSNPV stocks, low mutation rates and possibly weak selection on the virus are some factors that may have constrained the evolution of TnSNPV. We discuss our results in light of the geographic mosaic theory of coevolution and their implications for the use of TnSNPV as a biological control agent against T. ni.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1010923301770
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  • 17
    Electronic Resource
    Electronic Resource
    The structure of the antennae of the Florida Queen butterfly, Danaus gilippus berenice (Cramer) (1968)
    New York, NY : Wiley-Blackwell
    Journal of Morphology 125 (1968), S. 315-328 
    Details
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Interest in the structure of the antennae of the Florida Queen butterfly arises from the finding that a pheromone is active in their courtship. Light and electron microscopic techniques were used to study the sensilla on the antennae and three types of sensilla with perforated walls were identified. The most common of these are short, thin-walled pegs which are distributed over most of the antennal surface. Long, curved, thin-walled pegs occur in patches on the inner medial antennal surface. Multiple coeloconic sensilla are present having up to 50 pegs in one sensillum. On the outer 28 flagellar subsegments there are two such sensilla per subsegment. In addition there are on the antennae long, thick-walled hairs which are mechanoreceptors and probably also contact chemoreceptors. Sunken pegs, the function of which is not known, occur on the antennae. Grooved sensilla were found with the electron microscope but could not be identified with the light microscope. There was no indication of sexual dimorphism in sensilla types or numbers on the antennae.
    Additional Material: 1 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jmor.1051250305
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