Recent contributions to our knowledge of the neurone.

Ferris, H. B.

doi:10.1037/h0075992

Cited by 2 publications

(3 citation statements)

References 12 publications

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“…The impacts of individual mortality factors on these exotic populations can be appraised more readily, because communities involving introduced species are relatively young and simple, and factors that regulate population growth are few compared to the situation for endemic communities (McClure 1981(McClure , 1983b. externa and N. tsugae, native to Japan (Takahashi andTakagi 1957, Takagi 1963), have become serious pests of Tsuga canadensis Carriere, a North American species, in several states in the USA following their introduction into the New York City area early in this century (Sasscer 1912, Weiss 1914, Ferris 1936. Studies that compare the dynamics of a herbivore species in its native habitat with those where it has been introduced can provide new insight into the natural regulation of herbivore populations and into the validity of the popular approach for controlling exotic pests by introducing natural enemies from the homeland.…”

Section: Introductionmentioning

confidence: 99%

“…F. externa and N. tsugae, native to Japan (Takahashi andTakagi 1957, Takagi 1963), have become serious pests of Tsuga canadensis Carriere, a North American species, in several states in the USA following their introduction into the New York City area early in this century (Sasscer 1912, Weiss 1914, Ferris 1936. Both scales feed on the mesophyll of the young needles, and both attack and injure numerous species of conifers (McClure and Fergione 1977).…”

Section: Introductionmentioning

confidence: 99%

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Popualtion Dynamics of Japanese Hemlock Scales: A Comparison of Endemic and Exotic Communities

McClure¹

1986

Ecology

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The dynamics of endemic populations of two armored scales, Fiorinia externa and Nuculaspis (=Tsugaspidiotus) tsugae (Homoptera: Diaspididae), were studied in Japan and compared with the dynamics of introduced populations of these scales in the United States. In Japan both scales were distributed widely among the 13 natural and cultivated stands of Tsuga diversifolia and T. sieboldii sampled throughout Honshu, but scale densities were innocuous and low relative to those in North America. Density, survivorship, and fecundity of both scale species were significantly higher on hemlocks planted outside their natural range in Japan than on naturally occurring montane trees, and significantly higher on Tsuga species exotic to Japan than on Japanese hemlocks. I infer from this that trees growing outside their natural habitats are more susceptible to insect herbivores, presumably due to stress from less adequate growing conditions. Experiments conducted in a field plot in Kyoto, Japan, revealed that on each hemlock species scale fecundity was always higher among scales that had been transferred from another individual of that same hemlock species than among scales that had been transferred from an individual of a different hemlock species. These results supported those from a similar experiment involving exotic scale populations in Connecticut, USA, and indicated that scales residing on adjacent trees may be qualitatively different.Data from the field plot study in Kyoto and life table data gathered from 13 sites in Honshu revealed that endemic populations have the potential to attain densities injurious to host hemlocks, especially trees in cultivation. However, this seldom occurs because two hymenopterous parasitoids, Aspidiotiphagus citrinus and Arrhenophagus albitibiae, regularly killed from 90.2 to 94.2% of both scale species. Throughout Honshu the seasonal occurrence of the bivoltine adult parasitoids and vulnerable stages ofbivoltine F. externa and N. tsugae were synchronous, resulting in high parasitism rates and a low range of fluctuation in endemic scale populations. In contrast, Connecticut populations of As. citrinus are asynchronous with their scale host, F. externa, which is univoltine there. The resulting higher populations of the scale in Connecticut injure and kill their new host plant, Tsuga canadensis.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Popualtion Dynamics of Japanese Hemlock Scales: A Comparison of Endemic and Exotic Communities

McClure¹

1986

Ecology

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“…Two exotic scales of eastern hemlock, Tsuga canadensis Carriere, in the northeastern United States are Fiorinia externa Ferris and Tsugaspidiotus tsugae (Marlatt) (Homoptera: Diaspididae). Both species were introduced into the United States between 1908 and 1910 on exotic hemlocks shipped to the New York City area from Japan, and subsequently became established on native eastern hemlock (Sasscer 1912, Weiss 1914, Ferris 1936). The crawlers, or mobile firstinstar nymphs of both species preferentially colonize the undersides of hemlock needles where they insert their piercing stylets and suck the fluid from mesophyllic cells.…”

Section: Introductionmentioning

confidence: 99%

Competition Between Exotic Species: Scale Insects on Hemlock

McClure¹

1980

Ecology

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Two exotic armored scales, Fiorinia externa Ferris and Tsugaspidiotus tsugae (Marlatt), native to Japan occur sympatrically in the northeastern United States where they often attain high population densities on eastern hemlock, Tsuga canadensis Carriere. Both scales preferentially colonize the young needles of the lower hemlock crown, which intensities competition between them when food and space become limiting at high scale densities. Studies conducted for 2 yr in the greenhouse and in a hemlock forest located in Darien, Connecticut, demonstrated that summer generations of F. externa and T. tsugae compete intraspecifically and interspecifically at densities occurring in the field. F. externa had a greater advderse affect (reduced survival and fecundity) on itself and on T. tsugae than did T. tsugae have either on itself or on F. externa. The superior competitive ability of F. externa over T. tsugae was likely due to its earlier colonization time. Hatching in early June some 2—4 wk prior to its competitor, F. externa is afforded a distinct spatial and nutritional advantage (1) by colonizing young, nitrogen—rich needles at a time during the year when concentrations of foliar nitrogen and water are high, (2) by reducing the amount of foliar nitrogen available to T. tsugae nymphs, and (3) by forcing T. tsugae crawlers to colonize older, nitrogen—poor foilage where they subsequently suffer significantly greater mortality. Aspidiotihagus citrinus Crawford (Hymenoptera: Aphelinidae), a primary internal parasitoid of F. externa and T. tsugae, exhibited a density dependent response to both scales in single—species infestations in the Darien forest. In mixed infestations, however, the parasitoid did not selectively attack the more abundant species but parasitized each scale in proportion to its frequency. Because it did not discriminate between hosts, A. citrinus did not alter the outcome of the competition between summer generations of the two scales. The geographical distributions of the two scales in Faifield County, Connecticut, and their population trends for 3 yr at 20 sites where they occur sympatrically indicate that competition has excluded T. tsugae. At 18 to 20 sites coinhabited at different densities during 1976, T. tsugae was excluded or nearly excluded within 3 yr. Only at two sites, where T. tsugae was abundant and F. externa was sparse, was T. tsugae able to maintain its initial relative density.

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Recent contributions to our knowledge of the neurone.

Cited by 2 publications

References 12 publications

Popualtion Dynamics of Japanese Hemlock Scales: A Comparison of Endemic and Exotic Communities

Popualtion Dynamics of Japanese Hemlock Scales: A Comparison of Endemic and Exotic Communities

Competition Between Exotic Species: Scale Insects on Hemlock

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