RELATION OF MORTALITY CAUSED BY PARASITES TO THE POPULATION DENSITY OF HYPHANTRIA CUNEA

1976 ◽  
Vol 108 (11) ◽  
pp. 1291-1294 ◽  
Author(s):  
R. F. Morris
Keyword(s):  
Nova Scotia ◽  
Population Density ◽  
New Brunswick ◽  
Parasite Species ◽  
Natural Populations ◽  
Host Density ◽  
Delayed Response ◽  
Hyphantria Cunea ◽  
Cent Mortality ◽  
The Relationship

AbstractParasitism in natural populations of Hyphantria cunea Drury was measured in New Brunswick and Nova Scotia, 1957–1973. Thirteen parasite species were recovered during this period but only a few caused an appreciable degree of mortality. The per cent mortality showed an immediate rather than a delayed response to host density, the relationship being direct up to a density of about 10 host colonies per mile, then inverse. Possible reasons for this sort of relationship are discussed.

HYPERPARASITISM IN POPULATIONS OF HYPHANTRIA CUNEA

1976 ◽  
Vol 108 (7) ◽  
pp. 685-687 ◽  
Author(s):  
R. F. Morris
Keyword(s):  
Nova Scotia ◽  
Population Density ◽  
New Brunswick ◽  
Parasite Species ◽  
Hyphantria Cunea ◽  
The Mean

AbstractFour of the parasite species attacking Hyphantria cunea Drury spin their cocoons inside the colonial web of the host, where they are exposed to attack by five species of hyperparasites. Percentage hyperparasitism was measured over a 15-year period in permanent study areas in New Brunswick and Nova Scotia. The mean percentage was about 50%, with very wide variations from year to year. These variations were not related to the population density of H. cunea or its parasites and no model for hyperparasite-parasite interaction could be constructed.

PREDATION BY INSECTS AND SPIDERS INHABITING COLONIAL WEBS OF HYPHANTRIA CUNEA

1972 ◽  
Vol 104 (8) ◽  
pp. 1197-1207 ◽  
Author(s):  
R. F. Morris
Keyword(s):  
Population Dynamics ◽  
Nova Scotia ◽  
North America ◽  
Population Density ◽  
New Brunswick ◽  
Numerical Response ◽  
Initial Number ◽  
Hyphantria Cunea ◽  
The North ◽  
The Mean

AbstractThe number of predators inhabiting nests of Hyphantria cunea Drury was recorded annually for 13 years in four areas in New Brunswick and two areas on the coast of Nova Scotia. The most common groups were the pentatomids and spiders, which sometimes reproduced within the nests, but the mean number per nest was low in relation to the number of H. cunea larvae in the colonies. The rate of predation on fifth-instar larvae was low. Small or timid predators appeared to prey largely on moribund larvae or small saprophagans during the principal defoliating instars of H. cunea.No relationship could be detected between the number of larvae reaching the fifth instar and the number of predators in the colony; nor could any functional or numerical response of the predators to either the initial number of larvae per colony or the population density of colonies be found. It is concluded that the influence of the nest-inhabiting predators is small and relatively stable, and may be treated as a constant in the development of models to explain the population dynamics of H. cunea.H. cunea is a pest in parts of Europe and Asia, where it has been accidentally introduced from North America. The introduction to other continents of the North American predator, Podisus maculiventiis (Say), is discussed briefly.

RELATION OF PARASITE ATTACK TO THE COLONIAL HABIT OF HYPHANTRIA CUNEA

1976 ◽  
Vol 108 (8) ◽  
pp. 833-836 ◽  
Author(s):  
R. F. Morris
Keyword(s):  
Nova Scotia ◽  
New Brunswick ◽  
Colony Size ◽  
Parasite Species ◽  
Hyphantria Cunea ◽  
Plant Host

AbstractParasitism of Hyphantria cunea Drury was measured over a 17-year period in a series of permanent study areas in New Brunswick and Nova Scotia. The percentage of colonies attacked by parasites was independent of both plant host and colony size, but the percentage of larvae attacked within colonies decreased in the larger colonies. For most parasite species the percentage of larvae attacked per colony was relatively constant, regardless of the percentage of the colonies attacked in any area or year. Thus the colonial habit of H. cunea imposes a limit on the overall degree of parasitism that can be achieved by most of the parasite species.

LOGARITHMIC REGRESSION AS AN INDEX OF RESPONSES TO POPULATION DENSITY: COMMENT ON A PAPER BY M. P. HASSELL AND C. B. HUFFAKER

1969 ◽  
Vol 101 (4) ◽  
pp. 361-364 ◽  
Author(s):  
R. F. Morris ◽  
T. Royama
Keyword(s):  
Theoretical Model ◽  
Population Density ◽  
Density Dependence ◽  
Functional Significance ◽  
Natural Populations ◽  
Biological Significance ◽  
Host Density ◽  
Regression Coefficients ◽  
Forest Insects ◽  
Simulation Exercises

AbstractRegression coefficients derived from the Nicholson–Bailey parasite mode) by Hassell and Huffaker (1969) are interpreted, and their conclusions about the biological significance of changes in slope are shown to be invalid. It is demonstrated that the term "delayed density-dependence" has no functional significance because it includes density responses that range from inverse to direct, depending upon the particular theoretical model that is selected for simulation exercises. In natural populations of a number of forest insects, the net response of parasitism to host density is direct, not inverse.

INFLUENCE OF GENETIC CHANGES AND OTHER VARIABLES ON THE ENCAPSULATION OF PARASITES BY HYPHANTRIA CUNEA

1976 ◽  
Vol 108 (7) ◽  
pp. 673-684 ◽  
Author(s):  
R. F. Morris
Keyword(s):  
Biological Control ◽  
New Brunswick ◽  
Laboratory Experiments ◽  
Natural Populations ◽  
Host Population ◽  
Genetic Constitution ◽  
Short Term ◽  
Hyphantria Cunea ◽  
Genetic Changes ◽  
Insect Parasites

AbstractThe percentage encapsulation of its common insect parasites by Hyphantria cunea Drury was measured in natural populations in New Brunswick and Nova Scotia over a period of 17 years, and the variables affecting encapsulation were studied in laboratory experiments. Percentage encapsulation varied with the species, stage, and activity of the parasite, and the stage and genetic strain of the host. Differences in encapsulation from area to area and particularly from year to year were closely related to short-term changes in the genetic constitution of the host population resulting from natural selection pressures. The application of these results to biological control and to population modeling is discussed briefly.

OBSERVED AND SIMULATED CHANGES IN GENETIC QUALITY IN NATURAL POPULATIONS OF HYPHANTRIA CUNEA

1971 ◽  
Vol 103 (6) ◽  
pp. 893-906 ◽  
Author(s):  
R. F. Morris
Keyword(s):  
Experimental Data ◽  
Natural Selection ◽  
New Brunswick ◽  
Selection Pressure ◽  
Natural Populations ◽  
Hyphantria Cunea ◽  
Genetic Changes ◽  
Genetic Quality ◽  
Natural Regulation ◽  
Annual Changes

AbstractAnnual changes in genetic quality were measured in natural populations of Hyphantria cunea Drury for 12 years in New Brunswick and Nova Scotia. Models for heritability and natural selection pressure, derived independently from experimental data, are used to simulate the changes in quality over the same period. In seven of eight areas, observed and simulated trends are significantly correlated. Regressions between observed and calculated values, examined with respect to both means and slopes, suggest how these preliminary models may be refined. The influence of genetic changes on the natural regulation of population density is discussed briefly, but analysis is deferred to a later paper in this series on H. cunea.

On the Margins: Eastern Canadian Theatre as Post-colonialist Discourse

1996 ◽  
Vol 21 (1) ◽  
pp. 41-51
Author(s):  
Mary Elizabeth Smith
Keyword(s):  
Nova Scotia ◽  
New Brunswick ◽  
The Political ◽  
Lower Canada ◽  
Canadian Theatre ◽  
Political Controversy ◽  
Considerable Controversy ◽  
Ambivalent Attitude ◽  
The Relationship ◽  
National Borders

Canada became a country in 1867 through the Confederation of the two small eastern (Maritime) colonies of Nova Scotia and New Brunswick with the larger, more inland colonies of Upper and Lower Canada (Ontario and Quebec). Yet the flag remained the British Union Jack and the constitution resided in London. Canada's own flag was raised only in 1965, and the constitution repatriated only in 1982, both events accompanied by considerable controversy within the nation. The political controversy then (and now) reflects a constantly ambivalent attitude of Canadians towards the relationship between identity and nationalism, an ambivalence that encompasses protean forms of nationalism, including essentialist nationalism and a more elastic concept which recognizes the legitimacy of emotional and cultural ties beyond the national borders.

Editorial: Mathematical modelling of infectious diseases

Parasitology ◽  
2016 ◽  
Vol 143 (7) ◽  
pp. 801-804 ◽  
Author(s):  
ANDY FENTON
Keyword(s):  
Mathematical Modelling ◽  
Disease Ecology ◽  
Parasite Species ◽  
Control Strategies ◽  
Host Density ◽  
Community Size ◽  
Natural Systems ◽  
History Of ◽  
Models Of Disease ◽  
The Relationship

The field of disease ecology – the study of the spread and impact of parasites and pathogens within their host populations and communities – has a long history of using mathematical models. Dating back over 100 years, researchers have used mathematics to describe the spread of disease-causing agents, understand the relationship between host density and transmission and plan control strategies. The use of mathematical modelling in disease ecology exploded in the late 1970s and early 1980s through the work of Anderson and May (Anderson and May, 1978, 1981, 1992; May and Anderson, 1978), who developed the fundamental frameworks for studying microparasite (e.g. viruses, bacteria and protozoa) and macroparasite (e.g. helminth) dynamics, emphasizing the importance of understanding features such as the parasite's basic reproduction number (R0) and critical community size that form the basis of disease ecology research to this day. Since the initial models of disease population dynamics, which primarily focused on human diseases, theoretical disease research has expanded hugely to encompass livestock and wildlife disease systems, and also to explore evolutionary questions such as the evolution of parasite virulence or drug resistance. More recently there have been efforts to broaden the field still further, to move beyond the standard ‘one-host-one-parasite’ paradigm of the original models, to incorporate many aspects of complexity of natural systems, including multiple potential host species and interactions among multiple parasite species.

Organochlorine Residues in Brook Trout and Yellow Perch From New Brunswick and Nova Scotia (Canada) Lakes

1987 ◽  
Vol 22 (3) ◽  
pp. 352-364
Author(s):  
R. Peterson ◽  
S. Ray
Keyword(s):  
Nova Scotia ◽  
New Brunswick ◽  
Brook Trout ◽  
Yellow Perch ◽  
Intensive Agriculture ◽  
Fish Tissues ◽  
North Central ◽  
Ddt Metabolites ◽  
Headwater Lakes

Abstract Brook trout and yellow perch collected while surveying New Brunswick and Nova Scotia headwater lakes were analyzed for DDT metabolites, chlordane, hexacyclohexane isomers, hexachlorobenzene, toxaphene and PCB’s. Concentrations of DDT metabolites were much higher from fish taken from lakes in north-central N.B. (200-700 ng/g wet wt) than from fish taken elsewhere (<10 ng/g). Seventy to 90% of the DDT metabolites was DDE. Chlordane (3-13 ng/g) was analyzed in seven trout, six of them from central N.B. areas with intensive agriculture. Isomers of hexachlorocyclohexane were in highest concentration from north-central N.B. (10-20 ng/g), eastern N.S. (5-15 ng/g) and southern N.B. (5-20 ng/g). In most cases, alpha-hexachlorocyclohexane (lindane) was the isomer in highest concentration. Concentrations of hexachlorobenzene in fish tissues was highly variable with no obvious geographic bias. PCB’s were detected in very few fish, and no toxaphene was detected.

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