Expression of autogeny in relation to larval population density of Sarcophaga bullata Parker (Diptera: Sarcophagidae)

1973 ◽  
Vol 51 (11) ◽  
pp. 1189-1193 ◽  
Author(s):  
J. A. Baxter ◽  
A. M. Mjeni ◽  
P. E. Morrison
Keyword(s):  
Population Density ◽  
The Other ◽  
Larval Rearing ◽  
Population Densities ◽  
Larval Population ◽  
Sarcophaga Bullata ◽  
Other Hand ◽  
Rearing Conditions

The expression of autogeny in S. bullata was influenced by the larval rearing conditions. Low larval population densities resulted in large flies that were autogenous. On the other hand, high larval population densities produced small flies that were anautogenous, In anautogenous females the size and stage to which the follicles developed varied with the size of the fly. When reared on a sucrose–water diet, the females from an intermediate larval population density possessed larvae, mature eggs, degenerate follicles, or undeveloped follicles.

scholarly journals The Effects of Population Density on the Incidence of Developmental Deformities in Chemosensory Organs of Tobacco Hornworm Larvae (Lepidoptera: Sphingidae)

2020 ◽  
Vol 20 (4) ◽  
Author(s):  
Frank Hanson ◽  
Elizabeth Stanwyck ◽  
Alexander Bohorquez
Keyword(s):  
Life History ◽  
Population Density ◽  
Manduca Sexta ◽  
Life History Traits ◽  
Larval Density ◽  
Population Densities ◽  
Larval Population ◽  
Rate Of Development ◽  
Rearing Conditions ◽  
Chemosensory Organs

Abstract Cultures of Manduca sexta Johanssen in our laboratory were found to have larvae with missing or deformed mouthparts or antennae. Hypothesizing that these developmental deformities were caused by crowded rearing conditions, we reared larvae in four different population densities and recorded the incidence (% of larvae affected) and types of chemoreceptor deformities. Results showed that the incidence of these deformities was directly proportional to larval population density. Deformities of the maxilla and palp were the most frequent, followed by those of the antenna, epipharynx and maxillary styloconica. Life history traits of larval mass, food consumption, and rate of development were inversely related to larval density for both normal and deformed larvae. We discuss possible causes and mechanisms of these deformities and of changes to life history traits.

Effects of population density on female and male burrow characteristics in the fiddler crab, Uca bengali Crane, 1975

Crustaceana ◽  
2015 ◽  
Vol 88 (12-14) ◽  
pp. 1283-1299 ◽  
Author(s):  
Fahmida Wazed Tina ◽  
Mullica Jaroensutasinee ◽  
Krisanadej Jaroensutasinee
Keyword(s):  
Body Size ◽  
Population Density ◽  
Fiddler Crab ◽  
High Density ◽  
The Other ◽  
Low Density ◽  
Density Effects ◽  
Egg Incubation ◽  
Other Hand ◽  
Males And Females

We examined the effects of population density on body size and burrow characteristics ofUca bengaliCrane, 1975. We predicted that (1) males in high-density areas (HD) should be larger in size and build higher quality burrows than males in low-density areas (LD), and (2) HD females should be larger in size, but build lower quality burrows than LD females, as HD females can find higher numbers of good quality male burrows around them for breeding and egg incubation. Our results showed that males and females in HD were larger in size than those in LD. Since HD males were larger in size, they built higher quality burrows than males in LD. On the other hand, even though LD females were smaller in size than HD ones, they built higher quality burrows than HD females. Our results thus indicate that density effects both body size and burrow characteristics.

The Life System of Cardiaspina Albitextura (Psyllidae), 1950-74.

1975 ◽  
Vol 23 (4) ◽  
pp. 523 ◽  
Author(s):  
LR Clark ◽  
MJ Dallwitz
Keyword(s):  
Population Density ◽  
Natural Enemies ◽  
Average Rate ◽  
The Other ◽  
Population Densities ◽  
Insect Abundance ◽  
Complete Development ◽  
Rate Of Increase ◽  
Adverse Weather ◽  
Survival And Reproduction

In 1958-63 and 1964-71 the life systems of four kinds of test-forming psyllid that coexist on Eucalyptus blakelyi were investigated intensively in a comparative study of insect abundance. This paper deals mainly with C. albitextura, which was kept under observation from 1950 to 1974. (The others were two species of Glycaspis, Spondyliaspis sp, and Creiis costatus.) The results indicate that the differences in maximal abundance reached by the four kinds of psyllid are mainly the outcome of differences in their ability tg utilize the leaves of the host plant as a source of food, C. albitextura being much more effective than the other species. For the latter, it appears that the principal environmental determinant of abundance was the number of feeding places where nymphs could survive long enough to complete development. That number varied according to foliage and weather. C. albitextura also differed from the other species by having its population densities held for long periods far below the levels at which the food supply would be limiting, by restrictions imposed upon reproduction by adverse weather and foliage conditions (the latter being due partly to poor synchronization between the emergence of adults in spring and the occurrence of foliage attractive for oviposition), and by high mortalities due to natural enemies. The life system of C. albitextura lacks an element that can stabilize abundance at low population densities, but adverse environmental influences usually limit the rate of increase greatly when abundance is low. The magnitude of the average rate of increase to high levels of population density, and the length of time for which high average densities are maintained, depend upon the frequency with which favourable conditions of weather, foliage and predation combine to promote both survival and reproduction.

Big Houses in Kano Emirate

Africa ◽  
1974 ◽  
Vol 44 (2) ◽  
pp. 117-135 ◽  
Author(s):  
Polly Hill
Keyword(s):  
Population Density ◽  
Special Reference ◽  
The Other ◽  
Economic Conditions ◽  
Economic Organization ◽  
Other Hand ◽  
Opening Paragraph ◽  
The Village ◽  
Compare And Contrast

Opening ParagraphIn 1971–2 I undertook research in part of the very densely populated farming zone around Kano city (often called the Kano close-settled zone) in order to compare it with a Hausa village, Batagarawa, some 100 miles further north in Katsina Emirate, where I had lived and worked in 1967. At Batagarawa farmland is not scarce and members of the community are free to establish farms on uncultivated (bush) land, some of which is no further than a mile or so from the village. For some 30 to 40 miles or more around Kano city, on the other hand, there is little or no uncultivated bush and farmers with insufficient land are obliged to buy or to ‘borrow’ (aro) farmland from others. My purpose was to compare and contrast the socio-economic organization and economic conditions of farmers in the two localities, with special reference, in so far as this variable could be isolated, to population density.

scholarly journals Natural regeneration at different microclimatic sites in Zatec region

2019 ◽  
Vol 48 (No. 10) ◽  
pp. 441-450
Author(s):  
I. Kupka
Keyword(s):  
Natural Regeneration ◽  
The Other ◽  
Population Densities ◽  
Clear Cut ◽  
Site Type ◽  
Other Hand ◽  
Seedling Biomass

Natural regeneration is an important part of close-to-nature forestry. However, natural regeneration also has either natural or technological limits. Among the most important natural limits are a low sum of precipitation and site type. The study concentrates on Žatec region where the long term average sum of precipitation is only 440–450 mm per year. Dry periods during the vegetation time are quite frequent. The study was conducted on clear cut area, stand edge, shelterwood area and stand interior. The results showed the highest population densities in a shelterwood system, the lowest in the stand interior. On the other hand, the dry seedling biomass is lower for seedlings from shelterwood area than from clear cut area.

Dynamics of growth modified by larval population density in the flesh fly, Sarcophaga bullata

1983 ◽  
Vol 61 (3) ◽  
pp. 512-517 ◽  
Author(s):  
James A. Baxter ◽  
Paul E. Morrison
Keyword(s):  
Growth Rate ◽  
Population Density ◽  
Growth Curves ◽  
Feeding Period ◽  
Larval Population ◽  
Beef Liver ◽  
Flesh Fly ◽  
Sarcophaga Bullata ◽  
Growth Functions ◽  
Logistic Functions

Growth functions were fitted to the growth curves of larvae of the flesh fly, Sarcophaga bullata Parker (Diptera: Sarcophagidae), reared in conditions that were either uncrowded (25 larvae per 25 g beef liver) or crowded (400 larvae per 25 g beef liver). The growth curves took the form of logistic functions that were symmetrical for uncrowded larvae, but asymmetrical for crowded ones. Initially, crowded larvae grow faster than uncrowded larvae, a response in contrast with those of all other species of higher Diptera studied to date. Apparently, crowded larvae derived benefit from close intraspecific associations, for their rapid growth took place while they fed within dense aggregations. The growth rate of crowded larvae peaked early and growth ceased abruptly when the supply of food was exhausted. Their feeding period was reduced by 60% and their weight by 74% in comparison with those of uncrowded larvae.

Food Limitation of Larval Dragonflies: A Field Test of Spacing Behaviour

1986 ◽  
Vol 43 (9) ◽  
pp. 1720-1725 ◽  
Author(s):  
Robert L. Baker
Keyword(s):  
Population Density ◽  
Field Test ◽  
Food Limitation ◽  
Population Densities ◽  
Larval Population ◽  
Southern Ontario ◽  
Growth And Survival ◽  
Gut Fullness ◽  
Dependent Growth ◽  
Ischnura Verticalis

Density-dependent growth and survival of larval odonates may result from some larvae excluding others from profitable hunting sites. This hypothesis predicts that both degree and variation in food limitation should increase with population density; it also suggests that large larvae should show less food limitation than small larvae. I tested these predictions by analyzing food limitation, determined by mass of fecal pellets, and population density of larval Ischnura verticalis and Enallagma ebrium from a pond in southern Ontario. When data from all sampling days were combined, population densities of both species were negatively correlated with gut fullness but there was no correspondence between population density and gut fullness measured at different sites on any given day. Also, there was no correlation between population density and variation in food limitation and there was no evidence that small larvae suffered a greater degree of food limitation than larger larvae. A lack of discrete and persistent prey patches and/or low larval population densities may account for the lack of evidence that larvae are excluded from patches of prey.

Differences in energy partition between crowded and uncrowded individual barnacles (Balanus glandula Darwin)

1977 ◽  
Vol 55 (4) ◽  
pp. 643-647 ◽  
Author(s):  
R. S. S. Wu ◽  
C. D. Levings ◽  
D. J. Randall
Keyword(s):  
Population Density ◽  
Reproductive Output ◽  
Population Regulation ◽  
The Other ◽  
Body Tissue ◽  
Balanus Glandula ◽  
Energy Partition ◽  
Adequate Amount ◽  
Other Hand ◽  
Feeding Area

The egg: body tissue ratio and shell: tissue ratio, when expressed in terms of energy, may serve as a good indication of the energy partition of individual barnacles. When comparing these two ratios between crowded and uncrowded individual barnacles, a decrease in degree of crowding was associated with: (1) an increase in the egg: body tissue ratio and (2) a decrease in shell: tissue ratio of the individuals. This appears to suggest a difference in energy partition in the barnacles with different degrees of crowding. Uncrowded individuals, which acquire an adequate amount of energy, could channel more energy into egg output and hence produce more progeny. On the other hand, crowded individuals acquire a limited amount of energy and apparently use a larger proportion of their assimilated energy in (1) building body tissue rather than egg and (2) building a taller shell so as to increase the general feeding area of the population. The reduction in reproductive output when population density is high (and vice versa) could be an important mechanism in population regulation of the species.

Estimating Population Densities of Root Lesion Nematodes, Pratylenchus spp., from Soil Samples Using Dual Active and Passive Assays

2012 ◽  
Vol 13 (1) ◽  
pp. 4 ◽  
Author(s):  
Ann E. MacGuidwin ◽  
Breann E. Bender
Keyword(s):  
Population Density ◽  
Soil Samples ◽  
Scaling Factor ◽  
The Other ◽  
Testing Methods ◽  
Population Densities ◽  
Lesion Nematodes ◽  
The Mean ◽  
Time Of Year ◽  
Root Lesion Nematodes

Root lesion nematodes are versatile parasites that move freely between root and soil habitats. Most laboratories conduct separate assays for soil or root tissue, using time-of-year as the selecting factor. We used a dual assay that simultaneously extracts nematodes from soil and root fragments in soil samples to identify the value of soil versus root tests using 920 research samples collected 1 April to 15 May, and 853 clinic samples collected year round. Nematodes were recovered from both soil and root fragments regardless of the time of year or origin of the sample. When the data were summarized by cohort, the mean percentage of nematodes recovered from root fragments was 65% for the research samples, 59% for clinic samples submitted 1 March to 15 June, 56% for clinic samples submitted 16 June to 31 July, and 49% for clinic samples submitted after 1 August. Both the incidence and population density of root lesion nematodes was underestimated if only the soil or only the root fraction was considered, indicating the need for testing methods that consider both habitats. The variability among samples for the distribution of nematodes between root and soil habitats was high, negating the option of running one assay and using a constant scaling factor to account for the other. Accepted for publication 30 October 2012. Published 20 November 2012.

Poids des nouveau-nés et reproduction de Vipera aspis (Reptilia: Viperidae), dans des conditions naturelles et artificielles

1981 ◽  
Vol 2 (1) ◽  
pp. 51-62 ◽  
Author(s):  
Guy Naulleau ◽  
Hubert Saint Girons
Keyword(s):  
Litter Size ◽  
Small Extent ◽  
The Other ◽  
Natural Conditions ◽  
Pregnant Females ◽  
Other Hand ◽  
Rearing Conditions ◽  
Vipera Aspis

AbstractWe studied 36 pregnant females and 70 litters of Vipera aspis. Vipers were either recently caught, living in outdoor terrariums (semi-natural conditions), or living in the laboratory (artificial conditions). Following results were obtained: 1. There were significant correlations between the number of eggs and the weight of the litter and between the length and weight of the females. 2. The weight of hatchings does not depend, or only to a small extent, on the length or on the weight of the female, but is negatively correlated with the number of eggs. Hatching weight is generally higher in semi-natural and artificial conditions than in natural conditions. On the other hand, litter size was independent of the rearing conditions. 3. The weight of a litter at birth represents an average of 44 and 47% of the female's weight, respectively in natural and semi-natural conditions, where vipers breed generally once every two years; and only 34% in artificial conditions, where females breed once or twice a year. In all cases, this proportion is independent of the female's weight.

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