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Насекомые в целом

Насекомые.


Freshwater Biology

Volume 46 Issue 11 Page 1479 - November 2001

Полетная активность насекомых вдоль горных ручьев: адаптивное значение.

Flight activity of insects along a mountain stream: is directional flight adaptive?


Michael J. Winterbourn & Anna L. M. Crowe

1. Flight activity of Trichoptera, Plecoptera and Ephemeroptera was studied by

sticky trapping for 12months at five sites along a New Zealand mountain stream.

Over 19000 insects were captured by the traps, which were located in forest and

grassland reaches, including a reach with intermittent flow.

2. Most species occurred predominantly in forest or grassland, although some were

trapped throughout the stream. Longitudinal distributions of adults and their larvae

were strongly correlated.

3. Flight periods of 24 caddisflies, three mayflies and four stoneflies ranged from 2

to 12months. Six species were trapped in all months and 17 (55) in more than 5

months.

4. The most abundant forest-dwelling caddisfly species were over-represented on



the downstream sides of sticky traps located in, and immediately below, forest

indicating a majority was flying upstream. Upstream flight compensates for

downstream drift of larvae and should maximize the likelihood that forest-dwelling

species will locate preferred habitat for egg, larval and/or adult development. Unlike

the caddisflies, the stonefly Spaniocerca zelandica was over-represented on the

upstream sides of traps, suggesting that some adults may float or fly downstream

following emergence.

5. In contrast to forest-dwelling species, only one common caddisfly (Oxyethira

albiceps) was over-represented on the downstream sides of traps at grassland sites.

Unlike the forest-dwelling species, most species taken at the downstream sites

probably came from a variety of sources, including a nearby stream.

Насекомые: соотношение массы и длины тела.

Freshwater Biology

Volume 41 Issue 4 Page 653 - June 1999



Dry mass-length relationships for benthic insects:

a review with new data from Catamaran Brook, New Brunswick, Canada

Thomas A. Johnston and Richard A. Cunjak*

1.We summarized previously published mass-length relationships for aquatic

insects, and determined the relationship between dry body mass and body length

for eight genera and seven families of benthic insects from Catamaran Brook, New

Brunswick, Canada.

2.A power function was the most commonly used model in the earlier studies

and best described the observed mass-length relationship for taxa from Catamaran

Brook.

3.Predicted mass at length was highly variable (coefficient of variation_="



border=0 src="/na102/home/ACS/journals/entities/2265.png" 25%) among models

developed in different studies for the same family group. This variability

presumably resulted from both variation in the methods used to construct the

models, and in the natural spatio-temporal and taxonomic variation in mass at

length, although the relative contributions of these two sources cannot be

determined from existing data.

4.Several recommendations are made for the development and application of

mass-length equations in future studies.



Насекомые: влияние на грунт водотоков.

Authors: Statzner-B Fuchs-U Higler-LWG

Эрозия песка при деятельности подвижных хищных речных личинок насекомых - приложение в экологии и гидрологии.

Sand Erosion by Mobile Predaceous Stream Insects - Implications for Ecology and Hydrology

WATER RESOURCES RESEARCH 1996, Vol 32, Iss 7, pp 2279-2287

Abstract:

Despite increasing knowledge of the ability of keystone animal species (''ecosystem engineers'') to change their physical environment, there is little and inconsistent evidence that benthic invertebrates affect the erosion of bottom material in streams. Therefore we designed field stream experiments and observations to investigate the effect of mobile predaceous stonefly (Dinocras cephalotes) larvae on sand erosion. When short of prey, the stoneflies erode sand from stream riffles thereby deepening the interstices between cobbles. On the basis of reasonable assumptions, we speculate that Dinocras has an erosion potential of about 200-400 kg sand m(-2) yr(-1) at natural population densities under favorable flow conditions. We consider the possible implications of the bioturbation potential of stream invertebrates for ecology (habitat quality and disturbance) and hydrology (sand transport and stability of coarse stream bottoms), which call for joint research on this novel role invertebrates play in the functioning of stream ecosystems.


Насекомые: взаимосвязи водных детритофагов.

Ecological Entomology Volume 27 Issue 5 Page 541 - October 2002

Testing for context-dependence in a processing chain interaction

among detritus-feeding aquatic insects

Matthew P. Daugherty and Steven A. Juliano

Abstract1. Scirtid beetles may benefit mosquitoes Ochlerotatus triseriatus (Say) by consuming whole leaves and leaving behind fine particles required by mosquito larvae. Such interactions based on the sequential use of a resource that occurs in multiple forms are known as processing chains.

2. Models of processing chains predict that interactions can vary from commensal (0, +) to amensal (0, -), depending on how quickly resource is processed in the absence of consumers.

3. The scirtid-O.triseriatus system was used to test the prediction derived from processing chain models that, as consumer-independent processing increases, scirtids benefit mosquitoes less. Consumer-independent processing rate was manipulated by using different leaf species that vary in decay rate, or by physically crushing a single leaf type to different degrees.

4. Although scirtids increased the production of fine particles, the effects of scirtids on mosquitoes were weak and were not dependent on consumer-independent processing rate.

5. In the leaf manipulation experiment, a correlation between scirtid feeding and consumer-independent processing was detected. Numerical simulations suggest that such a correlation may eliminate shifts from commensal to amensal at equilibrium; because mosquito populations are typically not at equilibrium, however, this correlation may not be important.

6. There was evidence that mosquitoes affected scirtids negatively, which is inconsistent with the structure of processing chain interactions in models. Processing chain models need to incorporate more detail on the biology of scirtids and O.triseriatus, especially alternative mechanisms of interaction, if they are to describe scirtid-O.triseriatus dynamics accurately.



Насекомые: межвидовая конкуренция.

Ecological Entomology Volume 27 Issue 4 Page 396 - August 2002

A minimalist approach to the effects of density-dependent

competition on insect life-history traits

Philip Agnew, Mallorie Hide, Christine Sidobre and Yannis Michalakis

Abstract1. Due to its effects on the phenotypic and genotypic expression of life-history traits, density-dependent competition is an important factor regulating the growth of populations. Specifically for insects, density-dependent competition among juveniles is often associated with increased juvenile mortality, delayed maturity, and reduced adult size.

2. The aim of the work reported here was to test whether the established phenotypic effects of density-dependent competition on life-history traits could be reproduced in an experimental design requiring a minimal number of individuals. Larvae of the mosquito Aedes aegypti were reared at densities of one, two, or three individuals per standard Drosophila vial and in six different conditions of larval food availability. This design required relatively few individuals per independent replicate and included a control treatment where individuals reared at a density of one larva per vial experienced no density-dependent interactions with other larvae.

3. Increased larval densities or reduced food availability led to increased larval mortality, delayed pupation, and the emergence of smaller adults that starved to death in a shorter time (indicating emergence with fewer nutritional reserves).

4. Female mosquitoes were relatively larger than males (as measured by wing length) but males tended to survive for longer. These differences increased as larval food availability increased, indicating the relative importance of these two traits for the fitness of each sex. The role of nutritional reserves for the reproductive success of males was highlighted in particular.

5. This minimalist approach may provide a useful model for investigating the effects of density-dependent competition on insect life-history traits.

Насекомые: трофические взаимосвязи.

Ecological Entomology

Volume 25 Issue 2 Page 140 - May 2000



Health food versus fast food: the effects of prey quality and mobility

on prey selection by a generalist predator and indirect interactions

among prey species

Micky D. Eubanks and Robert F. Denno

1. In order to understand the relative importance of prey quality and mobility in indirect interactions among alternative prey that are mediated by a shared natural enemy, the nutritional quality of two common prey for a generalist insect predator along with the predator's relative preference for these prey was determined.

2. Eggs of the corn earworm Helicoverpa zea (Lepidoptera: Noctuidae) were nutritionally superior to pea aphids Acyrthosiphum pisum (Homoptera: Aphididae) as prey for big-eyed bugs Geocoris punctipes (Heteroptera: Geocoridae). Big-eyed bugs survived four times as long when fed corn earworm eggs than when fed pea aphids. Furthermore, only big-eyed bugs fed corn earworm eggs completed development and reached adulthood.

3. In two separate choice experiments, however, big-eyed bugs consistently attacked the nutritionally inferior prey, pea aphids, more frequently than the nutritionally superior prey, corn earworm eggs.

4. Prey mobility, not prey nutritional quality, seems to be the most important criterion used by big-eyed bugs to select prey. Big-eyed bugs attacked mobile aphids preferentially when given a choice between mobile and immobilised aphids.

5. Prey behaviour also mediated indirect interactions between these two prey species. The presence of mobile pea aphids as alternative prey benefited corn earworms indirectly by reducing the consumption of corn earworm eggs by big-eyed bugs. The presence of immobilised pea aphids, however, did not benefit corn earworms indirectly because the consumption of corn earworm eggs by big-eyed bugs was not reduced when they were present.

6. These results suggest that the prey preferences of generalist insect predators mediate indirect interactions among prey species and ultimately affect the population dynamics of the predator and prey species. Understanding the prey preferences of generalist insect predators is essential to predict accurately the efficacy of these insects as biological control agents.



Насекомые водотоков: конкуренция.

Authors: Hemphill-N

Disturbance and Variation in Competition Between 2 Stream Insects

ECOLOGY 1991, Vol 72, Iss 3, pp 864-872

UNIV-LOUISVILLE, DEPT BIOL, LOUISVILLE, KY 40292, USA

This study examined temporal and spatial variability in

competition as well as the relative importance of competition

and natural disturbance to Hydropsyche oslari and Simulium

vigatum in a southern California stream. These two filter-

feeding insects dominated the community studied, accounting for

99% of all individuals. I maintained four field treatments

every 2 wk for a year: (1) removal of Simulium; (2) removal of

Hydropsyche; (3) removal of both taxa and subsequent scrubbing

of the rock surfaces; and (4) unmanipulated controls.

Competition from Hydropsyche oslari restricted the spatial

distribution of Simulium virgatum in all seasons except late

winter in upstream but not in downstream sections of the study

site. Downstream abundance of Simulium was probably limited by

food availability, not competition from Hydropsyche. During the

winter, when floods occurred and densities were low, competition

between these insects had no significant impact on spatial

distributions. Although competition was seasonally variable, it

occurred frequently and was not rare.

Although disturbance mediated competition, competition was

more important in determining the abundance of Simulium in 1983-

1984, a drought year. Disturbance caused a 13% increase, while

competition caused a 34% decline in the simuliid population over

the year. It was not possible, however, to rank the importance

of competition and disturbance when considering both species

together. The relative importances were taxon specific. The

abilities of Simulium and Hydropsyche to recover quickly after

disturbance were inversely related to their ability to withstand

competition. In addition, the interaction between the two

factors was extremely important in determining the relative

abundance of both taxa through the year.

Competition and disturbance both played an important role

in regulating this community, at times accounting for up to 60%

reductions in the numbers of individuals present in the stream.

The relative importance of competition and disturbance in

Refugio Creek should vary from year to year depending on the

timing and intensity of winter storms.

Водные насекомые: регуляция численности.

Authors: Kohler-SL Hoiland-WK

Population Regulation in an Aquatic Insect - The Role of Disease

ECOLOGY 2001, Vol 82, Iss 8, pp 2294-2305

We studied the dynamics of a univoltine stream-dwelling

caddistly, Brachycentrus americanus, and its microsporidian

disease for 15 yr. The pathogen is highly virulent. with

infections generally resulting in death during the larval stage.

In most years, we sampled Brachycentrus immatures every 1-2 mo

to estimate population density and disease prevalence.

Brachycentrus population dynamics exhibited strong evidence for

direct and delayed (1 generation lag) density dependence and

appeared to cycle with a period of similar to4 yr. Pathogen

prevalence in Brachycentrus was > 10% in all generations and

frequently exceeded 50%. Disease prevalence also exhibited

cyclic behavior. with peaks in prevalence following

Brachycentrus generations with relatively high population

density. There was no evidence for direct density-dependent

parasitism. but there was strong evidence for density-dependent

infection delayed by one generation. A path analysis model

suggested that the disease mediated much of the strong density

dependence observed in Brachycentrus. Collectively, these

observations suggest that the pathogen is largely responsible

for driving observed Brachycentrus dynamics.




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