Oviposition Site Preference Research Articles

Oviposition Site Preference and Egg Hatchability ofAnopheles gambiae: Effects of Land Cover Types

We studied the oviposition site preference and egg hatchability of Anopheles gambiae Giles with water collected from farmlands, forests, and natural wetlands. Water types significantly affected oviposition preference. Mosquitoes deposited significantly more eggs in rainwater in both the dry and wet seasons than waters from forests and wetlands, suggesting that An. gambiae prefers water with few impurities for oviposition. In the dry season, An. gambiae females also deposited significantly more eggs in waters from farmlands than those from forests and natural wetlands, but these differences were not statistically significant during the wet season. In both indoor and natural conditions, egg mortality in natural wetland habitats was significantly higher than in farmland habitats. The average water temperature in natural wetland habitats was significantly lower than farmland habitats in the natural conditions, but it remained the same under indoor experimental conditions, suggesting that factors other than water temperature play an important role in egg hatchability. Together with the findings from previous studies on the effects of land cover on larval survivorship, our results support the hypothesis that variations in habitat conditions induced by different land cover types contribute to the heterogeneous spatial distribution of An. gambiae larvae in the western Kenya highland.

Can Specialized Pathogens Colonize Distantly Related Hosts? Schistosome Evolution as a Case Study

Can Specialized Pathogens Colonize Distantly Related Hosts? Schistosome Evolution as a Case Study

Oviposition site preference of the bamboo gall maker, Aiolomorphus rhopaloides (Hymenoptera: Eurytomidae), on bamboo in terms of plant-vigor hypothesis

Oviposition site preference of the bamboo gall maker, Aiolomorphus rhopaloides Walker, was investigated in a bamboo stand in terms of plant-vigor hypothesis. Galls in branches were distributed contagiously due to the difference in branch length. More galls were found on longer branches. Survival rates within galls, nitrogen content and gall size did not differ with branch-length class, suggesting that oviposition preference on longer branches is not attributed to better progeny fitness. The phenology of the buds where females oviposit and the greater number of buds on longer branches might contribute to female oviposition site preference.

Willow genotype, but not drought treatment, affects foliar phenolic concentrations and leaf‐beetle resistance

AbstractIn a greenhouse experiment we examined the effect of willow genotype and irrigation regime (moderate drought and well‐watered) on plant growth parameters, foliar nitrogen, and phenolic concentrations, as well as on the preference and performance of the blue leaf beetle, Phratora vulgatissima (L.) (Coleoptera: Chrysomelidae). The 10 vegetatively propagated willow genotypes in the experiments were F2 full‐sibling hybrids, originated from a cross between Salix viminalis (L.) (Salicaceae) (high in condensed tannins) and Salix dasyclados (L.) (Salicaceae) (rich in phenolic glycosides). Insect bioassays were conducted on detached leaves in Petri dishes as well as with free‐living insects on intact potted plants. The 10‐week long irrigation treatments caused statistically significant phenotypic differences in the potted willow saplings. Total biomass was somewhat higher in the well‐watered treatment. The root to total biomass ratio was higher in the drought‐treatment plants. There was significant genotypic variation in foliar nitrogen concentrations, and they were higher in the drought‐treatment plants. There was also a strong genotypic variation in each of the phenolic substances analyzed. Condensed tannins, which accounted for the greatest proportion of total phenolic mass, were higher in the well‐watered treatment. There was, however, no difference in levels of the other phenolics (salicylates, cinnamic acid, flavonoids, and chlorogenic acid) between irrigation treatments. The sum of these phenolics was higher in the well‐watered treatment. There was a strong variation in P. vulgatissima larval development on different willow genotypes, and larval performance was negatively correlated with levels of salicylates and cinnamic acid. There was, however, no effect of irrigation treatment on larval performance. Phratora vulgatissima preferred to feed on well‐watered plants, and we found a preference for oviposition there, but neither feeding nor oviposition site preference was affected by willow genotype. Adult feeding and oviposition preferences were not correlated with larval performance.

Oviposition Behavior in the Robber Fly <I>Mallaphora ruficauda</I> (Diptera: Asilidae)

Mallophora ruficauda Wiedemann (Diptera: Asilidae) is a pestiferous robber fly affecting beekeeping in the South American open grasslands. This insect preys upon other insects during its adult stage and parasitizes scarab beetle larva in the soil as larvae. As a first step toward population management, we studied basic reproductive behavioral traits. We investigated the size and fertility of egg clusters and whether females exhibit preferences for oviposition sites. We collected egg clusters close to bee farms in the Argentine grasslands and estimated egg eclosion rates and aggregation. We also measured the height at which clusters were found on both natural vegetation and artificial wire supports. We determined the number of eggs per egg cluster, eclosion rates, and egg developmental time. Egg clusters were usually highly aggregated in the field and were found on elevated places, including the tallest plant species. We discuss height selectivity in robber flies in relation to host availability and robber fly fecundity, as a means of increasing larval dispersal and hence encountering success with larval hosts.

Nest-site preference and maternal effects on offspring growth

Maternal preferences for oviposition sites are assumed to be adaptive, but offspring fitness is not always higher at preferred sites and, thus, further study of the selection pressures that influence oviposition behavior is warranted. Among birds, predation is regarded as the primary agent of selection on nest-site microhabitat preferences, but alternatives are rarely considered. We tested the hypothesis that avian nest-site preferences are an adaptive response to fitness costs imposed by variation in nest-site microclimate. We documented that Chestnut-collared Longspurs (Calcarius ornatus) strongly preferred to orient nests towards the southeast and showed that this preference influenced microclimate: nests facing southeast had the highest midday temperatures. Yet, preferences were not adaptive because nestlings in nests with the preferred orientation gained mass at a slower rate, had retarded skeletal growth, and reached a smaller final size. We experimentally tested this result by altering orientation of nests and confirmed, for the first time, that variation in nestling growth was causally linked to variation in nest microclimate arising from nest-orientation preferences. Adults responded to the high temperatures at preferred southeast-facing nests by spending more time shading young from the sun, apparently attempting to ameliorate heat costs. This response, however, resulted in parents spending less time feeding young, potentially explaining slower growth in these nests. Direct effects of higher temperatures may also play a role in slower growth. Although we lack an explanation for this apparently maladaptive preference, these results demonstrate that nest-site choices of birds can yield fitness costs imposed by variation in nest microclimate.

Environmental effects and the genetics of oviposition site preference for natural yeast substrates in Drosophila buzzatii

Habitat selection expressed as oviposition site preferences (OSP), is one component of the complex of behaviours of females seeking a place to oviposit. Drosophila buzzatii females lay their eggs in cactus necroses (rots), where the alternative oviposition sites are patches of adjacent or even partially mixed growing yeast species. The OSP exhibited by individual females is not absolute, but subject to environmental effects and the physiology of the fly, and may vary depending on the particular combination of yeast species present in a rot. Nevertheless, we have shown that OSP of D. buzzatii females is heritable, with evidence from variation among isofemale lines, direct estimation of heritability, generation means analysis and short term selection. Further, this genetic variation appears to be ubiquitous, polygenic and largely non-additive for all yeast species combinations. The consequences of such genotype-specific habitat selection for the maintenance of genetic variation are considered by an evaluation of our results in comparison with assumptions of models of habitat selection. As all assumed mechanisms of these models are apparently met, OSP for yeast species would seem to be a powerful force for the maintenance of genetic variation, and not only at loci affecting the choice of oviposition sites.

Ovarian Development and Ovipositional Preference of the Western Corn Rootworm (Coleoptera: Chrysomelidae) Variant in East Central Illinois

The rotation of maize, Zea mays L., and soybean, Glycine max (L.) Merr., has been the traditional cultural tactic to manage the western corn rootworm, Diabrotica virgifera virgifera LeConte, in the Corn Belt. The reduced effectiveness of this rotation as a pest management tool in east central Illinois, northern Indiana, and southern Michigan can be explained by the shift in the ovipositional behavior of the new variant of western corn rootworm. The objective of this study was to evaluate the influence of maize, soybean, oat, Avena sativa L., stubble, and alfalfa, Medicago sativa L., on the ovarian development and ovipositional preferences of the variant western corn rootworm. Field research was conducted near Urbana, IL, during 1998–2000. Gravid females were present throughout the season in all crops, and due to the prolonged period in which western corn rootworm females can lay eggs, none of the crops were immune from oviposition. Results indicated that the western corn rootworm variant oviposits in maize, soybean, oat stubble, and alfalfa. In 1998 and 1999, maize was the preferred oviposition site among crops; however, in 2000, maize, soybean, and oat stubble treatments had similar densities of western corn rootworm eggs. Lack of oviposition preference of the western corn rootworm variant demonstrated in this experiment represents a reasonable explanation of why the effectiveness of the rotation strategy to control western corn rootworm has diminished.

Ovarian development and ovipositional preference of the western corn rootworm (Coleoptera: Chrysomelidae) variant in east central Illinois.

The rotation of maize, Zea mays L., and soybean, Glycine max (L.) Merr., has been the traditional cultural tactic to manage the western corn rootworm, Diabrotica virgifera virgifera LeConte, in the Corn Belt. The reduced effectiveness of this rotation as a pest management tool in east central Illinois, northern Indiana, and southern Michigan can be explained by the shift in the ovipositional behavior of the new variant of western corn rootworm. The objective of this study was to evaluate the influence of maize, soybean, oat, Avena sativa L., stubble, and alfalfa, Medicago sativa L., on the ovarian development and ovipositional preferences of the variant western corn rootworm. Field research was conducted near Urbana, IL, during 1998-2000. Gravid females were present throughout the season in all crops, and due to the prolonged period in which western corn rootworm females can lay eggs, none of the crops were immune from oviposition. Results indicated that the western corn rootworm variant oviposits in maize, soybean, oat stubble, and alfalfa In 1998 and 1999, maize was the preferred oviposition site among crops; however, in 2000, maize, soybean, and oat stubble treatments had similar densities of western corn rootworm eggs. Lack of oviposition preference of the western corn rootworm variant demonstrated in this experiment represents a reasonable explanation of why the effectiveness of the rotation strategy to control western corn rootworm has diminished.

The life cycle of the cocoa stem borer Eulophonotus myrmeleon in Ghana

AbstractA female Eulophonotus myrmeleon at emergence contains fully developed eggs and may lay whether mated or not. There is no preferred oviposition site and eggs are deposited randomly on the tree or on plant debris. The larva tunnels into a stem, enlarging the gallery as it grows, and spends its entire immature life inside the stem. Survival to adulthood was 2–3%. Copyright © 2004 Whurr Publishers Ltd

Oviposition site preference of Pectinophora gossypiella (Lepidoptera: gelechiidae) on cotton and its effects on boll development

Pectinophora gossypiella (Saunders) eggs were distributed over all parts of cotton plants with usually one per site. During early season (July–August) females preferred to oviposit on CIM-70, CIM-109 and NIAB-78 which flowered earlier than the late maturing varieties, Alseemi-515 and CIM-135. On medium maturing varieties, 77% more eggs were laid in September and 14% in October. On late maturing varieties, 85% and 46% more eggs were laid during the corresponding period compared with CIM-70. Most oviposition on flower buds was during August (72.5%) and on bolls during September (70.6%) and October (85%), when few eggs were laid on vegetative parts. Females from diapause larvae lived on average 7.3 days with lower fecundity (75 eggs/female) compared with the non-diapause generation (9.0 days; 125 eggs/female). Females preferred half grown flower buds (7–10 days old) for oviposition, laying 82–94% of the total eggs compared with 7–11% on large flower buds. More bolls from rosette and healthy flowers during August were shed compared with September and October with significant differences between months. Shedding was minimum in CIM-70 and Alseemi-515 but the differences were non-significant. However, differences between these two varieties and NIAB-78, CIM-109 and CIM-135 were significant. Shedding of bolls was between 2nd and 12th day of boll formation, the maximum being from 4th to 6th day. More than 64% of bolls that developed from rosette flowers were shed, whereas, 8–10% were shrivelled on one side and the rest were normal. Bolls that developed from rosette flowers had fewer seeds and less lint than those which developed from healthy flowers.

Linking landscape patterns of resource distribution with models of aggregation in ovipositing stream insects

Summary Many species rely on resources that are discrete patches distributed across the landscape. Models of the coexistence of such taxa often require intraspecific aggregation of individuals on some patches, brought about by choices made during dispersal and patch location. Few studies have employed spatially explicit measures of dispersion to detect whether and how any aggregation of individuals is influenced by the dispersion of resource patches in natural landscapes. For two species of caddisfly (Hydrobiosidae) in two stream stretches, we mapped the spatial distribution of potential and exploited patches (emergent rocks as oviposition sites) and enumerated egg masses on each rock. Point pattern analysis, based on Ripley's K‐function, was used to describe the spatial pattern of potential and exploited oviposition sites, and to test hypotheses about how site selection behaviour of females influences dispersion. Emergent rocks were clumped and equally abundant in both stretches. As documented previously, egg masses of Ulmerochorema and Apsilochorema were aggregated within oviposition sites. Both species showed velocity‐specific preferences for oviposition sites: oviposition of Ulmerochorema occurred most often on rocks in fast flowing water (>0·30 m s−1); oviposition of Apsilochorema on rocks in slow water (<0·30 m s−1). Our perception of how caddisflies deposit eggs into the stream landscape varied with the neutral landscape model. The most informative neutral landscape compared the spatial pattern of oviposition sites with the underlying pattern of emergent rocks, while constraining the random selection of rocks to reflect species’ velocity preferences. Oviposition sites of Ulmerochorema were clumped, over and above the background pattern of emergent rocks. Oviposition sites of Apsilochorema were over‐dispersed. Hydrobiosid caddisflies appear to make decisions about egg‐laying at different scales. We propose a mechanistic explanation, based on what we know about the oviposition behaviour of these species, to explain how the observed patterns might arise. Our results emphasize the importance of quantifying resource patch use in natural (rather than artificial) landscapes.

Biology, ecology, and management of dogwood borer in eastern apple orchards

AbstractThe dogwood borer, Synanthedon scitula (Harris) (Lepidoptera: Sesiidae), has the broadest host range of the clearwing moths and is considered to be an economically important pest of many ornamental, fruit, and nut trees. Since the 1980s, dogwood borer has been recognized as an increasingly important, indirect pest of apple, Malus domestica Borkh. (Rosaceae), in eastern North America, owing mainly to increased plantings of apple on size-controlling rootstocks that promote the formation of adventitious root initials (burr knots) on the rootstock and scion. Burr knots appear to be preferred oviposition sites for dogwood borer females, although infestations can also be initiated in wounds, pruning cuts, and crotches on the branches and trunk. Larval feeding in burr knots does not adversely affect the growth and vigor of apple trees, but their mining outward from burr knots into vascular tissue can ultimately cause tree decline and death. Chlorpyrifos is the most effective insecticide for controlling dogwood borer. A supplemental label in the United States permits post-bloom, trunk drench applications of chlorpyrifos specifically for control of borers in apple, with several restrictions that preclude control of infestations higher in the tree. The ongoing review of pesticide tolerances dictated by the 1996 Food Quality Protection Act of the United States of America makes the long-term availability of this chemical uncertain. Cultural practices, such as deeper planting or berming, can reduce the likelihood of infestation of new apple plantings by dogwood borer, although they do not preclude infestations from developing above the graft union. This review and discussion is based on our contention that research toward the development of alternative, behaviorally based management strategies for dogwood borer in apple and other economically important host plants is warranted. Our review and synthesis of the dogwood borer literature revealed important gaps in knowledge about basic aspects of its biology that pertain directly to the development of alternative control tactics based on behavioral manipulation. There is considerable confusion surrounding the sex pheromone of dogwood borer and conflicting results on the response of males to isomers and blends of isomers of its purported pheromone. Studies using sex attractants to monitor its phenology in apple and non-apple habitats have yielded discrepant results and conclusions. Differences in the effectiveness of commercially available pheromone lures for trapping dogwood borer have been reported and the ability of pheromone traps to accurately reflect emergence or population density remains in question. Regardless of pronounced differences in the duration and modality of the seasonal flight of dogwood borer among different geographical regions within its range, the conclusion of univoltinism across most of its range has been perpetuated, based on extremely limited developmental data collected exclusively from individuals that developed on dogwood.

Morphological characteristics of sensilla on the female ovipositor of Lype phaeopa (Psychomyiidae; Trichoptera)

An important aspect of the association of Lype phaeopa (Stephens) with submerged wood is the oviposition behavior of adult females, which preferably oviposit their eggs on moist emergent or submerged parts of woody debris with a structured surface. The eggs are commonly deposited in cracks and crevices using the elongated ovipositor. Ovipositor morphology and various sensilla on the tip and along the ovipositor were studied by scanning electron microscopy and their possible function discussed. Structure of these sensilla and pre-oviposition behavior of the females point to a preference for certain oviposition sites on woody debris. This may be a key factor for the distribution and development of the larvae.

Morphological characteristics of sensilla on the female ovipositor of Lype phaeopa (Psychomyiidae; Trichoptera)

An important aspect of the association of Lype phaeopa (Stephens) with submerged wood is the oviposition behavior of adult females, which preferably oviposit their eggs on moist emergent or submerged parts of woody debris with a structured surface. The eggs are commonly deposited in cracks and crevices using the elongated ovipositor. Ovipositor morphology and various sensilla on the tip and along the ovipositor were studied by scanning electron microscopy and their possible function discussed. Structure of these sensilla and pre-oviposition behavior of the females point to a preference for certain oviposition sites on woody debris. This may be a key factor for the distribution and development of the larvae.

Parallel changes in enzyme activity and oviposition behavior in adults of Drosophila melanogaster submitted to alcohols, acetaldehyde or acetone

Summary Two geographic populations of D. melanogaster, French and African, which differ in their frequencies at the Adh locus and their ethanol tolerance, were tested for their oviposition site preference, mortality and activities of two enzymes involved in alcohol metabolism. To investigate the oviposition choice towards ethanol, 2-propanol, acetaldehyde et acetone, females of the two populations of D. melanogaster were exposed to a choice situation opposing a medium free-alcohol to a medium supplemented with one of the tested compounds. We noticed that the avoidance of media containing one the two studied alcohols, acetaldehyde or acetone, increased during the experiment. The most repellent medium for ovipositing females was that supplemented with 2-propanol or acetone. Besides, the study of female mortality on attractant or repellent media revealed that the most repulsive media were also the most lethal. Moreover, the treatment with ethanol, 2-propanol, acetaldehyde or acetone led to a reduction in alcohol dehydrogenase (ADH) and aldehyde dehydrogenase (ALDH) activities. A strong inhibition of ADH occurs (78.57%) in females a few days after the treatement with the tested products. Compared to ADH activity, ALDH activity was less reduced (51.78%). We suggest that fly mortality and the fly's aversion to alcoholic media might be linked to the decline of ADH and ALDH activities. The toxic effects of the used compounds appear more clearly in African flies than in French ones.

Oviposition site and food preference of the green June beetle (Coleoptera: Scarabaeidae).

Relative preferences of green June beetle, Cotinis nitida (L.), adults and grubs for different organic fertilizers were determined in field and laboratory choice experiments. Six organic fertilizer treatments (low rate of broiler litter, high rate of broiler litter, cow manure, hay, Milorganite, or no fertilizer [the control]) were applied to sandy-loam soil and exposed to adults in 2.7 by 3.7 by 2.4-m screen cages. More eggs and larvae were found in pots treated with broiler litter (43%), cow manure (23%), and hay (30%) than in pots treated with Milorganite (4%) or no fertilizer (0%). Orientation preferences of third-instar grubs were tested in Y-tube and satellite olfactometers. Of the five treatments (broiler litter, cow manure, hay, Milorganite, and a blank control), preference was greatest for broiler litter and cow manure, but all organic fertilizer treatments were generally preferred over the blank control. These experiments suggest that use of organic fertilizers may result in higher densities of green June beetle grubs both by attracting the ovipositing females, and by acting as a food attractant for the mobile larvae.

Pseudagrion lalakensespec. nov. from Borneo with notes on its ecology (Odonata: Coenagrionidae)

Abstract Pseudagrion lalakense, a new species of coenagrionid from Borneo, is described and figured. The species is phylogenetically close to the very widespread and eurytopic P. microcephalum and the two fly together. P. lalakense may be distinguished from microcephalum and several other similar blue species by the pattern on the thorax and abdomen in both sexes and by the form of the male terminal appendages. P. lalakense is highly stenotopic, being known only from highly acidic black-water marsh in two localities in Brunei where it is associated with the sedge Hydrolitha. Activity patterns of P. lalakense appear similar to those of P. microcephalum but the two species differ in their preferred perches and oviposition sites. A list of seven species of other odonates flying in the same habitat is provided.

Larval performance in relation to oviposition site preference in olive kernel moth (Prays oleae Bern., Yponomeutidae, Praydina)

Abstract1 The tri‐voltine moth Prays oleae Bern. spends its larval stages on the native olive tree (Olea europaea L. var. sylvestris Brot. and five cultivars, Oleaceae) mining the leaves, the flowers and the fruits in each generation; it seldom switches to other native or introduced confamilial plant species.2 In this study the pattern of oviposition of the olive moth was examined in olive fields and natural vegetation, in relation to in situ recruitment as an outcome of processes such as density dependence or risk spreading.3 Larval body size (width of epicranial sclerites) was also examined and compared between host substrates, years and morphological, physiological, ecological and nutritional attributes of the host.4 The factors influencing the oviposition pattern of the olive moth such as the carbon/nitrogen ratio, number of flowers, branch length and previous leaf damage were ranked differently in different cultivars.5 ‘Hot spots’, i.e. olive trees or parts of trees receiving a high egg load, were found to be the result of in situ recruitment.6 Physiological mortality among first instar larvae was significantly negatively correlated with the number of oviposited upon leaves; suggesting that the adult selects for oviposition the best available substrate.7 As adult moths selected leaves with minimal probability of abscission for oviposition, leaf abscission was not a major mortality factor, although first instar larvae reduced leaf longevity.8 Host quality did not affect all larval stages in the same way.9 The more nutritionally poor the substrate, the longer the duration of the larval stage feeding on it. The phenological timing of the insect life stages very closely tracks the phenological phases of its host plant, primarily focusing on the most nutritious host stage in terms of larval performance.

Hydrologic and behavioral constraints on oviposition of stream insects: implications for adult dispersal

The supply of recruits plays an important role in plant and animal population dynamics, and may be governed by environmental and behavioral constraints on animals. Mated females of the mayfly genus Baetis alight on rocks protruding from streams, crawl under water and deposit a single egg mass under a rock. We surveyed oviposition and emergence of a bivoltine population of B. bicaudatus in multiple stream reaches in one high-altitude watershed in western Colorado over 3years to establish qualitative patterns at a regional scale (entire watershed), and quantitative patterns over six generations at a local scale (one stream reach). We also measured characteristics of preferred oviposition substrates, performed experiments to test hypotheses about cues used by females to select oviposition sites, and measured mortality of egg masses in the field. Our goals were to determine whether: (1) hydrologic variation necessitated dispersal of females to find suitable oviposition sites; (2) the local supply of females could provide the supply of local recruits; and (3) local recruitment determined the local production of adults. The onset of oviposition corresponded with the decline of spring run-off, which differed dramatically among years and among sites within years. However, eggs appeared before any adults had emerged in 8 of 22 site-years, and adults emerged 2-3weeks before any eggs were oviposited in 3 site-years. Furthermore, the size distribution of egg masses differed from that predicted by the size distribution of females that emerged from seven of nine stream reaches. Protruding rocks and eggs appeared earlier each summer in smaller tributaries than in larger mainstream reaches, suggesting that hydrologic and behavioral constraints on oviposition may force females to disperse away from their natal reach to oviposit, and possibly explain the predominantly upstream flight of Baetis females reported in other studies. Local oviposition rates in one third-order stream-reach increased rapidly as soon as substrates protruded from the water surface, and females preferred large rocks that became available early in the flight season. However, females oviposited on <10% of all available rocks, and <65% of preferred rocks as determined by an empirical model. These data indicated that the timing of appearance of suitable oviposition sites determined the phenology of local recruitment, but that preferred oviposition sites were not saturated. Thus, the magnitude of local recruitment was not limited by the absolute abundance of preferred oviposition sites. Only 22% of egg masses observed in the field suffered mortality during their embryonic development, and per capita Baetis egg mass mortality was significantly lower on rocks with higher densities of egg masses. Thus, we suspect that specialized oviposition behavior may reduce the probability of egg mortality, potentially compensating for the costs of dispersal necessary to locate suitable oviposition sites. Finally, the number of adults that emerged at one stream reach was independent of the number of egg masses oviposited over six generations of Baetis; and local recruitment was not a function of the number of adults of the previous generation that emerged locally. The patterns of oviposition and emergence of Baetis found in this study are consistent with the following hypotheses. Recruitment of eggs in a stream reach is not limited by the local supply of adults, but is a function of the regional supply of dispersing adults, which are constrained by the spatial and temporal distribution of preferred oviposition habitat. Furthermore, subsequent local production of adults is not a function of the supply of recruits, arguing for post-recruitment control of local populations by processes operating in the larval stage (e.g., predation, competition, dispersal, disturbance). Processes affecting larval and adult stages of Baetis act independently and at different scales, thereby decoupling local population dynamics of successive generations.