Egg Inviability Research Articles

THE EFFECTIVENESS OF COMPOSTING USING STABILIZING URBAN SEWAGE SLUDGE COMPOUNDS

The purpose of this investigation was to verify the effectiveness of composting in the sanitization of sludge from urban sewage (SS). The treatments (T) used consisted of SS mixed with sugarcane bagasse (SB), tree pruning residues (TP), poultry litter (PL) or grass clipping (GC) at a carbon/nitrogen ratio of approximately 30/1 and ratios of T1 (SS+SB), T2 (SS+SB+TP), T3 (SS+SB+GC), T4 (SS+SB+PL) or T5 (SS+SB+TP+GC). Temperature was measured daily for over 280 days of composting. Every two weeks, the compounds were analyzed for thermotolerant coliforms and viable helminth eggs using the multiple-tube and Yanko techniques; and once each month to identify Cryptosporidium spp. and Giardia spp. (oo)cysts using the sucrose and zinc sulfate centrifugal flotation technique and nested PCR followed by sequencing. The maximum temperatures measured in the thermophilic phase of the compounds ranged from 55°C to 64.8°C, and at day 280, weight reductions of 27% (T1), 48% (T2), 63% (T3), 66% (T4) and 64% (T5) were observed. The absence of fecal coliforms was observed from day 98 (T4), day 126 (T1), day 196 (T3 and T5) and day 210 (T2). All treatments resulted in helminth egg inviability and the absence of protozoan (oo)cysts. Only T4 and T5 were positive for G. duodenalis according to the sequencing analysis. In conclusion, high temperatures during the composting thermophilic phase made the use of pathogens required by legislation unfeasible; therefore, it is important to investigate the viability of protozoa in compounds to ensure a safe final product for human and animal health.

A bacterium against the tiger: further evidence of the potential of noninundative releases of males with manipulated Wolbachia infection in reducing fertility of Aedes albopictus field populations in Italy.

Incompatible insect technique (IIT) is a population suppression approach based on the release of males with manipulated Wolbachia infection inducing egg inviability in wild females. We here present results of multiple field releases of incompatible ARwP males carried out in 2019 in a 2.7-ha green area within urban Rome (Italy) to assess the effect on Aedes albopictus egg viability. Data are compared with results obtained in 2018, when the approach was tested for the first time in Europe. An average of 4674 ARwP males were released weekly for 7 weeks, resulting in a mean ARwP:wild male ratio of 1.1:1 (versus 0.7:1 in 2018). Egg-viability dynamics in ovitraps significantly varied between treated and control sites, with an estimated overall reduction of 35% (versus 15% in 2018). The estimated proportion of females classified as mated with ARwP males was 41.8% and the viability rate of eggs laid by these females (9.5%) was on average significantly lower than that of females only mated with wild males (87.8%); however, high variability in fertility was observed. Values of ARwP male competitiveness were 0.36 and 0.73 based on the overall viability rate of eggs in ovitraps and on female fertility, respectively; thus, well above the conventional 0.2 threshold for an effective suppressive impact in the field. Results further support the potential of IIT as a tool to contribute to Ae. albopictus control in the urban context, stressing the need for larger field trials to evaluate the cost-efficacy of the approach in temperate regions. © 2023 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Egg viability of green turtles nesting on Raine Island, the world’s largest nesting aggregation of green turtles

Egg inviability at oviposition is a possible explanation for the high rate of early-stage embryo death of eggs laid by green turtles at Raine Island, the largest green turtle nesting aggregation in the world. We tested this possibility by assessing egg viability of freshly laid eggs. We found that green turtle eggs laid at Raine Island have high viability at their time of laying, and that there was no relationship between egg viability and early-stage embryo death or hatching success within a clutch. Hence, the inviable egg at oviposition hypothesis cannot explain the high death rate of early-stage embryos that is characteristic of green turtle clutches laid at Raine Island.

Mountain Plover habitat selection and nest survival in relation to weather variability and spatial attributes of black-tailed prairie dog disturbance

Abstract Habitat loss and altered disturbance regimes have led to declines in many species of grassland and sagebrush birds, including the imperiled Mountain Plover (Charadrius montanus). In certain parts of their range Mountain Plovers rely almost exclusively on black-tailed prairie dog (Cynomys ludovicianus) colonies as nesting habitat. Previous studies have examined Mountain Plover nest and brood survival on prairie dog colonies, but little is known about how colony size and shape influence these vital rates or patterns of habitat selection. We examined how (1) adult habitat utilization, (2) nest-site selection, and (3) nest success responded to a suite of local- and site-level variables on large prairie dog colony complexes in northeastern Wyoming. Abundance of adult Mountain Plovers was highest on points within older, “medium”-sized (100–500 ha) colonies with high cover of annual forbs and bare ground (5.8 birds km−2), but lower on extremely large (>2,000 ha) colonies (2.1 birds km−2). Nest sites were characterized by high proportions of annual forbs and bare ground and low cactus cover and vegetation height. Nest survival was higher for older nests, and nests with lower cactus cover, and decreased with increasing temperatures. Uncertainty was high for models of daily nest survival, potentially because of 2 competing sources of nest failure: nest depredation and nest abandonment or inviability of eggs. Drivers of these 2 sources of nest failure differed, with inclement weather and higher temperatures associated with nest abandonment or egg inviability. We highlight how prairie dogs alter vegetation structure and bare ground heterogeneously across the landscape, and how this in turn influences bird abundance and nest distribution at different temporal and spatial scales. Furthermore, our work reveals how partitioning the causes of nest failure during nest survival analyses enhances understanding of survival rate covariates.

Natural mortality factors of tomato leafminer Tuta absoluta in open-field tomato crops in South America.

Little importance has been given to the role of natural mortality factors (biotic and abiotic) in the regulation of tomato leafminer Tuta absoluta (Lepidoptera: Gelechiidae) populations. The present study determined the action of mortality factors on T. absoluta populations infesting cultivated tomato crops. Eighty ecological life tables for T. absoluta in field cultivated tomato plants were constructed and analyzed. Total T. absoluta mortality was 99.08%, with 38.76% mortality during the egg phase, 57.20% in the larva phase and 3.12% in the pupal phase. The main mortality factors during the egg stage were predation, parasitism and egg inviability. In the larval stage, the main mortality factors were predation, parasitism, entomopathogenic agents and physiological disorders. In the pupal stage, the main mortality factor was predation. The larvae of the third and fourth instar were more susceptible to the action of mortality factors and the predatory wasp, Protonectarina sylveirae, was the main insect predator of these larvae. The T. absoluta population is regulated under field conditions by the action of natural enemies of the larvae. The predatory wasp P. sylveirae is very important in the regulation of T. absoluta populations in open-field tomato crops in Brazil. © 2018 Society of Chemical Industry.

Stage-specific mortality, fecundity, and population changes in Cassida rubiginosa (Coleoptera: Chrysomelidae) on wild thistle

Cassida rubiginosa Müller (Coleoptera: Chrysomelidae), one of the most conspicuous defoliators of thistle weeds, is capable of severely damaging thistle leaves; however, populations rarely reach sufficient density for effective thistle control under natural conditions. To investigate the impact of natural mortality factors on C. rubiginosa populations, life table studies were conducted between 1996 and 1998 in Kanazawa, Japan. Egg mortality, mortality in early larvae, and lost fertility contributed strongly to total generational mortality in every year studied. Egg mortality was primarily attributable to parasitism by wasps of the genus Anaphes, and the impact of predation and egg inviability was small. Mortality factors that affected the larval and pupal stages were largely unknown. Under field conditions, females only realized approximately 8.1–13.7 % of their potential fecundity, varying from 36.0 to 61.4 eggs per individual. Since annual changes in lost fertility exhibited a similar pattern to those in generational mortality, fertility loss might be the key factor driving C. rubiginosa populations. These results suggest that reproduction is the most important process that determines the level and fluctuation of the C. rubiginosa population.

Causes of reduced clutch size in a tidal marsh endemic

We tested three hypotheses of clutch size variation in two subspecies of the swamp sparrow (Melospiza georgiana georgiana and M. g. nigrescens). Swamp sparrows follow the pattern of other estuarine endemics, where clutch size is smaller among tidal salt marsh populations (M. g. nigrescens) than their closest inland relatives (M. g. georgiana). Our results support predation risk and temperature, but not adult survival, as explanations of this pattern in swamp sparrows. Coastal nests were twice as likely to fail as inland nests, and parental activity around the nest site was positively related to clutch size at both sites. When brood size was controlled for, coastal adults visited nests less often and females vocalized less frequently during visits than inland birds, which may decrease nest detectability to predators. Coastal parents waited longer than inland birds to feed offspring in the presence of a model nest predator, but there was no difference in their response to models of predators of adults, as would be expected if coastal birds possessed increased longevity. Additionally, coastal females laid more eggs than inland females over a single season, following a within-season bet-hedging strategy rather than reducing within-season investment. Coastal territories experienced ambient air temperatures above the physiological zero of egg development more often, and higher temperatures during laying correlated with smaller clutches and increased egg inviability among coastal birds. Similar effects were not seen among inland nests, where laying temperatures were generally below physiological zero. Both subspecies showed an increase in hatching asynchrony and a decrease in apparent incubation length under high temperatures. Coastal individuals, however, showed less hatching asynchrony overall despite higher temperatures. Both air temperatures during laying and predation risk could potentially explain reduced clutch size in not only coastal plain swamp sparrows, but also other tidal marsh endemics.

Seasonal mortality factors of the coffee leafminer,Leucoptera coffeella

Seasonal population fluctuation of the coffee leafminer, Leucoptera coffeella (Guérin-Méneville & Perrottet) (Lepidoptera: Lyonetiidae), led to an investigation of its natural mortality factors during the rainy season when the population level is low and during the dry season when population peaks occur. Life-table data were collected from insecticide-free plots within a 3 ha coffee plantation on the upper, medium and lower canopy. Leafminer mortality was similar among the canopy parts but varied in the two seasons studied. During the rainy season, the generational mortality averaged 94.3%, with 50.2, 33.7 and 10.4% occurring during egg, larval and pupal stages, respectively. During the dry season, total mortality was 89%, with 13.2, 61.0 and 14.8% occurring during egg, larval and pupal stages, respectively. Marginal mortality rates during the rainy season were highest for physiological disturbances, rainfall and egg inviability; but, in the dry season, they were highest for predaceous wasps, physiological disturbances and parasitoids. Egg and larval stages accounted for most of the mortality variation in the rainy season, while the combination of larval and pupal mortality better described the generational mortality in the dry season. Variation in mortality during the rainy season was primarily associated with egg inviability, rainfall and parasitoids. In contrast, predatory wasps and physiological disturbances were the main factors associated with mortality variation during the dry season. These results suggest that weather conditions, natural enemies and plant quality attributes are the main determinants of the population dynamics of L. coffeella.

Natural mortality factors of Leucoptera coffeella (Lepidoptera: Lyonetiidae) on Coffea arabica

The natural mortality of the coffee leafminer, Leucoptera coffeella (Guérin-Méneville) was investigated in three strata of coffee plant canopy for three seasons through construction and analysis of ecological life tables. Mortality of the leafminer was similar on all thirds of the canopy. Total mortality of immature stages was 95%, with 38.5, 43.8 and 12.7% occurring during egg, larval, and pupal stages. Rainfall killed 39.3% of eggs and larvae, and together with egg inviability (16.3%) and Vespidae (11.3%), were the highest mortality factors. Six wasp parasitoids caused 8% of larval mortality. Egg and larva were the critical stages. Variation in mortality was primarily associated with egg inviability, rainfall, and parasitism by Horismenus sp. (Hymenoptera: Eulophidae). Physiological disturbances during molting and metamorphosis also contributed for fluctuations in mortality of the leafminer. Tactics of integrated pest management to enhance natural mortality of the leafminer while conserving or augmenting the action of natural enemies are discussed.

Natural selection and divergence in mate preference during speciation

Sexual isolation can evolve due to natural selection against hybrids (reinforcement). However, many different forms of hybrid dysfunction, and selective processes that do not involve hybrids, can contribute to the evolution of sexual isolation. Here we review how different selective processes affect the evolution of sexual isolation, describe approaches for distinguishing among them, and assess how they contribute to variation in sexual isolation among populations of Timema cristinae stick-insects. Pairs of allopatric populations of T. cristinae living on different host-plant species exhibit greater sexual isolation than those on the same host, indicating that some sexual isolation has evolved due to host adaptation. Sexual isolation is strongest in regions where populations on different hosts are in geographic contact, a pattern of reproductive character displacement that is indicative of reinforcement. Ecological costs to hybridization do occur but traits under ecological selection (predation) do not co-vary strongly with the probability of between-population mating such that selection on ecological traits is not predicted to produce a strong correlated evolutionary response in mate preference. Moreover, F1 hybrid egg inviability is lacking and the factors contributing to reproductive character displacement require further study. Finally, we show that sexual isolation involves, at least in part, olfactory communication. Our results illustrate how understanding of the evolution of sexual isolation can be enhanced by isolating the roles of diverse ecological and evolutionary processes.

Mortality dynamics and population regulation inBemisia tabaci

AbstractNatural mortality is an important determinant of the population dynamics of a species, and an understanding of mortality forces should aid in the development of better management strategies for insect pests. An in situ, observational method was used to construct cohort‐based life tables forBemisia tabaci(Gennadius) Biotype B (Homoptera: Aleyrodidae) over 14 generations on cotton in central Arizona, USA, from 1997 to 1999. In descending order, median marginal rates of mortality were highest for predation, dislodgment, unknown causes, egg inviability, and parasitism. The highest mortality occurred during the 4th nymphal stadium, and the median rate of immature survival over 14 generations was 6.6%. Predation during the 4th nymphal stadium was the primary key factor. Irreplaceable mortality was highest for predation and dislodgment, with the absence of these mortality factors leading to the greatest increases in estimated net reproduction. There was little evidence of direct or delayed density‐dependence for any mortality factor. Wind, rainfall, and predator densities were associated with dislodgment, and rates of predation were related to densities ofGeocorisspp.,Orius tristicolor(White),Chrysoperla carneas.l. Stephens, andLygus hesperusKnight. Simulations suggest that immigration and emigration play important roles in site‐specific dynamics by explaining departures from observed population trajectories based solely on endogenous reproduction and mortality. By a direct measurement of these mortality factors and indirect evidence of adult movement, we conclude that efficient pest management may be best accomplished by fostering greater mortality during the 4th stadium, largely through a conservation of predators and by managing immigrating adult populations at their sources.

Analysis of field and laboratory data to derive selenium toxicity thresholds for birds

In this paper, we critically evaluate the statistical approaches and datasets previously used to derive chronic egg selenium thresholds for mallard ducks (laboratory data) and black-necked stilts (field data). These effect concentration thresholds of 3%, 10% (EC10), or 20% have been used by regulatory agencies to set avian protection criteria and site remediation goals, thus the need for careful assessment of the data. The present review indicates that the stilt field dataset used to establish a frequently cited chronic avian egg selenium threshold of 6 mg/kg dry weight lacks statistical robustness (r2 = 0.19-0.28 based on generalized linear models), suggesting that stilt embryo sensitivity to selenium is highly variable or that factors other than selenium are principally responsible for the increase in effects observed at the lower range of this dataset. Hockey stick regressions used with the stilt field dataset improve the statistical relationship (r2 = 0.90-0.97) but result in considerably higher egg selenium thresholds (EC10 = 21-31 mg/kg dry wt). Laboratory-derived (for mallards) and field-derived (for stilts) teratogenicity EC10 values are quite similar (16-24 mg/kg dry wt). Laboratory data regarding mallard egg inviability and duckling mortality data provide the most sensitive and statistically robust chronic threshold (EC10) with logit, probit, and hockey stick regressions fitted to laboratory data, resulting in mean egg selenium EC10 values of 12 to 15 mg/kg dry weight (r2 = 0.75-0.90).

Regional Patterns of Wading Bird Productivity in Northeastern U.S. Estuaries

-We investigated wading bird productivity in four estuaries from Delaware Bay to Boston Harbor in northeastern U.S.A. over the period 1986-1998. To document and characterize reproductive performance of numerically dominant species for use in wildlife and habitat management planning, we recorded 1) number of eggs laid, 2) percent of eggs hatched, 3) percent of hatchlings surviving 10-15 days post-hatch, 4) number of nestlings produced, and 5) factors of offspring mortality in nests of Black-crowned Night Heron (Nycticorax nycticorax), Snowy Egret (Egretta thula), Cattle Egret (Bubulcus ibis), and Glossy Ibis (Plegadisfalcinellus). We randomly selected 30-50 nests of each species (as available) for study at colonies in Delaware Bay (1993-1998), New York Harbor (1986-1994), Cape Cod (1990-94), and Boston Harbor (1993-94). In addition, we recorded abundance of nesting wading birds and avian predators in most years of study. Colony size ranged from 120-8,300 nests. Clutch size of all species was greater at northern-most sites. Loss of eggs varied between estuaries for all species except Glossy Ibis. Hatching success ranged from 75-88% and differed between estuaries for Black-crowned Night Heron and Glossy Ibis. Hatchling survival ranged from 16-87% and was lowest in Delaware Bay for all species. Nestling production was lowest in Delaware Bay for all species. In general, predation was high in Delaware Bay and egg inviability was high in Boston Harbor. Predation of nestlings was greatest in Delaware Bay for Cattle Egret, but there were no differences between estuaries for other species. Proportions of avian predators to nesting herons did not explain high predation rates in Delaware Bay. Received 18 April 2001, accepted 21June 2001.

Gametic incompatibilities between races ofDrosophila melanogaster

Reproductive-isolating mechanisms between nascent species may involve sperm-egg recognition and have been best described in externally fertilizing organisms where such recognition is essential in preventing undesirable fertilizations. However, reproductive barriers in internally fertilizing species differ in significant ways, and a direct role for sperm-egg interactions has yet to be demonstrated. Females of many strains of Drosophila melanogaster from Zimbabwe, Africa, do not mate readily with cosmopolitan males. This polymorphism in mate choice is postulated to represent incipient speciation. We now report that, in one direction, crosses between the above populations produce far fewer offspring than reciprocal crosses due to a lower rate of egg hatch. We established that egg inviability in these crosses was due to defects in fertilization. Thus, even in taxa with internal fertilization, gametic incompatibility may be a mechanism relevant to reproductive isolation during incipient speciation.

Ecological Life Table of Tuta absoluta (Meyrick) (Lepidoptera: Gelechiidae)

An ecological life table was constructed, aiming to determine the critical stages and key mortality factors of Tuta absoluta (Lepidoptera: Gelechiidae). The total population mortality of this tomato leafminer was 92.3%. During the egg stage the mortality was 58.7%, mainly due to egg inviability. A total of 8.6% egg parasitism by Trichogramma pretiosum (Riley) (Hymenoptera: Trichogrammatidae) and 5.0% egg predation by Xylocoris sp. (Heteroptera: Anthocoridae), Cycloneda sanguinea (L.) (Coleoptera: Coccinellidae) and members of the family Phlaeothripidae (Thysanoptera) was observed. The mortality of the larval stage was 33.0%. This was considered to be the critical stage as it showed the highest apparent mortality (79.8%). Larval parasitism was low (0.1%), and was only found with Goniozus nigrifemur Ashmead (Hymenoptera: Bethylidae). Predators were responsible for 79.4% of larval mortality. Therefore, their attraction to and maintenance in the target area are important management tactics to be considered for T. absoluta control. The first and second instars were considered to be the most critical, and predation by the above mentioned species was the key mortality factor. The mortality at the pupal stage was low (0.6%) and was due to malformation.

Phenotypic consequences of incubation temperature and feeding regimen in captive-bred tarantulas

Eighteen oothecae of the African selenocosmiine spider Pterinochilus murinus were incubated at 22.5, 27.0, or 31.5°C. Neonates were reared under high or low feeding regimens. Potential influences of incubation temperature on incubation period, secondary sex ratio, egg inviability, embryo mortality, and juvenile mass at eclosion were examined using chi-square analysis and analysis of covariance. Potential direct and interactive effects of the temperature of incubation and feeding regimen on juvenile mortality, mass at 35 weeks, and duration of immature/mature life span and body mass/size in males were tested using multivariate analysis of covariance. Secondary sex ratio did not depart from parity within any experimental treatment. The strikingly small mass of spiders reared under the low feeding regimen was unaffected by incubation temperature and was equivalent between the sexes. Under the high feeding regimen, females in the 22.5 and 31.5°C incubation treatments had surpassed the mass of their male counterparts by week 35, but male and female mass was equivalent at 27.0°C. The most massive high-fed females were produced from the 31.5°C incubation temperature, while high-fed males were largest from 27.0°C, which also produced mature males of the greatest mass and body size. Captive-management implications are discussed. Zoo Biol 17:405–414, 1998. © 1998 Wiley-Liss, Inc.

Molecular and morphological evidence for hybridization between two ecologically distinct grasshoppers (Melanoplus sanguinipes and M. devastator) in California

This paper applies the biological species concept to two ecologically distinct species of grasshopper, Melanoplus sanguinipes and M. devastator, by testing for reproductive isolation in the field in California. Two independent techniques for assessing gene flow between species were employed. Firstly, we examined male genitalic morphology in populations from the foothills of the Sierra Nevada where the two species are parapatric. Two genetically based genitalic traits that differed between allopatric populations of each species formed a cline in this zone. Males captured in the field from the region of parapatry resembled offspring from interspecific laboratory hybridizations. Secondly, we surveyed electrophoretic variation of populations from across California and used F statistics to estimate levels of gene flow within and between species. Results from both morphology and F statistics suggested that these grasshoppers are not reproductively isolated in nature but that gene flow between species is reduced relative to within-species. These field results were consistent with a laboratory study that showed partial but not complete hybrid egg inviability. Because the hybrid zone is centred along an ecological transition, this system offers an opportunity to investigate whether adaptive changes across the zone contribute to reduced gene flow between species.

The Evolution of Clutch Size and Hatching Asynchrony in Altricial Birds: The Effect of Environmental Variability, Egg Failure and Predation

able offspring losses due to egg inviability, predation rate, costs of and environmental variability are considered together, in order to evaluate their joint effect and relative significance in the evolution of the clutch size in a fluctuating environment. The model shows, when laying additional eggs to track environmental variability and/or insure against egg inviability is of selective advantage. Environmental variability seems to be a key factor governing the pay-off of size adjustment. However, in contrast to Lack's brood reduction hypothesis, asynchronous hatching ensures not only the establishment of competitive asymmetries among chicks, but also significantly reduces the impact of predation on fitness of birds. The model predicts that laying surplus eggs may evolve when the daily risk of predation is high, provided that the extra eggs hatch asynchronously.

Organochlorines, Predators and Reproductive Success of the Red-Necked Grebe in Southern Manitoba

I assessed factors influencing the reproductive success of Red-necked Grebes (Podiceps grisegena) in Turtle Mountain Provincial Park, Manitoba, during 1980 and 198 1. Nesting losses were high as 78.9% of 697 eggs in 179 regularly observed nests failed to hatch. An additional 4.4% disappeared during the hatching process. Similar success rates among 137 eggs in 29 infrequently observed clutches indicated that observer presence did not adversely affect nesting success. Losses due to waves (2%) and intraspecific territoriality (6%) were minimal. Predators, particularly raccoons (Procyon lotor), accounted for half of the losses. Organochlorine residues contributed to many of the remaining losses. Average DDE levels (74.3 ppm, lipid weight) in 12 eggs were comparable to those reported in other recent studies, but average PCB levels (194.8 ppm) were unusually high. Average residue levels of 1 to 8 ppm were recorded for mirex, dieldrin, hexachlorobenzene, oxychlordane, heptachlor epoxide, and DDD. The average Ratcliffe Index (1.72) for 29 eggs collected during this study was significantly less than Ratcliffe Indices for 112 Red-necked Grebe eggs collected in North America prior to 1947 (9 = 1.84) or for 186 eggs collected in central Alberta in the early 1970s (x = 1.86). Other indications of thin-shelled eggs included the frequent disappearance of single eggs between nest checks (9%) and cracked eggs noted in several active nests. The estimated rate of egg inviability (25%) exceeded the 5% rate considered normal for most grebes. Egg inviability contributed to at least 23% of 191 eggs in 58 successful clutches being deserted after partial clutch hatching. A high incidence of renesting, 83.5% of 79 failed pairs, resulted in 51% of 114 breeding pairs hatching at least one young. An average of 2.5 young hatched per successful pair. This was reduced to 1.9 young per successful pair or 0.9 young per breeding pair at fledging. Fledging success was lower than recorded in most other Red-necked Grebe studies. Organochlorines, recent increases in unnatural predators, and human recreational activities have probably contributed to reduced productivity and population declines among Red-necked Grebe populations throughout North America.

Mortality Factors for Oberea schaumii (Coleoptera: Cerambycidae)1

The poplar branch borer, Oberea schaumii LeConte, was studied over a 5-year period in northern Michigan stands of trembling aspen, Populus tremuloides Michx. Objectives of the study were to describe the mortality and survival of natural populations of O. schaumii and to identify and assess the importance of causes for mortality. O. schaumii generally has a 3-year life cycle in northern Michigan, though some adults mature in 2 years and a significant proportion require 4 years. Most egg niches fail during the 1st year after oviposition because of egg inviability, parasitism, and desiccation. Parasites of these early larval stages were identified as Iphiaulax eurygaster (Brulle) (Braconidae). After the 1st year, the parasites Cenococlius sanguineiventris (Ashmead) (Braconidae) and Cremastus nordi Townes (Ichneumonidae) combined with woodpecker predation to make the last larval and pupal stages most hazardous to maturing larvae.