Life-history responses of larviparous Boettcherisca formosensis (Diptera: Sarcophagidae) to larval competition for food, including comparisons with oviparous Hemipyrellia ligurriens (Calliphoridae)

Abstract. 1 The effect of larval rearing density on life-history parameters of Boettcherisca formosensis Kirner & Lopes (Sarcophagidae) was investigated. Increases in rearing density resulted in lowered larval survivorship, shortened larval development time and production of smaller, shorter-lived adults with reduced fecundity.
2. B. formosensis is larviparous. Average brood size was 17.5±1.0 (mean±M) larvae, which was much less than the average number of mature larvae inside gravid females. Females apparently produced a series of small broods, distributing their offspring over a number of carcasses.
3. Compared with the oviparous species Hemipyrellia ligurriens (Wiedemann) (Calliphoridae), B. formosensis adults were larger and longer-lived, with a longer larval development time but shorter larval feeding period. However, females had a shorter pre-reproductive period, were less fecund, and had a lower life time reproductive investment.
4. B. formosensis had lower relative performance (measured by the composite index of performance, r') than H. ligurriens over the larval rearing density range, and was more sensitive to increases in density. Although the r' values suggest that the sarcophagid may be a competitively inferior species, other features which are not included in the index (such as larvipary, short larval feeding period and spreading of offspring from a single brood among carcasses) may be of significant adaptive value to B. formosensis.     

Effects of food stress and density in different life stages on reproduction in a butterfly

Availability of adequate nutrition and (rearing) density are among the most important factors affecting growth, development and reproduction in animals. In holometabolous insects diets and energetic needs change between life stages, with storing of larval resources, adult feeding and reproduction being linked strategies. Nevertheless, studies investigating nutritional (and density) effects across metamorphic boundaries are largely lacking. We aim at disentangling the functional basis of reproductive patterns by independently manipulating larval and adult (1) density and (2) access to food, respectively, in the tropical butterfly, Bicyclus anynana. (1) A high larval rearing density had, contrary to common wisdom, very little impact on body size, but reduced larval development time through increased growth rates. The latter is thought to be an adaptation to high densities, driven by the risk of larval food resources becoming exhausted before reaching metamorphosis. Larval density and male company during oviposition (i.e. adult density) had no detectable effects on female reproduction. (2) Larval food stress prolonged larval development time and reduced larval growth rate, body size, fecundity and reproductive investment. Detrimental effects on female reproduction were mediated through a reduction in body size. Additional negative effects of adult food stress on fecundity were largely confined to females being fed as larvae ad libitum, while those being previously starved showed reduced performance regardless of adult income. Effects on egg size were inconsistent and, overall, marginal. Our results show that restricted food access in different developmental stages may set different limits to reproduction, either posed by shortage of larval‐derived storage reserves (i.e. nitrogenous compounds) or adult income (i.e. carbohydrates). Thus, one should be cautious when stating that one or the other type of nutrients is ultimately limiting to reproduction. Rather, our findings highlight the importance of resource congruence and of considering both, larval‐ and adult‐derived resources for reproduction.     

Maternal effects and their consequences for offspring fitness in the Yellow Dung Fly

1. Maternal adult diet and body size influence the fecundity of a female and possibly the quality and the performance of her offspring via egg size or egg quality. In laboratory experiments, negative effects in the offspring generation have often been obscured by optimal rearing conditions.
2. To estimate these effects in the Yellow Dung Fly, Scathophaga stercoraria , how maternal body size and adult nutritional status affected her fecundity, longevity and egg size were first investigated.
3. Second, it was investigated how female age and adult nutritional experience, mediated through the effects of egg size or egg quality, influenced the performance of offspring at different larval densities.
4. Maternal size was less important than maternal adult feeding in increasing reproductive output. Without food restriction, large females had larger clutch sizes and higher oviposition rates, whereas under food restriction this advantage was reversed in favour of small females.
5. Offspring from mothers reared under nutritional stress experienced reduced fitness in terms of egg mortality and survival to adult emergence. If the offspring from low-quality eggs survived, the transmitted maternal food deficiency only affected adult male body size under stressful larval environments.
6. Smaller egg sizes due to maternal age only slightly affected the performance of the offspring under all larval conditions.     

Larval competition causes the difference in male ejaculate expenditure in Callosobruchus maculatus

The seed beetle Callosobruchus maculatus larvae exhibit two types of resource competition: scramble, in which a resource is shared, and contest, in which the resource is monopolized. This difference in larval behavior results in different adult densities. Under contest competition, adult density remains constant regardless of larval density, but under scramble competition, adult density increases with larval density. This in turn affects mating frequency during adulthood, and thus, the intensity of sexual selection operating on males. In this study, we examined the relationship between larval competition types and male reproductive investment in mating. We assessed the male ejaculate expenditure per mating across geographic strains of C. maculatus. The male investment (ejaculate expenditure) increased with the degree of scramble competition and decreased with the degree of contest competition. We therefore suggest that males experience different selective pressures depending on the type of larval competition: scramble type males are selected for increased reproductive investment.     

A trade-off between diapause duration and fitness in female parasitoids

Abstract 1. Diapause allows insects to cope with adverse weather conditions but also poses substantial fitness costs, e.g. through reduced survival of the diapausing stage or sublethal effects in the following season.
2. The energetic costs of diapause in females of the parasitoid Asobara tabida Nees (Hymenoptera: Braconidae) were assessed using experimental manipulation of diapause duration.
3. An increase in diapause length not only led to higher mortality among diapausing pupae but also caused a significant decrease in egg load, fat reserves, and dry weight of the emerging adult females.
4. Only larvae with sufficient resources were able to survive the entire diapause period and there was a trade-off between the metabolic costs of diapause and adult fitness components.
5. In contrast, the size (tibia length) of emerging females increased with increasing diapause duration. It is proposed that this may be due to a genetic correlation between larval dry weight and adult size, so that selection for heavier larvae would result in larger adults even when resources are limited.
6. Ultimately, the evolution of diapause duration and its consequences for adult performance will depend on the costs of overwintering and the ecological conditions in the habitat.     

幼虫密度对甜菜夜蛾生长发育与繁殖的影响

为了研究甜菜夜蛾Spodoptera exigua(Hübner)幼虫的密度对其发育及繁殖的影响,本实验观察了5种幼虫密度下（1,5,10,20,30头/瓶）,幼虫发育和成虫繁殖情况。结果表明：幼虫和蛹历期、存活率和蛹重均差异显著。幼虫和蛹历期均以20头/瓶的最短,1头/瓶的最长,其余随幼虫密度增加而延长;幼虫至蛹存活率以10头/瓶的最高,其余随幼虫密度增加而降低;1头/瓶的蛹最重,显著高于其他密度的,其余随幼虫密度增加而下降。尽管密度间成虫羽化率和产卵前期均无显著差异,但成虫产卵量、寿命和畸形率差异显著。1头/瓶的产卵量最多,其次为10头/瓶的,其余随幼虫密度增加而减少,30头/瓶的产卵量显著少于其他密度的; 密度在1～20头/瓶范围内,雌蛾寿命均较短,显著短于30头/瓶的,而雄蛾寿命以5头/瓶的最短,显著短于其他密度的（10头/瓶除外）,10头/瓶的次之,其余密度间差异不显著;不同幼虫密度下羽化的成虫畸形率差异显著,10头/瓶的最低,其余随幼虫密度增加而升高; 生命表结果表明甜菜夜蛾在10头/瓶下世代存活率和种群增长指数均最高,幼虫密度过低或过高均不利于种群增长;世代存活率（S）和种群增长指数（I）与幼虫密度之间的关系均呈抛物线关系：S =－0.2087x²+2.5694x+211.52 (R²=0.88),I=－0.0552x²+0.9166x+54.168 (R²=0.95)。结果提示幼虫密度影响甜菜夜蛾种群动态的重要生态因子之一。     

Competition between larvae in a butterfly Pieris napi and maintenance of different life-history strategies

1. In scramble competition all individuals suffer equally from competition, whereas in contest competition some individuals outperform the others. Generally, larger individuals gain asymmetric advantage in competition over smaller ones. Given the positive correlation between age and size, asynchronous birth may result in asymmetric competition among juveniles. 2. In Pieris napi (Lepidoptera: Pieridae), reproductive rate is determined by the females' intrinsic mating tactic. The early reproductive rate is high in females with a low mating frequency and low in females with a high mating frequency, whereas lifetime fecundity shows the opposite pattern. Thus, offspring of monandrous females start to develop in relatively low densities and they are relatively large when the offspring of highly polyandrous females start to hatch. 3. The purpose of this study was to explore if asymmetry in larval competition could outweigh the late-life benefits of polyandry. In a laboratory experiment, P. napi larvae of different ages were reared together in different densities. 4. Increasing density decreased both larval survival and reachable pupal mass, but had no effect on duration of larval period. Younger larvae suffered from high mortality and reduced size compared with the older larvae. Mortality decreased in the older cohort with increasing age difference between the cohorts, and the reverse occurred in the younger cohort. Increasing age difference between the cohorts was associated with increase in pupal mass in both cohorts. All the variables showed a lot of variation between broods of different females. 5. The results suggest that polyandrous females, or more generally females with a low early reproductive rate, may lose a great proportion of their late-life benefits, which may partly explain the maintenance of polymorphism in reproductive strategies within species.     

A minimalist approach to the effects of density-dependent competition on insect life-history traits

Abstract  1. 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.     

Asymmetric intraspecific competition among larvae of the damselfly Ischnura elegans (Zygoptera: Coenagrionidae)

Abstract. 1. A laboratory competition experiment is described in which the growth and development rates of larvae of the damselfly Ischnura elegans (Lind.) were measured over an entire instar.
2. Two larval instars which commonly occur together in the field were used in the experiment; they were maintained with a superabundance of prey and either larvae from the same or the larger/smaller instar.
3. Small larvae suffered increased development times and decreased size increases at the moult in the presence of large larvae but similar interference effects were not evident when these smaller larvae were in the presence of other small larvae.
4. Development time and size increases of large larvae were not significantly affected by the presence of small larvae.
5. Irrespective of the instar combinations investigated, interference effects were reduced when there were more perches available, although in only a few cases was this reduction significant.
6. The consequences of the asymmetric competition reported in the experiment for the study of lifetime reproductive success in damselflies are discussed. Late emerging adults may incur reduced reproductive success.     

幼虫密度对二点委夜蛾生长发育及繁殖的影响

【目的】在不同幼虫密度饲养条件下,研究二点委夜蛾Athetis lepigone生长发育及繁殖的情况,明确幼虫密度对该害虫的室内种群增长的影响。【方法】本实验设置5个幼虫饲养密度即1,5,10,20和30头/瓶(750 mL),分别观察5个饲养密度下该虫的各个龄期及整个幼虫发育历期及存活率、蛹重、蛹期以及成虫生殖情况。【结果】幼虫密度对该虫幼虫各龄期及整个幼虫发育历期及存活率、蛹重、蛹期以及成虫生殖情况均有显著性影响。整个幼虫发育历期随着密度的增加而缩短,10头/瓶达到最短(18.27 d),之后随着幼虫密度的增加而显著延长;幼虫至蛹的存活率随着密度增高而显著下降,30头/瓶最低(39.37%)。蛹期随着密度的增加而延长(10头/瓶除外)。蛹重和每雌产卵量均以1头/瓶最高,随着幼虫密度的增加而显著下降。雌雄蛾寿命均以10头/瓶最长,与1和5头/瓶没有显著性差异。生命表分析显示:二点委夜蛾的种群增长指数以5头/瓶最高,幼虫密度过低或者过高均不利于种群增长。【结论】幼虫密度是影响二点委夜蛾种群增长的重要因子之一。     

Assessment of Aedes albopictus (Skuse) (Diptera: Culicidae) clutch size in wild and laboratory populations

Aedes albopictus (Skuse) is an invasive mosquito species found across the southern U.S. with range expansion into many northern states. Intra‐ and interspecific larval competition have been evaluated for Ae. albopictus with respect to subsequent adult size, immature and adult survivability, and its capacity to vector pathogens as an adult. However, limited data are available on egg production as related to larval rearing conditions. Because Ae. albopictus is a container‐inhabiting mosquito that oviposits in resource‐limited habitats, it is found under variable density‐dependent conditions. Therefore, we examined the impact of specific rearing conditions on Ae. albopictus clutch size and adult body size; comparing the egg production values and wing lengths from known developmental densities to those from field‐collected populations. Field populations varied significantly among collection sites in mean clutch size (23 to 46). These clutch sizes were comparable to the mean clutch sizes of females reared at the larval densities of nine (20 eggs) and three (53 eggs) larvae per 3 ml of water in the laboratory. Field populations experienced density‐dependent effects impacting adult mosquito size. Mosquitoes from the four sample sites had mean wing lengths of 1.99, 2.47, 2.51, and 2.54 mm, which were less than the mean wing length of mosquitoes reared at larval densities of three larvae per 3 ml of water (2.57 mm).     

Avoidance of occupied hosts by the Hessian fly: oviposition behaviour and consequences for larval survival

Abstract 1. Unoccupied wheat plants and wheat plants occupied by conspecific eggs or larvae were presented to ovipositing female Hessian flies in choice tests.
2. The presence of conspecific eggs on the leaf surfaces of wheat plants did not appear to have any effect on the responses of ovipositing Hessian fly females.
3. The presence of conspecific larvae at the base and nodes of wheat plants for 1, 6, or 11 days had significant effects on Hessian fly oviposition. Eggs oviposited on plants were inversely proportional to larval densities and days of larval occupation.
4. Feeding by Hessian fly larvae is associated with several changes in wheat plants. One of these changes, the growth arrestment of the plant, was measured by recording the heights of plants used in oviposition tests. Plant heights were inversely proportional to both larval densities and days of occupation. Plant heights were directly proportional to eggs oviposited on plants.
5. The consequences of adult female avoidance of plants occupied by conspecific larvae were investigated by allowing females to oviposit on unoccupied plants and 1-day, 6-day, and 11-day larval occupied plants, then scoring at the end of the first larval instar the survival of the offspring that resulted from this oviposition.
6. Survival during the first larval instar was 88% for the offspring of females that oviposited on unoccupied plants, decreasing to 82, 31, and 4% on the 1-day, 6-day, and 11-day occupied plant treatments. On these four plant treatments, a positive correlation was found between larval performance (i.e. survival) and the preferences of ovipositing females.
7. On the four plant treatments, relationships between first-instar larval density and first-instar larval survival varied significantly. On unoccupied plants, survival was inversely proportional to density. On plants oviposited on at 6 days of larval occupation, survival was directly proportional to density.     

幼虫密度对草地螟生长发育及繁殖的影响

为了明确幼虫密度对草地螟Loxostege sticticalis种群增长的影响, 对室内条件下（温度22±1℃, RH 70%±5%, 光周期16L∶ 8D）不同幼虫密度[1, 10, 20, 30和40头/瓶（650 mL）］饲养的草地螟生长发育及繁殖进行了研究。结果表明: 幼虫密度对草地螟幼虫体色、 发育历期和存活率, 以及蛹重和成虫生殖等有显著影响。随着幼虫密度的增加, 幼虫体色黑化程度呈增强趋势, 幼虫密度大于10头/瓶时的体色黑化值均显著大于幼虫密度为1头/瓶时的体色黑化值（P<0.05）。20头/瓶的幼虫和蛹历期最短, 且随幼虫密度的增加而显著延长（P<0.05）。幼虫存活率以10头/瓶最高, 其他幼虫密度的幼虫存活率显著较低（P<0.05）。蛹重以1头/瓶的最重, 并随幼虫密度增加而显著下降（P<0.05）。成虫产卵量和交配率分别以1和20头/瓶的幼虫密度最高, 幼虫密度升高则产卵量、 交配率逐渐降低。成虫产卵历期随着幼虫密度的增加逐渐缩短。雌、 雄蛾寿命分别以10和20头/瓶幼虫密度时最长, 幼虫密度过高时雌雄蛾寿命又显著缩短（P<0.05）。生命表分析表明, 幼虫密度对草地螟种群增长指数有显著影响, 以10头/瓶幼虫密度的种群增长指数最高, 幼虫密度过高或过低时种群增长指数下降。据此认为, 幼虫密度是影响草地螟种群增长的重要因子之一。     

The relative importance of temperature and diet to larval development and adult size of the winter stonefly, Soyedina carolinensis (Piecoptera: Nemouridae)

SUMMARY. 1. Soyedina carolinensis Claassen, a leaf shredding stonefly, was reared in a series of three laboratory experiments from early instar to adult on different species of deciduous leaves and at various constant and fluctuating temperature regimes.
2. Experiment 1, which involved rearing larvae on fourteen different leaf diets at ambient stream temperatures, showed that diet significantly affected larval growth and adult size but did not affect overall developmental time.
3. Experiment 2, which involved rearing larvae on five different leaf diets at each of three fluctuating temperature regimes (viz ambient White Clay Creek (WCC), ambient WCC+3°C, and ambient WCC+6°C), showed that: (i) adding 6°C to the normal temperature regime of WCC was lethal to 99% of the larvae regardless of diet; and (ii) warming WCC by 3°C did not affect developmental time but did significantly reduce adult size relative to adults reared at WCC temperatures on certain diets.
4. Experiment 3, which involved rearing larvae on five different leaf diets at each of five constant temperatures (viz 5, 10, 15, 20, 25°C), showed that: (i) temperature significantly affected the mortality, growth, and development time of larvae whereas diet only affected larval growth and mortality; (ii) temperatures at or near 10°C yielded maximum larval growth and survival for most diets; (iii) at 5°C, larval mortality was high and growth was low resulting in a few small adults for most diets; (iv) larval mortality was at or near 100% at 15°C regardless of diet; and (v) no larvae survived at 20 and 25°C.     

Brood development into sexual females depends on the presence of a queen but not on temperature in an ant dispersing by colony fission,Aphaenogaster senilis

Abstract. 1. In eusocial insects, colony fission is a mode of dispersal by which a young queen leaves her nest with some workers to found a new colony. In these species, adult females (workers and the queen) should allocate most resources to increasing their colony size, which constrains the possibility of fission. In contrast, developing diploid larvae should have a preference for becoming a queen and having their own offspring, rather than becoming workers and rearing the offspring of other females. 2. In the ant Aphaenogaster senilis, queens are produced in very small numbers, suggesting that adult females control larval development. We used a 6‐year series of data on more than 300 nests to determine the annual cycle of worker and queen production. Although both overlapped, the latter mostly occurred in the second half of the summer, after a major peak of worker emergence. Young queens were also often produced in nests whose reproductive queen had died, thus allowing her replacement. Overall, we estimate that only 0.07% of diploid larvae actually develop into gynes. 3. Laboratory experiments indicated that brood is bipotent until the second larval instar. Diploid larval development into queen was favoured by the removal of the mother queen, but was not affected by rearing temperature. 4. Our data suggest that most diploid broods are forced by the adults to develop into workers rather than into gynes. However, when the queen is not present due to death or after a fission event, a few larvae are allowed to develop into gynes. One way for workers to limit the development of larvae might be by controlling the amount of food they receive.     

Interactions between adult and larval bluegill sunfish: positive and negative effects

Adult fish may affect the growth and survival of conspecific larvae through a variety of pathways, including negative interactions via competition for shared limiting resources or via predation (i.e., cannibalism), and positive interactions due to the consumption of larval predators and via resource enhancement (i.e., presence of adults increases availability of larval prey). To examine the overall effect of adult bluegill sunfish (Lepomis macrochirus) on larval bluegill, we conducted a field experiment in which we manipulated adult densities and quantified larval growth and survival, prey abundance, invertebrate predator abundance, and cannibalism. The presence of adult bluegill had a negative effect on final larval mass. This response was consistent with competition for zooplankton prey. Adult bluegill reduced the abundance of large zooplankton (e.g., Chaoborus and Daphnia), which were the dominant prey of bluegill larvae in the absence of adults. Larvae in the no-adult treatment also had significantly more prey in their stomachs compared to larvae in the presence of adults. Larval survival was maximized at intermediate adult densities and the overall production of larvae peaked at intermediate adult densities. The higher larval survival at intermediate adult densities is attributed to a reduction in invertebrate predators in treatments with adult bluegill; invertebrate predators experienced an 80% reduction in the presence of adult fish. Decreased larval survival at the highest adult density was not due to resource limitation and may be due to cannibalism, which was not directly observed in our study, but has been observed in other studies.     

Socially cued anticipatory adjustment of female signalling effort in a moth

Juvenile population density has profound effects on subsequent adult development, morphology and reproductive investment. Yet, little is known about how the juvenile social environment affects adult investment into chemical sexual signalling. Male gumleaf skeletonizer moths, Uraba lugens, facultatively increase investment into antennae (pheromone receiving structures) when reared at low juvenile population densities, but whether there is comparable adjustment by females into pheromone investment is not known. We investigate how juvenile population density influences the ‘calling'' (pheromone-releasing) behaviour of females and the attractiveness of their pheromones. Female U. lugens adjust their calling behaviour in response to socio-sexual cues: adult females reared in high juvenile population densities called earlier and for longer than those from low juvenile densities. Juvenile density also affected female pheromonal attractiveness: Y-maze olfactometer assays revealed that males prefer pheromones produced by females reared at high juvenile densities. This strategic investment in calling behaviour by females, based on juvenile cues that anticipate the future socio-sexual environment, likely reflects a response to avoid mating failure through competition with neighbouring signallers.     

粘虫幼虫密度对成虫飞行与生殖的影响

本文报道了不同幼虫密度下(1、10、20、30、40头/瓶-850m1)粘虫蛾飞行能力与产卵量的变化情况。对未取食1日龄成虫12h飞行能力的测定结果表明,不同幼虫密度羽化的成虫飞行力差异显著(P<0.05),其中以10头/瓶羽化的成虫飞行时间最长(平均225.4分),飞行距离最远(平均17.5km),飞行超过120min的个体为61.1%,超过10 km的为55%。其它处理的各项参数随幼虫密度的增加而下降。粘虫蛾的翅长、翅宽、翅面积和翅负荷随幼虫密度的增加而下降。除翊负荷外,其余各项参数在处理间的差异显著(P<0.05)。成虫飞行能力与蛹重或翅负荷不呈直线相关,但与蛹重具有一定的关系：当蛹重为300-400mg时, 强飞行个体均超过50%, 当小于300mg或大于400mg时,强飞行个体比例下降,当小于225mg时,强飞行个体为零。处理间的成虫产卵量差异显著(P<0.05),且随幼虫密度的增加而下降。密度内的蛹重与成虫产卵量的关系不明显,但密度间的蛹重与产卵量的关系高度相关(r=0.78,P<0.01)。这些结果表明,当粘虫幼虫密度达到一定的阈值时,便可能促使成虫迁飞,而不是等到种群密度很高时才进行迁飞。     

Larval competition in Chrysomya megacephala (F.) (Diptera: Calliphoridae): effects of different levels of larval aggregation on estimates of weight, fecundity and reproductive investment

In insects that utilize patchy and ephemeral resources for feeding and egg laying, the outcome of larval competition for food resources depends on the amount of resources and the spatial distribution of immatures among patches of food. In the present study, the results of larval competition for food in Chrysomya megacephala, in traits such as female weight, fecundity and reproductive investment, were different in situations where the level of larval aggregation (proportion of competitors per amount of food) was the same, but with densities of competitors and amounts of food proportionally different. These results are indicative that the larval competition may depend both on the larval density and the amount of food, in different situations with the same proportion of larvae per gram of food.     

Larval population density affects female weight and fecundity in the dung beetle Aphodius ater

1. Competition for food at high densities during larval development leads to reduced adult weight in the northern temperate dung beetle Aphodius ater. 2. Analysis of female beetles caught in the field showed that numbers of eggs and total egg load per female were correlated positively with beetle size. 3. Female beetles reared at different population densities during larval development in the laboratory were analysed with regard to their lifetime fecundity and reproductive lifespan. 4. High population densities during development had a negative influence on the number of eggs per female and on reproductive lifespan. Lifetime fecundity was correlated positively with female weight. 5. It was concluded that competition during larval development in the first generation of offspring will result in a lower number of offspring in the second generation in Aphodius ater, and thereby reduce parental fitness.