Adult feeding and lifetime reproductive success in the parasitoid Aphytis melinus

The diet of adult females of the parasitoid Aphytis melinus DeBach (Hymenoptera: Aphelinidae) includes host insects and sugar-rich foods such as nectar and honeydew. We compared the contributions of host feeding to longevity and fecundity in A. melinus females in the presence and in the absence of honey meals. First, we assessed the longevity of females that were not allowed to oviposit. While the longevity of females fed honey was significantly increased by host feeding (median ages were 30.5 days for host-fed females and 17 days for females not allowed to host feed), the lifespan of parasitoids not fed honey did not exceed 3 days for any individual and there was no effect of host feeding on longevity in this group. In the second set of experiments, we assessed the fecundity and longevity of females allowed to oviposit. We conducted two experiments, one in which honey was continuously available, and one in which honey was not available. In both experiments, daily observations were made of females that were either allowed to host feed or manually prevented from host feeding. In the presence of honey, host feeding significantly increased both fecundity and longevity, and in the absence of honey, parasitoids died within 2 days and host feeding had no significant effect on either fecundity or longevity. The lifetime fecundity of females fed honey but not hosts exceeded the initial egg complement by 60% on average. Approximately one host per day was used for host feeding whether honey was supplied or not, and each host-feeding meal contributed approximately 3.9 eggs to the lifetime fecundity of honey-fed females. In the last experiment, we compared the rate of egg resorption over a 36-h period in A. melinus females that were deprived of hosts and either fed honey or starved. While no egg resorption was detected in honey-fed females over this time period, starved females resorbed approximately 9 eggs. Thus, the availability of a sugar-rich food interacts strongly with host feeding in influencing longevity and fecundity and has a strong direct effect on egg resorption.     

A field study of size–fitness relationships in the parasitoid Asobara tabida

1. Many evolutionary models of parasitoid behaviour assume a positive correlation between size and fitness. In this paper we study the size–fitness relationship in the laboratory and in the field using females of the solitary parasitoid Asobara tabida (Hymenoptera: Braconidae).
2. In the laboratory, fecundity, fat reserves and longevity without food were positively correlated with size.
3. Release–recapture experiments in the field showed that dispersal diminishes fat reserves. Dispersal ability is size-dependent: larger females, with larger fat reserves, disperse over larger distances than smaller females.
4. The form of the relationship between size and fitness in the field was estimated in two ways: one based on a comparison of the size distribution of released and recaptured females; the other based on the egg load and fat reserves of wild-caught females. Both showed an accelerating increase of fitness with size.
5. The majority of females appeared to be time-limited. Therefore, the increase in fitness with size is predominantly due to a larger dispersal ability and not to a higher egg load.     

Lifetime gains and patterns of accumulation and mobilization of nutrients in females of the synovigenic parasitoid, Diglyphus isaea Walker (Hymenoptera: Eulophidae), as a function of diet

In nature, adult parasitoids feed to obtain and use nutrients for supplementing and/or replenishing some of their existing array of nutrient reserves. When adults feed on host or non-host food, they can enhance fitness, typically by increasing egg production or longevity. In the present study, ovigeny index (OI) and impact of female fitness, as well as physiological state on the reproductive strategies, were investigated in the synovigenic parasitoid, Diglyphus isaea, fed on host food (2-3rd instars of Liriomyza sativae larvae), non-host foods (10% honey solution) and starved (distilled water, control). The results showed that D. isaea was a strongly synovigenic parasitoid, of which OI value was 0.002. Both types of food enhanced the fecundity and prolonged the longevity of the females. D. isaea females fed on non-host food showed higher levels of gut sugar, body sugar and glycogen than those fed on host food, but the levels of lipid were higher in the host-fed females. D. isaea females seemed to show lipogenesis, with low rates of lipid catabolism sufficient to satisfy the requirement of egg maturation. Females might absorb lipids directly from the haemolymph of paralyzed hosts.     

The parasitoid of a fruit moth caterpillar utilizes fruit components as nutrient source to increase its longevity and fertility

Longevity and fecundity of female wasps are two decisive factors for the effectiveness of parasitoid species as biological control agents. Accessibility and suitability of nutrient sources determine parasitoid survival and reproduction. Host, nectar and honeydew feeding are frequent adult parasitoid behaviors to cover nutritional needs. Here we postulate that especially parasitoid species of endophytic herbivores might use plant tissue as a nutrient source that becomes accessible upon herbivory. We investigated the influence of plant consumption and host feeding on longevity and fecundity of Hyssopus pallidus, a gregarious ecto-parasitoid of caterpillars of the codling moth that feed inside apple fruits. Longevity of unmated and mated ovipositing female parasitoids was highest in treatments with fruit pulp. While longevity in this treatment was not significantly different from that with honey, it was significantly higher than in treatments without food, with water or with a host alone.Reproduction was significantly increased by these sugar-rich nutrient sources compared to the control with a host alone. In contrast, host feeding did not yield any significant contribution to longevity and fecundity in a series of bioassays with different host–parasitoid ratios and with differently aged and sized hosts, compared to controls without food.We conclude that in this synovigenic species host feeding does not contribute to longevity and fecundity, but females can increase survival and reproduction in the field relying solely on the plant tissue damaged by their host caterpillar.     

Costs and benefits of host feeding in the parasitoid wasp Trichogramma turkestanica

Females of the parasitoid wasp Trichogramma turkestanica Meyer (Hymenoptera: Trichogrammatidae) generally host feed after ovipositing on the first egg of Ephestia kuehniella Zeller (Lepidoptera: Pyralidae) they encounter. We measured the impact of host feeding on the fecundity and longevity of females, in absence of host or food, and on the fitness of their progeny. We also determined if the frequency of host feeding is influenced by the humidity level at which T. turkestanica females developed. Host feeding increased egg production by 70% but decreased female longevity. This impact of host feeding on the longevity of females is probably due to the allocation of carbohydrates to egg production at the expense of somatic maintenance. Humidity did not influence the occurrence or duration of host feeding. The size of individuals developing in eggs on which females host fed was smaller, indicating that their fitness was affected.     

Egg maturation dynamics of the parasitoid Microplitis rufiventris: starvation speeds maturation in early life

The number of mature eggs carried by a female parasitoid at any given moment (egg load) is a fitness‐related parameter affecting reproductive potential and impacting upon host population dynamics. Microplitis rufiventris Kokujev (Hymenoptera: Braconidae) is a solitary koinobiont endoparasitoid wasp of several noctuid pests, including Spodoptera littoralis. The number of mature eggs carried by females at emergence is approximately 50. The rate of egg maturation is strongly affected both by feeding status and access to host larvae. In early adult life, egg maturation rates are lower for 6–72 h in fed wasps compared with food‐deprived wasps. When given access to hosts, honey‐fed wasps live for approximately 9 days with high lifetime fecundity (226 eggs). By contrast to early adult life, the total realized fecundity is positively affected by feeding status, where water‐fed and starved females have 140 and 107 eggs, respectively. Egg resorption is most pronounced in the later life of females. The results suggest, in addition to confirming the effect of honey‐feeding on total fecundity, that fecundity of starved wasps includes rapid egg maturation early in life, which potentially could improve the performance of the parasitoid as a biological control agent.     

The effect of different dietary sugars and honey on longevity and fecundity in two hyperparasitoid wasps

In nature adult insects, such as parasitic wasps or 'parasitoids' often depend on supplemental nutritional sources, such as sugars and other carbohydrates, to maximize their life-expectancy and reproductive potential. These food resources are commonly obtained from animal secretions or plant exudates, including honeydew, fruit juices and both floral and extra-floral nectar. In addition to exogenous sources of nutrition, adult parasitoids obtain endogenous sources from their hosts through 'host-feeding' behavior, whereby blood is imbibed from the host. Resources obtained from the host contain lipids, proteins and sugars that are assumed to enhance longevity and/or fecundity. Here we conducted an experiment exploring the effects of naturally occurring sugars on longevity and fecundity in the solitary hyperparasitoids, Lysibia nana and Gelis agilis. Although both species are closely related, L. nana does not host-feed whereas G. agilis does. In a separate experiment, we compared reproduction and longevity in G. agilis reared on either honey, a honey-sugar 'mimic', and glucose. Reproductive success and longevity in both hyperparasitoids varied significantly when fed on different sugars. However, only mannose- and water-fed wasps performed significantly more poorly than wasps fed on four other sugar types. G. agilis females fed honey produced twice as many progeny as those reared on the honey-sugar mimic or on glucose, whereas female longevity was only reduced on the mimic mixture. This result shows not only that host feeding influences reproductive success in G. agilis, but also that non-sugar constituents in honey do. The importance of non-sugar nutrients in honey on parasitoid reproduction is discussed.     

Effect of Maruca vitrata (Lepidoptera: Crambidae) host plants on life‐history parameters of the parasitoid Apanteles taragamae (Hymenoptera: Braconidae)

Abstract The effect of four host plant species of the herbivore Maruca vitrata Fabricius (Lepidoptera: Crambidae) on development time, longevity, fecundity and sex ratio of the parasitoid Apanteles taragamae Viereck (Hymenoptera: Braconidae) was investigated under laboratory conditions. The larvae were parasitized when in the second instar. Maruca vitrata larvae were fed with flowers of four legumes, that is, Vigna unguiculata (cowpea), Sesbania rostrata, Lonchocarpus sericeus and Pterocarpus santalinoides, or an artificial diet both before and after parasitization. The parasitoid did not develop in hosts feeding on L. sericeus or V. unguiculata at 25°C, or on P. santalinoides at 25°C or 29°C. Apanteles taragamae had the shortest development time on artificial diet at both 25°C and 29°C while the longest development time was recorded on L. sericeus at 29°C. Female wasps took longer to develop compared to males at the two temperatures, regardless of the feeding substrate of their host. The longevity of the wasps at 25°C varied among feeding substrates, but not at 29°C. Survival rate of parasitized larvae depends on the feeding substrate. Moreover, infection of host larvae with Maruca vitrata multi‐nucleopolyhedrovirus (MaviMNPV) killed larger proportions of parasitized larvae at 25°C than at 29°C, which was likely caused by the difference in parasitoid developmental rate. The proportion of female parasitoids was lowest on L. sericeus. The daily fecundity showed a nonlinear trend regardless of the feeding substrate, indicating that A. taragamae is a pro‐ovigenic species. The data support the slow growth–high mortality hypothesis.     

Effects of a lipid-rich diet on adult parasitoid income resources and survival

Effectiveness of parasitoids as natural enemies in agro-ecosystems depends on key traits such as fecundity and longevity. Energy sources allocated into survival and reproduction can be mobilized from capital stores acquired during larval feeding, or from income resources through adult feeding. Adult parasitoids have a restricted diet consisting solely of carbohydrates and most species do not replenish lipid levels after emergence from their host. Here, we have adopted a novel approach that could improve pest elimination by parasitoids, in which we added different ratios of olive oil to the food of adults to reveal the potential of a lipid-rich diet to increase lipid levels and allocation into survival. Our results show that males of the parasitoid Cotesia glomerata had higher lipid levels when fed a diet containing a ratio of 90:10% honey to olive oil when compared to males at emergence and males fed honey-only. For females, lipid levels at emergence were similar to those of females fed a diet supplemented with a ratio of 75:25% honey to olive oil, yet in both of these treatments lipid levels were significantly higher when compared to females fed honey-only. This suggests that females on a lipid-containing diet economized on their lipid use. In contrast, the survival of males and females was negatively affected by the addition of olive oil and no differences in survival were found when wasps were fed 1 day on various ratios of honey to olive oil compared to honey-only. Our results show that the addition of a lipid source can increase or maintain nutrient availability and further research into lipid supplementation could minimize detrimental effects in order to increase the effectiveness of parasitoids in certain agro-ecosystems.     

Differential effects of flower feeding in an insect host–parasitoid system

In many insect host–parasitoid systems, both the host and its parasitoids forage on shared floral resources. As a result of insect behaviour, morphology and physiology, flower species may act selectively at different levels of such systems, e.g., between the trophic levels of hosts and parasitoids, between species within a guild, between sexes or individuals within a species or between life history traits within an individual. We asked if effects of selectivity are consistent across levels in the horse chestnut leafminer, Cameraria ohridella, and its parasitoid complex. Insects were exposed singly in no-choice feeding trials to twelve common flower species and their survival and reproduction were recorded. Only one of twelve flower species (Ranunculus acris) tended to selectively favour the longevity of leafminers, but not of parasitoids. No flower species were found to favour parasitoids only. Both trophic levels profited from feeding on Anthriscus sylvestris, however, parasitoids benefited up to eight times more than their hosts. No differences were found among the species of the parasitoid guild, but females lived significantly longer than males, and single individuals within species were able to exploit generally unfavourable flower species. Out of the seven flower species that increased the longevity of leafminer females, only Chaerophyllum hirsutum significantly enhanced the number of eggs laid. Fecundity was generally positively correlated with longevity of leafminer females, but two flower species (C. hirsutum, Taraxacum officinale) had an additional positive effect on fecundity. In conclusion, we demonstrated that flowers act differently on life history traits in a host–parasitoid system at a multitude of biological levels and that these effects are not always consistent across levels. Selective plant-derived resources can therefore modify herbivore–natural enemy interactions in ways that are more complex than currently appreciated.     

Sex differences in movement between natural feeding and mating sites and tradeoffs between food consumption,mating success and predator evasion in Mediterranean fruit flies (Diptera: Tephritidae)

Summary Systematic quantitative observations of the location and diel pattern of adult Mediterranean fruit fly, Ceratitis capitata (Wiedemann), activities were carried out in an orange grove and surroundings on the island of Chios in Greece. Natural fly foods were assessed for their contribution to fly longevity, fecundity and fertility. There were diel shifts in male and female location. Females required a substantial and varied diet to realize peak fecundity. This diet was acquired away from the primary host, orange. Foraging for food throughout most of the day on fig and non-host foliage (including feeding on bird droppings) as well as on fig fruit and grapes, females dispersed and fed more than males. A diet of grapes alone did not support any fecundity, contributing only to longevity. A diet of figs alone, on the other hand, sustained both longevity and egg production. Bird feces alone supported neither egg production nor longevity. However, when added to a diet of figs, bird feces significantly increased fly fecundity. Throughout most of the day, males aggregated in leks within the inner canopy of the primary host, orange. The arrival here during the warmest hours of the day of receptive females, followed by pair formation, reinforced the lek mating system on host foliage. In the afternoon, females shifted to orange fruit where they suffered from high predation mortality while ovipositing. Soon after, males also shifted to orange fruit, where they attempted matings with non-receptive ovipositing females. Male feeding on fig fruit occurred late in the day, a time when they were least likely to find a mate. Male survival did not differ between the natural diets. Tradeoffs between food consumption, mating success and predator evasion are discussed for each sex and related to fruit fly mating systems.     

Effect of adult feeding and timing of host exposure on the fertility and longevity of the parasitoid Anaphes flavipes

The parasitoid Anaphes flavipes (Foerster) (Hymenoptera: Mymaridae) is a gregarious egg parasitoid which is widely used in biological control against important crop pest beetles of the genus Oulema (Coleoptera: Chrysomelidae). Here, we present the first experimental examination of the influence of adult feeding and timing of host exposure on the longevity and fertility of this parasitoid. We confirmed a positive effect of adult feeding on longevity of both sexes. Fed parasitoids lived 3× longer than unfed ones. On the other hand, adult feeding and feeding time had no effect on female fertility. The number of hatched offspring was not increased by adult feeding, which suggests that the parasitoid emerges with already mature ovaries (proovigenic type). However, the fertility of fed females was strongly influenced by the timing of host egg exposure. By providing distinct groups of parasitoids with host eggs at different times, we were able to show lower fertility of fed females that had been offered host eggs more than 24 h after hatching. Our results thus show that the parasitoid's fertility is determined by her age at the time of parasitization rather than by feeding.     

The reproductive strategy of the gregarious parasitoid,Pteromalus puparum (Hymenoptera: Pteromalidae)

Summary Pteromalus puparum is a gregarious parasitoid of many butterfly pupae. Adult size, mortality, and sex ratio of P. puparum, as a parasitoid of Papilio xuthus, were unit weight of the host. Effects of female size on fecundity, wing load, and longevity were also examined.The highest total weight of progeny from the host was attained when the number of eggs per gram of the host was approximately 150. Positive correlations were observed between the size of the females and their fecundity and wing load. The maximum longevity of the female kept with honey but without hosts was attained when the initial number of parasitoids per g of the host was 150.Considering the total fecundity of all female progeny, the reproductively most efficient number of eggs to be deposited per g of the host was estimated to be approximately 300. However, as shortage of food for the adult females strongly affects their fecundity, the reproductively most efficient number of eggs to be deposited per g of the host was about 70 when the adult female progeny was not provided with food.The optimal number of eggs to be deposited when the emale oviposits in the host under field conditions is discussed.     

成虫取食对棉铃虫雌蛾繁殖的影响

试验对雌蛾设置５个食物处理,定量地研究了成虫取食对棉铃虫蛾繁殖和寿命的影响,成虫取食对雌蛾与寿命和主效量均显著影响,补充营养延长雌蛾寿命,提高产卵量,并且」补充营养对产卵量的影响比其对寿命的影响更大,分析表明被营养的作用在于提高雌蛾后期的存活率和产卵量,前期补充营养比后期补充营养具有更大的作用。雌雌全重及其蝮部干重受成廊和的自龄的双重影响,补充营养时雌蛾体重、腹部干重及其脂肪含量下降慢,补充营养可     

Altitudinal and environmental variation in lifespan in the Copper butterfly Lycaena tityrus

1.  Variation in longevity within and between natural populations is widespread, and understanding the relative importance of environmental and genetic factors as well as their interactions in mediating such variation is crucial in longevity research.
2.  In this study lifespan of adult copper butterflies was examined in relation to altitude, temperature (20 and 27 °C), sex and adult feeding.
3.  As expected, longevity increased with decreasing temperature, and sucrose-fed butterflies had longer lifespans compared to water-fed and finally non-fed individuals. The impact of feeding, especially of having access to water or not, was larger at the higher compared to the lower temperature.
4.  Regarding altitudinal patterns, increased lifespan in high-altitude populations was largely restricted to beneficial feeding conditions, while under carbohydrate deprivation low-altitude animals lived longer, suggesting that low-altitude butterflies do better under food stress.
5.  Differences in longevity between sexes were small at 20 °C, while females lived substantially longer than males at the higher temperature. Consequently, females may be less susceptible to high temperature stress than males. Further, males suffered more from food stress than females, suggesting that females are generally more stress resistant than males.
6.  Using a full factorial design, this study demonstrates that variation in longevity is caused by several factors, and additionally by substantial interactive effects. Consequently, patterns of variation in longevity are complex, and one needs to be cautious when neglecting this source of variation, by focussing on individual factors only.     

Honeydew feeding increased the longevity of two egg parasitoids of the pine processionary moth

The longevity of a generalist (Ooencyrtus pityocampae) and a specialist (Baryscapus servadeii) egg parasitoid of the pine processionary moth (Thau‐metopoea pityocampa) was compared under laboratory feeding conditions including water and honeydew from aphid species growing on maritime pine (Pinus pinaster) or pedunculate oak (Quercus robur). The longevity of both parasitoid species increased when specimens were fed with honeydew. This increase was larger for the generalist (3.7, 32.0 and 38.0 days) than for the specialist (3.0, 23.3 and 21.5 days) parasitoid species when fed with water, oak and pine aphid honeydew respectively. The phenology of the specialist species B. servadeii is well‐adapted with its host availability with or without food supply. The generalist species O. pityocampae could overlap its host emergence curve during 14.0–20.0 days when fed with oak and pine aphid honeydew respectively, vs. no overlap when no supplementary food was provided. Analysis of honeydew composition indicated that sugars and amino acids may have distinct effects on parasitoid longevity.     

Effect of Mating Frequency on Female Fitness in Caloglyphus Berlesei (Astigmata: Acaridae)

We studied the effect of mating frequency on female longevity and fecundity in the mite Caloglyphus berlesei. We tested the hypothesis that high promiscuity is selected for in this species because females receive nutrients during copulation. Females were constantly exposed to either one or four males and fed either a standard or poor diet. The prediction that frequent mating benefits females was not confirmed. On the contrary, females kept with four males had significantly lower longevity on both diets and on the standard diet they also had decreased fecundity compared to females exposed to one male. On the poor diet the number of males had no significant effect on fecundity. Thus, increased mating frequency had a detrimental effect on female fitness.     

MATING FREQUENCY AND FECUNDITY IN INSECTS

1. The paper summarizes the published evidence on the relation between mating frequency and fecundity in insects. There is experimental evidence of varying quality for 63 species and non-experimental evidence for about 60.
2. Repeated mating may be universally necessary for full fecundity and fertility in female insects (in species in which the females normally mate more than once).
3. The evidence is remarkably poor. We need more properly designed experiments (and not just observations of natural variation), with sufficient sample sizes and statistics, and measurements of the fecundities and fertilities of singly and multiply mated females, when the multiple matings are separated by many days or weeks. Most of the existing experiments of this sort are defective in some way.
4. In species with greater total fecundity and longevity, multiple mating may be more likely to enhance fertility than in species with small fecundity and short life span.
5. Females in naturally monandrous species do not show increased fecundity or fertility with repeated mating, whereas females of polyandrous species do.
6. There is no obvious connexion between paternal investment, in so far as we know about it, and the increase of fecundity by repeated mating.
7. There is a small tendency for females to breed more quickly and be shorter lived if they mate repeatedly.     

Life-history strategy in an oligophagous tephritid: the tomato fruit fly, Neoceratitis cyanescens

Abstract.  1. In phytophagous insects, life-history traits mainly depend on host plant range. Substantial longevity, high fecundity and larval competition are the major traits of polyphagous Tephritidae while species with a restricted host range generally exhibit a lower longevity and fecundity as well as mechanisms to avoid larval competition. Our aim in this study was to investigate the life history of an oligophagous species, the tomato fruit fly, Neoceratitis cyanescens (Bezzi).
2. We determined life tables under laboratory conditions in order to calculate the main demographic parameters of N. cyanescens and studied the influence of larval and adult diet on life-history traits.
3. The mean longevity of N. cyanescens females was 40 days. There was a strong synchronisation of female maturity. Oviposition showed an early peak at 9–13 days after a short pre-oviposition period (6 days). The absence of proteins in the adult diet both delayed ovarian maturation and decreased female fecundity. In addition, females originating from tomato fruits produced significantly more eggs than females originating from bugweed or black nightshade, showing that even the larval host plant may strongly affect the subsequent fecundity of adult females.
4. The traits of N. cyanescens are then discussed in the light of those documented for polyphagous and monophagous tephritids. Neoceratitis cyanescens displayed attributes intermediate between those of polyphagous and monophagous tephritids. Its smaller clutch size compared with polyphagous species and its specialisation on the Solanaceae family whose fruits contain toxic compounds may help in reducing intra- and inter-specific competition, respectively.     

Effects of eugregarine parasites on adult longevity in the polymorphic damselfly Mnais costalis Selys

Abstract.  1. The relationship between the abundance of midgut parasites (eugregarine trophozooites) and the survival of hosts (field-collected damselflies, Mnais costalis ) was investigated under laboratory conditions.
2. Males of M. costalis are morphologically and behaviourally polymorphic, typically existing as clear-winged non-territorial sneaks and orange-winged territorial fighters (the latter are larger in size). The survival cost of eugregarine infection for the two morphs was compared.
3. Orange-winged males showed shorter longevity compared to clear-winged males when they were fed at levels lower than the natural feeding rate, or when they were deprived of food. In contrast, morph longevity did not differ when they were fed until satiation every day.
4. Within each morph, the survival of damselflies was negatively correlated with the parasite abundance except when damselflies were fed until satiation.
5. The results suggest that the abundance of eugregarine parasites exerts a substantial cost, which is associated with the maintenance of alternative mating strategies, together with the higher developmental cost and energy expenditure of the fighter morph.