Brood rearing costs affect future reproduction in the precocial common goldeneye Bucephala clangula

Life-history theory assumes a trade-off between current reproductive effort and future reproductive success. There are a large number of studies demonstrating reproductive trade-offs in different animal taxa, particularly in birds. Most bird studies have focused on the costs of chick rearing in altricial species. These costs have been assumed to be low in precocial species, but this aspect has been little studied. We used long-term individual reproductive data from the common goldeneye Bucephala clangula , an iteroparous precocial duck with uniparental female care, to examine whether brood rearing carries costs that affect future reproductive performance. All females were experienced breeders, and possible differences in female quality were ruled out. We compared within-individual (between-year) changes in clutch size, hatching date and body mass between females that had reared a brood in the previous year and females that had not. It turned out that brood rearing involved a cost in terms of clutch size and hatching date the next year, but not in terms of body mass: females that had reared a brood in the previous year laid relatively smaller clutches and laid relatively later than females that had not reared a brood. Our results show that normal brood rearing in a precocial species involves costs that affect future reproduction.     

Performance of Amblyseius herbicolus on broad mites and on castor bean and sunnhemp pollen

Amblyseius herbicolus (Banks) is found associated with broad mites Polyphagotarsonemus latus in crops such as chili pepper in Brazil. The species has a potential for controlling P. latus, but little is known about its development and reproduction on this pest as well as on other food sources. We studied biological, reproductive and life table parameters of A. herbicolus on three different diets: broad mites, castor bean pollen (Ricinus communis) and sunnhemp pollen (Crotalaria juncea). The predator was able to develop and reproduce on all diets. However, its intrinsic growth rate was higher on the diet of broad mites or on castor bean pollen than on sunnhemp pollen. Differences among pollen species may be due to their nutritional content. Feeding on alternative food such as pollen can facilitate the predator’s mass rearing and maintain its population on crops when prey is absent or scarce. Other strategies of using pollen to sustain predator population and reduce pest damage are discussed.     

Continuous rearing of the predatory anthocorid Orius laevigatus without plant materials

The omnivorous anthocorid predator Orius laevigatus is an economically important biological control agent of several small arthropod pests including the western flower thrips Frankliniella occidentalis. Mass rearing systems for Orius bugs typically make use of plant materials such as bean pods as an oviposition substrate and moisture source. Omission of plant materials from the mass rearing system of these beneficial arthropods could drastically improve the cost‐effectiveness of their production and thus stimulate their use in augmentative biological control. This study investigated the effect of a plantless rearing system, using wax paper as a walking substrate, water encapsulated in Parafilm domes, and an artificial oviposition substrate made of Parafilm and moist cotton wool, on the developmental and reproductive fitness of O. laevigatus. Plantless rearing during four generations resulted in females with an 11% lower body weight and a pre‐oviposition period that was prolonged by 29%. However, other biological parameters were not negatively affected by the absence of plants. In addition, plantless‐reared females had similar predation rates on F. occidentalis larvae as their peers maintained on plants. Our study indicates that the omission of plant material from the production cycle of O. laevigatus is possible when Ephestia kuehniella eggs are provided as a nutritionally optimal food source.     

Development and reproduction of Geocoris varius (Hemiptera: Geocoridae) on two types of artificial diet

Biological control using the polyphagous predator big-eyed bug Geocoris varius (Uhler) (Hemiptera: Geocoridae) is currently being investigated in Japan. However, the production costs of G. varius are relatively high because the eggs of Ephestia kuehniella Zeller (Lepidoptera; Pyralidae) are used as the major food source for mass rearing. Development time and reproductive fitness were therefore examined for G. varius fed two types of artificial diet based on liver and ground pork. The diets were administered either by wrapping in Parafilm^® or by presenting the food in lyophilized form. The results were compared with those obtained by rearing G. varius on E. kuehniella eggs. Although development time of Geocoris varius fed the artificial diets was significantly delayed compared with G. varius fed on E. kuehniella eggs, delays are slight and not serious for mass rearing projects. The findings suggested that both artificial diets could be used to reduce the costs associated with mass rearing of G. varius.     

Carcass analysis to improve a meat-based diet for the artificial rearing of the predatory mirid bug Dicyphus tamaninii

Improvement of an existing meat-based diet has been obtained for rearing the generalist predator Dicyphus tamaninii (Heteroptera: Miridae). The approach followed, different from the classical addition/deletion method, was performing biochemical analysis of adult carcasses in order to have information about the nutritional status of the predator. Comparison of total, free amino acids and lipid composition of meat-reared and conventionally reared females allowed detecting some nutritional deficiencies. A reformulated diet with new sources of proteins and lipids was tested again with the predator. Some biological parameters of bugs that were inferior in the initial meat diet when compared with those of the conventionally reared insects, such as nymphal development time and fresh weight, have been improved with the reformulated diet.     

A semi-artificial rearing system for the specialist predatory ladybird Cryptolaemus montrouzieri

In the present study a semi-artificial rearing system for the Australian ladybird Cryptolaemus montrouzieri Mulsant (Coleoptera: Coccinellidae), a specialist predator of mealybugs, was developed. In a first step, a rearing system using eggs of the Mediterranean flour moth Ephestia kuehniella Zeller (Lepidoptera: Pyralidae) as a food and synthetic polyester wadding as an oviposition substrate was compared with a natural rearing system using the citrus mealybug, Planococcus citri (Risso) (Hemiptera: Pseudococcidae), as to its effects on the predator’s developmental and reproductive parameters. In a second series of experiments the performance of C. montrouzieri on bee pollen or on a mixture of E. kuehniella eggs and bee pollen was assessed. E. kuehniella eggs proved to be a suitable food to support larval development of the predator. Ladybird larvae reared on flour moth eggs developed two days faster and weighed approximately 10 % more than their counterparts reared on mealybugs. Despite a prolongation of the preoviposition period with ca. eight days and a decrease in egg hatch by about 10 %, C. montrouzieri females fed moth eggs accepted the synthetic wadding as an oviposition substrate and deposited the same number of eggs their counterparts maintained on mealybugs. A mixture of E. kuehniella eggs with pollen yielded similar developmental and reproductive rates as E. kuehniella eggs alone, but a diet of bee pollen alone was not adequate for the predator. Our findings indicate the potential of a rearing system using E. kuehniella eggs as a factitious food and synthetic wadding as an artificial oviposition substrate for the mass production of C. montrouzieri.     

Oviposition pattern of the predator Podisus nigrispinus (Heteroptera: Pentatomidae) under different temperatures

The daily reproductive rate of Podisus nigrispinus (Dallas) (Heteroptera: Pentatomidae) fed with Alabama argillacea (Hübner) (Lepidoptera: Noctuidae) larvae was studied at constant temperatures of 20, 23, 25, 28, 30 and 33±0.2°C, relative humidity of 60±10% and photoperiod of L:D 14:10. Daily reproductive rate of P. nigripinus was affected by age of this predator. Each P. nigrispinus female laid 5.3 (20°C) to 19.9 eggs/day (28°C) which developed into 4.3–16.5 nymphs, respectively. Highest daily reproductive rate of P. nigrispinus was recorded at 28 and 30°C for 5–30-day-old females. This predator showed higher daily reproductive rate than its prey A. argillacea at 25°C. It was also able to reproduce at temperatures from 20 to 33°C with maximum daily reproductive rate between 25 and 30°C. These results are important for optimizing mass rearing of P. nigrispinus in the laboratory.     

Plantless rearing of the zoophytophagous bug Nesidiocoris tenuis

Nesidiocoris tenuis Reuter (Heteroptera: Miridae) is widely distributed in the Mediterranean area, where it is used as an augmentative biological control agent of several pests. This zoophytophagous predator maintains a close relationship with its host plants using them not only to feed on, but also as an oviposition substrate. In the present study, a plantless rearing system was developed and developmental and reproductive parameters of bugs that had no access to plant material were compared with their counterparts living on plants. Eggs deposited in an artificial substrate took longer to develop and had lower hatching rates than those laid in tomato leaves. However, the biological parameters of nymphs that had hatched from the artificial substrate did not differ from those of nymphs that had emerged from plants, suggesting that, besides water, no essential nutrients are absorbed from the oviposition substrate during embryogenesis. Our results regarding the role of plant feeding indicate that water acquisition is the critical function of phytophagy in N. tenuis. In addition, supplementary nutrients derived from plants had a positive effect on adult weight and significantly enhanced survival in the absence of prey. Plantless rearing for five generations led to a prolonged preoviposition period and lower egg hatching rates and adult weights, but other developmental and reproductive parameters were not adversely affected. Our experiments suggest that prolonged plantless rearing of N. tenuis is possible provided that the mirid has access to a nutritionally superior food like Ephestia kuehniella eggs.     

Harmonia axyridis: an environmental risk assessment for Northwest Europe

In this paper, we summarize the international situation with respect to environmental risk assessment for biological control agents. Next, we apply a recently designed, comprehensive risk evaluation method consisting of a stepwise procedure to evaluate the environmental risks of Harmonia axyridis in Northwest Europe. This resulted in the very clear conclusion that H. axyridis is a potentially risky species for Northwest Europe, because it is able to establish, it has a very wide host range including species from other insect orders and even beyond the class of Insecta, it may feed on plant materials, it can cover large distances (>50 km per year), it does move into non-target areas, it may attack many non-target species including beneficial insects and insects of conservation concern, its activities have resulted in the reduction of populations of native predators in North America, it is known as a nuisance in North America and recently also in Northwest Europe, and it may develop as a pest of fruit in North America. Considering the H. axyridis case, current knowledge would lead to the conclusion that, although the predator is capable to effectively control several pest species, its risks are manifold and it should, thus, not have been released in Northwest Europe. At the time of the first releases in Nortwest Europe in 1995, the available scientific literature made clear that H. axyridis is a large sized polyphagous predator and has a great reproductive capacity in comparison with other ladybird beetles, and that there was a need to study non-target effects because of its polyphagous behaviour. In retrospect, this information should have been sufficient to reject import and release of this species, but it was apparently ignored by those who considered release of this predator in Northwest Europe. The case of Harmonia releases in Northwest Europe underlines that there is an urgent need for harmonized, world-wide regulation of biological control agents, including an information system on risky natural enemy species.     

Nutritional value of brine shrimp cysts as a factitious food for Orius laevigatus (Heteroptera: Anthocoridae)

Decapsulated cysts of the brine shrimp Artemia franciscana were assessed as a factitious food for rearing the anthocorid predator Orius laevigatus. Developmental and reproductive traits of O. laevigatus reared for a single generation on A. franciscana from three geographical locations or on gamma-irradiated eggs of the Mediterranean flour moth Ephestia kuehniella were compared. There was no effect of diet on nymphal survival but nymphal period on E. kuehniella eggs (12.2 days) was 0.7-1.6 days shorter than on the Artemia diets. The predator developed 0.5-1 day faster on cysts from San Francisco Bay (USA) than on cysts from Great Salt Lake (USA) or Macau (Brazil). Fecundity on brine shrimp cysts from different locations was similar to that on flour moth eggs (142-187 eggs/female). The biochemical composition of decapsulated cysts from San Francisco Bay was compared with that of E. kuehniella eggs. Depending on the type of analysis, Artemia cysts contained higher or similar amounts of protein as compared with E. kuehniella eggs, but amino acid patterns were generally similar. Flour moth eggs were almost three times richer in fatty acids than brine shrimp cysts, with some marked differences in fatty acid profiles. Because nutrient imbalances in a diet may be expressed only after several generations of rearing, the predator was cultured for three consecutive generations on A. franciscana cysts from San Francisco Bay. In the third generation on brine shrimp cysts, nymphs took 18% longer to develop, and adults were shorted-lived and about 60% less fecund than those maintained on E. kuehniella eggs. Brine shrimp cysts may be used as a supplement in the mass production of O. laevigatus but may not be a suitable food for long-term culturing of the predator.     

Sex‐specific mass loss in chick‐rearing South Polar Skuas Stercorarius maccormicki– stress induced or adaptive?

Mass loss of chick‐rearing birds can be the direct consequence of physiological stress (reproductive stress hypothesis) or an adaptive mass adjustment in response to the increased demands on flight efficiency during the flight‐intensive chick‐rearing period (adaptive mass loss hypothesis). To test which of these hypotheses best explains mass loss in South Polar Skuas Stercorarius maccormicki rearing chicks, a food supplementation experiment was carried out in the austral summer 2000/01 at King George Island, Antarctica. Half of the breeding pairs were fed about 20% of the chick's daily energy demand every second day and chick growth and adult nest attendance were recorded. Parents were caught at the start and the end of chick‐rearing to calculate adult mass loss. Male parents of food‐supplemented pairs attended their nest territories more than control males but females kept their attendance constant. Chick growth was only minimally affected and the treatment probably had no fitness consequences. Male Skuas in control pairs had a higher deviation from the body size–mass regression at the end of chick‐rearing compared with the start, supporting the stress hypothesis, whereas female deviation remained unchanged. Males of food‐supplemented pairs were heavier than unsupplemented males at the end of the breeding cycle but not significantly so. Food‐supplemented females were lighter at the end, supporting the adaptive mass loss hypothesis. Adult mass loss is thus best explained by the reproductive stress hypothesis in males but by the adaptive mass loss hypothesis in females. However, the two hypotheses are not mutually exclusive and the results do not exclude the possibility that mass loss in females is stress‐induced but the amount of mass lost is an adaptive adjustment to the reliability of the food supply. The finding that members of a breeding pair may follow different strategies of mass adjustment has implications for the use of mass loss as an index of parental effort. Without knowing which strategy each sex has adopted it is of little use to compare mass loss between parents.     

Mass‐rearing conditions do not affect responsiveness to sex pheromone and flight activity in sweetpotato weevils

For ensuring the effectiveness of sterile insect technique (SIT) programmes, maintaining the reproductive competitiveness and dispersal ability of mass‐reared sterile males is essential. Inadvertent selection is an important genetic process that frequently occurs during mass rearing to produce sterile males. We investigated the effect of mass‐rearing conditions on the responsiveness to sex pheromones and spontaneous flight activity of males of the sweetpotato weevil Cylas formicarius (Coleoptera: Brentidae). There were no significant differences in the responsiveness to sex pheromones and spontaneous flight activity between wild and mass‐reared strains. These results indicate that mass‐reared strains of C. formicarius might not cause serious problems for implementing SIT programmes.     

The acoustic structure of suricates'' alarm calls varies with predator type and the level of response urgency.

The variation in the acoustic structure of alarm calls appears to convey information about the level of response urgency in some species, while in others it seems to denote the type of predator. While theoretical models and studies on species with functionally referential calls have emphasized that any animal signal considered to have an external referent also includes motivational content, to our knowledge, no empirical study has been able to show this. In this paper, I present an example of a graded alarm call system that combines referential information and also information on the level of urgency. Acoustically different alarm calls in the social mongoose Suricata suricatta are given in response to different predator types, but their call structure also varies depending on the level of urgency. Low urgency calls tend to be harmonic across all predator types, while high urgency calls are noisier. There was less evidence for consistency in the acoustic parameters assigned to particular predator types across different levels of urgency. This suggests that, while suricates convey information about the level of urgency along a general rule, the referential information about each category of predator type is not encoded in an obvious way.     

A theoretical investigation of the effect of predators on foraging behaviour and energy reserves

Data show that when small birds are exposed to a model of a predator, their body mass may either increase or decrease. Although attempts have been made to explain the data using previous models, these models are based on a constant level of predation and hence are not appropriate for making predictions about the response of a bird to the sight of a predator. We have developed a novel model that includes encounters between a bird and potential predators. We show that, depending on the biology of the predator, optimal body mass may either increase or decrease. The model also makes predictions about the foraging behaviour of the bird after it has seen a predator.     

The Contribution of Extrafloral Nectar to Survival and Reproduction of the Predatory Mite Iphiseius Degenerans on Ricinus Communis

The phytoseiid mite Iphiseius degenerans (Berlese) is an effective predator of western flower thrips, Frankliniella occidentalis (Pergande), in Dutch greenhouses. In the Mediterranean area, castor bean, Ricinus communis L., is known as a year-round host plant for this predatory mite. On flowering castor bean plants in greenhouses, I. degenerans can be found in densities of more than 100 per leaf. For this reason, the plant is being used as a banker plant to augment biological control. It has been shown that pollen produced by the large apical flowers sustains reproduction and development for these mites. The objective of this study was to measure the contribution of the extrafloral nectar of this plant to the reproductive success of this predatory mite. A study conducted at 25°C in presence of free water showed that (1) I. degenerans is unable to develop beyond the protonymphal stage when fed only nectar and leaf tissue, (2) its ovipositional rate is higher when pollen is supplemented with nectar, (3) its reproduction ceases within a few days when fed on nectar only, but the predator can survive for several weeks and resume oviposition when fed pollen again and (4) the feeding of young females for one or two weeks with nectar only extends their longevity by approximately the same period and only slightly diminishes their lifetime reproductive potential (R0), as compared to mites continuously fed pollen. It can be concluded that extrafloral nectar can provide an important contribution to population growth and maintenance of I. degenerans on R. communis, particularly in pre- and post-blooming periods. Assuming these predators are beneficial to the plant in clearing them of herbivorous mites and thrips, this relationship may be regarded as an example of plant–predator mutualism. The combination of pollen and extrafloral nectar makes castor bean an ideal rearing and banker plant for I. degenerans.     

Fishing top predators indirectly affects condition and reproduction in a reef-fish community

To examine the indirect effects of fishing on energy allocation in non-target prey species, condition and reproductive potential were measured for five representative species (two-spot red snapper Lutjanus bohar, arc-eye hawkfish Paracirrhites arcatus, blackbar devil Plectroglyphidodon dickii, bicolour chromis Chromis margaritifer and whitecheek surgeonfish Acanthurus nigricans) from three reef-fish communities with different levels of fishing and predator abundance in the northern Line Islands, central Pacific Ocean. Predator abundance differed by five to seven-fold among islands, and despite no clear differences in prey abundance, differences in prey condition and reproductive potential among islands were found. Body condition (mean body mass adjusted for length) was consistently lower at sites with higher predator abundance for three of the four prey species. Mean liver mass (adjusted for total body mass), an indicator of energy reserves, was also lower at sites with higher predator abundance for three of the prey species and the predator. Trends in reproductive potential were less clear. Mean gonad mass (adjusted for total body mass) was high where predator abundance was high for only one of the three species in which it was measured. Evidence of consistently low prey body condition and energy reserves in a diverse suite of species at reefs with high predator abundance suggests that fishing may indirectly affect non-target prey-fish populations through changes in predation and predation risk.     

What is an apex predator?

Large ‘apex’ predators influence ecosystems in profound ways, by limiting the density of their prey and controlling smaller ‘mesopredators’. The loss of apex predators from much of their range has lead to a global outbreak of mesopredators, a process known as ‘mesopredator release’ that increases predation pressure and diminishes biodiversity. While the classifications apex‐ and meso‐predator are fundamental to current ecological thinking, their definition has remained ambiguous. Trophic cascades theory has shown the importance of predation as a limit to population size for a variety of taxa (top–down control). The largest of predators however are unlikely to be limited in this fashion, and their densities are commonly assumed to be determined by the availability of their prey (bottom–up control). However, bottom–up regulation of apex predators is contradicted by many studies, particularly of non‐hunted populations. We offer an alternative view that apex predators are distinguishable by a capacity to limit their own population densities (self‐regulation). We tested this idea using a set of life‐history traits that could contribute to self‐regulation in the Carnivora, and found that an upper limit body mass of 34 kg (corresponding with an average mass of 13–16 kg) marks a transition between extrinsically‐ and self‐regulated carnivores. Small carnivores share fast reproductive rates and development and higher densities. Large carnivores share slow reproductive rates and development, extended parental care, sparsely populated territories, and a propensity towards infanticide, reproductive suppression, alloparental care and cooperative hunting. We discuss how the expression of traits that contribute to self‐regulation (e.g. reproductive suppression) depends on social stability, and highlight the importance of studying predator–prey dynamics in the absence of predator persecution. Self‐regulation in large carnivores may ensure that the largest and the fiercest do not overexploit their resources.     

重大外来入侵害虫——美国白蛾生物防治技术研究

美国白蛾Hyphantria cunea(Drury)是重大外来入侵害虫,对我国林业和园林绿化造成重大危害,尤其是近年来美国白蛾传入北京,严重威胁着我国“绿色奥运”的顺利举办和首都园林绿化及生态环境安全。根据美国白蛾多发生在居民区、乡镇和城市的特点,作者开展对环境安全的生物防治技术研究。汲取前苏联等国家从美国白蛾的原产地引进天敌进行生物防治没有成功的经验和教训,立足调查和寻找我国本土天敌。经过21年的努力,发现和筛选出白蛾周氏啮小蜂Chouioia cunea Yang(新属新种)这种寄生美国白蛾的特优天敌;研究这种小蜂的行为学、生态学、生物学、解剖学及人工大量繁殖、放蜂防治技术;筛选出人工大量繁殖小蜂的替代寄主,解决小蜂的大量繁殖的瓶颈问题;通过放蜂防治试验,取得良好的防治效果。同时,筛选出防治美国白蛾的高毒力HcNPV病毒毒株,研制出美国白蛾人工饲料,利用人工饲料大量饲养美国白蛾幼虫,然后接种扩增病毒,成功解决HcNPV病毒大量扩增生产和常年生产的技术难题,做到病毒的规模化生产和常年生产,保证大面积生产防治的需要和病毒质量。研究出利用天敌昆虫和病原微生物综合应用的防治模式:在美国白蛾幼虫期喷洒HcNPV病毒,蛹期释放白蛾周氏啮小蜂,达到既控制当代美国白蛾的危害,又有效抑制其下代的种群数量,取得长期的持续控制美国白蛾的防治效果。上海市、大连市、烟台市和青岛市利用该项技术已经完全控制美国白蛾,特别是上海市利用本项生物防治技术防治后,已经连续6年没有再发现美国白蛾。由于该项生物防治技术利用的是自然界原有的控制害虫的生态因子,因而对环境安全,做到既消灭害虫,又保证生态环境和人畜的安全,也保护生物多样性。该项研究成果也为北京采用“绿色”防治技术有效控制美国白蛾提供重要的科技支撑和技术保障。     

Effect of mass rearing on the genetic diversity of the predatory mite Amblyseius swirskii

Amblyseius swirskii Athias‐Henriot (Acari: Phytoseiidae) is a predatory mite used to control whiteflies and thrips in protected crops. This biocontrol agent, originating from the Eastern Mediterranean region, has been mass‐reared for commercial use since 2005 and is widely used in augmentative biocontrol programs. As a polyphagous predator, it has to cope with different biotic and abiotic factors. However, possible adaptation to mass rearing for production might be hindering its resilience and capacity for optimum performance in the field. In this study, we investigated the effect of long‐term mass rearing on the genetic diversity of A. swirskii. We identified six microsatellite loci from whole‐genome nanopore sequencing of A. swirskii and used these in a comparative analysis of the genetic diversity and differentiation in eight wild populations collected from Israel in 2017 and a commercially available population. Our results indicate that the commercial population is 2.5× less heterozygous than the wild A. swirskii. Furthermore, the commercial population has the highest genetic differentiation from all the natural populations, as indicated by higher pairwise F_st values. Overall, we show that commercially reared A. swirskii have reduced genetic variation compared to their wild counterparts, which may reduce their performance when released to control pests in an integrated pest management (IPM) context.