繁育川硬皮肿腿蜂替代寄主的筛选

在室内用直接接蜂和药物麻醉寄主后接蜂的方法,对杉棕天牛Callidium villosulumFairmaire、粗鞘双条杉天牛Semanotus sinoauster Gressitt、苹眼天牛Bacchisa dioica (Fairmaire)、星天牛Anoplophora chinensis (Forster)、玉米螟Ostrinia furnacalis (Guenée)、大螟Sesamia inferens (Walker)、桃蛀螟Dichocrocispunctiferalis Guenée、鞭角华扁叶蜂Chinolyda flagellicornis（Smith）、家蝇Musca domestica vicina Macquart和黄粉甲Tenebrio molitor L. 等10种昆虫作为川硬皮肿腿蜂Scleroderma sichuanensis Xiao繁蜂替代寄主的适合性进行了系统的测试,比较了川硬皮肿腿蜂在不同供试寄主上的寄生率、出蜂率、发育历期、后代的雌性比率、寄生繁殖能力和冷藏对成蜂存活的影响。结果表明,不同寄主及寄主的不同处理间只有寄生率和出蜂率两项指标可能有显著差异,能反映繁蜂寄主的适合性。据此,从10种供试寄主中筛选出黄粉甲和玉米螟两种优良的繁蜂替代寄主,为该蜂的大规模繁殖及应用奠定了基础。     

管氏肿腿蜂对黄粉甲的寄生行为

在人工扩繁条件下观察管氏肿腿蜂Scleroderma guani对中间寄主黄粉甲Tenebrio molitor的寄生行为,其过程可分为：搜寻-识别-螯刺-清理和取食-产卵-护幼。雌蜂在寄生黄粉甲蛹时上蜂速度和螯刺率变异大,上蜂前时间为1.4～7.0天, 螯刺率为8.7%～91.7%,影响两者的因素包括： 雌蜂的交配状况、寄主状况及繁育温度等。蜂毒螯入寄主后可使其组织不腐烂而适于被寄生,被螯刺后的蛹可表现为 “保鲜”状态,平均“保鲜”时间为12.6天。蜂在蛹体的平均产卵量为30粒,最多为91粒。蜂卵在蛹体上分布合理,有利于幼虫有效利用寄主营养并避免拥挤和取食竞争。母蜂对幼虫期的发育具保护行为,包括护卵和保护幼虫正常发育并能搬运老熟幼虫集中结茧化蛹。     

Influence of larval experience on preference of a subterranean insect Delia antiqua on Allium hosts

Numerous studies have reported that larval experience can affect subsequent host plants selection and future oviposition decisions of many different species, but the investigation of pre‐imaginal experiences on host preference of adults has rarely been tested for soil‐dwelling insects. In this study, we present evidence that larval feeding experience can affect adult host preference in the onion maggot, Delia antiqua. By rearing D. antiqua on different host plants, we were able to examine the role of the natal host of different generations and the effect of larval density on host‐choice behaviour. We also performed bioassays by means of switched host treatment to evaluate the host‐selection principle. Choice bioassays among the three host species demonstrated that D. antiqua females preferred to oviposit on their natal host in each generation and host‐switching treatments. Additionally, increasing larval density could intensify this ovipositional preference on the natal host. The overall results showed that host preference of female D. antiqua is determined by larval experience and density. These findings also add support for the controversial Hopkins’ host‐selection principle.     

寄主体型大小对管氏肿腿蜂生殖潜力的影响

【目的】揭示寄主体型大小对肿腿蜂生殖潜力的影响,进一步认识寄生蜂准社会行为的进化以及为大规模繁殖和利用肿腿蜂的生物防治实践提供科学依据。【方法】以管氏肿腿蜂Sclerodermus guani和寄主青杨天牛Saperda populnea幼虫为材料,为雌蜂终身连续提供称重的寄主,观察逐日产卵量及在无抚育条件下其子代蜂发育至成虫的表现,分析产卵时期(早、中和晚期)、寄主体重对产卵量及其子代发育指标的影响。【结果】寄主体重和产卵期均影响管氏肿腿蜂终身产卵量,产卵量随寄主体重增大而呈二次函数式增大,但随产卵期延长而大幅减小。寄主体重和产卵期互作影响管氏肿腿蜂子代蜂存活率、岀蜂数、成虫体重和性比等子代发育指标,表现在:(1)产卵早期所产子代蜂的存活率随寄主体重增大而略降低,产卵中期所产子代蜂存活与寄主体重无关,产卵晚期所产子代蜂的存活率可能与寄主体重无关;(2)产卵早期和晚期产子代蜂的羽化成虫数和性比不受寄主体重的影响,但产卵中期产的子代蜂出蜂数随寄主体重增大而增加,性比随寄主体重增大而逐渐减小;(3)产卵早期产的子代雌蜂体重随寄主体重增大而呈二次函数式增大,而产卵中期产的子代蜂体重不受寄主体重的影响。【结论】寄主体型大小对管氏肿腿蜂早期产卵量及其子代蜂发育表现有显著影响。     

Choosy mothers pick challenging plants: maternal preference and larval performance of a specialist herbivore are not linked

1. Maternal preference is a dynamic process and interactions between preference and performance are fundamental for understanding evolutionary ecology and host association in insect–plant interactions. In the present study, the hypothesis of preference–performance was tested by offering solanaceous specialist Leptinotarsa decemlineata (Say) (Coleoptera: Chrysomelidae) larvae and adult females four plant congeners that ranged in suitability. 2. Larval feeding, development, oviposition, plant glycoalkaloids, and headspace volatiles in the four plant species were analysed to examine the extent of variation, which might explain performance–preference differences. 3. It was found that larval performance was mismatched with adult oviposition preferences. Adults laid more eggs on Solanum immite Dunal plants, which were poor hosts for larval development, feeding, and survival, compared to the other three Solanum species. 4. Chemical plant defenses, in general, did not correlate with performance or preference, but some plant volatiles may have played a role in resolving female choice. Glycoalkaloids such as solanine and chaconine were detected in similar amounts in preferred and non‐preferred hosts, but there was significantly more limonene in the headspace of S. immite than in S. tuberosum L. 5. The present findings suggest that we must consider the risk‐spreading hypothesis in cases where preference and performance are not positively correlated, particularly in specialist herbivores that can feed on a diversity of congener plants and may attempt to expand their exploits to other solanaceae species.     

Variable correspondence of female host preference and larval performance in a phytophagous ladybird beetle Epilachna pustulosa (Coleoptera: Coccinellidae)

Genetic and environmental factors causing intraspecific variation of the thistle Cirsium kamtschaticum Ledeb. as a host plant of the phytophagous ladybird Epilachna pustulosa Kôno were investigated through simple food-choice tests and rearing of larvae. Two thistle clones (T1U₁ and T4H₂) were used, originally growing approximately 12 km apart. A previous study showed that adult female ladybirds preferred T1U₁ to T4H₂, and that larval performance was better on T1U₁, when leaves from the clones in situ were examined. The two clones retained their characteristics with respect to beetle preference after transplantation into a common garden. However, the difference between T1U₁ and T4H₂ with respect to larval performance was reduced after the transplantation. When leaves from shoots of T1U₁ exposed to different sunlight intensities were offered, adult female ladybirds did not show obvious preferences. Larval eclosion rates increased significantly with the increase in leaf sunlight intensity exposure. These results suggest strongly that both genetic and environmental factors are involved in interclonal variation of thistle quality in beetle preference and/or performance. It is suggested that the quality of thistle leaves for larval performance is largely affected by environmental factors, while leaf quality for beetle preference may be determined strictly by genetic factors. Under certain conditions, E. pustulosa females may behave maladaptively, preferring plants not appropriate for larval growth, or not choosing plants appropriate for the larval growth.     

Disappearance of eggs from nonparasitized nests of brood parasite hosts: the evolutionary equilibrium hypothesis revisited

The evolutionary equilibrium hypothesis was proposed to explain variation in egg rejection rates among individual hosts (intra‐ and interspecific) of avian brood parasites. Hosts may sometimes mistakenly reject own eggs when they are not parasitized (i.e. make recognition errors). Such errors would incur fitness costs and could counter the evolution of host defences driven by costs of parasitism (i.e. creating equilibrium between acceptors and rejecters within particular host populations). In the present study, we report the disappearance of host eggs from nonparasitized nests in populations of seven actual and potential hosts of the common cuckoo Cuculus canorus. Based on these data, we calculate the magnitude of the balancing parasitism rate provided that all eggs lost are a result of recognition errors. Importantly, because eggs are known to disappear from nests for reasons other than erroneous host rejection, our data represent the maximum estimates of such costs. Nonetheless, the disappearance of eggs was a rare event and therefore incurred low costs compared to the high costs of parasitism. Hence, costs as a result of recognition errors are probably of minor importance with respect to opposing selective pressure for the evolution of egg rejection in these hosts. We cannot exclude the possibility that low or intermediate egg rejection rates in some host populations may be caused by spatiotemporal variation in the occurrence of parasitism and gene flow, creating a variable influence of opposing costs as a result of recognition errors and the costs of parasitism.     

栗山天牛幼虫天敌白蜡吉丁肿腿蜂的转主寄主研究

在利用白蜡吉丁肿腿蜂Sclerodermus pupariae防治世代周期长、 发育整齐的害虫栗山天牛Massicus raddei中, 我们发现该天敌只在寄主1-3龄幼虫时具有良好的寄生效果, 而对3龄以上的中老龄幼虫基本不寄生。为了了解释放白蜡吉丁肿腿蜂后其种群能否在栎树林间延续下去, 达到持续控制靶标害虫的效果, 我们调查了其在栎树林间的转主寄主。结果表明： 白蜡吉丁肿腿蜂除了寄生栗山天牛外, 还能寄生双簇天牛Moechotypa diphysis、 四点象天牛Mesosa myops和栎块斑吉丁Lamprodila virgata幼虫。白蜡吉丁肿腿蜂寄生不同转主寄主幼虫的成功率差异显著, 对栎块斑吉丁和双簇天牛幼虫的寄生率最高, 分别为76.67%和73.33%。寄生上述4种寄主时, 其雌蜂在不同寄主上的产卵前期、 产卵量及第2代雌蜂出蜂量、 出蜂率、 体长和寿命等差异不显著, 只有幼虫期和蛹期历期及第2代雌蜂有翅率和雌雄性比略有差异。室内模拟林间寄生试验表明, 白蜡吉丁肿腿蜂对双簇天牛和四点象天牛幼虫的寄生率较高。对双簇天牛和四点象天牛野外生活史研究发现, 这2种天牛幼虫在白蜡吉丁肿腿蜂不适宜寄生的栗山天牛中老龄幼虫期、 蛹期和成虫期均大量存在, 表明双簇天牛和四点象天牛是白蜡吉丁肿腿蜂在栎树林中的主要转主寄主。本研究说明, 在利用白蜡吉丁肿腿蜂生物防治栗山天牛中, 白蜡吉丁肿腿蜂在林间寄生栗山天牛的1-3龄幼虫后, 可转移寄生双簇天牛等转主寄主, 以延续其种群, 待下一代栗山天牛幼龄幼虫出现时再转移寄生栗山天牛, 达到持续控制栗山天牛的防治效果。     

管氏肿腿蜂密度对其寄生及繁衍能力的影响

本研究以管氏肿腿蜂Sclerodermus guani雌成蜂为研究对象,拟探明寄生蜂密度对其寄生及繁衍能力的影响,为该寄生蜂行为生物学研究提供科学依据。本研究以松墨天牛Monochamus alternatus幼虫(0.350～0.450 g)为寄主,设置8种不同雌蜂密度(1～8头/寄主),对比分析不同雌蜂密度下,管氏肿腿蜂的寄生行为和效能,以及雌蜂生殖力和子代适合度变化。结果表明,随雌蜂密度增加,管氏肿腿蜂蛰刺发生前历时、寄主麻痹历时及产卵前历时均缩短。基于Hassell-Varley数据模型分析(E=0.9023×P^-0.9378),雌蜂的寻找效应随自身密度增加而逐渐变小,雌蜂间的干扰降低了寄生效能。雌蜂生殖力随其密度增加而降低,单雌平均产卵量及产雌量明显下降,雌蜂密度为1头/寄主时,单雌产卵量分别是4头/寄主和8头/寄主处理下的1.4倍和2.4倍。子代适合度也随雌蜂密度增加而变化,子代发育历期明显缩短,低龄幼虫存活率和单雌体重均下降。雌蜂密度为1头/寄主时,其子代发育历期最长,平均为26.7 d, 8头/寄主时最短,平均为24.0 d。雌蜂密度为1头/寄主时...     

Conspecific Avoidance During Foraging in Venturia canescens (Hymenoptera: Ichneumonidae): The Roles of Host Presence and Conspecific Densities

We explored the effects of the presence of conspecifics on host patch choice decisions made by the parasitoid Venturia canescens. Different odor sources were located in plastic boxes at the end of each arm of a glass Y-tube olfactometer. In a set of experiments, odor sources were either (a) host kairomone patches with or without conspecifics (5 or 20) or (b) two odor sources located in successive boxes (a host kairomone patch and a patch with 20 conspecifics in one arm versus a host patch and an empty patch in the other). Our results indicate that V. canescens avoids competition only at high conspecific densities. Avoidance occurs only when foraging wasps perceive the combined odors from host kairomones and conspecific females. Separating the host patch from conspecific parasitoids does not perturb avoidance behavior.     

Oviposition preference and larval performance of Epiphyas postvittana (Lepidoptera: Tortricidae) on Botrytis cinerea (Helotiales: Sclerotiniaceae) infected berries of Vitis vinifera (Vitales: Vitaceae)

In this paper we tested the behavior of gravid Epiphyas postvittana in selecting the most‐appropriate site for oviposition thus benefitting offspring performance. Our hypothesis was built on Jaenike's preference–performance hypothesis (also referred to as the “mother‐knows‐the‐best” hypothesis). To test this, we used the interacting Epiphyas postvittana, its host Vitis vinifera, and the pathogenic microbe Botrytis cinerea system. Populations of E. postvittana and B. cinerea often exist concurrently on V. vinifera in Australasia and their interaction and mutual influence are currently being explored, although the suggestion presently is that the relationship between E. postvittana and B. cinerea is mutualistic. We tested the effect of volatiles from B. cinerea‐infected berries and uninfected (control) berries of V. vinifera on the oviposition behavior of E. postvittana. We also characterized the effects of B. cinerea infection on the berries of V. vinifera on the growth and development of E. postvittana. Contrary to the preference–performance hypothesis, oviposition choices made by gravid E. postvittana did not result in the best offspring survival, development, and performance. The preference for oviposition by E. postvittana was strongly influenced by the olfactory and tactile cues. She laid fewer eggs on B. cinerea‐infected berries compared to uninfected berries of V. vinifera. The larvae of E. postvittana showed no preference to uninfected berries of V. vinifera. The larvae fed on B. cinerea‐infected berries of V. vinifera showing greater survival rate, shorter time to pupation, greater pupal mass, and on becoming adults they laid more numbers of eggs than the larvae that were enabled to feed on uninfected berries. The larvae of E. postvittana transport the conidia of B. cinerea and transmit grey‐mould disease to uninfected berries of V. vinifera.     

The effect of pathogens on selection against deleterious mutations in Drosophila melanogaster

In natural populations, fitness is reduced by both deleterious mutations and parasites. Few studies have examined interactions between these two factors, particularly at the level of individual genes. We examined how the presence of a bacterial pathogen, Pseudomonas aeruginosa, affected the selection against each of eight deleterious mutations in Drosophila melanogaster. We found that mutations tended to become more deleterious in the presence of disease. This increase in the average selection was primarily due to three genes with the remainder showing little evidence of change.     

Host preference of a temperate mistletoe: Disproportional infection on three co‐occurring host species influenced by differential success

The mistletoe Tristerix verticillatus (Loranthaceae) parasitizes within a small area of the Yerba Loca Nature Sanctuary near Santiago, Chile, three co‐occurring hosts: Schinus montanus (Anacardiaceae), Fabiana imbricata (Solanaceae) and Berberis montana (Berberidaceae). Previous studies suggest that T. verticillatus may be favoured when parasitizing S. montanus relative to the other two host species. We hypothesize that infection of S. montanus is not proportional to its local abundance or appearance, that S. montanus is more intensively parasitized than other available hosts, and that host provenance is a determinant of the fate of the infecting seed. We compare the incidence of infection of T. verticillatus in relation to local availability and appearance variables, and the intensity of infection of T. verticillatus, on the three co‐occurring host species. We then test the effects of host provenance on mistletoe seed establishment success with a seed cross inoculation experiment varying the donor and receptor hosts. Finally, we test whether there are differences in establishment success between manually processed seeds and seeds defecated by the avian disperser Mimus thenca (Passeriformes: Mimidae). Our results show that the three hosts have an aggregated spatial distribution. Schinus montanus was parasitized at a higher rate than expected by its local availability and appearance, and inoculated seeds showed differential development depending on the origin of the seeds: seeds from T. verticillatus parasitizing S. montanus inoculated to S. montanus twigs showed higher germination and lower mortality than seeds from T. verticillatus parasitizing F. imbricata inoculated to S. montanus twigs. Furthermore, seeds defecated by the avian disperser, M. thenca, had higher adherence and reduced mortality when compared to manually processed seeds. The disproportional host infection found is discussed in terms of the differential establishment of mistletoe seeds, morphological characteristics of hosts and the behaviour of dispersing birds.     

Genotypic and phenotypic variation in transmission traits of a complex life cycle parasite

Characterizing genetic variation in parasite transmission traits and its contribution to parasite vigor is essential for understanding the evolution of parasite life‐history traits. We measured genetic variation in output, activity, survival, and infection success of clonal transmission stages (cercaria larvae) of a complex life cycle parasite (Diplostomum pseudospathaceum). We further tested if variation in host nutritional stage had an effect on these traits by keeping hosts on limited or ad libitum diet. The traits we measured were highly variable among parasite genotypes indicating significant genetic variation in these life‐history traits. Traits were also phenotypically variable, for example, there was significant variation in the measured traits over time within each genotype. However, host nutritional stage had no effect on the parasite traits suggesting that a short‐term reduction in host resources was not limiting the cercarial output or performance. Overall, these results suggest significant interclonal and phenotypic variation in parasite transmission traits that are not affected by host nutritional status.     

Natural selection on quantitative immune defence traits: a comparison between theory and data

Parasites present a threat for free‐living species and affect several ecological and evolutionary processes. Immune defence is the main physiological barrier against infections, and understanding its evolution is central for predicting disease dynamics. I review theoretical predictions and empirical data on natural selection on quantitative immune defence traits in the wild. Evolutionary theory predicts immune traits to be under stabilizing selection owing to trade‐offs between immune function and life‐history traits. Empirical data, however, support mainly positive directional selection, but also show variation in the form of selection among study systems, immune traits and fitness components. I argue that the differences between theory and empirical data may at least partly arise from methodological difficulties in testing stabilizing selection as well as measuring fitness. I also argue that the commonness of positive directional selection and the variation in selection may be caused by several biological factors. First, selection on immune function may show spatial and temporal variation as epidemics are often local/seasonal. Second, factors affecting the range of phenotypic variation in immune traits could alter potential for selection. Third, different parasites may impose different selective pressures depending on their characteristics. Fourth, condition dependence of immune defence can obscure trade‐offs related to it, thus possibly modifying observed selection gradients. Fifth, nonimmunological defences could affect the form of selection by reducing the benefits of strong immune function. To comprehensively understand the evolution of immune defence, the role of above factors should be considered in future studies.     

Ultrastructural characterization of olfactory sensilla and immunolocalization of odorant binding and chemosensory proteins from an ectoparasitoid Scleroderma guani (Hymenoptera: Bethylidae)

The three-dimensional structures of two odorant binding proteins (OBPs) and one chemosensory protein (CSP) from a polyphagous ectoparasitoid Scleroderma guani (Hymenoptera: Bethylidae) were resolved bioinformatically. The results show that both SguaOBP1 and OBP2 are classic OBPs, whereas SguaCSP1 belongs to non-classic CSPs which are considered as the "Plus-C" CSP in this report. The structural differences between the two OBPs and between OBP and CSP are thoroughly described, and the structural and functional significance of the divergent C-terminal regions (e.g., the prolonged C-terminal region in SguaOBP2 and the additional pair of cysteines in SguaCSP1) are discussed. The immunoblot analyses with antisera raised against recombinant SguaOBP1, OBP2, and CSP1, respectively, indicate that two SguaOBPs are specific to antennae, whereas SguaCSP1, which are more abundant than OBPs and detected in both male and female wasps, expresses ubiquitously across different tissues.We also describe the ultrastructure of the antennal sensilla types in S. guani and compare them to 19 species of parasitic Hymenoptera. There are 11 types of sensilla in the flagellum and pedicel segments of antennae in both male and female wasps. Seven of them, including sensilla placodea (SP), long sensilla basiconica (LSB), sensilla coeloconica (SC), two types of double-walled wall pore sensilla (DWPS-I and DWPS-II), and two types of sensilla trichodea (ST-I and ST-II), are multiporous chemosensilla. The ultralsturctures of these sensilla are morphologically characterized. In comparison to monophagous specialists, the highly polyphagous generalist ectoparasitoids such as S. guani possess more diverse sensilla types which are likely related to their broad host ranges and complex life styles. Our immunocytochemistry study demonstrated that each of the seven sensilla immunoreacts with at least one antiserum against SguaOBP1, OBP2, and CSP1, respectively. Anti-OBP2 is specifically labeled in DWPS-II, whereas the anti-OBP1 shows a broad spectrum of immunoactivity toward four different sensilla (LSB, SP, ST-I and ST-II). On the other hand, anti-CSP1 is immunoactive toward SP, DWPS-I and SC. Interestingly, a cross co-localization pattern between SguaOBP1 and CSP1 is documented for the first time. Given that the numbers of OBPs and CSPs in many insect species greatly outnumber their antennal sensilla types, it is germane to suggest such phenomenon could be the rule rather than the exception.     

MalAvi: a public database of malaria parasites and related haemosporidians in avian hosts based on mitochondrial cytochrome b lineages

Research in avian blood parasites has seen a remarkable increase since the introduction of polymerase chain reaction-based methods for parasite identification. New data are revealing complex multihost-multiparasite systems which are difficult to understand without good knowledge of the host range and geographical distribution of the parasite lineages. However, such information is currently difficult to obtain from the literature, or from general repositories such as GenBank, mainly because (i) different research groups use different parasite lineage names, (ii) GenBank entries frequently refer only to the first host and locality at which each parasite was sampled, and (iii) different researchers use different gene fragments to identify parasite lineages. We propose a unified database of avian blood parasites of the genera Plasmodium, Haemoproteus and Leucocytozoon identified by a partial region of their cytochrome b sequences. The database uses a standardized nomenclature to remove synonymy, and concentrates all available information about each parasite in a public reference site, thereby facilitating access to all researchers. Initial data include a list of host species and localities, as well as genetic markers that can be used for phylogenetical analyses. The database is free to download and will be regularly updated by the authors. Prior to publication of new lineages, we encourage researchers to assign names to match the existing database. We anticipate that the value of the database as a source for determining host range and geographical distribution of the parasites will grow with its size and substantially enhance the understanding of this remarkably diverse group of parasites.     

用替代寄主繁殖的川硬皮肿腿蜂的学习行为

采用Y型嗅觉仪进行双向选择实验,研究了用替代寄主黄粉虫蛹繁殖的川硬皮肿腿蜂寄主搜索过程中的学习行为。结果表明,川硬皮肿腿蜂羽化期和成虫初期经历松枝皮、松针、松节油、杉枝皮等的挥发物后,雌蜂对这些挥发物的选择性明显提高,但对杉叶挥发物无明显的学习行为。羽化期和成虫初期是否投放新鲜寄主,对雌蜂的气味选择性没有明显的影响。成蜂取食黄粉虫蛹和蜂蜜时均可联系性学习松枝和杉枝气味。取食并经历杉枝和松枝挥发物4天和8天的寄生蜂之间对相应气味的选择性无显著差异。     

Larval experience of stable fly,Stomoxys calcitrans Linneaus, 1758 (Diptera: Muscidae) does not influence oviposition preference in gravid females

1. Hopkins' host selection principle (HHSP) proposes that, in holometabolous insects, gravid females prefer to oviposit on their developmental substrate. This hypothesis is widely explored in phytophagous insects, but few studies have considered blood‐feeding insects. In this study, the HHSP was tested using the haematophagous stable fly, Stomoxys calcitrans (Diptera: Muscidae). Using no‐choice and two‐choice tests, the study first sought to demonstrate whether S. calcitrans larvae recognise their rearing substrate. 2. It was found that when a rearing substrate is offered to S. calcitrans larvae singly (no‐choice) or associated with a non‐rearing substrate (two‐choice), they were able to recognise the substrate in which they developed. This ability disappeared when larvae were transferred to another substrate for 5 h. 3. Next, using oviposition bioassays, it was investigated whether information gathered by pre‐imaginal stages during their development can persist into the adult stages after metamorphosis. It was hypothesised that gravid females emerging from clean and uncleaned pupae reared on sheep and camel dung would still prefer to lay on their rearing substrate. The results revealed that gravid females did not prefer to oviposit on their developmental substrate. In addition, failure to recognise and prefer their developmental substrate was found in gravid females that had emerged from puparia that were cleaned as well as those contaminated with sheep dung. 4. It is concluded that S. calcitrans adult preference is not influenced by their offspring's experience. Overall, the HHSP was not supported by our study, suggesting that this principle may not apply to generalist insects characterised by high plasticity in oviposition substrate acceptance.     

Effectively vertical transmission of a Drosophila‐parasitic nematode: mechanism and consequences

1. Long‐term control of insects by parasites is possible only if the parasite populations persist. Because parasite transmission rate depends on host density, parasite populations may go extinct during periods of low host density. Vertical transmission of parasites, however, is independent of host density and may therefore provide a demographic bridge through times when their insect hosts are rare. 2. The nematode Howardula aoronymphium, which parasitises mycophagous species of Drosophila, can experience both horizontal and effectively vertical transmission, relative rates of which depend, in theory at least, on the density of hosts at breeding sites. 3. A nine‐generation experiment was carried out in which nematodes were transmitted either exclusively vertically or primarily horizontally. This experiment revealed that these parasites can persist and exhibit positive population growth even when there is only vertical transmission. 4. Assays at the end of the experiment revealed that the vertically transmitted nematodes had suffered no inbreeding depression and that they were similar to the horizontally transmitted nematodes in terms of virulence, infectivity, within‐host growth rate, and fecundity. Thus, vertical transmission of H. aoronymphium did not appear to compromise the ability of these parasites to control Drosophila populations.