The Response of Host-Seeking Cephenemyia Females to Visual Cues Associated with Anatomically-Modified Baited Deer Models

Females of C. jellisoni larviposited significantly more often on deer models with black or blue muzzles than on models with red or white muzzles. Females of C. apicata only larviposited on models with black muzzles. For C. jellisoni, which sprays larvae into nostrils, a model having a muzzle with no nostrils received no larvipositions, but females larviposited into all nostril depressions placed in abnormal positions on muzzles. For C. apicata, which targets the lips, there was no significant difference in the number of larvipositions on muzzles with nostrils in abnormal positions or when muzzles were oriented in different positions. For both species there was no significant difference in the number of larvipositions on models when CO₂ was released at different parts of the body.     

Invasion of black-tailed deer by nose bot fly larvae (Diptera: Oestridae: Oestrinae)

Invasion of black-tailed deer (Odocoileus hemionus columbianus) by larvae of the nose bot flies (Cephenemyia apicata and C. jellisoni) was investigated by obssrving their expulsion by larviparous females and their subsequent activity on the host. The drying uterine fluid encasing larvae ( = larval packet) delays desiccation, ensures adhesion to hairs, and immediately dissolves upon contact with saliva. Contrary to the widely accepted nasal mode of invasion, larvae placed on muzzles of deer crawl ventrally toward the upper lip, enter the mouth, and then crawl caudally along the hard palate or tongue toward the throat. Hair located between the muzzle and nostril prevents larvae from entering the nostrils. A natural per os mode of invasion, heretofore unrecognized, is proposed. This is initiated by: (1) females depositing larval packets on the muzzle of deer, or (2) deer licking larval packets from contaminated areas around the muzzle. The positive thermotropism of larvae is compatible with such a per os mode of entry into the host.     

Host Specific Cephenemyia of Deer Repelled by Non-Host Odors

Females of Cephenemyia apicata and C. jellisoni made significantly fewer (P?<?0.05) larvipositions on baited models of black-tailed deer paired with a camouflaged sheep than on similar models operated without a paired sheep. Models were baited with CO₂ and 1-octen-3-ol. In the absence of natural sheep odors these host specific flies were attracted to and larviposited on sheep models baited with CO₂ and octenol and to CO₂-baited odorless models of cows and horses. These results indicate that odors associated with sheep repelled host-seeking Cephenemyia females from baited deer models. Under natural conditions repellent odors of non-host species may assist in maintaining host specificity of these Cephenemyia species and in flies not wasting time and energy responding to non-host odors.     

First finding of larviposition in Calliphora loewi from an island relict forest

Larviposition is widespread in blowflies, but among Calliphora species this behavior has seldom been described. The evidence of larviposition in C. loewi is here reported for the first time and discussed in relation with other blowfly species exhibiting the same behavior. The blowfly C. loewi is considered oviparous but surprisingly, female specimens from Madeira Island (Portugal) were found to carry few large larvae (one to three larvae up to 5.1 mm in size) in the ovipositor and abdomen. The finding of larviposition behavior in C. loewi from Madeira Island is at present enigmatic and further studies are needed to clarify the reproductive biology of this species.     

Host‐searching responses to herbivory‐associated chemical information and patch use depend on mating status of female solitary parasitoid wasps

1. In a tritrophic interaction system consisting of plants, herbivores, and their parasitoids, chemicals released from plants after herbivory are known to play important roles for many female parasitoids to find their hosts efficiently. On the plant side, chemical information associated with herbivory can act as an indirect defence by attracting the natural enemies of the host herbivores. 2. However, mated and virgin females of haplodiploid parasitoids might not necessarily respond to such chemical cues in the same way. Since virgin females can produce only sons, they might refrain from searching for hosts to invest eggs until copulation, in order to produce both sexes. 3. Here, we investigated differential host‐searching behaviours shown by mated and virgin females in the solitary parasitoid wasp, Cotesia vestalis, in response to herbivory‐associated chemical information from cruciferous plants infested by their host larvae, Plutella xylostella. 4. Mated females showed a significantly higher flight preference for host‐infested plants over intact plants, while no preference was observed with virgin females. Mated females also showed more intensive antennal searching and ovipositor probing behaviours to leaf squares with wounds caused by hosts than did virgin females. Furthermore, mated females stayed longer in host patches with higher parasitism rates than virgin females. 5. These results indicate that mating status of C. vestalis females clearly influences their host‐searching behaviour in response to herbivory‐associated chemical information and patch exploitation. Female parasitoids seem to forage for hosts depending on their own physiological condition in a tritrophic system.     

Sting frequency and progeny production of lab-cultured Cotesia marginiventris

A laboratory experiment was conducted to determine the impact of sting frequency on progeny production of Cotesia marginiventris (Cresson) (Hymenoptera: Braconidae), a solitary, koinobiont endoparasitoid of noctuid pests. In replicated trials, young, mated, host-deprived C. marginiventris females were exposed to three Spodoptera exigua (Hübner) (Lepidoptera: Noctuidae) early instar larvae, one at a time, in Petri dish arenas, and observed as they stung these hosts once, twice, or thrice. The average amount of time that elapsed between stinging a host ranged from a minimum of 3 min, when females were exposed to unstung hosts, to a maximum of 8–11 min when females were exposed to previously stung hosts. Sting frequency had no effect on the yield of C. marginiventris progeny; approximately 90% of hosts, in all treatment groups, yielded a parasitoid mature larva, which spun a cocoon. No hosts yielded more than one parasitoid. The percentage of adult female progeny tended to increase with sting frequency; hosts that were stung thrice yielded 60% female C. marginiventris adults. The production of female progeny may depend on the egg allocation pattern of C. marginiventris females as well as the competitive interactions between siblings developing inside a shared host. This study suggests that S. exigua larvae can sustain 2–3 stings without diminishing their ability to yield a C. marginiventris mature larva. Provisioning enclosures with enough hosts to exceed the daily (per capita) oviposition rate of C. marginiventris females might limit the repeated stinging of the same hosts.     

Use of computed tomography as a non‐invasive method for diagnosing cephenemyiosis in roe deer (Capreolus capreolus)

This study was conducted to assess the reliability of computed tomography (CT) for diagnosing bot fly infestations by Cephenemyia stimulator (Clark) (Diptera: Oestridae) in roe deer (Capreolus capreolus L.) (Artiodactyla: Cervidae). For this purpose, the heads of 30 animals were analysed, firstly by CT and then by necropsy, which was used as the reference standard method. The prevalence values obtained by both methods were identical; the prevalence of infestation was 40.0% overall, and was higher in males (45.5%) than in females (25.0%). These results highlight the usefulness of CT as an alternative or non‐invasive method for diagnosing cephenemyiosis in live‐captured roe deer and in hunting trophies or museum collections that cannot be destroyed or damaged.     

Germination sensitivities to water potential among co‐existing C3 and C4 grasses of cool semi‐arid prairie grasslands

An untested theory states that C₄ grass seeds could germinate under lower water potentials (Ψ) than C₃ grass seeds. We used hydrotime modelling to study seed water relations of C₄ and C₃ Canadian prairie grasses to address Ψ divergent sensitivities and germination strategies along a risk‐spreading continuum of responses to limited water. C₄ grasses were Bouteloua gracilis, Calamovilfa longifolia and Schizachyrium scoparium; C₃ grasses were Bromus carinatus, Elymus trachycaulus, Festuca hallii and Koeleria macrantha. Hydrotime parameters were obtained after incubation of non‐dormant seeds under different Ψ PEG 6000 solutions. A t‐test between C₃ and C₄ grasses did not find statistical differences in population mean base Ψ (Ψ_b(50)). We found idiosyncratic responses of C₄ grasses along the risk‐spreading continuum. B. gracilis showed a risk‐taker strategy of a species able to quickly germinate in a dry soil due to its low Ψ_b(50) and hydrotime (θ_H). The high Ψ_b(50) of S. scoparium indicates it follows the risk‐averse strategy so it can only germinate in wet soils. C. longifolia showed an intermediate strategy: the lowest Ψ_b(50) yet the highest θ_H. K. macrantha, a C₃ grass which thrives in dry habitats, had the highest Ψ_b(50), suggesting a risk‐averse strategy for a C₃ species. Other C₃ species showed intermediate germination patterns in response to Ψ relative to C₄ species. Our results indicate that grasses display germination sensitivities to Ψ across the risk‐spreading continuum of responses. Thus seed water relations may be poor predictors to explain differential recruitment and distribution of C₃ and C₄ grasses in the Canadian prairies.     

Growth,development, and behaviour of the parasitised and unparasitised larvae of a shelter‐building moth and consequences for the resulting koinobiont parasitoid

Most attention to size‐time trade‐offs of insects has focused on herbivore risk, with considerably less attention paid to parasitoids. Here, we focus on parasitoid risk, comparing the fates of unparasitised herbivore hosts and parasitised hosts that protect the parasitoids. Success of a koinobiont parasitoid (host grows after parasitisation) depends on maintaining a delicate balance with its host, thereby ensuring its own survival while the host grows. To evaluate growth rate–mortality rate relationships of host and parasitoid, we compared several aspects of the growth, phenology, and behaviour of unparasitised fern moth [Herpetogramma theseusalis (Walker) (Lepidoptera: Crambidae)] larvae and larvae parasitised by Alabagrus texanus (Cresson) (Hymenoptera: Braconidae), a solitary koinobiont (one parasitoid per host) wasp. Host larvae feed and construct shelters on sensitive fern, Onoclea sensibilis L. (Dryopteridaceae). Alabagrus texanus parasitise early‐instar moths in late summer, which overwinter in their host, emerging in mid‐summer to pupate and eclose. During the autumn following hatching and the immediately following spring, parasitised and unparasitised moth larvae did not differ in size, took similar time to choose between satisfactory and unsatisfactory foods, and built similar shelters. Prior to any other changes noted, more parasitised than unparasitised larvae also died when severely starved. Parasitised larvae subsequently grew less and pupated later than unparasitised ones (small size, slow growth), but consumed similar amounts of food. Although the numerically dominant parasitoid of fern moths, we concluded that A. texanus do not efficiently exploit their hosts.     

Female preference and larval performance of sunflower moth,Homoeosoma electellum,on sunflower pre‐breeding lines

The preference–performance hypothesis for insect herbivores predicts that adult females should preferentially choose hosts on which their offspring perform better. We tested this hypothesis for the sunflower moth, Homoeosoma electellum (Hulst) (Lepidoptera: Pyralidae), using 16 sunflower (pre‐breeding) lines, derived from a number of wild species of Helianthus, including Helianthus annuus L., Helianthus deserticola Heiser, Helianthus paradoxus Heiser, Helianthus praecox Engelm. & Gray ssp. hirtus (Heiser) Heiser, Helianthus praecox Engelm. & Gray ssp. runyonii (Heiser) Heiser, Helianthus petiolaris Nutt., Helianthus resinosus Small, and Helianthus tuberosus L. (Asteraceae), that are suitable for introducing wild sunflower germplasm into commercial cultivars. Female moths showed a range of ovipositional preference measures to the various lines. Combined data for three Helianthus species represented by multiple lines showed significant differences in female preference with respect to the parental species. Larval performance, determined by proportion of infested neonate larvae reaching the pupal stage, or mean pupal weight, varied across the lines and, as for the female preference data, also showed significant differences among the three parental Helianthus species represented by multiple lines. These data suggest that the characteristics in the pre‐breeding lines influencing female sunflower moth preference and larval performance likely originate from the parental species and may be consistently transferred to the derived pre‐breeding lines. Of particular note with regard to potential plant resistance mechanisms, lines derived from H. tuberosus showed consistent low preference–performance measures. Female preference and larval performance (for both measures) were strongly correlated, indicating that females preferred plants and lines on which larvae performed better, in support of the preference–performance hypothesis.     

Inter‐specific competition and competition‐free space in the tephritid parasitoids Utetes anastrephae and Doryctobracon areolatus (Hymenoptera: Braconidae: Opiinae)

相似文献   

Hunger‐dependent and sex‐specific antipredator behaviour of larvae of a size‐dimorphic mosquito

1. Modification of behaviours in the presence of predators or predation cues is widespread among animals. The costs of a behavioural change in the presence of predators or predation cues depend on fitness effects of lost feeding opportunities and, especially when organisms are sexually dimorphic in size or timing of maturation, these costs are expected to differ between the sexes. 2. Larval Aedes triseriatus (Say) (Diptera: Culicidae) were used to test the hypothesis that behavioural responses of the sexes to predation cues have been selected differently due to different energy demands. 3. Even in the absence of water‐borne predation cues, hungry females (the larger sex) spent more time browsing than did males, indicating a difference in energy needs. 4. In the presence of predation cues, well‐fed larvae of both sexes reduced their activity more than did hungry larvae, and males shifted away from high‐risk behaviours to a greater degree than did females, providing the first evidence of sex‐specific antipredator behaviour in foraging mosquito larvae. 5. Because sexual size dimorphism is common across taxa, and energetic demands are probably correlated with size dimorphism, this research demonstrates the importance of investigating sex‐specific behaviour and behavioural responses to enemies, and cautions against generalising results between sexes.     

Non‐pathogenic aquatic bacteria activate the immune system and increase predation risk in damselfly larvae

相似文献   

Tick infestation (Acari: Ixodidae) in roe deer (<Emphasis Type="Italic">Capreolus capreolus</Emphasis>) from northwestern Spain: population dynamics and risk stratification

During the 2007 and 2008 hunting seasons (April–October) the skin of 367 roe deer (Capreolus capreolus L.), hunted in different preserves from Galicia (Northwestern Spain), were examined for ticks (Acari: Ixodidae). The overall prevalence of infestation by ticks was 83.1%. The predominant species was Ixodes ricinus (83.1%), whereas a single Dermacentor marginatus specimen appeared in one roe deer. All developmental stages of I. ricinus were found parasitizing roe deer, the adults being the most frequent (82.2%), followed by nymphs (45.6%) and larvae (27.2%). The mean intensity of infestation by I. ricinus was 43.2 ± 49.85; most of them were adults (30.7 ± 31.64) and in a lesser extend nymphs (16.9 ± 24.74) and larvae (10.7 ± 29.90). Ixodes ricinus was present all over the study with percentages that oscillated between 100% in spring and 57.4% in autumn. CHAID algorithm showed the sex of roe deer as the most influential factor in tick prevalence, followed by the climatic area. The different developmental stages of I. ricinus were more frequent in males than in females, and the prevalence of adults and larvae were higher in roe deer from coastal areas than in those from mountainous and central areas, whereas nymphs were more frequent in mountainous areas. Host age and density were not determinants for tick infestation. Our results confirm that roe deer are important hosts for I. ricinus in northwestern Spain, serving as a vehicle for the geographic distribution of these ticks.     

Female response to predation risk alters conspecific male behaviour during pre‐copulatory mate guarding

Mating behaviour often increases predation risk, but the vulnerability within mating pairs differs between the sexes. Such a sex difference is expected to lead to differences in responses to predation risk between the sexes. In the two‐spotted spider mite Tetranychus urticae, males engage in pre‐copulatory mate guarding because only the first mating results in fertilisation. We investigated (i) whether pre‐copulatory pairs are more conspicuous to the predatory mite Phytoseiulus persimilis than solitary females, (ii) whether the vulnerability to the predator differs between sexes within the pre‐copulatory pair, (iii) whether each sex of T. urticae responds to predation risk during pre‐copulatory mate guarding and (iv) whether T. urticae's response to predation risk affects predator behaviour. Because T. urticae females are immobile during pre‐copulatory mate guarding, we observed male behaviour to evaluate effects of predation risk. We found that the predators detect more pre‐copulatory pairs than solitary females and that more females than males of the pre‐copulatory pairs are preyed upon by the predators. The preference of spider mite males for pre‐copulatory pairs versus solitary females was affected by whether or not the female had been exposed to predators during development. Male T. urticae exposed to predation risk did not alter their behaviour. These results suggest that only the most vulnerable sex, that is the female, responds to predation risk, which modifies male behaviour. Regardless of T. urticae females’ experience, however, P. persimilis detected more T. urticae pre‐copulatory pairs than solitary females, suggesting that pre‐copulatory mate guarding itself is dangerous for T. urticae females when these predators are present. We discuss our results in the context of sex‐dependent differences in predation risk.     

Spatial density‐dependent parasitism and specificity in the robber fly Mallophora ruficauda (Diptera: Asilidae)

The density‐dependence in parasitism by the robber fly Mallophora ruficauda (Diptera: Asilidae) on scarab beetle larvae (Coleoptera: Scarabaeidae) populations was studied in the present research. Mallophora ruficauda is a pestiferous species common in the open grasslands of the Pampas region of South America. Adults are predators of insects and larvae are solitary parasitoids of third instar larvae of several species of scarab beetle (Coleoptera: Scarabaeidae). In contrast with most studied host‐parasitoid interactions, host searching by M. ruficauda is carried out by both larvae and adults. Typically, robber fly females lay eggs on tall grasses from where larvae drop to the ground, and attack hosts which are buried in the soil. We carried out our study at two spatial scales close to 14 apiaries located in the provinces of Buenos Aires and Entre Ríos (Argentina). We found that parasitism is density‐independent at the larger spatial scale and inversely density‐dependent at the smaller one. We also found that M. ruficauda selects Cyclocephala signaticollis among several scarab beetle species. Specificity is observed both at large and small spatial scales. We discuss the implications of both host specificity and host searching behaviour on the observed parasitism patterns.     

Behavioral ecology ofMyiopharus doryphorae (riley) andM. aberrans (townsend), tachinid parasitoids of the colorado potato beetle

The behavior ofMyiopharus doryphorae andM. aberrans, North American tachinid parasitoids of the Colorado potato beetle, was recorded under field and laboratory conditions throughout three growing seasons in western Massachusetts. Eight common behaviors associated with resting, searching, feeding, and larviposition were distinguished, which together accounted for nearly all daytime activity of the females of both tachinids. Several of these behaviors, and in particular larviposition, were closely related to temperature but differed between species. A sequence of five defensive behaviors by the different larval stages of the Colorado potato beetle prevented larviposition in 49% of resisted attempts and perhaps one-fourth of total larviposition attempts byMyiopharus species, yet both parasitoids were highly successful in allocating their progeny during most of the summer. Second- and third-instar beetle larvae were least effective in resisting larviposition. Females of bothMyiopharus species actively guarded recently parasitized hosts from otherMyiopharus females for a period of several minutes after larviposition during the last month of the growing season when second- and third-instar Colorado potato beetle larvae were most scarce. Laboratory studies based on the field observation that femaleM. aberrans doggedly pursued circum-diapausing adult beetles led to the first recorded account ofM. aberrans larvipositing in adult hosts. Flies gained access to a beetle’s vulnerable abdominal dorsum at the instant it lifted its elytra to initiate flight. The late-season switch ofM. aberrans to adult Colorado potato beetles contributed to a seasonal sequence of larviposition-related behaviors concordant with prevailing host densities, which should lend complementarity toM. doryphorae andM. aberrans as biological controls of pest populations.     

Host activity and wasp experience affect parasitoid wasp foraging behaviour and oviposition on nematode‐infected larvae of the forestry pest Hylobius abietis

1. Entomopathogenic nematodes (EPN) are currently being used as introduced biological control agents against the larvae of the native European forestry pest Hylobius abietis L. which develop under the bark of stumps and roots of newly dead conifer trees. 2. The potential for resource competition between gregarious ectoparasitoid Bracon hylobii Ratz and EPN by recording oviposition and related behaviours of B. hylobii females on EPN‐infected H. abietis larvae was investigated. Wasps did not parasitise EPN‐infected host larvae that were dead when presented, but naÏve and experienced wasps parasitised live EPN‐infected hosts. NaÏve wasps parasitised live EPN‐infected hosts significantly less frequently than healthy hosts only when the infected larvae were close to death (i.e. died during 24‐h trial). Parasitism by experienced wasps was unaffected by host infection. 3. Wasp probing and oviposition were positively associated with the amount of host movement. Preventing H. abietis larvae from chewing on bark significantly reduced parasitism by naÏve, but not experienced wasps. 4. The number of eggs per clutch was not affected by bark chewing or EPN‐infection of H. abietis larvae. 5. NaÏve and experienced B. hylobii parasitised two abnormal hosts (larvae of coleopteran Rhagium bifasciatum Fabricius and lepidopteran Galleria mellonella L.), both of which moved and chewed on bark during trials. 6. It was concluded that B. hylobii can use vibrational cues generated by host movement and feeding to locate hosts at short range and accepts unsuitable (EPN‐infected or abnormal) hosts as long as these create such cues. The implications for competition between B. hylobii and EPN and possible ways of minimising it when applying EPN are discussed.     

Analysis of solitariness in a parasite—host system (Muscidifurax raptor,Hymenoptera: Pteromalidae—Ceratitis capitata,Diptera: Tephritidae)*

Abstract. 1. The behaviour of the parasite Muscidifurax raptor Girault and Sanders was studied when searching for hosts, puparia of the Mediterranean fruit fly, Ceratitis capitata (Wiedemann). At low density females tend to avoid encountering parasitized hosts. This tendency decreases as density of searching females increases. 2. The proportional avoidance of superparasitism was calculated and the effect of increasing number of encounters per host on this parameter was analysed. 3. The mechanisms of solitariness were studied. These mechanisms include: outer marking of the hosts by the female parasite and deliberate physical attack of the newly hatched larvae to eliminate as yet unhatched eggs. 4. In cases of intraspecific competition between larvae, young first or second instar larvae usually have the advantage over older larvae.     

Ovipositional discrimination by Microplitis rufiventris females between healthy and granulosis virus-infected Spodoptera littoralis larvae

Ovipositional choice tests by Microplitis rufiventris females (Hym., Braconidae) between granulosis virus‐infected (GVI) and non‐infected (NI) Spodoptera littoralis larvae (Lep., Noctuidae), were assessed using discriminatory methods for re‐isolating the NI and virus‐infected hosts after removing the female parasitoid. When M. rufiventris females were given a choice between NI and GVI S. littoralis hosts, the adult females exhibited marked preference (P < 0.01) for the NI (i.e. higher quality) hosts. In this case, M. rufiventris females and S. littoralis GV (SlGV) did not significantly compete for the same type of host larvae and are, generally, compatible. However, when the choice was given between two low qualities of S. littoralis hosts, i.e. virus‐free previously parasitized hosts and viral‐infected hosts a significant preference (P < 0.01) of the parasitoid females for the GVI larvae was observed. In this case, the parasitoid would be at a disadvantage when competing with GV for the same host. However, the parasitoid could be used as an additional tool for the dissemination of biocontrol viruses within different pest populations, i.e. hosts other than S. littoralis. Importantly, the results showed different strategies of parasitoid female in egg‐laying management. When M. rufiventris female was given a choice between healthy and SlGVI hosts, the female deposited more eggs than when she was given a choice between two low qualities of host larvae. The results of the study may have implications in pest management strategies using M. rufiventris and SlGV against S. littoralis larvae.