Species-specificity and individual variation in the song of male Nathusius’ pipistrelles (<Emphasis Type="Italic">Pipistrellus nathusii</Emphasis>)

Sequences of the advertisement calls produced by male Nathusius’ pipistrelles (Pipistrellus nathusii) during the autumn mating period were recorded from individuals at two separate sites in Antrim, Northern Ireland, in August 2004. Several male roosts were found at these sites in close proximity to a single maternity roost, each containing approximately 200 adult females and their young. Analysis of measured parameters of four identified call types revealed that there were significant differences in call structure between sites and between individuals. Playback experiments, performed outside the adult female and juvenile roost sites, comprised of experimental advertisement call sequences of P. nathusii, Pipistrellus pygmaeus and Pipistrellus pipistrellus and control sound recorded without bats present (silence). Response was measured by simultaneously recording ultrasound during playbacks and counting the number of echolocation pulses identified as those of P. nathusii above a predetermined amplitude threshold. Significantly greater numbers of P. nathusii echolocation pulses were recorded during playback of male P. nathusii advertisement calls than during playback of congeners’ advertisement calls and control sound. The number of echolocation pulses recorded was similar during playback of P. pipistrellus and P. pygmaeus advertisement calls and silence. We suggest that, due to call complexity, male P. nathusii advertisement calls should be classified as ‘song’. Species-specificity and individual variation suggests that the songs of male P. nathusii have the potential to play a role in mate attraction and mate assessment.     

Individual experience-based foraging can generate community territorial structure for competing ant species

To gain additional territory while defending existing territory, animals must acquire and use information regarding resource characteristics and competitive pressure. For social organisms like ants, individual workers have experiences to acquire information, but territory establishment is a colony level behavior. Colony behavior, in turn, affects community structure. Here, I investigate how an individual ant’s previous experience affects its future foraging behavior and how individual behaviors can scale up to community territorial structure for two coexisting Formica species. To do this, I combine a field survey, a multi-agent computer simulation, and a manipulation experiment. The field survey shows that workers of both species co-occur on many trees early in the season, but ants on trees become segregated by species as the season progresses. The simulation demonstrates how this segregated spatial distribution can result from ants using a foraging strategy in which individuals show a preference for foraging sites based on previous experience. The experiment suggests that these ants are indeed capable of experience-based foraging behavior; ants preferentially return to sites where they have had positive experiences and avoid sites where they have had negative experiences. Results from this study suggest that spatially explicit information can be collected and stored by individuals to facilitate colony territorial structure, and that future investigations of community territory formation should include effects of individual previous experience.     

Foraging in the seed-harvester ant genus Pogonomyrmex: are energy costs important?

Energy intake and expenditure on natural foraging trips were estimated for the seed-harvester ants, Pogonomyrmex maricopa and P. rugosus. During seed collection, P. maricopa foraged individually, whereas P. rugosus employed a trunk-trail foraging system. Energy gain per trip and per minute were not significantly different between species. There was also no interspecific difference in energy cost per trip, but energy cost per minute was lower for P. maricopa foragers because they spent on average 7 min longer searching for a load on each trip. Including both unsuccessful and successful foraging trips, average energy gain per trip was more than 100 times the energy cost per trip for both species. Based on this result, we suggest that time cost incurred during individual foraging trips is much more important than energy cost in terms of maximizing net resource intake over time. In addition, because energy costs are so small relative to gains, we propose that energy costs associated with foraging may be safely ignored in future tests of foraging theory with seed-harvesting ant species.     

Comparisons of forager distributions from matched honey bee colonies in suburban environments

We conducted experiments designed to examine the distribution of foraging honey bees (Apis mellifera) in suburban environments with rich floras and to compare spatial patterns of foraging sites used by colonies located in the same environment. The patterns we observed in resource visitation suggest a reduced role of the recruitment system as part of the overall colony foraging strategy in habitats with abundant, small patches of flowers. We simultaneously sampled recruitment dances of bees inside observation hives in two colonies over 4 days in Miami, Florida (1989) and from two other colonies over five days in Riverside, California (1991). Information encoded in the dance was used to determine the distance and direction that bees flew from the hive for pollen and nectar and to construct foraging maps for each colony. The foraging maps showed that bees from the two colonies in each location usually foraged at different sites, but occasionally they visited the same patches of flowers. Each colony shifted foraging effort among sites on different days. In both locations, the mean flight distances differed between colonies and among days within colonies. The flight distances observed in our study are generally shorter than those reported in a similar study conducted in a temperate deciduous forest where resources were less dense and floral patches were smaller.     

Variation in composition of predator-attracting allelochemicals emitted by herbivore-infested plants: Relative influence of plant and herbivore

Summary During foraging, natural enemies of herbivores may employ volatile allelochemicals that originate from an interaction of the herbivore and its host plant. The composition of allelochemical blends emitted by herbivore-infested plants is known to be affected by both the herbivore and the plant. Our chemical data add new evidence to the recent notion that the plants are more important than the herbivore in affecting the composition of the volatile blends. Blends emitted by apple leaves infested with spider mites of 2 different species,T. urticae andP. ulmi, differed less in composition (principally quantitative differences for some compounds) than blends emitted by leaves of two apple cultivars infested by the same spider-mite species,T. urticae (many quantitative and a few qualitative differences). Comparison between three plant species — apple, cucumber and Lima bean — reveals even larger differences between volatile blends emitted upon spider-mite damage (many quantitative differences and several qualitative differences).     

Pursuit-deterrent communication between prey animals and timber rattlesnakes (Crotalus horridus): the response of snakes to harassment displays

A thorough understanding of communication requires an evaluation of both the signaler and receiver. Most analyses of prey–predator communication are incomplete because they examine only the behavior of the prey. Predators in these systems may be understudied because they are perceived as less tractable research subjects, due to their more cryptic hunting behaviors and secretive lifestyles. For example, research on interactions between rodents and rattlesnakes has focused on the behavior of rodent signalers, while responses of snakes have been virtually unexamined. Rattlesnakes are ambush predators, and capture rodents by waiting at foraging sites for long periods of time. In this study, I take advantage of the sedentary nature of this foraging strategy and use fixed videography to record natural encounters between timber rattlesnakes (Crotalus horridus) and their prey. Three different prey species were found to exhibit conspicuous visual displays to snakes, both when snakes were actively foraging, and when they were basking. After receiving displays, foraging snakes left their ambush sites and moved long distances before locating subsequent ambush sites, indicating that they responded to displays by abandoning attempts to ambush prey in the vicinity of signalers. This study represents the first quantitative analysis of the response of free-ranging snakes to signals from their prey, and elucidates a technique by which such quantitative data can be more easily obtained.     

Dance precision of <Emphasis Type="Italic">Apis florea</Emphasis>—clues to the evolution of the honeybee dance language?

All honeybee species make use of the waggle dance to communicate the direction and distance to both food sources and potential new nest sites. When foraging, all species face an identical problem: conveying information about profitable floral patches. However, profound differences in nesting biology (some nest in cavities while others nest in the open, often on a branch or a cliff face) may mean that species have different requirements when dancing to advertise new nest sites. In cavity nesting species, nest sites are a precise location in the landscape: usually a small opening leading to a cavity in a hollow tree. Dances for cavities therefore need to be as precise as possible. In contrast, when the potential nest site comprises a tree or perhaps seven a patch of trees, precision is less necessary. Similarly, when a food patch is advertised, dances need not be very precise, as floral patches are often large, unless they are so far away that recruits need more precise information to be able to locate them. In this paper, we study the dance precision of the open-nesting red dwarf bee Apis florea. By comparing the precision of dances for food sources and nest sites, we show that A. florea workers dance with the same imprecision irrespective of context. This is in sharp contrast with the cavity-nesting Apis mellifera that increases the precision of its dance when advertising a potential new home. We suggest that our results are in accordance with the hypothesis that the honeybees’ dance communication initially evolved to convey information about new nest sites and was only later adapted for the context of foraging.     

Determinants of male spacing behavior in microtines: an experimental manipulation of female spatial distribution and density

Theory on microtine mating systems predicts that male spacing behavior will be related to female spatial and temporal distribution. However, data from a natural population of field voles, Microtus agrestis, indicated a potential influence of female density on the spacing behavior of males. Therefore, I experimentally investigated the relative importance of female density and female spatial distribution for the spacing behavior of males in M. agrestis. Males were radio-tracked in enclosed natural habitats in which females at different densities were placed in two different spatial arrangements: clumped versus even distribution. Female density was the main factor determining male spacing behavior. At the high female density males had smaller home ranges and moved shorter distances between radio-tracking recordings. Also, home ranges were more exclusive at high female density. However, since there was a significant positive correlation between home range size and range overlap, range exclusiveness seemed to be influenced by female density indirectly through the effect of range size. Female spatial distribution, on the other hand, had no influence on male home range exclusiveness.     

Comparative electrophysiological analysis of plant odor perception in females of threePapilio species

Summary Antennae of femalePapilio butterflies perceive many volatile plant constituents with widely differing, constituent-specific sensitivities. We compared the responses of threePapilio species to volatiles from host and non-host plants to assess species-specificity and the degree of evolutionary conservatism in olfactory responses.Since previous studies had demonstrated that the polar constituents in odor fromDaucus carota stimulate oviposition behavior inPapilio polyxenes, we collected headspace volatiles fromD. carota, Pastinaca sativa (both Apiaceae) andArtemisia dracunculus (Asteraceae) and separated the polar fraction of these volatiles by gas chromatography. GC-coupled electroantennograms (GC-EAG) were recorded from the speciesPapilio polyxenes, P. machaon hippocrates andP. troilus. In addition, the responses of the three species to five compounds known as generally occurring constituents of plant odor were recorded. The relative sensitivities for these compounds were nearly identical in all threePapilio species. The response spectra to the separated plant volatiles also showed considerable similarities among the species.From the limited set of GC peaks evoking a response in one of the species, 64% (D. carota), 44% (P. sativa) and 29% (A. dracunculus) also evoked a response in both of the other species. The responses of the two closely related Apiaceae feeders (P. polyxenes, P. m. hippocrates) to volatiles fromD. carota were more similar to each other than was either to the response ofP. troilus, which feeds on Lauraceae. However, this was not true for the responses to volatiles fromP. sativa. The least congruence among the three species was found in the responses to volatiles fromA. dracunculus, a non-host for all of them. The differences and similarities found in the response profiles of the threePapilio species are discussed with respect to evolutionary adaptation to host odor versus evolutionary conservatism in adaptation of olfactory receptors.     

Social organization in the bat Pipistrellus pipistrellus

Summary The social organization of the pipistrelle bat (Pipistrellus pipistrellus) was studied by means of bat boxes in southern Sweden. The males set up territories around a roosting site in the beginning of the summer at the same time as the females formed nursing colonies. After breeding, the females joined the single males in their day roosts establishing transient mating harems. Subsequently, immatures arrived at the mating grounds. The immature females, which probably attained sexual maturity during their first autumn, were admitted to the day roosts of the harem males, in contrast to the immature males. The size of the harem was dependent on the total number of females present on the mating grounds. The size, however, was also restricted by some factor, presumably the quantity of food resources in the surroundings of the specific roost site, or the capability of the harem male for mating. The mating system in the pipistrelle bat is best characterized as a resource defence polygyny. Available data on other related temperate species indicate a similar social organization in Pipistrellus nathusii and Nyctalus noctula.     

Food availability and diet composition of three coexisting Mediterranean limpets (Patella spp.)

The gut contents of three intertidal patellid limpets were analysed by collecting foraging specimens on a breakwater on the Tyrrhenian coast (central Italy) between May 1988 and October 1989. The three species coexist there showing a different, but partially overlapping zonation: Patella aspera dominates the infralittoral fringe; the majority of P. caerulea inhabits the lower midlittoral, while P. rustica is most abundant in the upper midlittoral. The algae present on slivers of substratum over which each limpet collected was moving were identified. Moreover, floristic surveys were made along the shore in order to characterize the algal cover of the different zonal belts. The floristic study revealed that the basic elements of algal communities typical of western Mediterranean rocky shores are present in the study area. The algae found on the slivers under the foraging limpets were generally representative of the algal community typical of the same zone. There was a marked difference between the diets of P. rustica and P. aspera due to the fact that the first species forages on a few low lying epilithic and endolithic Cyanophyceae, while P. aspera feeds on a large number of species belonging to all the main algal classes and life forms considered, including frondose epilithics and epiphytics. The diet of P. caerulea resembles that of P. aspera in algal heterogeneity, but is dominated by Cyanophyceae as in P. rustica. A detailed analysis of the differences between gut contents of each limpet species and the relative slivers showed an obvious general correspondence, but revealed also that the diets of the three species do not completely reflect the availability of algae. These findings suggest that the basic diet segregation mechanism between the three populations is their zonal separation. However, the difference in gut contents of heterospecific limpets foraging in the same zone suggests the existence of supplementary morphy-functional or behavioural mechanisms for diet segregation between the three species.     

Benthic macrophyte communities in the Ghar El Melh lagoon (North Tunisia)

This work deals with the biodiversity and distribution of benthic macrophytes in the Ghar El Melh lagoon, a Mediterranean coastal lagoon located in the North of Tunisia. An inventory was made of the benthic flora and submerged macrophyte communities were mapped during two successive campaigns (the summer of 1999 and the winter of 2000). The following 24 macrophyte species were identified: seven red algae, two brown algae, 11 green algae, and four marine angiosperms. The results were compared with available data from the literature. Ruppia cirrhosa is the most dominant species. It is found in all lagoon parts, except in the west sector.Ruppia beds are usually associated withCladophora forming heterogeneous communities. During summerRuppia cirrhosa shows a large distribution, covering an area of ca. 21.4 km², with dense, extensive beds covering 80–100%. In winter, severalCladophora species have a very large distribution as well, covering nearly an area of 28.5 km² with an average cover of 46%. The green algaeCaulerpa prolifera is confined to the eastern part of the lagoon which is mainly affected by seawater. In comparison with previous situations, many transformations were observed in biodiversity and spatial distribution of the dominant communities. Thus,Cymodocea nodosa andZostera beds, which dominated in the 1970s, were replaced byZostera andCaulerpa prolifera in the 1980s and are currently succeeded byRuppia cirrhosa andCladophora. Restoration of the Ghar El Melh lagoon will enable an increase in the exchange with the open sea and the circulation of water, in particular in the confined zones. This should considerably improve the water quality and would positively influence the phytobenthic communities.     

Oceanographic characteristics of areas used by Cory’s shearwaters during short and long foraging trips in the North Atlantic

Many breeding seabird species are central-place foragers and constrained to find productive prey patches within their foraging ranges. We assessed how different populations of a pelagic seabird species, the Cory’s shearwater Calonectris diomedea, breeding in oceanic and neritic conditions, cope with these constraints in the North Atlantic, during both incubation and chick-rearing periods. We analysed 237 foraging trips to study the movements and oceanographic characteristics of foraging habitats of seven different populations of Cory’s shearwaters. Generally, oceanic populations exhibited higher foraging effort, by travelling more time and to more distant areas, and larger home ranges and feeding areas, than the neritic population (i.e. breeding on an island within the Portuguese continental platform). On their short trips (i.e. ≤4 days), birds from the different populations fed mostly in shallower waters around the colony. During long trips (i.e. ≥5 days), feeding areas of both oceanic and neritic populations were characterized by high concentration values of chlorophyll-a, low sea-surface temperature and shallower habitats, with oceanic populations of the Azores exploiting areas north of the islands over known seamounts and frontal regions. Birds from other oceanic population (Selvagens) also exploited the African continental shelf system on their long trips. The home ranges of the different populations overlapped widely, but there was a general spatial segregation in terms of the core feeding areas at the population level. Core feeding areas and areas of foraging overlap between different populations should be important to inform conservation management measures, such as the definition of Marine Important Bird Areas for seabirds over the North Atlantic.     

Oviposition stimulants and deterrents control acceptance ofAlliaria petiolata byPieris rapae andP. napi oleracea

Summary Differential acceptance of garlic mustard,Alliaria petiolata byPieris rapae L. andP. napi oleracea is explained by their differential sensitivities to oviposition stimulants and deterrents in the plant. Fractions containing the stimulants and deterrents were isolated by solvent partitioning between water and n-butanol and by open-column chromatography followed by HPLC.P. napi oleracea showed no preference when offered a choice ofA. petiolata or cabbage, but was strongly stimulated to oviposit by post-butanol water extracts ofA. petiolata. The most abundant glucosinolate in this extract was identified as sinigrin, which could explain the high degree of stimulatory activity.P. rapae preferred cabbage plants overA. petiolata, and the relatively low stimulatory activity was also associated with the glucosinolate-containing aqueous extract. However, this species was strongly stimulated by a fraction that contained small amounts of glucotropaeolin along with unknown compounds. Deterrents to both species were found in the butanol extract fromA. petiolata, andP. napi oleracea was more sensitive thanP. rapae to these deterrents. Some HPLC fractions from the BuOH extract were strongly deterrent toP. napi oleracea, but were inactive toP. rapae. The ecological significance of these behavioral differences between the twoPieris species is discussed.     

Mechanisms of habitat segregation between an invasive (Mytilus galloprovincialis) and an indigenous (Perna perna) mussel: adult growth and mortality

The invasive mussel Mytilus galloprovincialis and the indigenous mussel Perna perna coexist intertidally on the south coast of South Africa through partial vertical habitat segregation: M. galloprovincialis dominates the upper shore and P. perna the lower shore. Recruitment patterns can explain the zonation of P. perna, but not the invasive species. We examined the role of post-recruitment interactions by measuring spatial and temporal differences in adult growth and mortality rates of the two species. Specifically, we tested the hypothesis that interspecific differences in growth and mortality reflect adult distribution patterns. The two study locations, Plettenberg Bay and Tsitsikamma, are 70 km apart with two sites (separated by 300–400 m) per location, each divided into three vertical zones. Growth was measured seasonally using different marking methods in 2001 and 2003. Cumulative adult mortality was measured through summer in 2003/2004. Both species generally grew more slowly upshore, but they showed different effects of season. For P. perna, growth was significantly reduced in winter in the low zone, but unaffected by season in the high zone. For M. galloprovincialis, growth was either unaffected by season or increased in winter, even in the high zone. Thus, growth of P. perna and M. galloprovincialis was reduced under cool winter and warm summer temperatures, respectively; and while growth was more similar between species in summer, M. galloprovincialis grew much faster than P. perna in winter. Mortality of P. perna increased upshore. For M. galloprovincialis, mortality was not zone-dependent and was significantly greater than for P. perna on the low-shore and (generally) across the shore in Tsitsikamma. Both species had higher growth and mortality rates in Plettenberg Bay than in Tsitsikamma. Thus, P. perna seems able to maintain spatial dominance on the low-shore and at certain sites because of higher mortality of M. galloprovincialis. We conclude that seasonality in growth of the two species reflects their biogeographic affinities and that coexistence is possible through pre-recruitment effects that limit the vertical distribution of P. perna and post-recruitment effects that limit M. galloprovincialis.     

Choosing rewarding flowers; perceptual limitations and innate preferences influence decision making in bumblebees and honeybees

Flowers exhibit great intra-specific variation in the rewards they offer. At any one time, a significant proportion of flowers often contain little or no reward. Hence, foraging profitably for floral rewards is problematic and any ability to discriminate between flowers and avoid those that are less rewarding will confer great advantages. In this study, we examine discrimination by foraging bees among flowers of nasturtium, Tropaeolum majus. Bee visitors included carpenter bees, Xylocopa violacea, which were primary nectar robbers; honeybees, Apis mellifera, which either acted as secondary nectar robbers or gathered pollen legitimately and bumblebees, Bombus hortorum, which were the only bees able to gather nectar legitimately. Many flowers were damaged by phytophagous insects. Nectar volume was markedly lower in flowers with damaged petals (which were also likely to be older) and in flowers that had nectar-robbing holes. We test whether bees exhibit selectivity with regards to the individual flowers, which they approach and enter, and whether this selectivity enhances foraging efficiency. The flowers approached (within 2 cm) by A. mellifera and B. hortorum were non-random when compared to the floral population; both species selectively approached un-blemished flowers. They both approached more yellow flowers than would be expected by chance, presumably a reflection of innate colour preferences, for nectar standing crop did not vary according to flower colour. Bees were also more likely to accept (land on) un-blemished flowers. A. mellifera gathering nectar exhibited selectivity with regards to the presence of robbing holes, being more likely to land on robbed flowers (they are not able to feed on un-robbed flowers). That they frequently approached un-robbed flowers suggests that they are not able to detect robbing holes at long-range, so that foraging efficiency may be limited by visual acuity. Nevertheless, by using a combination of long-range and short-range selectivity, nectar-gathering A. mellifera and B. hortorum greatly increased the average reward from the flowers on which they landed (by 68% and 48%, respectively) compared to the average standing crop in the flower population. Overall, our results demonstrate that bees use obvious floral cues (colour and petal blemishes) at long-range, but can switch to using more subtle cues (robbing holes) at close range. They also make many mistakes and some cues used do not correlate with floral rewards.     

Responses of three mouse species to deterrent chemicals in the monarch butterfly. I. Taste and toxicity tests using artificial diets laced with digitoxin or monocrotaline

Summary Of three common mouse species at the Mexican overwintering sites of the monarch butterfly, onlyPeromyscus melanotis eats monarchs. We hypothesized thatP. aztecus andReithrodontomys sumichrasti reject monarchs because they are more sensitive to the bitter taste and/or toxic effects of the cardiac glycosides (CGs) and pyrrolizidine alkaloids (PAs) in the butterflies. Two-choice preference tests revealed no difference in taste avoidance thresholds to free base and N-oxide forms of the PA, monocrotaline, but very different avoidance thresholds to the CG, digitoxin. Avoidance thresholds forR. sumichrasti andP. aztecus were, in respective order, 1020 and 34 times less than that forP. melanotis. We also tested the toxic sensitivity of juvenile mice by chronically feeding diets containing digitoxin or monocrotaline at concentrations similar to those used in the preference tests. No species developed CG toxicity, but bothP. melanotis andP. aztecus developed moderate PA toxicity (R. sumichrasti was not tested for PA toxicity).P. aztecus grew more slowly and manyP. melanotis had hepatic metabolic lesions. Thus, the three mouse species responded very differently to the taste and toxic properties of CGs and PAs at ecologically relevant concentrations: 1) CGs were taste rejected by all species exceptP. melanotis, while PAs were not; and 2) PAs were toxic, while CGs were not.     

Sexual segregation in distribution,diet and trophic level of seabirds: insights from stable isotope analysis

Considerable attention has focused on inter- and intraspecific variation in trophic niches of marine predators. Although this has revealed evidence for sexual segregation in distribution in some species, few studies have been able to address sex-related dietary specialisation. Stable isotope analysis of blood cells collected from albatrosses and petrels at South Georgia during chick-rearing indicated a difference in δ¹³C, suggesting that females fed to the north of males, only in two species with male-biased sexual size dimorphism; in no species did sexes differ in trophic level (δ¹⁵N). Based on a wider review, significant differences between sexes in isotope signatures were much more common in seabirds during the pre-laying or breeding than the nonbreeding period, presumably reflecting greater between-sex partitioning of resources when foraging ranges are more constrained and competition is greater. Sex differences, or their absence, were usually consistent across successive stages during the pre-laying and breeding periods, but not necessarily year-round nor between populations. Significant differences in isotope signatures between males and females were extremely rare in monomorphic species, suggesting a link between sexual size dimorphism and segregation in diet or distribution. Among the Southern Ocean albatrosses, sex differences in δ¹³C suggested the underlying mechanism was related to habitat specialisation, whereas in other size-dimorphic taxa (both male- and female-biased), sex differences were more common in δ¹⁵N than δ¹³C and therefore more consistent with size-mediated competitive exclusion or dietary specialisation.     

Chemical mimicry of cuticular hydrocarbons – how does Eremostibes opacus gain access to breeding burrows of its host Parastizopus armaticeps (Coleoptera, Tenebrionidae)?

Summary. Breeding burrows of Parastizopus armaticeps armaticeps, a fossorial desert tenebrionid beetle, are cleptoparasitised by the closely related Eremostibes opacus. Gas chromatographic analyses show a high congruity of the cuticular hydrocarbons of both species. We compare these hydrocarbon patterns with those of four other Stizopina species and the Scaurini Herpiscius sommeri. In a bioassay, dummies treated with cuticular hydrocarbon extracts of E. opacus and the P. a. bifidus parasite E. bushmanicus were mostly ignored by P. a. armaticeps, whereas dummies with applied extracts of the remaining species were heavily attacked. We show that there is a correlation between agonistic behaviour of P. a. armaticeps towards the intruder and the chemical similarity of the cuticular hydrocarbons of the two species. Furthermore, we produced quantitatively modified hydrocarbon patterns of E. barbatus by changing the temperature at which this species was kept. The new 30 °C type was chemically similar to E. opacus, and was frequently ignored by P. a. armaticeps, whereas a reduction of the temperature to 20 °C only had minor effects on the hydrocarbon pattern. Furthermore, we show that the addition of one single component, heptacosane, to the cuticular hydrocarbon extract of E. opacus alters the host’s reaction. We discuss the role of cuticular hydrocarbons for the recognition of this host-parasite system and the relevance of quantitative characters in the hydrocarbon pattern for the discrimination of the host.