Net energetic advantage drives honey bees (Apis mellifera L) to nectar larceny in Vaccinium ashei Reade

Carpenter bees (Xylocopa spp.) act as primary nectar thieves in rabbiteye blueberry (Vaccinium ashei Reade), piercing corollas laterally to imbibe nectar at basal nectaries. Honey bees (Apis mellifera L) learn to visit these perforations and thus become secondary nectar thieves. We tested the hypothesis that honey bees make this behavioral switch in response to an energetic advantage realized by nectar-robbing flower visits. Nectar volume and sugar quantity were higher in intact than perforated flowers, but bees (robbers) visiting perforated flowers were able to extract a higher percentage of available nectar and sugar so that absolute amount of sugar (mg) removed by one bee visit is the same for each flower type. However, because perforated flowers facilitate higher rates of bee flower visitation and the same or higher rates of nectar ingestion, they are rendered more profitable than intact flowers in temporal terms. Accordingly, net energy (J) gain per second flower handling time was higher for robbers on most days sampled. We conclude that the majority evidence indicates an energetic advantage for honey bees that engage in secondary nectar thievery in V. ashei.Communicated by R. Page     

Co-evolution-driven cuticular hydrocarbon variation between the slave-making ant Rossomyrmex minuchae and its host Proformica longiseta (Hymenoptera: Formicidae)

Summary. Proformica longiseta exists as two populations in the Sierra Nevada Mountains in Spain, only one of which is parasitized by the slave-maker ant Rossomyrmex minuchae. To investigate the possible effect of co-evolutionary pressures on cuticular hydrocarbon (CHC) profiles (the presumed nestmate recognition cues), we performed a comparative analysis of the CHC of R. minuchae and P. longiseta colonies from both the allopatric and sympatric populations; the latter includes samples of enslaved as well as free-living workers. Discriminant analyses based on these chemical profiles showed two clear profile groups: the first comprised R. minuchae and both enslaved and free-living P. longiseta from the sympatric population; and the second the allopatric P. longiseta workers. As expected, the profiles of the two sympatric P. longiseta groups (enslaved and free-living) were distinct; but, interestingly, those of the enslaved P. longiseta and its parasite R. minuchae were also distinguishable. This indicates that despite their cohabitation each species maintains its own chemical identity. Profile similarity between the sympatric free-living P. longiseta and its parasite may explain the lower than expected aggression observed during raids. We further speculate that in view of the differences between the sympatric and allopatric population of P. longiseta, co-evolutionary pressures have driven changes in the profile of the former to better match that of its parasite R. minuchae. Such an adjustment may have enabled nests of the sympatric P. longiseta to endure multiple raids by the parasite (due to the reduced aggression) and thus to continue to reproduce despite the damage inflicted by the raids.     

The chemical basis for trail recognition in Lasius nipponensis (Hymenoptera: Formicidae)

Summary. In this paper we report on the chemical basis for trail recognition in Lasius nipponensis. On and near trails in the field, workers became aggressive against conspecific intruders and succeeded in protective contests, while intruders usually avoided confrontation. Such asymmetric interactions were also observed in the laboratory when two non-nestmate workers were sequentially placed in a clean glass dish, while mutual aggression was observed when they were placed simultaneously. Asymmetric aggression was also observed when the workers were placed in a dish previously conditioned by other workers, or when the dish was treated with the hexane rinse of the conditioned dish. The rinse contained a series of hydrocarbons, in which components and proportion were almost identical to those of the cuticular hydrocarbons of the workers, except for a lack of n-alkanes. Amounts of the hydrocarbons that remained on the dish were very small when all the tarsi of the workers were incapacitated. We therefore consider that the hydrocarbons are not adhesion of the cuticular hydrocarbons but secretion from the tarsi of workers, and serve as a key signal for trail recognition in this ant.     

Trail discrimination signal of Lasius japonicus (Hymenoptera: Formicidae)

Summary. Trail-following behavior of Lasius japonicus was colony-specific in the field, while trail pheromone activity was not. We found that the footprint substance caused colony-specific trail-following behavior only when working in conjunction with the trail pheromone. The footprint substance alone did not lead the workers to follow trails. The substance consisted mainly of hydrocarbons with composition almost identical to that of cuticular hydrocarbons, except for the absence of n-alkanes. Nestmate workers shared footprint hydrocarbon profiles as well as cuticular hydrocarbons, but the profiles differed among colonies. We therefore consider that the footprint hydrocarbon profiles serve as the trail discrimination signal in L. japonicus.     

Labial gland marking secretion in males of two Scandinavian cuckoo bumblebee species (genusPsithyrus)

Summary Chemical components of the cephalic labial gland secretion, which most likely is used as a precopulatory attracting signal, were identified in males of the cuckoo bumblebeesPsithyrus vestalis (Geoffroy) andP. bohemicus (Seidl.) by gas chromatography-mass spectrometry (GC-MS). The former species has geranylcitronellyl acetate as main component, plus in decreasing amounts geranylcitronellol, an eicosadienal, an eicosenol, and an eicosenal. Another 17 fatty acid derivatives are present in minor amounts. The labial secretion ofP. vestalis differs distinctly in its chemistry from that of all of the 8 other ScandinavianPsithyrus species. In the taxonomically closely related (same subgenus)P. bohemicus, the labial gland secretion contains 16 fatty acid derivatives, of which 12 (75%) are present also in the secretion ofP. vestalis. Thus, both the labial gland secretions, and morphological traits lend support to the hypothesis that the two species share a common ancestor. The reproductive isolation between them is, at least in part, supported by the inclusion of a second biosynthetical pathway (the mevalonic acid pathway producing terpenoids) inP. vestalis, in addition to the pathway common to both species (the polyketide pathway producing fatty acid derivatives).     

Chick recognition and acceptance: a weakness in magpies exploited by the parasitic great spotted cuckoo

Hosts of brood parasites have evolved the ability to discriminate non-mimetic and even mimetic eggs, but not non-mimetic chicks. Here we demonstrate that the great spotted cuckoo Clamator glandarius does not provide its magpie Pica pica host with a super-normal stimulus that helps to avoid recognition, because single cuckoo chicks introduced into otherwise unparasitized magpie nests are not fed at a higher frequency than single magpie chicks introduced to parasitized magpie nests. Another series of experiments demonstrated that magpies have the ability to discriminate cuckoo chicks, mainly when these are introduced at the end of the nestling period, and especially when the cuckoo chick together with a magpie chick is presented to adult magpies outside the nest. This supports the idea that cuckoos exploit the obligatory reaction of magpies to feed all young that have been hatched in their nests and whose signatures they have learnt. Furthermore, the experimental cuckoo chicks in parasitized magpie nests were more likely to be accepted than they were in non-parasitized nests. This supports the hypothesis that magpies may learn to recognise their own nestlings as those present in the nest and may indicate that a comparison between cuckoo and magpie nestlings is the basis of discrimination.     

Tarsal secretion marks food sources in bumblebees (Hymenoptera: Apidae)

Summary Scent-marking of artificial food sources by workers of the bumblebee,Bombus terrestris, was investigated. Odour marks deposited on artificial flowers were subsequently collected and chemically analysed. Alkanes and alkenes were identified as the main components. The behaviour mediating capacity of synthetic mixtures of the identified compounds was bioassayed using an artificial flower system. A mixture of alkanes and alkenes, close to natural proportions, released regular foraging behaviour. The reaction proved to be dose-dependent.     

Queen dimorphism and reproductive strategies in the fire ant Solenopsis geminata (Hymenoptera: Formicidae)

Alate trapping studies of a monogyne population of the fire ant Solenopsis geminata indicate that two sizes of gynes are produced. Macrogynes, which participate in late spring and summer mating flights, are larger, fattier, and more than twice as heavy as microgynes, which participate in fall mating flights. Three patterns of gyne production were observed in 51 colonies studied: 35 produced macrogynes only, 9 produced microgynes only, and 7 produced both morphs, contributing to both summer and fall mating flights. Behavioral evidence and rearing studies suggest that macrogynes found new colonies independently, whereas microgynes achieve colony queen status by infiltrating or being adopted by established colonies. Of the total number of female alates collected from the trapped colonies, 56% were microgynes. However, because of their smaller size and lower fat content, microgynes made up only one-third of the caloric investment in female alates. By measuring the thorax lengths of queens from mature colonies, we determined that at least 56% were macrogynes and 35% or more were microgynes. These results indicate that as a reproductive strategy, colony investment in microgyne production may have at least as high a payoff as investment in macrogyne production.This is publication #24 of the Fire Ant Research Team     

Parent-absent begging in the Brown-headed Cowbird (<Emphasis Type="Italic">Molothrus ater</Emphasis>): the role of short-term need and nestmate size

Although it is well-established that nestlings of many altricial species beg when parents are away from the nest, we have a poor understanding of parent-absent begging in brood parasites, including the proximate factors that may influence begging frequency and intensity. In this study, I examined how parent-absent begging was influenced by competitive asymmetries between host and Brown-headed Cowbird (Molothrus ater) nestlings under disparate levels of short-term need. Food-deprived cowbird nestlings begged more frequently and for a greater proportion of parent-absent period than when food-supplemented, with similar patterns observed in hosts of different sizes. In contrast, three metrics of cowbird begging intensity varied relative to host size but not due to differences in short-term need. Cowbirds consistently begged more frequently and intensively than host nestlings for a given level of short-term need, providing evidence that cowbird begging displays are more frequent and intense than non-parasitic nestlings during both feeding visits and parent-absent periods. In sum, the frequency of begging by cowbirds was only influenced by short-term need, whereas begging intensity during parent-absent events was only influenced by the host against which cowbirds competed. This study demonstrates that host size and short-term need had differing influences on the frequency and intensity of parent-absent begging in cowbirds, although both factors are likely important in limiting the evolution of parent-absent begging in cowbirds. Because it appears to provide no immediate benefits yet may decrease fitness, parent-absent begging should be included in future theoretical models investigating the evolution of begging displays in nestling birds.     

Shifting foraging strategies in colonies of the social wasp Polybia occidentalis (Hymenoptera, Vespidae)

Social insect colonies can be expected to forage at rates that maximize colony fitness. Foraging at higher rates would increase the rate of worker production, but decrease adult survival. This trade-off has particular significance during the founding stage, when adults lost are not replaced. Prior work has shown that independent-founding wasps rear the first workers rapidly by foraging at high rates. Foraging rates decrease after those individuals pupate, presumably reducing the risk of foundress death. In the swarm-founding wasps, colony-founding units have many workers, making colony death by forager attrition less likely. Do swarm-founding wasps show similar shifts in foraging rates during the founding stage? We measured foraging rates of the swarm-founding wasp, Polybia occidentalis at four stages of colony development. At each stage, foraging rates correlated with the number of larvae present, which, in the founding stages, correlated with the number of cells in the new nest. Thus, foraging rates appear to be demand-driven, with the level of demand in the founding stage set by the size of nest that is constructed. During the founding stage, foraging rates per larva were high initially, suggesting that colonies minimize the development times of larvae early in the founding stage. Later in the stage, foraging rates decreased, which would reduce worker mortality until new workers eclose. This pattern is similar to that shown for independent-founding wasps and likely results from conflicting pressures to maximize colony growth and minimize the risk of colony death by forager attrition.     

Species-specificity in trail pheromones and Dufour's gland contents ofCamponotus atriceps andC. floridanus (Hymenoptera: Formicidae)

Summary By means of gas chromatography, gas chromatographic coupled mass spectrometry, trail-following experiments and electrophysiological recordings from worker antennae, the major trail pheromone components from the hindgut of the formicine speciesCamponotus atriceps andC. floridanus were identified as 3,5-dimethyl-6-(1-methylpropyl)-tetrahydropyran-2-one and nerolic acid, respectively. The Dufour's gland contents of both species, investigated by gas chromatographic coupled mass spectrometry, show significant differences.Pheromones 104: Janssen E, Übler E, Bauriegel L, Kern F, Bestmann H-J, Attygalle AB, Steghaus-Kovacs S, Maschwitz U: Trail pheromone of the Ponerinae antLeptogenys peuqueti (Hymenoptera: Formicidae): a multicomponent mixture of related compounds     

Chemistry of the postpharyngeal gland secretion and its implication for the phylogeny of IberianCataglyphis species (Hymenoptera: Formicidae)

Summary A comparative morphological and chemical study of six endemic species ofCataglyphis from the Iberian Peninsula:C. ibericus, C. rosenhaueri, C. hispanicus, C. humeya, C. velox andC. floricola and the Moroccan speciesC. bombycinus is described. The morphological study relied primarily on genitalia characteristics, whereas the chemical study concentrated on the postpharyngeal gland constituents. Cladograms based on the morphological and chemical data were performed using Ward's method. The dendrogram based on morphological features revealed that the IberianCataglyphis can be classified into three species groupsalbicans, altisquamis andemmae. The same pattern occurred when the dimethylalkanes constituents of the postpharyngeal gland were utilised as character states, with a slight displacement of species within thealtisquamis group. However, when the complete hydrocarbon blend was utilised major discrepancies in the dendrograms occurred.Cataglyphis velox proved to be very similar toC. bombycinus, whereasC. floricola clustered with the other two species of thealtisquamis group. Based on the geographical distribution and paleontological data (Tinaut 1993) it is assumed thatC. floricola recently invaded the Iberian Peninsula. Based on the chemical findings we postulate that chemical character displacement occurred inC. floricola as a result of its sympatry withC. velox after the former colonized the Iberian Peninsula. We further discuss the possible reason for the different dendrograms obtained when only the dimethylalkanes are considered and its implication for the communicative role of the postpharyngeal gland secretion in these ants.     

12种杀菌剂制剂对半闭弯尾姬蜂的急性毒性及安全性评价

采用试管药膜法测定了12种杀菌剂制剂对半闭弯尾姬蜂成蜂的急性接触毒性,结合安全性系数评价了供试药剂对半闭弯尾姬蜂的安全性。急性毒性测定结果表明,氟硅唑和啶菌噁唑对半闭弯尾姬蜂成蜂的接触毒性最高,LC50值分别为220.022和223.115 mg·L-1;其次为多抗霉素、丙森锌和戊唑醇,LC50值分别为436.496、472.358和638.638 mg·L-1;其余7种杀菌剂制剂嘧霉胺、啶酰菌胺、苯醚甲环唑、多菌灵、嘧菌酯、嘧菌环胺和异菌脲对半闭弯尾姬蜂成蜂的触杀毒性都较低,LC50值均大于1 000 mg·L-1。安全性评价结果表明,丙森锌和啶菌噁唑对半闭弯尾姬蜂成蜂具有高风险性,安全系数分别为0.16和0.42;嘧霉胺、多抗霉素、氟硅唑和戊唑醇为中等风险性,安全系数分别为1.43、1.56、2.20和3.23;其余6种杀菌剂制剂啶酰菌胺、苯醚甲环唑、多菌灵、嘧菌酯、嘧菌环胺和异菌脲对半闭弯尾姬蜂表现为低风险性,安全系数均大于5。结果显示:甾醇脱甲基抑制剂氟硅唑、戊唑醇和啶菌噁唑以及苯胺基嘧啶类杀菌剂嘧霉胺、有机硫杀菌剂丙森锌和抗菌素多抗霉素对半闭弯尾姬蜂成蜂具有急性毒性风险,在有害生物综合治理中应谨慎使用,特别是啶菌噁唑和丙森锌,以免对半闭弯尾姬蜂造成不良影响和危害。     

A stingless bee (Melipona panamica) indicates food location without using a scent trail

The study of location specification in recruitment communication by bees has focused on two dimensions: direction and distance from the nest. Yet the third dimension, height above ground, may be significant in the tall and dense forest habitats of stingless bees. Foragers of the stingless bee Scaptotrigona postica recruit to a specific three-dimensional location by laying a scent trail. Stingless bees in the genus Melipona are thought to have a more sophisticated recruitment system that communicates distance through sounds inside the nest and direction through pointing zig-zag flights outside the nest. However, prior research on Melipona has not examined height communication or even established that foragers can recruit newcomers to a specific location. We used identical paired feeders to investigate recruitment to food in M panamica on Barro Colorado Island, Panama. We trained foragers from an observation hive to one feeder and monitored both feeders for the subsequent arrival of newcomers. We changed the relative positions of the feeders to test for correct direction, distance, and canopy-level communication. A 40-m canopy tower located inside the forest enabled us to examine canopy-level communication. We found that M. panamica foragers can recruit to a specific (1) direction, (2) distance, and (3) canopy level. To test the possibility that foragers accomplish this by means of a scent trail, we placed the colony on one shore of a small cove and trained bees over 116 m of open water to a feeder located on the opposite shore. We also placed a second feeder on this shore, equidistant from the colony but 20 m from the first feeder. Significantly more newcomers consistently arrived at the feeder visited by the foragers. Thus foragers evidently do not need a scent trail to communicate direction. Inside the nest, a forager produces pulsed sounds while visibly vibrating her wings after returning from a good food source. She is attended by other bees who cluster and hold their antennae around her, following her as she rapidly spins clockwise and counterclockwise. Locational information may be encoded in this behavior. However, foragers may also directly lead newcomers to the food source. Further experiments are planned to test for such piloting and other communication mechanisms.     

The ability of conditioned Microplitis croceipes (Hymenoptera: Braconidae) to distinguish between odors of aflatoxigenic and non-aflatoxigenic fungal strains

Summary. The parasitic wasp Microplitis croceipes (Cresson) (Hymenoptera: Braconidae) learns to associate odors with food resources and subsequently exhibits a characteristic food-seeking behavior when encountering the learned odor. Wasps so conditioned, learned and subsequently demonstrated an ability to distinguish among aflatoxigenic and non-aflatoxigenic Aspergillus flavus and A. parasiticus strains. The effects of fungal species, strain, age (5, 10-12, 20, and 30 d) and growth media (potato dextrose agar, peanut agar and corn agar) on the learning and recognition responses of the conditioned wasps were examined. The level of differentiation between fungal strains by conditioned wasps was lowest when working with 5-d-old fungal cultures but increased with age and generally peaked with 20-d-old fungi. Wasps responded generally stronger to the fungal strain conditioned to independent of growth media. This ability of parasitic wasps to learn and distinguish fungal odors can open new avenues in insect learning.     

Cleptoparasitism increases the host finding ability of a polyphagous parasitoid species,<Emphasis Type="Italic"> Rhopalicus tutela</Emphasis> (Hymenoptera: Pteromalidae)

Host finding abilities were investigated in the braconid Coeloides bostrichorum and the pteromalid Rhopalicus tutela, two ectoparasitoid wasps attacking the late instar of the bark beetle Ips typographus. Under laboratory conditions, important differences in the host-searching behaviour of these species were found, R. tutela being highly mobile as compared to C. bostrichorum. In the presence of C. bostrichorum, R. tutela behaved as a cleptoparasitoid, displacing the females from their oviposition sites and stealing the hosts previously located by the braconid. This behaviour facilitated host finding in R. tutela and could partly explain the relative success of the polyphagous R. tutela when occurring with the more specialised C. bostrichorum.Communicated by R.F.A. Moritz     

Experimental support for the use of egg uniformity in parasite egg discrimination by cuckoo hosts

Common cuckoo (Cuculus canorus) parasitism drastically reduces the reproductive success of their hosts and selects for host discrimination of cuckoo eggs. In a second stage of anti-parasite adaptation, once cuckoos can lay eggs that mimic those of their hosts, a high uniformity of host egg appearance within a clutch may favour cuckoo egg discrimination. Comparative evidence provides indirect support for this hypothesis although experimental support is currently lacking. Here, we studied the effect of experimentally decreased uniformity of host egg appearance on cuckoo egg discrimination by great reed warbler (Acrocephalus arundinaceus) hosts in a population in which long-term cuckoo parasitism has led to high levels of cuckoo–host egg mimesis. We manipulated host clutch uniformity by adding extra spots to fresh host eggs just after they were laid. Rejection of non-mimetic experimental eggs added to these nests was compared with those in control nests in which uniformity was not altered. Previously, by over-painting real spots in a control group of nests, we showed a negligible effect of our paints on hosts’ perception of their eggs. We show that for the great reed warbler, non-mimetic experimental eggs were relatively more tolerated in experimental nests, i.e. with lower uniformity (40%) than in control nests (5%). This is the first experimental study, to our knowledge, which demonstrates a reduced discrimination of foreign eggs as a consequence of an increase of egg phenotypes variation perception in a cuckoo host.     

Chemical recognition of queen cells by honey bee workersApis mellifera (Hymenoptera: Apidae)

Summary Honey bee workers are able to nurse or to destroy and thus to recognize the capped queen cells containing a pupa. Fatty acid esters, especially methyl oleate, methyl palmitate and ethyl oleate were found in significant amounts on the queen pupal cuticle. Methyl oleate, the major component, along with smaller amounts of methyl linoleate and methyl linolenate, were involved in the recognition of queen cells by workers. In natural conditions of the colony, queen cells containing a paraffin pupal lure with methyl oleate were accepted 5.9 days by workers, releasing about 1.8 queen pupa equivalents during that period, when control cells (without ester) were kept only 2.1 days. Although these esters are non specific to honey bees, they are of great importance in social regulation of the honey bee colony.     

Attraction,deterrence or intoxication of bees (Apis mellifera) by plant allelochemicals

The influence of 63 dietary allelochemicals (alkaloids, terpenes, glycosides,etc.) on the feeding behaviour of bees (Apis mellifera) was tested in terms of deterrency and attraction. For 39 compounds a deterrent (mostly alkaloids, coumarins and saponins) and for 3 compounds an attractive response (mostly terpenes) was obtained in choice tests, which allowed the calculation of respective ED₅₀-values. Under no-choice conditions, 17 out of 29 allelochemicals caused mortality at concentrations between 0.003 and 0.6%. Especially toxic were alkaloids, saponins, cardiac glycosides and cyanogenic glycosides. These data show that bees which are confronted with plant allelochemicals in nectar and pollen, are not especially adapted (i.e. insensitive) to the plants' defence chemistry. GLC and GLS-MS data are given on the alkaloid composition of nectar and pollen ofBrugmansia aurea, Atropa belladonna andLupinus polyphyllus.     

Information transfer during recruitment in the ant<Emphasis Type="Italic"> Lasius niger</Emphasis> L. (Hymenoptera: Formicidae)

In this paper, we used the food-correlated search behavior observed in foraging ants returning to a previously rewarding site to study information transfer during recruitment in the ant Lasius niger. We hypothesized that, if information about the characteristics of the food is conveyed during recruitment, food-correlated search tactics should also be observed in recruited workers. Our results show that the characteristics of the trajectories of recruited workers are comparable to those of scout ants returning to a site or prior food find and depend more on the type (prey/sugar) than on the quality (sugar concentration) of the food discovered by the scouts. Independent of sugar concentration, workers recruited to a source of sugar search with a greater sinuosity than workers recruited to a prey. Experimental manipulation of the recruitment signals (chemical trail and contact between ants) shows that the trail pheromone laid down by recruiting ants does not play a role in the modification of trajectory sinuosity. This change appears to be most likely triggered by a direct perception of the residue of sugar smeared on the body of the recruiting workers coming back to the nest.Communicated by J. Heinze