Kin Recognition in the largely Solitary Bee,Manuelia postica (Apidae: Xylocopinae)

The recognition of conspecifics is a central issue to social behaviour. In eusocial hymenopterans, kin recognition has been clearly demonstrated. Manuelia postica is a largely solitary bee species in which larvae develop inside individual cells within a nest and remain isolated from conspecifics until the destruction of partitions by adults. Nestmate recognition in M. postica has been previously demonstrated under experimental conditions. Isolation between individuals during development and nestmate recognition ability in adult females make M. postica an ideal species for testing the occurrence of kin recognition capacity in females. Kin recognition was demonstrated through cross‐fostering field experiments involving the single transfer of recently enclosed larvae, and subsequent laboratory recognition bioassays with emerging females. Results suggest kin recognition occurs through self‐referent phenotype matching. Given the basal position of Manuelia in the phylogeny of the Apidae, kin recognition may represent an ancestral recognition mechanism in Apidae species phylogenetically more derived than M. postica.     

Host Location by Ichneumonid Parasitoids is Associated with Nest Dimensions of the Host Bee Species

Parasitoid fitness depends on the ability of females to locate a host. In some species of Ichneumonoidea, female parasitoids detect potential hosts through vibratory cues emanating from them or through vibrational sounding produced by antennal tapping on the substrate. In this study, we (1) describe host location behaviors in Grotea gayi Spinola (Hymenoptera: Ichneumonidae) and Labena sp. on nests of Manuelia postica Spinola (Hymenoptera: Apidae), (2) compare nest dimensions between parasitized and unparasitized nests, (3) correlate the length of M. postica nests with the number of immature individuals developing, and (4) establish the relative proportion of parasitized nests along the breeding period of M. postica. Based on our results, we propose that these parasitoids use vibrational sounding as a host location mechanism and that they are able to assess host nest dimensions and choose those which may provide them with a higher fitness. Finally, we discuss an ancestral host?Cparasitoid relationship between Manuelia and ichneumonid species.     

Evolution of social behaviour in the primitively eusocial wasp Ropalidia marginata: do we need to look beyond kin selection?

Ropalidia marginata is a primitively eusocial wasp widely distributed in peninsular India. Although solitary females found a small proportion of nests, the vast majority of new nests are founded by small groups of females. In such multiple foundress nests, a single dominant female functions as the queen and lays eggs, while the rest function as sterile workers and care for the queen''s brood. Previous attempts to understand the evolution of social behaviour and altruism in this species have employed inclusive fitness theory (kin selection) as a guiding framework. Although inclusive fitness theory is quite successful in explaining the high propensity of the wasps to found nests in groups, several features of their social organization suggest that forces other than kin selection may also have played a significant role in the evolution of this species. These features include lowering of genetic relatedness owing to polyandry and serial polygyny, nest foundation by unrelated individuals, acceptance of young non-nest-mates, a combination of well-developed nest-mate recognition and lack of intra-colony kin recognition, a combination of meek and docile queens and a decentralized self-organized work force, long reproductive queues with cryptic heir designates and conflict-free queen succession, all resulting in extreme intra-colony cooperation and inter-colony conflict.     

Spatial Nest‐Settlement Decisions in Digger Wasps: Conspecifics Matter more than Heterospecifics and Previous Experience

Research into the driving forces behind spatial arrangement of wasp nests has considered abiotic environmental factors, but seldom investigated attraction or repulsion towards conspecifics or heterospecifics. Solitary female digger wasps (Hymenoptera) often nest in dense aggregations, making these insects good models to study this topic. Here, we analysed the nesting patterns in an area shared by three species of the genus Bembix, in a novel study to discover whether female wasps are attracted to or repulsed by conspecific nests, heterospecific nests or their own previously established nests when choosing nest‐digging locations. Early in the season, each species showed a clumping pattern of nests, but later in the season, a random distribution of nests was more common, suggesting an early conspecific attraction. Such behaviour was confirmed by the fact that females started building their nests more frequently where other females of their species were simultaneously digging. The distances between subsequent nests dug by individual females were shorter than those obtained by random simulations. However, this pattern seemed to depend on the tendency to dig close to conspecifics rather than remain in the vicinity of previous nests, suggesting that females' experience matters to future decisions only on a large scale. Nesting patches within nest aggregations largely overlapped between species, but the nests of each species were generally not closer to heterospecific nests than expected by chance, suggesting that females are neither repulsed by, nor attracted to, congenerics within nest aggregations. A role of the spatial distribution of natural enemies on the observed nesting patterns seemed unlikely. Bembix digger wasp nest aggregations seem thus to be primarily the result of female–female attraction during nest‐settlement decisions, in accordance with the ‘copying’ mechanisms suggested for nesting vertebrates.     

木蜂的巢内行为和交配策略

木蜂Xylocopa作为蜜蜂科的一个重要类群, 用来研究昆虫社会进化早期阶段具有重要意义。本文综述了近年来木蜂的营巢习性、 社会性行为和交配策略的研究进展。木蜂巢的建筑与巢内巢室的分布、 巢室的大小、 贮备蜂粮的效率和被寄生的敏感性等均有一定的关系。在筑巢地点, 随着木蜂种群数量的增加, 同种雌蜂之间的资源存在着竞争, 木蜂对巢室的守卫加强, 更多地表现为对同种雌蜂的守卫以及防御其他的天敌入侵。其社会多态性由独栖性向社会性演化, 主要表现为独栖性、 亚社会性、 半社会性、 共生性和准社会性等方式, 甚至同一种群内会出现不同的社会性行为。在交配策略上, 木蜂的雄蜂在外部形态特征上具有适应交配和寻找雌蜂的进化特征, 并且具有复杂的领地行为。这些研究理论对于我们深刻理解木蜂的行为生物学具有重要意义, 同时也有助于进行更深层次的社会性蜂类演化进程的探索。     

Surface Chemicals Inform about Sex and Breeding Status in the Biparental Burying Beetle Nicrophorus vespilloides

The multicomponent nature of chemical cues and signals are not very well understood. One reason for the often found complexity of chemical blends might be that they provide multiple messages. Burying beetles which use vertebrate carcasses as food for their larvae and defend these carcasses against inter- and intraspecific competitors are able to recognise the sex and breeding status of conspecifics. Studies have shown that the chemical composition of cuticular lipids is correlated with sex and breeding status, but there is no definitive evidence that these chemicals function in recognition. In the present study, we performed behavioural bioassays to directly asses the role of chemical cues in the recognition system of the burying beetle Nicrophorus vespilloides . After finding a carcass, females were more tolerant of dead males than of females. The behaviour was reversed when a solvent extract from the opposite sex was applied. An earlier experiment had shown that females breeding on a carcass treat non-breeding males more aggressively than breeding ones. In the present study, we could trigger the same dichotomous behaviours by presenting a single elytron from a breeding and a non-breeding beetle. In an additional experiment, females tolerated the elytra of non-breeding beetles if we had first applied an extract from a breeding beetle to these elytra. Our study is the first behavioural proof that female burying beetles obtain multiple information from chemical cues.     

Helping behaviour in facultatively eusocial hover wasps: an experimental test of the subfertility hypothesis

A candidate explanation for the evolution of eusociality is that helpers are physiologically constrained such that helping is their only realistic option. We tested this subfertility hypothesis in a species of facultatively eusocial hover wasp (Hymenoptera, Stenogastrinae: Liostenogaster flavolineata) by seeing whether helpers that were forced to nest on their own were able to mature their own eggs. One focal helper was left alone on each of 22 nests, from which all other adult wasps (including the dominant) were permanently removed. After 18 days, all but one of the 19 focal helpers that remained on their nests had ovarian development and insemination status characteristic of dominants, and the majority had probably laid eggs. This was in striking contrast to the reproductive status of other helpers removed from the same nests at the start of the experiment. These results provide convincing experimental evidence that females do not become helpers because of some unconditional physiological constraint. There is currently no unequivocal support for the subfertility hypothesis in facultatively eusocial Hymenoptera lacking morphological castes. Copyright 1999 The Association for the Study of Animal Behaviour.     

Lasioglossum (Dialictus) tenax (Sandhouse) (Hymenoptera: Halictidae) as a solitary sweat bee

Summary Nine nests ofLasioglossum (Dialictus) tenax were excavated near Calgary, Alberta, Canada over a time period encompassing the entire brood production period in 1988. Each nest contained a maximum of one active adult female, nest productivity peaked in mid July, protandry was noted and no significant size difference between foundresses and the earlier emerging females was detected. These data suggest that this species is solitary. These results are compared with data for the sympatrically nesting eusocial speciesL. (D.) laevissimum.     

An alternative strategy for maintenance of eusociality after nest destruction: new nest construction in a primitively eusocial wasp

Although nests are central to colonial life in social insects, nests are sometimes damaged by predators or natural disasters. After nest destruction, individuals usually construct new nests. In this case, a sophisticated mechanism like the scent trail pheromone used in large insect colonies that recruit individuals to new nest sites would be important for the maintenance of eusociality. In independent-founding Polistes wasps, it is well known that queens enforce workers physiologically on the natal nests even if evidence of trail pheromone use has not been exhibited. We investigated the effect of the queen on an alternative strategy for the maintenance of eusociality by first females after nest destruction in the primitively eusocial wasp Polistes chinensis. We predicted that the first females in queen-absent colonies have various behavioral options after nest destruction. Even if the females construct new nests cooperatively with other individuals, the new nest construction should be conducted more smoothly in queen-present colonies because the queens regulate the behavior of wasps. We made wasps construct new nests by removing the entire brood from existing nests. The presence of the queen did not cause variation in the alternative strategy of the first females, as the first females (workers) usually constructed new nests cooperatively irrespective of the queen-presence. Thus, the workers in the queenpresent colonies affiliated to the new nest construction more smoothly and constructed new nests more efficiently than workers in the queen-absent colonies. Our results suggest that the presence of the queen is important for maintaining eusociality in primitively eusocial wasps after nest destruction. Received 8 February 2005; revised 5 October 2005; accepted 17 October 2005.     

An overview of proximate factors affecting the nesting behavior of solitary wasps and bees (Hymenoptera: Aculeata) in preexisting cavities in wood

Guilds of Aculeate solitary wasps and bees that nest in preexisting cavities in wood are important components of terrestrial ecosystems because they engage in several ecological interactions (e.g. predation and pollination) with other species of plants and animals. Spatial and temporal variations in richness and abundance of solitary wasps and bees can be related to changes in environmental structure and in the diversity of other groups of organisms. The nesting period of these Aculeata is their most critical life cycle stage. Females of solitary wasp and bee species invest relatively more time constructing and provisioning their nests than do females of social species. Differently from species that nest in the soil or construct exposed nests, the main factors affecting the reproductive success of solitary species nesting in preexisting wood holes are still unknown. Our objective is to provide an overview of the role of proximate causes of nesting failure or success among solitary wasps and bees (Aculeata), for designing effective conservation and management strategies for these Hymenoptera.     

Not all who wander are lost: nest fidelity in <Emphasis Type="Italic">Xylocopa virginica</Emphasis> examined by mark recapture

Relocation to novel nests (sometimes called drifting) in flying Hymenoptera is often interpreted as the result of navigation error and guard bees erroneously admitting foreign individuals into the nest. We studied nest fidelity and nest relocation of both females and males in a nesting aggregation of Xylocopa virginica in southern Ontario, Canada, where females can nest either solitarily or socially. Adult female and male bees were trapped at nest entrances, individually paint marked, and then released. Subsequent recapture patterns were used to assess nest fidelity: that is, how faithful individuals were to their home nest and how often they moved to another nest. Bees were considered to have relocated if they were recaptured in a nest different from the one in which they were initially trapped, indicating that they had spent at least one night in a new nest. Some females were only captured in one nest, some occasionally moved to new nests, temporarily or permanently, and a few were never caught in the same nest twice. In addition, females relocated to nests that were further away in 2007 when population density was low, suggesting that they seek out and claim nesting spaces when they are available. Males relocated more frequently than females, with most drifting from nest to nest in no obvious pattern. This indicates that males spend the night wherever space is available or in nests nearest to their territories. This study reveals that for both female and male X. virginica, nest membership is not as stable as once thought.     

The Significance of the Vestibular Cell in Trap Nesting Wasps (Hymenoptera: Crabronidae): Does its Presence Reduce Mortality?

In a study carried out with the trap-nesting solitary wasp Trypoxylon attenuatum (Hymenoptera: Crabronidae) in 2000, we analysed the significance of different nest characteristics, like the vestibular cell and empty intercalary cells, and its role in the reduction of mortality. Analysis of the presence of the vestibular cell suggested that it represents a nest completion structure, whose presence reduces mortality in the initial stages (M1) but does not affect that due to chrysidid parasitoids (MP). The length of such vestibular cell was found to depend mainly on the space between the last provisioned cell and the exterior, pointing to a possible role in the reduction of the remaining space that could be used by other females to establish a nest exterior to the completed one. The empty intercalary cells were smaller than the vestibular cells, did not affect M1 or MP mortality rates in the nest, and exhibited an “aggregated” pattern of occurrence. This suggests that they could be the result of “abnormal” behaviour by the female owning the nest. The total mortality rate decreased with the increase in the number of cells in the nests, also being greater in nests established at low heights above the ground. M1 was lower in the innermost cells, while MP increased towards the interior and in the nests with more cells. The distribution in the nests of cells parasitized by Trichrysis cyanea (the main natural enemy found in the wasp population studied) reflects an “aggregated” pattern, suggesting repeated attacks against certain nests.     

Comparative analysis of septic injury-inducible genes in phylogenetically distant model organisms of regeneration and stem cell research, the planarian Schmidtea mediterranea and the cnidarian Hydra vulgaris

Background

Host-parasite interactions are among the most important biotic relationships. Host species should evolve mechanisms to detect their enemies and employ appropriate counterstrategies. Parasites, in turn, should evolve mechanisms to evade detection and thus maximize their success. Females of the European beewolf (Philanthus triangulum, Hymenoptera, Crabronidae) hunt exclusively honeybee workers as food for their progeny. The brood cells containing the paralyzed bees are severely threatened by a highly specialized cuckoo wasp (Hedychrum rutilans, Hymenoptera, Chrysididae). Female cuckoo wasps enter beewolf nests to oviposit on paralyzed bees that are temporarily couched in the nest burrow. The cuckoo wasp larva kills the beewolf larva and feeds on it and the bees. Here, we investigated whether H. rutilans evades detection by its host. Since chemical senses are most important in the dark nest, we hypothesized that the cuckoo wasp might employ chemical camouflage.

Results

Field observations suggest that cuckoo wasps are attacked by beewolves in front of their nest, most probably after being recognized visually. In contrast, beewolves seem not to detect signs of the presence of these parasitoids neither when these had visited the nest nor when directly encountered in the dark nest burrow. In a recognition bioassay in observation cages, beewolf females responded significantly less frequently to filter paper discs treated with a cuticular extract from H. rutilans females, than to filter paper discs treated with an extract from another cuckoo wasp species (Chrysis viridula). The behavior to paper discs treated with a cuticular extract from H. rutilans females did not differ significantly from the behavior towards filter paper discs treated with the solvent only. We hypothesized that cuckoo wasps either mimic the chemistry of their beewolf host or their host's prey. We tested this hypothesis using GC-MS analyses of the cuticles of male and female beewolves, cuckoo wasps, and honeybee workers. Cuticle extracts of Hedychrum nobile (Hymenoptera: Chrysididae) and Cerceris arenaria (Hymenoptera: Crabronidae) were used as outgroups. There was little congruence with regard to cuticular compounds between H. rutilans females and honeybees as well as females of C. arenaria and H. nobile. However, there was a considerable similarity between beewolf females and H. rutilans females. Beewolf females show a striking dimorphism regarding their cuticular hydrocarbons with one morph having (Z)-9-C25:1 and the other morph having (Z)-9-C27:1 as the major component. H. rutilans females were more similar to the morph having (Z)-9-C27:1 as the main component.

Conclusion

We conclude that H. rutilans females closely mimic the composition of cuticular compounds of their host species P. triangulum. The occurrence of isomeric forms of certain compounds on the cuticles of the cuckoo wasps but their absence on beewolf females suggests that cuckoo wasps synthesize the cuticular compounds rather than sequester them from their host. Thus, the behavioral data and the chemical analysis provide evidence that a specialized cuckoo wasp exhibits chemical mimicry of the odor of its host. This probably allows the cuckoo wasp to enter the nest with a reduced risk of being detected by olfaction and without leaving traitorous chemical traces.     

Seasonal change of nest survival and related aspects in an aggregation ofLasioglossum duplex (Dalla torre), a eusocial halictine bee (Hymenoptera: Halictidae)

Nest survival in an aggregation of a eusocial halictine bee, Lasioglossum duplex, was censused through an annual cycle. Out of 2,500 nests marked at the beginning of solitary phase in the spring, only 25.5% attained eusocial phase. But 60.5% of 636 nests attaining eusocial phase successfully produced sexual offspring. This shows that solitary phase is the most vulnerable period in the annual cycle. A very low productivity in eusocial phase in the census year was clarified from examination of 99 nests in the autumn. The number of prospective foundresses surviving to the next year was estimated upon the number of brood cells in examined nests and of old females surviving these nests. Deviation between this estimate and the number of nests made in the next spring was 8.8%, confirming a drop of population size to less than one third in the next year. Some nests solitarily made in the summer by dispersed females were examined. Productivity in such nests was extremely low, hence these nests should contribute virtually nothing to the next generation. Possible factors affecting the low productivity in eusocial phase were enumerated though none of these were supported by concrete evidence. Some considerations were given on the relation between obtained results and colony life cycle in eusocial insects, particularly in halictine bees.     

Maternal investment in a bee species with facultative nest guarding and males heavier than females

1. Maternal investment can be influenced by several factors, especially maternal quality and possibilities for future reproduction. Mass provisioning Hymenoptera are an excellent group for measuring maternal investment because mothers distribute food sources to each brood cell for each offspring separately. Generally in aculeate Hymenoptera, larger females produce larger offspring and invest more in female offspring than in male offspring. 2. This study investigated patterns of maternal investment in Ceratina chalcites, which has an uncommon type of sexual size dimorphism in Hymenoptera: on average, males are heavier than females. It was found that larger females produce a significantly higher proportion of male offspring, as males are the costlier sex in this species. 3. Facultative nest guarding by females was observed. Females can guard offspring until adulthood, as is typical for bees of genus Ceratina (34.43% of nests); however, in the majority of cases (65.56% of nests), females plug and abandon the nest. Significant differences were found in the amount of investment between guarded and unguarded nests. Guarded nests had a greater number of provisioned brood cells and a higher proportion of male offspring. It is suggested that mothers have two facultative strategies – either she makes a large investment in the offspring of one nest or she abandons the first nest and carries out a second nesting elsewhere.     

Comb cutting inRopalidia plebeiana: a new process of colony fission in social wasps (Hymenoptera: Vespidae)

Summary Females of an Australian polistine wasp,Ropalidia plebeiana, often use their mandibles to cut their nest-comb in spring, dividing it into two or more completely independent nests. Prior to the division, each of the major egg layers, often with some subordinates, tended to occupy a different part of a single comb. These females gnawed cells in the intermediate zone between such territories, and ultimately divided the comb. Many other females also built new nests near the nest aggregations, but addition of new nests by comb cutting represented 34.8 % of the increase in nest number. This method of colony fission is so far unknown in any eusocial Hymenoptera.     

Shared reproduction and sex ratio adjustment to clutch size in a socially polymorphic orchid bee

Nests of the primitively eusocial orchid bee Euglossa viridissima are generally founded by a solitary female but can be reactivated by female offspring, in the presence or absence of the mother. The population therefore exists of solitary and social nests that co-occur in an area. A female can stay as a subordinate helper under a dominant female or disperse to become a solitary foundress. Yet, the costs and benefits of the different social phenotypes are so far little understood. Here, we compared solitary and social nests of orchid bees. We used offspring of solitary and social nests to calculate offspring sex ratio, and applied molecular markers to calculate intranidal relatedness, infer maternity and test whether sociality may have a genetic component. We found that social nests had on average more brood than solitary nests. The overall sex ratio in the population did not differ from 1:1. However, social nests tended to produce a split sex ratio with some nests producing mainly males and others mainly female offspring. Regardless of social phenotype, the number of offspring was correlated with the sex ratio, with smaller nests having a more female-biased offspring. In social nests, not all offspring resulted from a single-mated mother, which was also the case for some solitary nests. This suggests shared reproduction in social nests and may be an indication that intraspecific parasitism and nest takeover are not uncommon. Structure analyses did not reveal different genetic background of the two social phenotypes. Our results suggest that there is no clear benefit that favours one of the two social phenotypes over the other and that the population is kept at balance in terms of sex ratio.     

Nest mate recognition in ants with complex colonies: within- and between-population variation

The ability to recognize kin is widespread, and especially importantin highly social organisms. We studied kin recognition by assessingpatterns of aggression within and between nests of the antLeptothorax longispinosus. Colonies of this species can befractionated into subunits, a condition called polydomy. Theproblem of recognizing relatives is therefore more complexwhen those relatives can live in two or more different places.We hypothesized that spatial subdivision may have resulted ina stronger genetic component to kin recognition than in caseswhere colonies live in a single location. To test our hypothesiswe assessed recognition capabilities for two populations ofthis ant that differ in the complexity of their colonies. Ina New York, USA, population, polydomy is very common, and coloniesalso can have multiple queens. By contrast, a population inWest Virginia, USA, has colonies that typically are monogynousand rarely are polydomous. We conducted introductions of antsbetween different nests collected in the same neighborhood,with self-introductions and alien introductions as controls.Nests from the two populations showed corresponding differencesin their aggression towards intruders. For New York nests, the extent of genetic similarity was the single best predictor ofaggression, whereas for West Virginia nests aggression wasjointly influenced by genetic similarity and spatial distance.In both populations, we found nest pairs for which aggressionwas nonreciprocal; these probably reflect recognition errors by one of the nests. After the ants were maintained in the laboratoryfor 3 months, their aggression scores rose and fewer recognitionerrors were made. Thus nest-mate and colony-mate recognitionin this species are mediated primarily by endogenous cues (geneticsimilarity); the importance of exogenous cues for nest materecognition depends on the population's social system.     

Nest and Nestmate Recognition by a Fungus-growing Ant,Apterostigma collare Emery (Hymenoptera: Formicidae)

The ability of Apterostigma collare workers to differentiate their nest from other nests and their nestmates from non-nestmates was examined. In field tests, workers that were removed from their nest were accepted back into their own nests, but were rejected when they were placed onto a nearby (≤ 1 m) nest or a distant (≥ 100 m) nest. In the laboratory, when given a choice between a fragment of their own nest and a fragment of a second nest (near or distant), workers selected their own nest material rather than the material of the second nest. For the nestmate recognition bioassay, two workers from one nest were placed together in an arena with a worker from a second nest. In most bioassays, the nestmates were tolerant of each other, but they were intolerant of the non-nestmate. The results demonstrate that A. collare workers have the ability to recognize nestmates and their nests. The results also suggest that each nest of A. collare is an independent colony.     

Availability and depletion of fat reserves in halictid foundress queens with a focus on solitary nest founding

Foundress queens of social Hymenoptera require considerable amounts of energy for survival, solitary nest founding, provisioning of the first brood, and egg production. Energy reserves in insects mostly consist of fat. We investigated how hibernation and the subsequent flight season, especially the solitary nest founding phase, influenced the abdominal fat content of gynes in the primitively eusocial sweat bee, Lasioglossum malachurum (Hymenoptera, Halictidae). In our study population, sexuals are produced in both the second and the third broods. Emerging gynes of the third brood had significantly more fat than those of the second brood, whereas there was no such difference in males. As expected, fat reserves in samples of female sexuals caught at emergence, after hibernation, during solitary nest founding, and at the end of the social phase of the nest cycle indicate a severe decrease of reserves that was highest during the 7 weeks of the solitary founding phase. Thus, the amount of fat reserves of foundress queens seems to be crucial, particularly for nest founding. However, investment of energy reserves in the solitary nest founding phase has probably to be balanced with the subsequent social phase in a way that maximizes the queen’s fitness. Possible consequences for the complexity and progress of the nest cycle are discussed.