A simulation model of biological control of social wasps (Vespinae) using mermithid nematodes

Abstract

The nematode (Pheromermis spp.) is a potential biocontrol agent for wasps (Vespula spp.) in countries where invasive populations of wasps cause serious economic, social, and conservation problems. Using a simulation model previously developed for hornets, which belong to a genus with a similar biology to Vespula, we investigated the possibility of using nematodes as a biological control agent. The model wasp colony was exposed to different simulated levels of nematode infection during colony development, and the final number of wasp sexuals produced recorded. The model predicted that early and high levels of wasp infection had the greatest effect on reducing sexual production. However, even colonies with high (80%) levels of infection were still able to produce some sexuals, indicating that wasp colonies are resilient to infections. The model identified several key areas needing further research, including the effects of nematodes on the behaviour and physiology of wasps, of lengthening the infective period, and of increasing infection levels in both the wasps and intermediate transport hosts.     

春季城市中华蜜蜂的食物结构与蜂蜜金属元素含量——以四川省内江市为例

中华蜜蜂Apis cerana cerana是我国重要的本土传粉者,为评价城市生境对中华蜜蜂的生态价值,在四川省内江市城区人工饲养蜂群,调查和测定了其春季的食物来源和蜂蜜质量。结果表明,春季城市园林中开花植物资源丰富,中华蜜蜂可有效地采集花蜜、花粉等食物资源;城郊农作物也是其积极采集的食物对象。除油菜Brassica napus var.oleifera初花期外,蜂蜜中油菜花粉比例均低于50%,表明即使存在开花大宗作物,春季园林植物仍然是城市蜂群重要的食物来源。蜂蜜中金属元素含量在不同蜂群、时间存在一定差异,未检测出危害较大的铬、镉和铅,但样品中检测出微量的铝和钒,且城市蜂蜜锌含量总体高于非城市,提示蜂蜜无重金属污染,但应注意风险防范。本研究对于理解城市园林植物为访花昆虫提供的食物质量和指导城市养蜂具有参考价值。     

Effects of prey quality on social wasps when given a choice of prey

The effect of prey quality on foraging behavior and colony demographics of the social wasp Polistes fuscatus was examined by providing a choice between non‐toxic prey (Manduca sexta caterpillars) and sublethally toxic prey (Junonia coenia caterpillars), and then comparing the performance of these colonies to others given only the non‐toxic prey. In the choice, one of two types of Manduca were used: those fed an artificial diet or those fed plantain (Plantago lanceolata), which contains iridoid glycosides (IGs) that Junonia coenia store but which Manduca does not. Despite the negative correlation between the number of Junonia prey used and number of adult offspring produced, when a surplus of non‐toxic prey was available, the wasps did not completely avoid the toxic prey. However, they were more discriminating when the choice was between Manduca fed an artificial diet and Junonia fed plantain vs. when both prey species had eaten the plantain. Because the wasps had a choice of prey types and had a surplus of prey on about one‐third of the days, the wasps were able to take enough non‐toxic prey to avoid some of the negative consequences of IGs. For example, the total number of wasp offspring per nest was not affected, but mean weight of female offspring per colony was less for colonies given both prey types eating plantain, compared to that for colonies fed only non‐toxic prey, or those given a choice of non‐toxic prey vs. toxic prey. In addition, compared to the control (only non‐toxic prey), the proportion of males produced was less in the treatment that provided a clear contrast between non‐toxic and toxic prey. Why these wasps did not avoid the toxic prey is discussed.     

Suburban sprawl: environmental features affect colony social and spatial structure in the black carpenter ant,Camponotus pennsylvanicus

1. In social insects, the number of nests that a colony inhabits may have important consequences for colony genetic structure, the number of queens, sex allocation, foraging efficiency, and nestmate recognition. Within the ants, colonies may either occupy a single nest (monodomy) or may be organised into a complex network of nests and trails, a condition known as polydomy. 2. The current study is a large‐scale, long‐term, comprehensive field examination of various features of colony social and spatial structure in the facultatively polydomous black carpenter ant, Camponotus pennsylvanicus (DeGeer). The study examined the density, persistence, and the spatiotemporal distribution of colonies across a gradient of land disturbance associated with urban development. The temporal and spatial pattern of nest use was compared between fragmented landscapes where nesting sites were interspersed among human‐built structures (urban plots) and less disturbed landscapes with higher tree density (suburban plots). In addition, nesting site fidelity and changes in colony spatial structure were monitored over 7 years. 3. Long‐term monitoring and extensive sampling over a large spatial area allowed the first comprehensive insight into the spatiotemporal dynamics of colony and population structure in C. pennsylvanicus. A total of 1113 trees were inspected over 233 ha. Camponotus pennsylvanicus were active on 348 of the 1113 trees (31%) and these represented 182 distinct colonies. The colonisation rate remained relatively stable over 7 years suggesting that an equilibrium point had been reached. Relative to the suburban plots, tree density was 65% lower in the urban plots. The proportion of trees colonised by C. pennsylvanicus was significantly higher in the urban plots suggesting that intraspecific competition for nesting sites may be especially high in areas with lower tree density. Colony spatial structure also differed significantly between habitats and a higher incidence of monodomy was observed in the urban environment. The average number of trees per colony across all subplots was 1.95 (range 1–4) indicating that C. pennsylvanicus are weakly polydomous. 4. The composite picture that emerges for C. pennsylvanicus colonies in the urban habitat is a chain reaction of events: (i) the urban habitat has a lower tree density, (ii) lower tree density results in higher tree colonisation rate, (iii) higher tree colonisation rate results in simpler colony spatial structure (i.e. higher incidence of monodomy), and (iv) simpler colony spatial structure results in numerically smaller colonies. Long‐term monitoring of the spatiotemporal pattern of nest site use in selected colonies revealed a unique trend. While worker counts in selected colonies remained relatively stable throughout the course of the study, colony spatial structure changed considerably with 28% of colonies experiencing a change. Furthermore, the likelihood of detecting a change in colony spatial structure increased with the amount of time passing from the initial inspection. 5. In conclusion, tree density has a significant effect on a number of important colony features in C. pennsylvanicus. Besides tree density, other environmental features such as human‐built structures cause habitat fragmentation and may act as natural barriers to worker dispersal and/or foraging. Such barriers may ultimately affect the social and/or spatial structure at both the colony and the population level.     

Antibacterial potential of Nidus vespae built by invasive alien hornet,Vespa velutina nigrithorax,against food‐borne pathogenic bacteria

The yellow‐legged hornet, Vespa velutina nigrithorax, is an invasive social wasp found in temperate regions and is recognized as a hazardous insect, as it often attacks humans and honeybees. Nidus vespae (nests of social wasps) are traditionally used as a medicinal ingredient; thus, V. v. nigrithorax may be useful as a biological resource. Extracts of Nidus vespae built by V. v. nigrithorax were examined for their antibacterial activity screening against six food‐borne pathogenic bacteria, and the ethyl acetate and butanol layer of the extract exhibited inhibitory activity against the pathogenic bacteria. We determined the antibacterial activity of Nidus vespae built by V. v. nigrithorax for the first time.     

Body size and sperm quality in queen‐ And worker‐produced ant males

Workers of many species of social Hymenoptera have functional ovaries and are capable of laying haploid, unfertilized eggs, at least in the absence of a queen. Except for honeybees, it remains largely unknown whether worker‐produced males have the same quality as queen‐produced males and whether workers benefit in direct fitness by producing their sons. Previous studies in the monogynous ant Temnothorax crassispinus revealed that a high proportion of males in natural and laboratory colonies are worker offspring. Here, we compare longevity, body size, sperm length and sperm viability between queen‐ and worker‐produced males. We either split queenright colonies into queenright and queenless halves or removed the queen from a fraction of the queenright colonies and then examined the newly produced males. Male quality traits varied considerably among colonies but differed only slightly between queen‐ and worker‐produced males. Worker‐produced males outnumbered queen‐produced males and also had a longer lifespan, but under certain rearing conditions sperm from queen‐produced males had a higher viability.     

New microsatellite loci for the socially diverse paper wasp genus Ropalidia

The Polistine wasps include both independent‐founding species, with small, single‐queen colonies founded by one or a few potential queens, and swarm‐founding species, which have larger societies, many queens and initiate colonies as a swarm of queens and workers. Swarm‐founding evolved from independent‐founding and Ropalidia is the only genus with both types, making it an excellent model system for understanding this dramatic shift in colony organization. We have isolated 18 polymorphic microsatellite loci from three species of Ropalidia, including two independent‐founding and one swarm‐founding species. These loci will allow us to reconstruct colony social and genetic structures in this important genus.     

Heavy Metal (Hg,Cr, Cd,and Pb) Contamination in Urban Areas and Wildlife Reserves: Honeybees as Bioindicators

The degree of heavy metal (Hg, Cr, Cd, and Pb) pollution in honeybees (Apis mellifera) was investigated in several sampling sites around central Italy including both polluted and wildlife areas. The honeybee readily inhabits all environmental compartments, such as soil, vegetation, air, and water, and actively forages the area around the hive. Therefore, if it functions in a polluted environment, plant products used by bees may also be contaminated, and as a result, also a part of these pollutants will accumulate in the organism. The bees, foragers in particular, are good biological indicators that quickly detect the chemical impairment of the environment by the high mortality and the presence of pollutants in their body or in beehive products. The experiment was carried out using 24 colonies of honeybees bred in hives dislocated whether within urban areas or in wide countryside areas. Metals were analyzed on the foragers during all spring and summer seasons, when the bees were active. Results showed no presence of mercury in all samples analyzed, but honeybees accumulated several amounts of lead, chromium, and cadmium. Pb reported a statistically significant difference among the stations located in urban areas and those in the natural reserves, showing the highest values in honeybees collected from hives located in Ciampino area (Rome), next to the airport. The mean value for this sampling station was 0.52 mg kg⁻¹, and July and September were characterized by the highest concentrations of Pb. Cd also showed statistically significant differences among areas, while for Cr no statistically significant differences were found.     

Habitat influences on urban avian assemblages

Urbanization is increasing across the globe and there is growing interest in urban ecology and a recognition that developed areas may be important for conservation. We review the factors influencing urban avian assemblages, focusing on habitat type and anthropogenic resource provision, and analyse data from a common bird monitoring scheme to assess some of these issues. The review suggests that (1) local factors are more important than regional ones in determining the species richness of urban avian assemblages, raising the potential for the management of urban sites to deliver conservation; (2) habitat fragmentation frequently influences urban avian assemblages, with the effects of patch size being greater than those of isolation, and (3) urban bird assemblages appear to respond positively to increasing the structural complexity, species richness of woody vegetation and supplementary feeding, and negatively to human disturbance. Data from Britain's Breeding Bird Survey, combined with habitat data obtained from aerial photographs, were used to assess a number of these issues at the resolution of 1‐km squares. Green‐space constituted 45% of these squares, and domestic gardens contributed 50% of this green‐space, though their contribution to large continuous patches of green‐space was negligible. There was no significant positive correlation between the densities of individual species in urban areas and surrounding rural areas. Rural species richness declined with increasing latitude, but urban species richness was not correlated with latitude. This contrast contributes to slightly higher avian species richness in rural squares in Southern England than urban ones. Occupancy and abundance were strongly positively correlated in urban avian assemblages, and some indicator species of conservation concern occurred in few urban areas and at low densities. Such species will require conservation action to be precisely targeted within urban areas. Of the urban indicators of conservation concern, only the House Sparrow Passer domesticus and Common Starling Sturnus vulgaris were more abundant in urban than rural areas. Moreover, the densities of these two species were strongly and positively correlated, indicating that they may be limited by shared resources, such as nest‐sites or supplementary food. There was little evidence that high densities of nest‐predating corvids were associated with reduced densities of their prey species. Species richness and the densities of individual species frequently declined with an increasing number of buildings. Current trends for the densification of many British urban areas are thus likely to be detrimental for many bird species.     

Social parasitism by Cape honeybee workers in colonies of their own subspecies (Apis mellifera capensis Esch.)

Social parasitism is widespread in the eusocial insects. Although social parasites often show a reduced worker caste, unmated workers can also parasitize colonies. Cape honeybee workers, Apis mellifera capensis, can establish themselves as social parasites in host colonies of other honeybee subspecies. However, it is unknown whether social parasitism by laying workers also occurs among Cape honeybee colonies. In order to address this question we genotyped worker offspring of six queenless A. m. capensis colonies and determined the maternity of the reproducing workers. We found that three non-nestmate workers dominated reproduction in a host colony and produced 62.5% of the progeny. Our results show that social parasitism by laying workers is a naturally occurring part of the biology of Cape honeybees. However, such social parasitism is not frequently found (6.41% of the total worker offspring) probably due to co-evolutionary processes among A. m. capensis resulting in an equilibrium between selection for reproductive dominance in workers, colony maintenance and queen adaptation. Received 28 July 2005; revised 19 September and 11 November 2005; accepted 16 November 2005.     

Species and Colony Components in the Recognition Odor of Young Social Wasps: Their Expression and Learning (Polistes biglumis and P. atrimandibularis; Hymenoptera: Vespidae)

In Polistes, nestmate recognition relies on the learning of recognition cues from the nest. When wasps recognize nestmates, they match the template learned with the odor of the encountered wasp. The social wasp Polistes biglumis use the homogeneous odor of their colony to recognize nestmates. When these colonies become host colonies of the social parasite P. atrimandibularis, colony odor is no longer homogeneous, as the parasite offspring have an odor that differs from that of their hosts. In trying to understand how the mechanism of nestmate recognition works in parasitized colonies and why parasite offspring are accepted by hosts, we tested the responses of resident Polistes biglumis wasps from parasitized and unparasitized colonies to newly emerged parasites and to nestmate and non-nestmate conspecifics. The experiments indicate that immediately upon eclosion both young parasites and young hosts lack a colony odor and that colony odor can be soon acquired from the accepting colony. In addition, while residents of nonparasitized colonies recognize only the odor of their species, resident hosts of parasitized colonies have learned a template that fits the odors of two species.     

Effective paternity in natural colonies of Japanese native bumble bees

Kin selection theory predicts a high coefficient of genetic relatedness among nestmates, explaining the frequent evolution of eusociality in a social hymenopteran colony. The bumble bee is a primitively eusocial hymenoptera whose colonies are founded by a single queen. In such a monogynous colony, mating frequency of the queen is the sole factor that affects genetic relatedness among nestmates. Although the queens of most bumble bee species are known to be monandrous, there are some species that are known to be polyandrous. Here, we estimated the effective paternity in the native colonies of Japanese bumble bees, Bombus ardens, B. diversus, and B. honshuensis, using genetic polymorphic data of microsatellites. We found no evidence for polyandry in any investigated colonies, which suggests that within-colony genetic relatedness is very high for all of these colonies.     

The origin and evolution of social life in the Stenogastrinae (Hymenoptera,Vespidae)

The Stenogastrinae are a subfamily of the Vespidae. The main difference between these and other social wasps (Polistinae and Vespinae) is a jelly-like substance that the Stenogastrinae secrete from the Dufour 's gland and use in many functions of their biology. It is suggested that this substance greatly contributed to the evolution of social life in these wasps by making it possible to nourish the brood with liquid food and store it in the nest, thus favoring also the evolution of the behavioral mechanisms which facilitated interactions between adults. Social organization of the colonies may have been kept at a low level through a basic system of continuous temporary helper replacement, while the evolution of large colonies was restrained, as well as by the poor quality of construction material, low egg-laying capacity and limited production of abdominal substance, imperfect social regulatory mechanisms, and the absence of defensive mechanisms of the colonies against large predators.     

Social encapsulation of the small hive beetle (<Emphasis Type="Italic">Aethina tumida</Emphasis> Murray) by European honeybees (<Emphasis Type="Italic">Apis mellifera</Emphasis> L.)

Summary European and African subspecies of honeybees (Apis mellifera L.) utilize social encapsulation to contain the small hive beetle (Aethina tumida Murray), a honeybee colony scavenger. Using social encapsulation, African honeybees successfully limit beetle reproduction that can devastate host colonies. In sharp contrast, European honeybees often fail to contain beetles, possibly because their social encapsulation skills may be less developed than those of African honeybees. In this study, we quantify beetle and European honeybee behaviours associated with social encapsulation, describe colony and time (morning and evening) differences in these behaviours (to identify possible circadian rhythms), and detail intra-colonial, encapsulated beetle distributions. The data help explain the susceptibility of European honeybees to depredation by small hive beetles. There were significant colony differences in a number of social encapsulation behaviours (the number of beetle prisons and beetles per prison, and the proportion of prison guard bees biting at encapsulated beetles) suggesting that successful encapsulation of beetles by European bees varies between colonies. We also found evidence for the existence of circadian rhythms in small hive beetles, as they were more active in the evening rather than morning. In response to increased beetle activity during the evening, there was an increase in the number of prison guard bees during evening. Additionally, the bees successfully kept most (~93%) beetles out of the combs at all times, suggesting that social encapsulation by European honeybees is sufficient to control small populations of beetles (as seen in this study) but may ultimately fail if beetle populations are high.Received 20 January 2003; revised 21 April 2003; accepted 29 April 2003.     

Colony cycle in the south-eastern coastal populations of Ropalidia plebeiana, the only Ropalidia wasp occurring in temperate Australia

Of the 22 species of Ropalidia occurring in Australia, only R. plebeiana is distributed in temperate areas. This wasp is abundant in the south‐eastern coastal regions of Australia, where it forms huge nest aggregations. Based on our observations in late autumn and early spring, as well as information in the literature, we outline the colony cycle of R. plebeiana in the south‐eastern coastal area of New South Wales. The nesting period lasts for approximately 9.5 months, which is unusually long for temperate polistine wasps. Most foundresses seem to return to their natal nests in early spring (mid‐August to early September) to start their own colonies by reusing pre‐existing nest combs, and the pre‐emergence stage (before the emergence of the first adult brood) lasts for approximately 3.5 months. Reproductives (gynes and males) start to emerge as adults in early March, and the reproductive‐producing period lasts until the end of May. Both the pre‐emergence stage and the reproductive‐producing period are much longer than in other temperate polistine wasps, which is discussed in terms of fluctuating temperature conditions in the area and the formation of nest aggregations, a peculiar habit for temperate populations of R. plebeiana.     

Pest occurrence of Aedes rossicus close to the Arctic Circle in northern Sweden

Major nuisance species are found among the floodwater mosquitoes and snow‐pool mosquitoes, with the former being the main reason for mosquito control in most areas. Nuisance species vary with the area, and previous reports from northern areas conclude that the nuisance is most often caused by snow‐pool mosquitoes. We investigated the mosquito fauna and abundances of host‐seeking females using CDC traps baited with carbon dioxide, in Övertorneå city near the Arctic Circle in northern Sweden, after earlier complaints about massive mosquito nuisance. The abundance of host‐seeking female mosquitoes was high in 2014, with a maximum of ～15,400 individuals per CDC trap night, of which 89% was the floodwater mosquito Aedes rossicus. Surprisingly, the main nuisance species was a floodwater mosquito, occurring at the northernmost location it has ever been recorded in Sweden. Our report is probably the first documentation of such large numbers of Aedes rossicus in any locality and probably the first documentation of a severe floodwater mosquito nuisance near the Arctic Circle. Given the historical data on river discharge in the area, the nuisance is recurrent. We conclude that in northern localities, as well as in more southern localities, production of floodwater mosquitoes is a natural component of the floodplain fauna of rivers with a fluctuating water flow regime. Also, the floodwater mosquitoes Aedes sticticus and Aedes vexans were found north of their formerly known distribution in Sweden.     

Male production by non-natal workers in the bumblebee, Bombus deuteronymus (Hymenoptera: Apidae)

Social insect societies are considered to be composed of many extremely cooperative individuals. While workers are traditionally believed to behave altruistically, recent studies have revealed behaviors that are more selfish. One such example is intraspecific social parasitism, where workers invade conspecific colonies and produce male offspring that are reared by unrelated host workers. Such intraspecific parasitism has been reported in honeybees (Apis cerana, and A. florea) and “semi-wild” bumblebee colonies of Bombus terrestris. Here we report on intraspecific social parasitism by workers in “wild” colonies of the bumblebee B. deuteronymus. Three of the 11 B. deuteronymus colonies studied were invaded by non-natal workers, of which 75% became reproductive and produced 19% of the adult males. The invading non-natal workers produced significantly more males than resident natal workers and the non-natal brood was not discriminated against by the natal workers.     

Volatiles from green‐lipped mussel as a lead to vespid wasp attractants

Vespid wasps (Vespula vulgaris L. and V. germanica Fab. Hymenoptera; Vespidae) are highly abundant in 1 million ha of New Zealand's indigenous beech forests (Nothofagus spp.) and have had detrimental effects on the New Zealand native fauna. This hyperabundance is due in part to the vast supply of carbohydrate‐rich honeydew produced by scale insects Ultracoelostoma spp. native to New Zealand. Current control methods include the use of wet cat food as a protein source with insecticide as a lure‐and‐kill‐based system, but there are problems with fresh baits degrading rapidly, and a more durable formulation would enable the expansion and longevity of wasp control. Four crude protein baits were tested for vespid attraction. Green‐lipped mussels had the highest vespid catch of the crude baits tested, and aged and fresh mussels were equally attractive. From headspace analysis of the green‐lipped mussel volatiles, a series of butanoate esters, 3‐octanone and 1‐octen‐3‐ol were identified as possible attractants. These compounds were tested individually and in various blend combinations for the attraction of Vespula wasps in matagouri vegetation at the edge of beech forests. We found synergistic effects between single attractive compounds when tested in various combinations, and the multicomponent lures were more attractive to these wasps than heptyl and octyl butanoate, previously identified attractants for vespid species. The new multicomponent lures could form the basis for a new generation of attractants for social wasps that can provide sustained control methods for invasive vespid wasps.     

Nestmate recognition in a neotropical polygynous wasp

In social insects, nestmate recognition systems can be dynamic and modulated in response to various kinds of genetic and environmental cues. For example, multiple-queen colonies can possess weak recognition abilities relative to single-queen colonies, due to broader exposure to heritable and environmentally derived nestmate recognition cues.We conducted field experiments to examine nestmate recognition ability in a neotropical polygynous wasp, Polybia paulista. Despite the fact that the effective queen number in P. paulista is the highest ever recorded in polygynous wasps, this species exhibits a well functioning nestmate recognition system, which allows colony entry only to nestmate individuals. Similar to other social Hymenoptera, young wasps express colony specific chemical signatures within several days after emergence. This is the first study to show that the polygynous epiponine wasp is able to distinguish nestmates from non-nestmates. Received 23 May 2006; revised 6 October 2006; accepted 23 October 2006.     

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.