Recruitment Of Foragers Research Articles

Partial Solar Eclipse Affects <i>Apis Mellifera</i> L Forging Activity

Bees use sun’s position for navigation and thus a solar eclipse may affect this capability. Present study was conducted during partial solar eclipse on June 21, 2020 at Ludhiana, Punjab. Apis mellifera L foragers’ activity at the hive entrance was recorded through a digital bee counter. Bees’ activity increased normally, i.e. 771 and 823 bees/ 15 mins coming in and going out of the hive, respectively before the start of eclipsephase. At peak obscuration it decreased slightly but non-significantly. Changes in hive temperature andhumidity might have limited the recruitment of foragers. Hence, no peak activity was recorded duringpeak obscuration, which otherwise was recorded on ordinary days at 1345 hr.

Necrophagy in Honey Bees (Apis mellifera L.); A Forensic Application of Scent Foraging Behavior

Scent training and field detection trials were conducted to determine if honey bee (Apis mellifera) foraging behavior could be employed as a practical application in the location of vertebrate carrion. Resource recognition and querying trials consisted of two components. Honey bees were trained to associate chemical compounds found in decaying tissues with a high-quality food source via introduction of the compounds into a sugar solution. Randomized scented and non-scented sugar solution choices were subsequently provided to hived bees at varying distances within a rural outdoor study area. Following initial forager recruitment by scouts, twice the number of bees were observed feeding at carrion-scented stations. Additional field trials performed using wildlife carrion reinforced experimental results. Scent trained scout bees showed a marked interest in decomposing wildlife remains by aerially investigating and landing on the carrion. These findings demonstrate honey bee retention of carrion sensory recognition capabilities and support the crabronid wasp hypothesis of honey bee evolutionary origins. Applications for forensic remains detection, wildlife trafficking interdiction, and endangered species conservation are indicated.

Busier bees: increasing nest traffic in commercial bumblebee colonies

Commercially-reared bumblebee colonies contribute to the pollination of crops globally. If the efficiency of commercial colonies at providing pollination services could be increased, it would have implications for agricultural outputs. Commercial colonies are sold with an internal nectar reservoir on which bees can forage from within the nest. Nectar stores in naturally-produced nectar pots of colonies can affect forager recruitment and activity outside the nest. Thus, it is possible that artificial nectar reservoirs could impact the foraging activity of colonies. To investigate this, commercial Bombus terrestris audax colonies were placed in a university parkland campus. Colonies were split into three treatment groups: those with (1) access to an unaltered nectar reservoir; (2) access to a diluted reservoir; and (3) no reservoir access. Foraging observations were made for all colonies over a 19-day period. The mass of each colony was measured and demographic data were collected. Colonies with diluted reservoirs had 131% and 39% more bees entering and leaving than colonies with no reservoir access and unaltered reservoirs respectively. Both treatments with access to a nectar reservoir gained more mass, had a higher proportion of pollen foraging bees, and had more workers, males, larvae and pupae, than colonies with no access to a reservoir. These results demonstrate that manipulating the availability and concentration of internal nectar reservoirs of commercial B. terrestris colonies significantly affects the number of bees entering and leaving the colony. Dilution of the nectar reservoir could be a strategy for increasing the pollination services commercial colonies provide to crops. Further research in commercial crops is required before such a strategy could be implemented on farms.

Modeling honeybee communication using network of spiking neural networks to simulate nectar reporting behavior

The paper presents the findings of the research that attempted to mathematically model the cognitive behavior that could arise due to the interaction between honeybees in a colony during forager recruitment process. The model defines a honeybee as a spiking neural network, and colony as a network of spiking neural networks. The proposed mathematical model has been evaluated by analyzing the cognitive behavior generated by the main network which represents honeybees’ interaction as interactions of component networks (i.e. spiking neural networks). Accordingly, behavior of the component network, that represents an unemployed forager in the colony, was examined under different scenarios by setting networks’ parameters to simulate ecological situations in the colony. The reporting of different level of quantity of nectar sources by scouts to the colony, an attempt made by a scout to attract more unemployed foragers for foraging, and influence by dancing foragers to attract other unemployed foragers for foraging are those ecological colony states that have been tested in this research. The results of all these cases have supported that the proposed mathematical model can sufficiently simulate the unemployed forager’s behavior during recruitment process.

Parallel foraging cycles for different resources in leaf‐cutting ants: a clue to the mechanisms of rhythmic activity

1. Leaf‐cutting ants display regular diel cycles of foraging, but the regulatory mechanisms underlying these cycles are not well known. There are, however, some indications in the literature that accumulation of leaf tissue inside a nest dampens recruitment of foragers, thereby providing a negative feedback that can lead to periodic foraging. We investigated two foraging cycles occurring simultaneously in an Atta colombica colony, one involving leaf harvesting and the other exploiting an ephemeral crop of ripe fruit.2. Leaf harvesting followed a typical diel pattern of a 10–12 h foraging bout followed by a period of inactivity, while fruit harvesting occurred continuously, but with a regular pre‐dawn dip in activity that marked a 24 h cycle.3. Although the results of the present study are drawn from a single field colony, the difference found is consistent with a mechanism of negative feedback regulation acting in parallel on two resources that differ in their rates of distribution and processing, creating cycles of formation and depletion of material caches.4. This hypothesis should provoke further interest from students of ant behaviour and some simple manipulative experiments that would begin to test it are outlined. Any role of resource caches in regulating foraging by Atta colonies may have similarities to the logistics of warehouse inventories in human economic activity.

Stress-mediated Allee effects can cause the sudden collapse of honey bee colonies

The recent rapid decline in global honey bee populations could have significant implications for ecological systems, economics and food security. No single cause of honey bee collapse has yet to be identified, although pesticides, mites and other pathogens have all been shown to have a sublethal effect. We present a model of a functioning bee hive and introduce external stress to investigate the impact on the regulatory processes of recruitment to the forager class, social inhibition and the laying rate of the queen. The model predicts that constant density-dependent stress acting through an Allee effect on the hive can result in sudden catastrophic switches in dynamical behaviour and the eventual collapse of the hive. The model proposes that around a critical point the hive undergoes a saddle-node bifurcation, and that a small increase in model parameters can have irreversible consequences for the entire hive. We predict that increased stress levels can be counteracted by a higher laying rate of the queen, lower levels of forager recruitment or lower levels of natural mortality of foragers, and that increasing social inhibition can not maintain the colony under high levels of stress. We lay the theoretical foundation for sudden honey bee collapse in order to facilitate further experimental and theoretical consideration.

An energetics-based honeybee nectar-foraging model used to assess the potential for landscape-level pesticide exposure dilution.

Estimating the exposure of honeybees to pesticides on a landscape scale requires models of their spatial foraging behaviour. For this purpose, we developed a mechanistic, energetics-based model for a single day of nectar foraging in complex landscape mosaics. Net energetic efficiency determined resource patch choice. In one version of the model a single optimal patch was selected each hour. In another version, recruitment of foragers was simulated and several patches could be exploited simultaneously. Resource availability changed during the day due to depletion and/or intrinsic properties of the resource (anthesis). The model accounted for the impact of patch distance and size, resource depletion and replenishment, competition with other nectar foragers, and seasonal and diurnal patterns in availability of nectar-providing crops and wild flowers. From the model we derived simple rules for resource patch selection, e.g., for landscapes with mass-flowering crops only, net energetic efficiency would be proportional to the ratio of the energetic content of the nectar divided by distance to the hive. We also determined maximum distances at which resources like oilseed rape and clover were still energetically attractive. We used the model to assess the potential for pesticide exposure dilution in landscapes of different composition and complexity. Dilution means a lower concentration in nectar arriving at the hive compared to the concentration in nectar at a treated field and can result from foraging effort being diverted away from treated fields. Applying the model for all possible hive locations over a large area, distributions of dilution factors were obtained that were characterised by their 90-percentile value. For an area for which detailed spatial data on crops and off-field semi-natural habitats were available, we tested three landscape management scenarios that were expected to lead to exposure dilution: providing alternative resources than the target crop (oilseed rape) in the form of (i) other untreated crop fields, (ii) flower strips of different widths at field edges (off-crop in-field resources), and (iii) resources on off-field (semi-natural) habitats. For both model versions, significant dilution occurred only when alternative resource patches were equal or more attractive than oilseed rape, nearby and numerous and only in case of flower strips and off-field habitats. On an area-base, flower strips were more than one order of magnitude more effective than off-field habitats, the main reason being that flower strips had an optimal location. The two model versions differed in the predicted number of resource patches exploited over the day, but mainly in landscapes with numerous small resource patches. In landscapes consisting of few large resource patches (crop fields) both versions predicted the use of a small number of patches.

Hydrocarbons emitted by waggle-dancing honey bees increase forager recruitment by stimulating dancing.

Hydrocarbons emitted by waggle-dancing honey bees are known to reactivate experienced foragers to visit known food sources. This study investigates whether these hydrocarbons also increase waggle-dance recruitment by observing recruitment and dancing behavior when the dance compounds are introduced into the hive. If the hydrocarbons emitted by waggle-dancing bees affect the recruitment of foragers to a food source, then the number of recruits arriving at a food source should be greater after introduction of dance compounds versus a pure-solvent control. This prediction was supported by the results of experiments in which recruits were captured at a feeder following introduction of dance-compounds into a hive. This study also tested two nonexclusive behavioral mechanism(s) by which the compounds might stimulate recruitment; 1) increased recruitment could occur by means of increasing the recruitment effectiveness of each dance and/or 2) increased recruitment could occur by increasing the intensity of waggle-dancing. These hypotheses were tested by examining video records of the dancing and recruitment behavior of individually marked bees following dance-compound introduction. Comparisons of numbers of dance followers and numbers of recruits per dance and waggle run showed no significant differences between dance-compound and solvent-control introduction, thus providing no support for the first hypothesis. Comparison of the number of waggle-dance bouts and the number of waggle runs revealed significantly more dancing during morning dance-compound introduction than morning solvent-control introduction, supporting the second hypothesis. These results suggest that the waggle-dance hydrocarbons play an important role in honey bee foraging recruitment by stimulating foragers to perform waggle dances following periods of inactivity.

Modeling colony collapse disorder in honeybees as a contagion.

Honeybee pollination accounts annually for over $14 billion in United States agriculture alone. Within the past decade there has been a mysterious mass die-off of honeybees, an estimated 10 million beehives and sometimes as much as 90% of an apiary. There is still no consensus on what causes this phenomenon, called Colony Collapse Disorder, or CCD. Several mathematical models have studied CCD by only focusing on infection dynamics. We created a model to account for both healthy hive dynamics and hive extinction due to CCD, modeling CCD via a transmissible infection brought to the hive by foragers. The system of three ordinary differential equations accounts for multiple hive population behaviors including Allee effects and colony collapse. Numerical analysis leads to critical hive sizes for multiple scenarios and highlights the role of accelerated forager recruitment in emptying hives during colony collapse.

Foraging by forest ants under experimental climatic warming: a test at two sites

Climatic warming is altering the behavior of individuals and the composition of communities. However, recent studies have shown that the impact of warming on ectotherms varies geographically: species at warmer sites where environmental temperatures are closer to their upper critical thermal limits are more likely to be negatively impacted by warming than are species inhabiting relatively cooler sites. We used a large-scale experimental temperature manipulation to warm intact forest ant assemblages in the field and examine the impacts of chronic warming on foraging at a southern (North Carolina) and northern (Massachusetts) site in eastern North America. We examined the influence of temperature on the abundance and recruitment of foragers as well as the number of different species observed foraging. Finally, we examined the relationship between the mean temperature at which a species was found foraging and the critical thermal maximum temperature of that species, relating functional traits to behavior. We found that forager abundance and richness were related to the experimental increase in temperature at the southern site, but not the northern site. Additionally, individual species responded differently to temperature: some species foraged more under warmer conditions, whereas others foraged less. Importantly, these species-specific responses were related to functional traits of species (at least at the Duke Forest site). Species with higher critical thermal maxima had greater forager densities at higher temperatures than did species with lower critical thermal maxima. Our results indicate that while climatic warming may alter patterns of foraging activity in predictable ways, these shifts vary among species and between sites. More southerly sites and species with lower critical thermal maxima are likely to be at greater risk to ongoing climatic warming.

Combined pesticide exposure severely affects individual- and colony-level traits in bees

Reported widespread declines of wild and managed insect pollinators have serious consequences for global ecosystem services and agricultural production1-3. Bees contribute around 80% of insect pollination, so it is imperative we understand and mitigate the causes of current declines4-6. Recent studies have implicated the role of pesticides as exposure to these chemicals has been associated with changes in bee behaviour7-11 and reductions in colony queen production12. However the key link between changes in individual behaviour and consequent impact at the colony level has not been shown. Social bee colonies depend on the collective performance of numerous individual workers. So whilst field-level pesticide concentrations can have a subtle/sublethal effect at the individual level8, it is not known whether bee societies can buffer such effects or if it results in a severe cumulative effect at the colony level. Furthermore, widespread agricultural intensification means bees are exposed to numerous pesticides when foraging13-15, yet the possible combinatorial effects of pesticide exposure have rarely been investigated16,17. Here we show that chronic exposure of bumblebees to two pesticides (neonicotinoid and pyrethroid) at concentrations that could approximate field-level exposure impairs natural foraging behaviour and increases worker mortality leading to significant reductions in brood development and colony success. We found worker foraging performance, particularly pollen collecting efficiency, was significantly reduced with observed knock-on effects for forager recruitment, worker losses and overall worker productivity. Moreover, we provide evidence that combinatorial exposure to pesticides increases the propensity of colonies to fail.

Do invasive ants respond more strongly to carbohydrate availability than co‐occurring non‐invasive ants? A test along an activeAnoplolepis gracilipesinvasion front

AbstractInvasions by non‐native insects can have important ecological impacts, particularly on island ecosystems. However, the factors that promote the success of invaders relative to co‐occurring non‐invasive species remain unresolved. For invasive ants, access to carbohydrate resources via interactions with both extrafloral nectary‐bearing plants and honeydew‐excreting insects may accelerate the invasion process. A first step towards testing this hypothesis is to determine whether invasive ants respond to variation in the availability of carbohydrate resources, and whether this response differs from that of co‐occurring, non‐invasive ants. We investigated the effect of carbohydrate subsidies on the short‐term foraging and hemipteran‐tending behaviours of the invasive antAnoplolepis gracilipes(Formicidae) and co‐occurring ant species on an extrafloral nectary‐bearing plant by experimentally manipulating carbohydrate levels and tracking ant recruitment. We conducted experiments in 2 years at two sites: one site was invaded byA. gracilipesprior to 2007 and the other became invaded during the course of our study, allowing pre‐ (2007) and post‐invasion (2009) comparisons. Short‐term increases in carbohydrate availability increased the density ofA. gracilipesworkers on plants by as much as 400% and reduced tending of honeydew‐excreting insects by this species by up to 89%, with similar responses across years. In contrast, ants at the uninvaded site in 2007 showed a weak and non‐significant forager recruitment response. Across all sites,A. gracilipesworkers were the only ants that responded to carbohydrate manipulations in 2009. Furthermore, ant–carbohydrate dynamics at a site newly invaded byA. gracilipesquickly diverged from dynamics at uninvaded sites and converged on those of the site with an established invasion. These findings suggest that carbohydrate resources may be particularly important forA. gracilipesinvasions, and underscore the importance of species interactions, particularly putative mutualisms, in facilitating exotic species invasions.

Floral resources foraged by Geotrigona argentina (Apidae, Meliponini) in the Argentine Dry Chaco forest

This study is the first contribution to knowledge of the relationships between Geotrigona argentina and the plants of the Argentine Dry Chaco forest. A total of 1260 g of honey (corresponding to 146 pots) and 763 g of pollen (63 pots) stored in four underground nests was studied. The honey pots from each nest were homogenised and the four honey samples were analysed by melissopalynological methods, whereas the pollen pots were studied individually. Both classical counts and counts affected by the volume of the pollen types were carried out. Pollen data were statistically analysed. Additional data on both protein and lipid content is also provided. A total of 39 pollen taxa were identified. Pollen collection was focused on a few pollen taxa: Prosopis, Castela coccinea, Maytenus and Capparis; these taxa, together with Ziziphus mistol and Pisonia zapallo, were also important nectar sources. The preliminary results show that pollen collection varied seasonally, being most diverse in the summer when G. argentina incorporates herbaceous plants into its diet. The pollen collection spectrum of G. argentina is similar to that of other Trigonina bees in that the main plant species collected are a few large shrubs or trees, whose flowering consists of small and clustered flowers. Pots with large amounts of monofloral loads with pollen from only a few species suggests an organised foraging behaviour that includes the recruitment of foragers, such as that observed in other eusocial bees.

Intraspecific competition in the ant Camponotus cruentatus: should we expect the ‘dear enemy’ effect?

The mechanisms of competition and resource domination were analysed in the Mediterranean ant Camponotus cruentatus. In a plot located in southern Spain mature colonies are overdispersed, which is indicative of territoriality in other species. Unexpectedly, however, workers from neighbouring colonies commonly foraged in areas that overlapped by more than 44%. This suggests that while mature colonies possibly prevent the establishment of new colonies in the vicinity of their nests, they do not limit the intrusion of alien foragers. In contrast, rich food sources located in common foraging areas are aggressively defended, generally leading to their domination by the nest that discovered them first. Resource exploitation further requires rapid recruitment of foragers and soldiers to transport food as well as to exclude competitors. Complementary to the field experiments we conducted laboratory bioassays to assess intercolonial aggression. Group encounters showed that workers of C. cruentatus were equally aggressive towards alien ants irrespective of whether they were sympatric neighbours (and had possibly had contact), sympatric nonneighbours (which had probably had no contact), or allopatric. This was corroborated by analysis of the hydrocarbons that generally serve as colony recognition cues. This mixture, which contains an unusual proportion of trimethylalkanes, showed important colony specificity. The high intraspecific aggression shown indiscriminately by workers indicates that the ‘dear enemy’ effect does not exist in this species and suggests that scarce resources are worth defending against intraspecific competitors. We discuss several proximate and ultimate constraints that may prevent the general occurrence of this process in ants.

Wasps enter and leave their nest at regular intervals

We present, for the first time, definitive evidence that common wasps (Vespula vulgaris) do not leave and enter their colony in a random uncoordinated way, as has previously been suggested; nor are their movements temporally clustered, as has also been suggested. Rather, these movements are regular in time, more regular than the Poisson process generated by the independent actions of individuals would generate. The potential consequences of this for within-nest recruitment of foragers are briefly discussed.

Condition-dependent response to changes in pollen stores by honey bee ( Apis mellifera ) colonies with different parasitic loads

The impact of a parasitic infestation may be influenced by nutritional state, in both individuals and colonies. This study examined the interaction between pollen storage and the effects of an infestation by the mite, Varroa jacobsoni Oudemans, in colonies of the honey bee, Apis mellifera L. We manipulated the pollen storage and mite infestation levels of colonies, and measured pollen foraging and brood rearing. Increased pollen stores decreased both the number of pollen foragers and pollen load size, while initially at least foragers from colonies with moderate infestations carried smaller pollen loads than those from lightly infested colonies. Over the course of the experiment, all colonies significantly increased pollen-foraging rates and pollen consumption, which was presumably a seasonal effect. Lightly infested colonies exhibited a larger increase in pollen forager number than moderately infested colonies, suggesting that more intense mite infestations compromised forager recruitment. Brood production was not affected by the addition of pollen, but moderately infested colonies were rearing significantly less brood by the end of the experiment than lightly infested colonies. Furthermore, the efficiency with which colonies converted pollen to brood decreased as the pollen storage level decreased and the infestation level increased. The results of this study may indicate that honey bee colonies adaptively alter brood-production efficiency in response to parasitic infestations and seasonal changes.

Variations of brain biogenic amines in mature honeybees and induction of recruitment behavior

Mature honeybees ( Apis mellifera L.) old enough to forage (>3 weeks) were segregated into three activity groups: waggle dancers (active foragers), followers of the dancers (potential recruits) and resting bees (not involved in foraging). Dopamine (DA) pathways in the brain of honeybees seemed to be involved in regulation of forager recruitment. Brain DA and N- β-alanyldopamine (NBAD) levels in the dancers were always higher than in followers, and an increased number of dancers was observed after feeding the colony dihydroxy-phenylalanine (DOPA). Dopamine is hypothesized to modulate the neural activity in the calyx of the mushroom bodies related to recruitment behavior. No consistant effect of octopamine (OA) or serotonin (5HT) on recruitment behavior was observed. Levels of all biogenic amines were strongly effected by season and day-to-day whether changes. Some diurnal changes were also observed.

Scavenging byPheidole pallidulaa key for understanding decision-making systems in ants

The usual evolutionary and ecological approaches to foraging in social insects often lack an investigation at the level of both individual behavioural complexity and social mechanisms ruling the emergence of adaptive collective strategies. The prey scavenging behaviour of the dimorphic antPheidole pallidulawas used in this study to investigate (1) how individuals estimate the size of prey, (2) how they modulate their behaviour and communication and (3) how these modulations generate the diversity of collective foraging patterns. For a pile of small prey (fruit flies), the recruitment of foragers was slow because of the weak intensity of individual trail-laying behaviour and the long time spent by ants wandering around the food. In contrast, for a large prey item (a cockroach), strong recruitment was induced by ants that dashed back to the nest laying a more continuous chemical trail. Experiments with small immovable prey showed that the tractive resistance of prey was the key parameter the foragers used to estimate prey size and that it ruled their trail-laying intensity. These data allow us to generate a model about decision making in scavenging. The rules leading to collective choice in a foraging or an agonistic context are discussed. On the basis of these findings, some theoretical stances in sociobiology and some shortcomings in current approaches to cooperation in social insects are considered.

Systematics and bionomics of the apoid obligate necrophages: the Trigona hypogea group (Hymenoptera: Apidae; Meliponinae)

A systematic revision and biological account is given of the only apoid obligate necrophages, the Trigona hypogea group, along with descriptions of Trigona necrophaga sp. nov. and the male of Trigona crassipes. Trigona necrophaga is endemic to eastern Panama and possibly the Choco; T. hypogea and T. crassipes are sympatric throughout the Amazon Basin and the Guianas. The lack of a corbicula on the hind leg and reduction of giant setae on the labial palpi, workers foraging upon carrion, lack of stored pollen in nests, and complete absence of pollen grains in larval provisions demonstrate obligate necrophagy in all three social, stingless bee species. Evolution of T. hypogea and T. crassipes from a common ancestor in the Amazon Basin is postulated, and T. necrophaga is likely to be an offshoot of T. crassipes. Morphology links T. crassipes and T. hypogea, but nest architecture joins necrophaga and crassipes. Facultative necrophagy in Trigona probably became obligate due to preadaptations including (1) massive forager recruitment via pheromone trails; (2) aggressive foraging on carrion exudates; (3) apical mandibular teeth; (4) rapid location of novel resources; (5) beneficial microbes in bee glandular secretions that metabolize protein and produce antibiotics, and (6) queen cells and food storage pots of the same size and close proximity. Accidental placement of regurgitated, partly-digested carrion in queen cells may have promoted admixture of hypopharyngeal glandular secretions and microbes with harvested liquid carrion. The most derived species, T. necrophaga, may have additional mutualist microbes because only this species has distinctive grey-green protein, and five Bacillus species in food pots and brood cells. No unusual anatomical features were found in worker bees. All three species make sweet, clear honey that contains some pollen but is of unknown origin.

Effects of Intercropping Groundnut with Sunnhemp on Termite Incidence and Damage in India

The effects of intercropping groundnut with sunnhemp on termite incidence and damage were studied in the rainy and post-rainy season at ICRISAT Center in central India. Termite incidence in different cropping systems was determined by baiting with bamboo stakes. Damage to groundnut plants and pods was evaluated at harvest. Intercropping groundnut with sunnhemp did not affect termite abundance or damage to groundnut. These results contrast with a Colombian intercropping study in which sunnhemp exudates repelled cassava burrowing bugs. Termite biology, including recruitment of foragers and construction of protected runways, may have reduced exposure to sunnhemp, thereby minimizing effects.