A stingless bee (Melipona seminigra) uses optic flow to estimate flight distances

Foragers of a stingless bee, Melipona seminigra, are able to use the optic flow experienced en route to estimate flight distance. After training the bees to collect food inside a flight tunnel with black-and-white stripes covering the side walls and the floor, their search behavior was observed in tunnels lacking a reward. Like honeybees, the bees accurately estimated the distance to the previously offered food source as seen from the sections of the tunnel where they turned around in search of the food. Changing the visual flow by decreasing the width of the flight tunnel resulted in the underestimation of the distance flown. The removal of image motion cues either in the ventral or lateral field of view reduced the bees' ability to gauge distances. When the feeder inside the tunnel was displaced together with the bees feeding on it while preventing the bee from seeing any image motion during the displacement the bees experienced different distances on their way to the food source and during their return to the nest. In the subsequent test the bees searched for the food predominantly at the distance associated with their return flight.     

The repellent effect of two pyrethroid insecticides on the honey bee*

ABSTRACT. . An improved model for the repellent effect of pyrethroid insecticides on insects was developed using small colonies of honey bees, Apis mellifera L., in flight cages. Conditioning to scented feeders allowed the separation of foraging bees from a single colony into paired treatment and control groups. The repellent response was characterized as a sublethal toxic effect resulting in transitory inhibition of activity. Permethrin and cypermethrin were shown to be contact repellents to honey bees; exposure was primarily to the tarsi and abdominal venter. Repellency was fully reversible within 24 h. No permanent effects on either memory function or foraging efficiency were observed following acute exposure.     

Thorax vibrations of a stingless bee (<Emphasis Type="Italic">Melipona seminigra</Emphasis>). I. No influence of visual flow

An important question in stingless bee communication is whether the thorax vibrations produced by foragers of the genus Melipona upon their return to the nest contain spatial information about food sources or not. As previously shown M. seminigra is able to use visual flow to estimate flight distances. The present study investigated whether foraging bees encode the visually measured distance in their thorax vibrations. Bees were trained to collect food in flight tunnels lined with a black-and-white pattern on their side walls and floor, which substantially influenced the image motion they experienced. When the bees had collected inside the tunnels the temporal pattern of their vibrations differed significantly from the pattern after collecting in a natural environment. These changes, however, were not associated with the visual flow experienced inside the tunnel. Bees collecting in tunnels offering little visual flow (stripes parallel to flight direction) modified their vibrations similarly to bees collecting in tunnels with high image motion (cross stripes). A higher energy expenditure due to drastically reduced flight velocities inside the tunnel is suggested to be responsible for changes in the thorax vibrations. The bees' vibrations would thus reflect the overall energetic budget of a foraging trip.     

苜蓿切叶蜂授粉扩散行为及苜蓿种子增产效应的研究

对苜蓿切叶蜂(Megachilerotundata)为苜蓿授粉的田间群体扩散行为和苜蓿种子增产效应研究表明,以授粉后苜蓿种子增产效应为指标,发现苜蓿切叶蜂以蜂箱为中心向四周扩散,随着距离增大,蜂的扩散及授粉效应逐渐降低。但不同方向其扩散及授粉效应不同,以苜蓿种子产量Y≥50g·m^-2为高效区,50g·m^-2>Y≥30g·m^-2为中效区,30g·m^-2>Y≥15g·m^-2为低效区。在高效区和中效区内,东北方向扩散距离最远,分别为50和60m,其次是东和北;在低效区,向北扩散距离最远,可达100m,其次是东北和西北;西、南、西南和东南扩散距离较短。据此做出了高效区、中效区和低效区的苜蓿切叶蜂授粉扩散行为图,由此可直观地看到3个区的范围.     

Techniques for Contamination Assessment During Drilling for Terrestrial Subsurface Sediments

Details about the procedures for drilling a ca. 150 m long drill core in a terrestrial setting under contamination controlled conditions are presented. Different to previous studies we only used commercially available drilling equipment to reduce the cost of operation significantly. The goals were (1) to minimize, (2) to monitor and, if possible, to quantify the contamination of the recovered sediments, and (3) to identify the different sources of contamination. Both the potential contamination of the sample material by surface microorganisms and non-indigenous material was assessed. To estimate the infiltration of drill mud into the core, fluorescent microspheres, having about half the size as microorganisms, were added to the mud. The drilling technique used was mud rotary drilling. With the exception of the very beginning of the drilling operations, the drill mud was devoid of any allochthonous hydrocarbons potentially derived from the drilling equipment or drill additives, and its biomarker composition reflected the varying organo-facies that were penetrated. Due to the lack of allochthonous hydrocarbons in the drill mud, its infiltration into the sediment cannot be traced by organic geochemical biomarker analysis. Microspheres proved to be a sensitive tool for the assessment of infiltration of drill mud into the core. The concentration of microspheres in the drill mud decreased continuously during the drilling, most probably caused by seepage of mud through leaks and attachment of spheres to the surface scum in the mud pit. Microscopic enumeration of the microspheres showed great variability in the depth of penetration of mud into the core, apparently unaffected of lithology. The sampling of the core material in the laboratory was carried out inside an anaerobic chamber. Several techniques for subsampling were used, according to sediment properties. The overall results indicate that, if strict contamination control protocols are employed, it is possible to recover uncontaminated samples at reasonable cost with commercially available drilling equipment.     

Effect of Foraging Distance on the Thermal Behaviour of Honeybees during Dancing,Walking and Trophallaxis

By means of infrared thermography and without disturbing social interactions, the correlation between thoracic temperature in honeybees, Apis mellifera carnica, upon their return to the hive and their foraging distance was investigated. Thoracic temperature while dancing and walking and during trophallactic contact with hive bees decreased with increasing flight distance. In bees foraging 0.5, 1, 1.5 and 2 molar sucrose solutions from a distance of 120 m, dancing temperature amounted to 38.4, 40.1, 40.9 and 40.6 °C, respectively; while in bees foraging from a distance of 2950 m it amounted to 36.6, 38.4, 38.6 and 39.1 °C, respectively. The rate of decrease in dancing temperature per 1000 m increase in flight distance was 0.64, 0.47, 0.81 and 0.54 °C with a 0.5, 1, 1.5 and 2 molar sucrose solution, respectively. Both at short and at long flight distances, the relationship between thoracic temperature and sucrose concentration of the food followed a non-linear curve, which flattened at concentrations higher than 1 mol/1. The experiments showed that inside the hive the foragers' level of thermoregulation depends not only on the energy (sugar) content of the food; but rather, the level of thermoregulation corresponds to the general quality of the food source, which includes both energy content and distance from the hive. Because the thermal behaviour of foragers correlates with several behavioural parameters indicating the bees' foraging tendency and their eagerness to dance, thoracic temperature seems to be a correlate of the profitability of foraging.     

Standard yet unusual mechanisms of long-distance dispersal: seed dispersal of Corymbia torelliana by bees

Mellitochory, seed dispersal by bees, has been implicated in long-distance dispersal of the tropical rain forest tree, Corymbia torelliana (Myrtaceae). We examined natural and introduced populations of C. torelliana for 4 years to determine the species of bees that disperse seeds, and the extent and distance of seed dispersal. The mechanism of seed dispersal by bees was also investigated, including fruit traits that promote dispersal, foraging behaviour of bees at fruits, and the fate of seeds. The fruit structure of C. torelliana , with seed presented in a resin reward, is a unique trait that promotes seed dispersal by bees and often results in long-distance dispersal. We discovered that a guild of four species of stingless bees, Trigona carbonaria, T. clypearis, T. sapiens , and T. hockingsi, dispersed seeds of C. torelliana in its natural range. More than half of the nests found within 250 m of fruiting trees had evidence of seed transport. Seeds were transported minimum distances of 20–220 m by bees. Approximately 88% of seeds were dispersed by gravity but almost all fruits retained one or two seeds embedded in resin for bee dispersal. Bee foraging for resin peaked immediately after fruit opening and corresponded to a peak of seed dispersal at the hive. There were strong correlations between numbers of seeds brought in and taken out of each hive by bees ( r =  0.753–0.992, P  < 0.05), and germination rates were 95 ± 5%. These results showed that bee-transported seeds were effectively dispersed outside of the hive soon after release from fruits. Seed dispersal by bees is a non-standard dispersal mechanism for C. torelliana, as most seeds are dispersed by gravity before bees can enter fruits. However, many C. torelliana seeds are dispersed by bees, since seeds are retained in almost all fruits, and all of these are dispersed by bees.     

Hybrid carrot seed crop pollination by the fly Calliphora vicina (Diptera: Calliphoridae)

Many insect species can contribute to crop pollination; however, most growers remain highly dependent on the managed honey bee (Apis mellifera L.) for this service. The European Blue Blow Fly Calliphora vicina Robineau‐Desvoidy, 1830 is one species with potential use as a pollinator. It occurs worldwide and is easy to rear. Caged trials conducted within a hybrid carrot (Daucus carota L.) seed crop found C. vicina to be an effective pollinator. Seed yield (number and weight) from field‐grown carrot plants caged with C. vicina, but excluding all other large flower visitors (body width > 3 mm), was similar to seed yield from uncaged plants in the presence of honey bees (Apis mellifera L.) and other insects. In contrast, caged plants without C. vicina produced 10‐fold less seed. Under open field conditions, C. vicina spent an average of 71.0 s per umbel compared to 54.4 s for honey bees; however, under caged conditions, C. vicina spent more time on average per umbel (128.9 s). Counts of C. vicina and honey bees on umbels outside of cages and C. vicina inside cages found that honey bees were most abundant on days with maximum temperature > 25°C, while C. vicina was more abundant on cooler days around 20°C. C. vicina may therefore be a useful pollinator of crops grown in isolation cages for plant breeding purposes as well as in open fields when climatic conditions are less favourable for optimal honey bee activity.     

Multiple routes of pesticide exposure for honey bees living near agricultural fields

Populations of honey bees and other pollinators have declined worldwide in recent years. A variety of stressors have been implicated as potential causes, including agricultural pesticides. Neonicotinoid insecticides, which are widely used and highly toxic to honey bees, have been found in previous analyses of honey bee pollen and comb material. However, the routes of exposure have remained largely undefined. We used LC/MS-MS to analyze samples of honey bees, pollen stored in the hive and several potential exposure routes associated with plantings of neonicotinoid treated maize. Our results demonstrate that bees are exposed to these compounds and several other agricultural pesticides in several ways throughout the foraging period. During spring, extremely high levels of clothianidin and thiamethoxam were found in planter exhaust material produced during the planting of treated maize seed. We also found neonicotinoids in the soil of each field we sampled, including unplanted fields. Plants visited by foraging bees (dandelions) growing near these fields were found to contain neonicotinoids as well. This indicates deposition of neonicotinoids on the flowers, uptake by the root system, or both. Dead bees collected near hive entrances during the spring sampling period were found to contain clothianidin as well, although whether exposure was oral (consuming pollen) or by contact (soil/planter dust) is unclear. We also detected the insecticide clothianidin in pollen collected by bees and stored in the hive. When maize plants in our field reached anthesis, maize pollen from treated seed was found to contain clothianidin and other pesticides; and honey bees in our study readily collected maize pollen. These findings clarify some of the mechanisms by which honey bees may be exposed to agricultural pesticides throughout the growing season. These results have implications for a wide range of large-scale annual cropping systems that utilize neonicotinoid seed treatments.     

Effects of recent experience on foraging decisions by bumble bees

The temporal and spatial scales employed by foraging bees in sampling their environment and making foraging decisions should depend both on the limits of bumble bee memory and on the spatial and temporal pattern of rewards in the habitat. We analyzed data from previous experiments to determine how recent foraging experience by bumble bees affects their flight distances to subsequent flowers. A single visit to a flower as sufficient to affect the flight distance to the next flower. However, longer sequences of two or three visits had an additional effect on the subsequent flight distance of individual foragers. This suggests that bumble bees can integrate information from at least three flowers for making a subsequent foraging decision. The existence of memory for floral characteristics at least at this scale may have significance for floral selection in natural environments.     

The Ethological–Physiological Response of <Emphasis Type="Italic">Apis mellifera</Emphasis> L. Bees to Carbohydrate Lead Contamination

The response of bees to lead contamination of a carbohydrate feed has been studied. It was established that Pb in sucrose solution had a toxic and repelling effect on the bees. It was found that the amount of contaminated feed consumed by the bees decreased with a corresponding increase in the content of Pb in it. It is noted that this element accumulates unevenly in different body parts and parts of the digestive tract of the bees, thereby affecting their metabolic activity and accelerating processes of physiological aging, and the specific reaction of the bees to contaminated feed is expressed in their rejection of its consumption and in inhibition of their locomotion.     

Cryptococcus neoformans in bird excreta in the city zoo of Cali,Colombia

The presence of Cryptococcus neoformans was studied in bird excreta and in the air circulating in and around bird cages in the City Zoo of Cali, Colombia, between August 1994 and April 1995, using a sunflower seed agar culture medium for fungus isolation. A total of 380 samples was studied, 110 from droppings and 270 from Petri dishes placed inside(148) and outside (122) the cages. C. neoformansvar neoformans was found in only two cases, one from bird excreta (0.9%) and the other from air inside a cage (0.7%). The former positive sample was collected from the cracks of a dead tree where two crested caracaras (Polyborusplancus) roosted; the feces were dry, accumulated,and with a pH of 6. The other positive sample was found inside the cage of these birds; however, samples taken in a dispersion study at 0.5, 1, 5 and 10 m around this cage were all negative. It appears that this low isolation rate is due to adequate cleaning and disinfection procedures used in the city zoo of Cali.This revised version was published online in October 2005 with corrections to the Cover Date.     

Investigation of the potential for microbial contamination of deep granitic aquifers during drilling using 16S rRNA gene sequencing and culturing methods

Total number of bacteria, viable counts of aerobic and anaerobic heterotrophic bacteria and 16S rRNA gene diversity were investigated during drilling of three boreholes in the walls of the Äspö hard rock laboratory tunnel, at depths ranging from 380 to 446 m below sea level. Water samples were taken from the drill water source, the drilling equipment and from the drilled boreholes. The drill water was kept under nitrogen atmosphere and all equipment was steam cleaned before the start of a new drilling. Total and viable counts of bacteria in the drilled boreholes were several orders of magnitude lower than in the samples from the drilling equipment, except for sulphate reducing bacteria. A total of 158 16S rRNA genes that were cloned from the drill water source, the drilling equipment and the drilled boreholes were partially sequenced. The drilled boreholes generally had a 16S rRNA diversity that differed from what was found in samples from the drilling equipment. Several of the sequences obtained could be identified on genus level as one of the genera Acinetobacter, Methylophilus, Pseudomonas and Shewanella. In conclusion, the tubing used for drill water supply constituted a source of bacterial contamination to the rest of the drilling equipment and the boreholes. The results show, using molecular and culturing methods, that although large numbers of contaminating bacteria were introduced to the boreholes during drilling, they did not establish in the borehole groundwater at detectable levels.     

Circadian Activity Rhythm of the Foragers of a Eusocial Bee (Scaptotrigona aff depilis,Hymenoptera, Apidae,Meliponinae) outside the Nest

In all bee colonies of the Meliponinae subfamily, activity inside the nest is temporally organized around the oviposition by the queen, assisted by nurse bees. This class is constituted by young bees that remain inside the nest. In a colony of Scaptotrigona aff depilis, the oviposition cycle occurs in a 3-hour period. The foragers are older bees that collect food for the colony in the field. Other tasks in the nest are performed by workers of ages intermediate between nurses and foragers. With the aim of studying activity rhythms, foragers were kept under constant light, with food constantly available and no flight restriction. The results showed that, although inside the nest the prevailing period is 3 hours, the activity of the foragers is a circadian rhythm, synchronized by the light/dark cycle and probably influenced by other environmental cycles as temperature and the availability of food sources.     

Risk of alfalfa transgene dissemination and scale-dependent effects

Pollen can function as a vehicle to disseminate introduced, genetically engineered genes throughout a plant population or into a related species. The measurement of the risk of inadvertent dispersal of transgenes must include the assessment of accidental dispersion of pollen. Factors to be considered include the rate of pollen spread, the maximal dispersion distance of pollen, and the spatial dynamics of pollen movement within seed production fields; none of which are known for alfalfa (Medicago sativa L.), an insect-pollinated crop species. Using a rare, naturally occurring molecular marker, alfalfa pollen movement was tracked from seed and hay production fields. Results indicated that leafcutter bees (Megachile spp.) used in commercial seed production show a directional, non-random bias when pollinating within fields, primarily resulting in the movement of pollen directly towards and away from the bee domicile. Within-field pollen movement was detected only over distances of 4 m or less. Dispersal of pollen from alfalfa hay and seed production fields occurs at distances up to 1000 m. By examining widely dispersed, individual escaped alfalfa plants and their progeny using RAPD markers, gene movement among escaped alfalfa plants has been confirmed for distances up to 230 m. The outcrossing frequency for large fields was nearly 10-times greater than that of research-sized plots. A minimum isolation distance of 1557 m may be required to prevent gene flow in alfalfa. Data suggest that complete containment of transgenes within alfalfa seed or hay production fields would be highly unlikely using current production practices. Received: 20 March 1999 / Accepted: 11 November 1999     

Longitudinal study of the contamination of air and of soil surfaces in the vicinity of pig barns by livestock-associated methicillin-resistant Staphylococcus aureus

During 1 year, samples were taken on 4 days, one sample in each season, from pigs, the floor, and the air inside pig barns and from the ambient air and soil at different distances outside six commercial livestock-associated methicillin-resistant Staphylococcus aureus (LA-MRSA)-positive pig barns in the north and east of Germany. LA-MRSA was isolated from animals, floor, and air samples in the barn, showing a range of airborne LA-MRSA between 6 and 3,619 CFU/m(3) (median, 151 CFU/m(3)). Downwind of the barns, LA-MRSA was detected in low concentrations (11 to 14 CFU/m(3)) at distances of 50 and 150 m; all upwind air samples were negative. In contrast, LA-MRSA was found on soil surfaces at distances of 50, 150, and 300 m downwind from all barns, but no statistical differences could be observed between the proportions of positive soil surface samples at the three different distances. Upwind of the barns, positive soil surface samples were found only sporadically. Significantly more positive LA-MRSA samples were found in summer than in the other seasons both in air and soil samples upwind and downwind of the pig barns. spa typing was used to confirm the identity of LA-MRSA types found inside and outside the barns. The results show that there is regular airborne LA-MRSA transmission and deposition, which are strongly influenced by wind direction and season, of up to at least 300 m around positive pig barns. The described boot sampling method seems suitable to characterize the contamination of the vicinity of LA-MRSA-positive pig barns by the airborne route.     

Influence of flight time and flight environment on distance communication by dancing honey bees

Forager honey bees communicate the distance of food sources to nest mates through waggle dances, but how do bees measure these distances? Recent work suggests that bees measure distance flown in terms of the extent of image motion (integrated optic flow) that is experienced during flight. However, it is known that optic flow also regulates the speed of flight. Therefore, the duration of the flight to a destination is likely to co-vary with the optic flow that is experienced en route. This makes it difficult to tease apart the potential roles of flight duration and optic flow as cues in estimating distance flown. Here we examine whether flight duration alone can serve as an indicator of distance. We trained bees to visit feeders at two sites located in optically different environments, but positioned such that the flight durations to the two sites were similar. The distance estimates for the two sites, as reported in the waggle dance, were compared. We found that dances differed significantly between the two sites, even though flight times were similar. Flight time perse was a poor predictor of waggle dance behaviour. We conclude that foraging bees do not simply signal flight time as their measure of distance in the waggle dance; the environment through which they fly plays a dominant role. Received 11 April 2005; revised 16 May 2005; accepted 3 June 2005.     

Utilization of Fluorescent Microspheres and a Green Fluorescent Protein-Marked Strain for Assessment of Microbiological Contamination of Permafrost and Ground Ice Core Samples from the Canadian High Arctic

Fluorescent microspheres were applied in a novel fashion during subsurface drilling of permafrost and ground ice in the Canadian High Arctic to monitor the exogenous microbiological contamination of core samples obtained during the drilling process. Prior to each drill run, a concentrated fluorescent microsphere (0.5-μm diameter) solution was applied to the interior surfaces of the drill bit, core catcher, and core tube and allowed to dry. Macroscopic examination in the field demonstrated reliable transfer of the microspheres to core samples, while detailed microscopic examination revealed penetration levels of less than 1 cm from the core exterior. To monitor for microbial contamination during downstream processing of the permafrost and ground ice cores, a Pseudomonas strain expressing the green fluorescent protein (GFP) was painted on the core exterior prior to processing. Contamination of the processed core interiors with the GFP-expressing strain was not detected by culturing the samples or by PCR to detect the gfp marker gene. These methodologies were quick, were easy to apply, and should help to monitor the exogenous microbiological contamination of pristine permafrost and ground ice samples for downstream culture-dependent and culture-independent microbial analyses.     

The effect of presence of a queen upon outbreak of a hairless-black syndrome in the honey bee

Mortalities in 68 populations, of about 100 bees each, confined to small cages containing a piece of comb were tabulated daily and symptoms of the disease were observed until all bees had died. Various experimental treatments were administered, the most important of which was the presence or absence of a queen in each population. Queenless populations usually showed some bees chewing and nibbling upon others (a symptom of the disease) in 3–5 days, whereas queenright units usually did not show this symptom for 10 days or longer. Average length of life in queenless units was about three-fourths as long as in queenright units. Some confirmation of these results was obtained from larger populations allowed to fly in a flight cage.