Even as demand for their services increases, honey bees (Apis mellifera) and other pollinating insects continue to decline in Europe and North America. Honey bees face many challenges, including an issue generally affecting wildlife: landscape changes have reduced flower-rich areas. One way to help is therefore to supplement with flowers, but when would this be most beneficial? We use the waggle dance, a unique behaviour in which a successful forager communicates to nestmates the location of visited flowers, to make a 2-year survey of food availability. We “eavesdropped” on 5097 dances to track seasonal changes in foraging, as indicated by the distance to which the bees as economic foragers will recruit, over a representative rural-urban landscape. In year 3, we determined nectar sugar concentration. We found that mean foraging distance/area significantly increase from springs (493 m, 0.8 km2) to summers (2156 m, 15.2 km2), even though nectar is not better quality, before decreasing in autumns (1275 m, 5.1 km2). As bees will not forage at long distances unnecessarily, this suggests summer is the most challenging season, with bees utilizing an area 22 and 6 times greater than spring or autumn. Our study demonstrates that dancing bees as indicators can provide information relevant to helping them, and, in particular, can show the months when additional forage would be most valuable.

OBJECTIVE The retention of patients on antiretroviral therapy (ART) is key to achieving global targets in response to the HIV epidemic. Loss to follow-up (LTFU) can be substantial, with unknown outcomes for patients lost to ART programmes. We examined changes in outcomes of patients LTFU over calendar time, assessed associations with other study and programme characteristics and investigated the relative success of different tracing methods. METHODS We performed a systematic review and logistic random-effects meta-regression analysis of studies that traced adults or children who started ART and were LTFU in sub-Saharan African treatment programmes. The primary outcome was mortality, and secondary outcomes were undocumented transfer to another programme, treatment interruption and the success of tracing attempts. RESULTS We included 32 eligible studies from 12 countries in sub-Saharan Africa: 20 365 patients LTFU were traced, and 15 708 patients (77.1%) were found. Compared to telephone calls, tracing that included home visits increased the probability of success: the adjusted odds ratio (aOR) was 9.35 (95% confidence interval [CI] 1.85–47.31). The risk of death declined over calendar time (aOR per 1-year increase 0.86, 95% CI 0.78–0.95), whereas undocumented transfers (aOR 1.13, 95% CI 0.96–1.34) and treatment interruptions (aOR 1.31, 95% CI 1.18–1.45) tended to increase. Mortality was lower in urban than in rural areas (aOR 0.59, 95% CI 0.36–0.98), but there was no difference in mortality between adults and children. The CD4 cell count at the start of ART increased over time. CONCLUSIONS Mortality among HIV-positive patients who started ART in sub-Saharan Africa, were lost to programmes and were successfully traced has declined substantially during the scale-up of ART, probably driven by less severe immunodeficiency at the start of therapy.

-To investigate the distances at which honey bee foragers collect nectar and pollen, we analysed 5,484 decoded waggle dances made to natural forage sites to determine monthly foraging distance for each forage type. Firstly, we found significantly fewer overall dances made for pollen (16.8 %) than for non-pollen, presumably nectar (83.2 %; P <2.2×10−23 ). When we analysed distance against month and forage type, there was a significant interaction between the two factors, which demonstrates that in some months, one forage type is collected at farther distances, but this would reverse in other months. Overall, these data suggest that distance, as a proxy for forage availability, is not significantly and consistently driven by need for one type of forage over the other.forage availability / waggle dance / Apis mellifera / nectar / pollen

SummaryNoise is universal in information transfer. In animal communication, this presents a challenge not only for intended signal receivers, but also to biologists studying the system. In honey bees, a forager communicates to nestmates the location of an important resource via the waggle dance. This vibrational signal is composed of repeating units (waggle runs) that are then averaged by nestmates to derive a single vector. Manual dance decoding is a powerful tool for studying bee foraging ecology, although the process is time-consuming: a forager may repeat the waggle run 1- >100 times within a dance. It is impractical to decode all of these to obtain the vector; however, intra-dance waggle runs vary, so it is important to decode enough to obtain a good average. Here we examine the variation among waggle runs made by foraging bees to devise a method of dance decoding. The first and last waggle runs within a dance are significantly more variable than the middle run. There was no trend in variation for the middle waggle runs. We recommend that any four consecutive waggle runs, not including the first and last runs, may be decoded, and we show that this methodology is suitable by demonstrating the goodness-of-fit between the decoded vectors from our subsamples with the vectors from the entire dances.

Since 1994, more than €41 billion has been spent in the European Union on agri-environment schemes (AESs), which aim to mitigate the effects of anthropomorphic landscape changes via financial incentives for land managers to encourage environmentally friendly practices [1-6]. Surprisingly, given the substantial price tag and mandatory EU member participation [2], there is either a lack of [1] or mixed [1, 2, 7] evidence-based support for the schemes. One novel source of data to evaluate AESs may be provided by an organism that itself may benefit from them. Honeybees (Apis mellifera), important pollinators for crops and wildflowers [8, 9], are declining in parts of the world from many factors, including loss of available forage from agricultural intensification [10-13]. We analyzed landscape-level honeybee foraging ecology patterns over two years by decoding 5,484 waggle dances from bees located in the center of a mixed, urban-rural 94 km(2) area, including lands under government-funded AESs. The waggle dance, a unique behavior performed by successful foragers, communicates to nestmates the most profitable foraging locations [14-16]. After correcting for distance, dances demonstrate that honeybees possess a significant preference for rural land managed under UK Higher Level AESs and a significant preference against rural land under UK Organic Entry Level AESs. Additionally, the two most visited areas contained a National and Local Nature Reserve, respectively. Our study demonstrates that honeybees, with their great foraging range and sensitive response to forage quality, can be used as bioindicators to monitor large areas and provide information relevant to better environmental management.

In bumble bees (Bombus spp.), where workers within the same colony exhibit up to a tenfold difference in mass, labor is divided by body size. Current adaptive explanations for this important life history feature are unsatisfactory. Within the colony, what is the function of the smaller workers? Here, we report on the differential robustness to starvation of small and large worker bumble bees (Bombus impatiens); when nectar is scarce, small workers remain alive significantly longer than larger workers. The presence of small workers, and size variation in general, might act as insurance against times of nectar shortage. These data may provide a novel, adaptive explanation, independent of division of labor, for size polymorphism within the worker caste.

In a recognition context, discriminating agents decide whether to accept or to reject. In the honeybee, entrance guards distinguish between nestmates and intruders. Those below a threshold of dissimilarity are accepted. However, the threshold is dependent on ecological conditions and may shift to become either restrictive or permissive, depending on the frequency of intrusion and cost of admitting an intruder. Previous research on the honeybee has shown that both the number of guards and their acceptance threshold to conspecific non-nestmates can change dramatically over weeks owing to changing nectar availability and robbing intensity. This project investigated whether these changes could also occur rapidly, over minutes, in response to sudden increases in conspecific intruders (robber bees). We induced high levels of intrusion at nest entrances and determined changes in the number of guards, the number of fights per guard, and the acceptance thresholds of guards. Our results show a rapid response within 15 min. At the level of individual guards, acceptance declined from 83 to 55% for nestmates and 67 to 43% for conspecific nonnestmates. Also, per individual guard, mean fights increased from 0.005 to 0.06 fights/guard. At the colony level, the mean number of guards at the entrance rose from 1.9 to 2.3, and overall acceptance in a 3-min trial declined from 74 to 52% for nestmates and 59 to 30% for conspecific non-nestmates. These results show that honeybees can make rapid behavioural shifts at both the colony and the individual levels.

In pollination, plants provide food reward to pollinators who in turn enhance plant reproduction by transferring pollen, making the relationship largely cooperative; however, because the interests of plants and pollinators do not always align, there exists the potential for conflict, where it may benefit both to cheat the other [1, 2]. Plants may even resort to chemistry: caffeine, a naturally occurring, bitter-tasting, pharmacologically active secondary compound whose main purpose is to detract herbivores, is also found in lower concentrations in the nectar of some plants, even though nectar, unlike leaves, is made to be consumed by pollinators. [corrected]. A recent laboratory study showed that caffeine may lead to efficient and effective foraging by aiding honeybee memory of a learned olfactory association [4], suggesting that caffeine may enhance bee reward perception. However, without field data, the wider ecological significance of caffeinated nectar remains difficult to interpret. Here we demonstrate in the field that caffeine generates significant individual- and colony-level effects in free-flying worker honeybees. Compared to a control, a sucrose solution with field-realistic doses of caffeine caused honeybees to significantly increase their foraging frequency, waggle dancing probability and frequency, and persistency and specificity to the forage location, resulting in a quadrupling of colony-level recruitment. An agent-based model also demonstrates how caffeine-enhanced foraging may reduce honey storage. Overall, caffeine causes bees to overestimate forage quality, tempting the colony into sub-optimal foraging strategies, which makes the relationship between pollinator and plant less mutualistic and more exploitative. VIDEO ABSTRACT.