There is increasing worldwide concern about the impacts of pesticide residues on honey bees and bee colony survival, but how sublethal effects of pesticides on bees might cause colony failure remains highly controversial, with field data giving very mixed results. To explore how trace levels of the neonicotinoid pesticide imidacloprid impacted colony foraging performance, we equipped bees with RFID tags that allowed us to track their lifetime flight behavior. One group of bees was exposed to a trace concentration (5 μg/kg, ppb) of imidacloprid in sugar syrup while in the larval stage. The imidacloprid residues caused bees to start foraging when younger as adults and perform fewer orientation flights, and reduced their lifetime foraging flights by 28%. The magnitude of the effects of a trace imidacloprid concentration delivered only during larval stage highlights the severity of pesticide residues for bee foraging performance. Our data suggest that neonicotinoids could impact colony function by imbalancing the normal age based division of labor in a colony and reducing foraging efficiency. Understanding this mechanism will help the development of interventions to safeguard bee colony health.

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Patterns in within-day hive weight data from two independent datasets in Arizona and California were modeled using piecewise regression, and analyzed with respect to honey bee colony behavior and landscape effects. The regression analysis yielded information on the start and finish of a colony’s daily activity cycle, hive weight change at night, hive weight loss due to departing foragers and weight gain due to returning foragers. Assumptions about the meaning of the timing and size of the morning weight changes were tested in a third study by delaying the forager departure times from one to three hours using screen entrance gates. A regression of planned vs. observed departure delays showed that the initial hive weight loss around dawn was largely due to foragers. In a similar experiment in Australia, hive weight loss due to departing foragers in the morning was correlated with net bee traffic (difference between the number of departing bees and the number of arriving bees) and from those data the payload of the arriving bees was estimated to be 0.02 g. The piecewise regression approach was then used to analyze a fifth study involving hives with and without access to natural forage. The analysis showed that, during a commercial pollination event, hives with previous access to forage had a significantly higher rate of weight gain as the foragers returned in the afternoon, and, in the weeks after the pollination event, a significantly higher rate of weight loss in the morning, as foragers departed. This combination of continuous weight data and piecewise regression proved effective in detecting treatment differences in foraging activity that other methods failed to detect.

The monitoring of introduced species is becoming more important as global trade intensifies. Although ants make up a larger proportion of species on the list of the most invasive species in the world compared with other groups, little is known about the occurrence of those introduced in France, especially inside heated buildings. Here we review the literature available for mainland France and Belgium and report the results of a survey conducted with the help of tropical building managers between 2014 and 2016. We report for the first time in France the presence of Technomyrmex vitiensis and Plagiolepis alluaudi in multiple greenhouses. Technomyrmex difficilis was also found in one greenhouse for the first time in Europe. The diversity of introduced ants in greenhouses is very low, and these buildings are most often dominated by one or two species. We compared the most recent data and those collected throughout the 20 th century, and showed that ant communities have changed substantially. Greenhouses could be responsible for the introduction of invasive species because they regularly import exotic plants, but we found no evidence that the three species of invasive ants present outdoors in France were introduced from greenhouses, where they rarely occur. We also report that introduced ants are pests in greenhouses because they disperse scale insects and kill biological control agents. The suppression of these ants could ease the maintenance of plants inside greenhouses.

Measuring individual foraging performance of pollinators is crucial to guide environmental policies that aim at enhancing pollinator health and pollination services. Automated systems have been developed to track the activity of individual honey bees, but their deployment is extremely challenging. This has limited the assessment of individual foraging performance in full‐strength bee colonies in the field. Most studies available to date have been constrained to use downsized bee colonies located in urban and suburban areas. Environmental policy‐making, on the other hand, needs a more comprehensive assessment of honey bee performance in a broader range of environments, including in remote agricultural and wild areas. Here, we detail a new autonomous field method to record high‐quality data on the flight ontogeny and foraging performance of honey bees, using radio frequency identification (RFID). We separate bee traffic into returning and exiting tunnels to improve data quality solving many previous limitations of RFID systems caused by traffic jams and the parasitic coupling of RFID antennae. With this method, we assembled a large RFID dataset made of control bee colonies from experiments conducted in different locations and seasons. We hope our results will be a starting point to understand how ontogenetic and environmental factors affect the individual performance of honey bees and that our method will enable large‐scale replication of individual pollinator performance studies.

Authors' contributions TC collected colonies, reared them, performed the experiments and statistical analyses, and wrote the manuscript. CD designed the study, contributed to statistical analysis and wrote the manuscript. RP collected colonies, and assisted in rearing and experiments. MM designed the study, wrote the manuscript, and supervised the project. All authors read and approved the final manuscript. Within-colony phenotypic diversity can play an essential role in some eusocial insect taxa by increasing the performance of division of labor, thereby increasing colony fitness. Empirical studies of the effect of phenotypic diversity on colony fitness mostly focused on species with discrete castes (workers, soldiers) or with continuously and highly morphologically variable workers, which is not the most common case. Indeed, most species exhibit continuous but limited worker morphological variation. It is still unclear whether this variation impacts colony fitness. To test this, we reduced the worker size diversity in 25 colonies of the ant Temnothorax nylanderi and compared their performances to 25 control colonies. We reared these colonies in the laboratory and measured the effect of treatment (reduced diversity or control) and colony size (number of workers) on colony performance at six challenges, as well as on worker mortality and brood production. The reduction of worker size diversity did not affect colony performance nor mortality and brood production. As expected, colony performance and brood production increased with colony size. These results suggest that worker size diversity may not be under positive selection in this species, but rather the product of a lack of developmental canalization. We propose that social life could decrease the selective pressures maintaining developmental canalization, subsequently leading to higher size diversity without necessarily increasing colony performance. 4 Significance statementIn social insects, nestmate size diversity is commonly thought to improve division of labour and colony performance. This has been clearly demonstrated in species with high size diversity, either discrete or continuous, but this is unclear in most of the social insects that exhibit low size diversity. We experimentally decreased worker size diversity in the ant Temnothorax nylanderi, a species with low worker size diversity. Reducing worker size diversity had no effect on colony performance, worker mortality or brood production. Our findings support the hypothesis that low size diversity is merely the product of developmental noise and is not necessarily adaptive. We propose that social life could relax the selective pressures maintaining developmental and social canalizations, subsequently leading to size diversity.5

Precise, objective data on brood and honey levels in honey bee colonies can be obtained through the analysis of hive frame photographs. However, accurate analysis of all the frame photographs from medium- to large-scale experiments is time-consuming. This limits the number of hives than can be practically included in honeybee studies. Faster estimation methods exist but they significantly decrease precision and their use requires a larger sample size to maintain statistical power. To resolve this issue, we created ‘CombCount’ a python program that automatically detects uncapped cells to speed up measurements of capped brood and capped honey on photos of frames. CombCount does not require programming skills, it was designed to facilitate colony-level research in honeybees and to provide a fast, free, and accurate alternative to older methods based on visual estimations. Six observers measured the same photos of thirty different frames both with CombCount and by manually outlining the entire capped areas with ImageJ. The results obtained were highly similar between both the observers and the two methods, but measurements with CombCount were 3.2 times faster than with ImageJ (4 and 13 min per side of the frame, respectively) and all observers were faster when using CombCount rather than ImageJ. CombCount was used to measure the proportions of capped brood and capped honey on each frame of 16 hives over a year as they developed from packages to full-size colonies over about 60 days. Our data describe the formation of brood and honey stores during the establishment of a new colony.

Chemical miticides are used routinely in honey bee colonies worldwide as treatment for the parasitic mite Varroa destructor , but there have been very few long-term colony-level field studies of the impacts of miticides on the bees themselves. Lab-based studies with individual bees or bees in small groups have highlighted many negative effects of miticides on bee behaviour and physiology; hence, there is an urgent need to better understand the consequences of miticides on honey bee colonies in an apicultural setting. Here we compared effects of commercial treatments of the miticides tau-fluvalinate and thymol, and controls, on honey bee colonies and bee foraging behaviour over five months, from autumn through winter in Sydney, Australia. Since V. destructor does not occur in Sydney, in this study, we could isolate the direct effects of the miticides from indirect effects resulting from reduced mite load. We found the autumn treatment of either miticide caused no significant change in bee adult or brood population or size of food stores. The average temperature in the thymol group differed from the temperature in the control group and was lower during winter. Neither miticide reduced bee longevity. Tau-fluvalinate caused bees to start foraging earlier in life and perform shorter trips, but no other effects on foraging behaviour were documented. To conclude, in Sydney, Australia, limited negative effects of autumn thymol or tau-fluvalinate treatments were observed on bees or bee colony performance. miticides / acaricides / Varroa destructor / RFID / continuous weight measurement