Supplemental data Effects of imidacloprid exposure on honey bee colony growth and activity

To better understand how exposure to a low (5 ppb) concentration of imidacloprid affects honey bee colonies we conducted five field experiments involving a total of 54 bee colonies. In each experiment, bee colonies in one treatment group were fed sugar syrup adulterated with 5ppb imidacloprid over six weeks, and colonies in the other group were fed unadulturated sugar syrup over the same time period. Treatments were intended to simulate nectar collection by the colonies. No commercial agriculture existed within 10 km of the sites. We collected data from hive assessments, including adult bee mass and mass of food resources, and the total surface area of capped brood; and we collected data from sensors, including continuous hive weight, internal temperature and, for two years of the study, internal CO2 concentration. We measured Varroa mite fall before and after treatment each year of the study, and for 3 years of the study we measured the dry weight of newly-emerged adult bees.

为探究低浓度（5 ppb）吡虫啉（imidacloprid）暴露对蜜蜂蜂群的影响，我们开展了五项野外试验，共纳入54个蜜蜂蜂群。在每项试验中，一个处理组的蜂群在六周内被饲喂掺有5ppb吡虫啉的糖浆，另一组对照组则在相同周期内饲喂未掺加吡虫啉的纯糖浆。该处理方案旨在模拟蜂群的自然花蜜采集过程。所有试验场地10公里范围内均无商业化农业活动。我们通过两类途径采集数据：一是蜂箱评估数据，包括成年蜂体重、食物资源总质量以及封盖育幼巢房的总表面积；二是传感器监测数据，包括连续记录的蜂箱重量、箱内温度，以及试验周期内两年的箱内二氧化碳（CO₂）浓度。本研究每年均在处理前后采集瓦螨（Varroa mite）落网数量，且在其中三年的试验中，测定了新羽化成年蜂的干重。