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.

为明确低浓度（5 ppb）吡虫啉（imidacloprid）暴露对蜜蜂蜂群的影响，我们开展了五项田间试验，共计纳入54群蜜蜂。每项试验中，一组处理群连续六周饲喂掺有5 ppb吡虫啉的糖浆，另一对照组则饲喂同期未掺加任何药剂的空白糖浆。该处理方案旨在模拟蜂群采集花蜜的自然行为。所有试验场地10公里范围内均无商业化农业种植区域。我们通过两类途径采集试验数据：一是蜂箱评估数据，包括成蜂体重、食物储备总重量以及封盖幼虫巢房总面积；二是传感器监测数据，包括连续记录的蜂箱重量、箱内温度，本研究持续两年期间还同步采集了箱内二氧化碳（CO₂）浓度数据。本研究每年均会在处理前后测定瓦螨（Varroa mite）落螨量；同时在其中三年的试验周期内，我们还测定了新羽化成蜂的干重。