Nurses had the highest proportion with mites, followed by foragers and then newly emerged bees (“new bees”). Results based on seven trials (each trial using a different source colony), with 1–4 in Michigan, USA, and 5–7 in Jiangxi, China. Numbers inside each “nurse” bar indicate age of the nurses. Different letters on top of each bar denote significant differences (P < 0.05) using G-tests for individual trials, or Fisher’s Protected Least Significant Difference Tests after analysis of variance showed a significant effect (Overall). From Xie et al., Scientific Reports 6, 28228