In the field study of repellents, each repellent-laden canvas cloth drag was pulled through a stretch of vegetation, repellent side down, for 40 passes. The researchers then quickly hung up the canvas (as shown here) so they could count and record all ticks to species. Then, they continued to observe ticks for a three-minute period and counted how many ticks detached within that period. (Photo by Xia Lee, Ph.D.)