THE DAY WAS SUNNY AND CLEAR, NOT TOO WARM, with a slight breeze from the west. It was midmorning in August in the coastal foothills of Marin County in California. Below, the valleys were still shrouded in fog. Mount Tamalpais to the east and Pine Creek Mountain to the northwest were visible in the distance. I was picking my way over a small hilltop, through stiff, waist-high, clawing branches of chaparral when suddenly a large, black insect took flight in front of me. It was about the size and shape of a bumble bee. I had seen several bees earlier but this one flew differently. It circled me a few times, then landed in plain view on a manzanita bush. Cautiously, I moved in to get a closer look. Again, it took flight, circled a few times, and landed. This time, I could see it clearly. It was black with white sides and large erect wing lobes; it was a rodent bot fly, a Cuterebra ! Again it flew, only this time a second similar fly joined in the circuitous flight path. After a brief pursuit, both landed nearby. I was delighted. Adult bot flies are rare in nature. Collecting a rodent bot has been likened to the bagging of a big game trophy. With net in hand, I stealthily stalked the first fly and, taking careful aim, swung the net and caught it. This trophy now was mine. As I stalked the second fly, I discovered several more in pursuit flights. Suddenly, I realized that the hilltop was an aggregation site. This chance encounter led me on a 30-yr sojourn into the study of the fascinating mating behavior of bot flies.