I then followed their route for about a hundred and fifty yards until they came to a tall ash, and all along this line they buzzed at various fixed spots. At the far end, near a pollard oak, the track divided into two as shown in the plan. On some days all the bees flew in the direction I have described, but on others some arrived from the opposite direction. From observations made on favourable days, I think that the majority of individuals must fly in a wide circle. They stop every now and then to suck at flowers. I confirmed that whilst in flight they move at about ten miles an hour, but they lose a considerable amount of time at the buzzing places. The routes remain the same for a considerable time, and the buzzing places are fixed within an inch. I was able to prove this by stationing five or six of my children each close to a buzzing place, and telling the one farthest away to shout out " here is a bee " as soon as one was buzzing around. The others followed this up, so that the same cry of " here is a bee " was passed on from child to child without interruption until the bees reached the buzzing place where I myself was standing.
This sketch of the grounds of Down House shows the part of the male bumblebee flight route studied by Darwin with the help of his children. What fun must have been to have him as a dad!
Freeman, R.B. (1968). Charles Darwin on the routes of male bumblebees. BULLETIN OF THE BRITISH MUSEUM (NATURAL HISTORY) HISTORICAL SERIES , 3 (6), 177-189.
Stiles, Edmund W. (1976). Comparison of Male Bumblebee Flight Paths: temperate and tropical. Journal of the Kansas Entomological Society., 49 (2), 266-274.