Flight of a Four-Winged Butterfly That Preys on Winged Ants
The raised tail as a rudder, and three wing positions for oblique gliding descent
Leonardo describes the flight of the fourth species of butterfly, a large black-and-yellow insect that devours winged ants, drawn twice with its four equal, separate wings and a raised tail. He explains that the creature holds its tail high and steers with it as a rudder: lowering it to descend, raising it to climb, and bending it right or left to turn, while its four wings are worked in short, whirling courses to catch the darting ants. A further passage sets out three principal positions the wings take in an oblique glide without beating, keyed to the letters a b c, a e f and their descent lines a d, a g and a o.
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Steering with the tail as a rudder
The butterflies fly with four equal, separate wings and always with the tail held high, making of it a rudder for every varied motion. To descend it lowers the tail; to climb it raises it; to turn right or left it bends the tail to that side, and likewise for all the oblique motions interposed among these four principal ones. This greatest of the species is black and yellow.
Whirling courses to seize winged ants
The insect uses its four wings in short, whirling courses when it wants to prey on the small winged ants, sometimes moving the right wing forward and the left behind, and sometimes the left forward and the right behind, because the rudder made of the tail does not govern the greater or lesser speed of its motion.
Three wing positions in an oblique glide
For creatures that descend obliquely without beating the wings, the first position is a b c, where the wing-tips and the opposite tail angles are of equal height and the descent runs along a d. In the second, a e f, the tips and tail angles are of varied height with the left wing higher and the descent along a g. The third is contrary, the left wing lower than the right and the motion toward a o, with the wings set at n m.