The coupling of day butterflies lasts only a few minutes, among night butterflies it is often prolonged for a day and a night, as in sphinx, phalenes, noctuelles. If it is a reward, it is due to their long courageous voyages in quest of the female whom they have divined. The great-peacock moth covers several leagues of country in the attempt to satisfy his desire. Blanchard tells of a naturalist who having caught a female bombyx and put her in his pocket, returned home escorted by a cloud of over two hundred males. In spring, in a place where the great-peacock is so rare that one with difficulty finds one or two per year, the presence of a caged female will draw a hundred males, as Fabre has shown by experiment. These feverish males are endowed with very brief ardour. Whether or no they have touched a female, they live but two or three days. Enormous insects, larger than a humming-bird, they do not eat; their bocal pieces are merely an ornament, a decor: they are bora to reproduce and to die. The males seem infinitely more numerous than the females, and it is probable that not more than one in an hundred can accomplish his destiny. He who misses the pursued female, who arrives too late, is lost: his life is so short that it would be very difficult for him to discover a second. It is true that in normal circumstances the female should stop emitting her sexual odour as soon as she has been ridden; the males are thus attracted by the same female through a proportionately shorter time and there is this much less chance of their searches being unfruitful. Is it their sense of smell alone that guides them?