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?
At 8 a. m. at Fabre's place in Serignan, one saw the cocoon of a lesser-peacock moth open; a female emerged and was immediately imprisoned in a wire cage. At noon a male arrived, the first that Fabre, who had lived there all his life, had ever seen. The wind was blowing from the north. The male came from the north, that is to say, against the scent. At two o'clock ten had arrived. Having come as far as the house without hesitation, they were troubled, got the wrong window, wandered from room to room, never went directly toward the female. One would say that at this point they should have used another sense, perhaps sight, despite their being crepuscular creatures, or that the cage bothered them. Perhaps also it is the custom for the female to come and play before them? It is, in any case, evident that sense of smell plays an important rôle; the mystery would not be less great if one supposed the bringing into play of a special sense, that of sexual orientation. Fabre has obtained equal success with the female of a very rare butterfly, the oak bombyx, or banded minime: in one morning sixty males arrived, turning about the prisoner. One has observed analogous if not identical things in certain serpents, in mammifera: everyone has seen dogs in the country, drawn by a female in heat, coming from a considerable distance, nearly a league, without one's being able to say how their organism had got the news.