On the other hand, it is impossible to conceive what labour this delicate work demands; what perseverance Fabre has required painfully to extract one grain of gold; to glean and unite the definite factors, the positive documents, which served as foundations for each of his essays; lucid, limpid, and captivating as the most delightful of fairy-tales. We are charmed, fascinated, and astonished; we see nothing of the groping advance, the checks, and all the toil and the patience demanded. We do not suspect the long waiting, the hesitation, the desperate length of the inquiries. For example, to establish the curious relations which exist between the wasps and the Volucellae, what long and repeated experiments were needful! His notebooks, in which he records, from day to day, all that he sees, are evidence of this. What watches in the alley of lilacs, year after year, to decipher the mechanism and the mode of construction of the hunting-net of the Epeïra! Some of these histories, like that of the hyper-metamorphosis of the Meloë, were only completed as the result of twenty-five years of assiduous inquiry, while forty years were required to complete that of the Scarabaeus sacer, for his observation of it was always partial; it is almost always impossible to divine what one cannot see from the little that one does see; and as a rule one must return to the same point over and over again in order to fill up lacunae. The majority of the insects which Fabre has studied are solitary, and are only to be encountered singly, scattered over wide areas of country. Some live only in determined spots, and not elsewhere, such as the famous Cerceris, or the yellow-winged Sphex, of which no trace is to be found beyond the limits of the Carpentras countryside. The proper season must be watched for; one must be ready at any moment to profit by a lucky chance, and resign oneself to interminable watches at the bottom of a ravine, or keep on the alert for hours under a fiery sun. Often the chance goes by, or the trail followed proves false; but the season is over, and one must wait for the return of another spring. The trade of observer in many cases resembles the exhausting labours of the Sisyphus beetle, painfully pushing his pellet up a rough and stony path; so that the team halts and staggers at every moment, the load spills over and rolls away, and all has to be commenced over again. We can now cast back, in order to consider at leisure the immortal study which marked the beginning of his fame, with the greater interest and profit in that Fabre has been able, during his retirement, to generalize and extend his discovery. (7/35.) Let us first of all note how the observation which Dufour had made of the nest of the Cerceris was transformed in his hands, and what developments he was able to evolve therefrom.