The hatching-period varies, of course, according to the temperature and also according to certain conditions which I am not yet in a position to specify. One cocoon, woven in July, gives birth to the perfect insect in the course of August, two or three weeks after the larva’s period of activity; another, dating from August, opens a month later, in September; a third, no matter what its date of origin during the summer quarter, goes through the winter and does not burst until the end of June. By combining the birth-certificates recorded, I seem to distinguish three generations in the year, generations which are often but not invariably realized. The first appears at the end of June: this is the one whose cocoons have gone through the winter; the second is seen in August and the third in September. So long as the very hot weather lasts, evolution is rapid: three or four weeks suffice to complete the Pelopæus’ cycle. When September arrives, the fall in temperature puts an end to these precocious broods; and the last larvæ have to wait for the return of the hot weather before they can undergo their transformation. CHAPTER V ABERRATIONS OF INSTINCT So far as the Pelopæus is concerned, my part as an observer is concluded, a part of no great interest, I am the first to admit, if we limit its scope merely to the data which it is able to supply. That the insect frequents our dwellings, that it builds a mud nest victualled with Spiders, that it weaves itself a bag which looks as it it were cut out of an onion-skin: all these details matter to us but little. They may please the collector who zealously sets down everything, down to the nervation of a wing, in order to throw a little light on his systematic arrangements; but the mind nourished with more serious ideas sees nothing in all this but the food of an almost puerile curiosity. Is it really worth while to spend our time, the time which escapes us so swiftly, this stuff of life, as Montaigne calls it, in gleaning facts of indifferent moment and of highly contestable utility? Is it not childish to enquire so minutely into an insect’s actions? Too many interests of a graver kind hold us in their grasp to leave us any leisure for these amusements. That is how the harsh experience of age impels us to speak; that is how I should conclude, as I bring my investigations to a close, if I did not perceive, amid the chaos of my observations, a few gleams of light touching the loftiest problems which we are privileged to discuss.