Perhaps the number of days elapsing between the stinging of the caterpillar and of the moth was not sufficient to enable the virus to act upon the organism to the requisite degree. It might need a longer space of time to bring about the inward modifications caused by the action of the poison on the insect’s organism. The Cetonia-larvæ will perhaps be able to dispense with this period. I have a set of twelve of them, stung twice over, first in October and then in May. The perfect insect bursts its cocoon at the end of July. Ten months therefore have elapsed since the first sting and three months since the second. Is the adult now immune? Not at all. When subjected to the Scorpion, my twelve vaccinated specimens all perish, no more and no less quickly than their fellows who were born quietly in their heap of rotten leaves. Twelve others, pricked only once, in May, succumb with the same promptness. In the case of both sets, my devices, which inspired me with confidence at first, miscarry pitifully, to my extreme confusion. I try another method, that of transfusion of blood, which is related to serotherapy. Since it resists the Scorpion’s sting, the larva of the Cetonia must have blood endowed with special qualities, apt to neutralize the virulence of the poison. If transferred from the larva to the adult, might not this blood communicate its qualities and render the perfect insect invulnerable? I give a Cetonia-grub a superficial wound with the point of a needle. The blood spouts forth abundantly. I collect it in a watch-glass. A glass tube of small diameter, drawn out to a sharp point, serves as an injector. I charge it by suction with the fluid collected, varying the dose from a cubic millimetre to ten and twenty times as much. By blowing into the tube I transfer the liquid into some point of the adult Cetonia, particularly on the ventral surface, where a needle has prepared the way for the fragile injector. The insect stands the operation very well. The richer by a little larval blood and not seriously wounded, it presents every appearance of blooming health. Now what comes of this treatment? Nothing at all. I wait a day or two to give the injected fluids time to diffuse and act. The Cetonia is then presented to the Scorpion. Veil your face, O foolish physiologist: the creature perishes as it would have done before your presumptuous attempts at surgery. We cannot manipulate animals as we can the reagents of chemistry. CHAPTER V THE LANGUEDOCIAN SCORPION: PRELUDES TO THE WEDDING