THE MODERN THEORY OF INSTINCT

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The larvæ of the various Hunting Wasps require their prey to be incapable of movement, so that there may be no resistance on the victim’s part, which would be a source of danger to the fragile egg and, later, to the grub. Moreover, for all its lethargy, it must still be alive; for the grub would refuse to feed on a corpse. The fare provided must be fresh meat and not preserved stuff. I have already laid stress on these two antagonistic conditions, immobility and life, and enlarged on them so fully that I need hardly dwell upon them for a second time. I have shown how the Wasp realizes them by the medium of a paralysis which destroys movement and leaves the organic principle of life intact. With a skill which our most famous vivisectors would envy, the insect drives its poisoned sting into the nerve-centres, the seat of muscular incitation. The operator confines herself to one stroke of the lancet, or else gives two, three or more, according to the structure of the particular nervous system and to the number and grouping of the ganglia. The course of the sting is determined by the exact anatomy of the victim.