The Melasoma-beetles and Longicornes are more sensitive to the action of the ammonia. The injection of the corrosive drop pretty quickly renders them motionless; and, after a few convulsions, the insect seems dead. But this paralysis, which would have persisted in the Dung-beetles, the Weevils and the Buprestes, is only temporary here: within a day, motion is once more apparent, as energetic as ever. It is only when the dose of ammonia is of a certain strength that the movements fail to reappear; but then the insect is dead, quite dead, for it soon begins to decay. It is impossible, therefore, to produce complete and persistent paralysis in Beetles that have their ganglia far apart by the same measures which proved so efficacious in Beetles with ganglia close together: the utmost that we can obtain is a temporary paralysis whose effects pass off within a day. The demonstration is conclusive; the Cerceres that prey on Beetles conform in their selection to what could be taught only by the most learned physiologists and the finest anatomists. One would vainly strive to see no more in this than casual coincidences: it is not in chance that we shall find the key to such harmonies as these. CHAPTER IV THE YELLOW-WINGED SPHEX Under their powerful armour, which no dart can penetrate, the insects of the Beetle tribe offer but a single vulnerable spot to the sting-bearing enemy. This defect in the breastplate is known to the murderess, who drives in her poisoned dagger there and at one blow strikes the three motor centres, for she selects her victims from the Weevil and Buprestis families, whose nervous system is centralized to the requisite degree. But what will happen when the prey is an insect clad not in mail but in a soft skin, which the Wasp can stab here or there indifferently, in any part of the body that chances to be exposed? In that case are the blows still delivered scientifically? Like the assassin who strikes at the heart to cut short the dangerous resistance of his victim, does the assailant follow the tactics of the Cerceres and wound the motor ganglia by preference? If that be so, then what happens when these ganglia are some distance apart and so independent in their action that paralysis of one is not necessarily followed by paralysis of the others? These questions will be answered by the story of a Cricket-huntress, the Yellow-winged Sphex (Sphex flavipennis).