xxiv President' ] s Address. [Aug* 28, 



floor of the body, on the ventral surface, not the dorsal one, and that 

 the insertion of its sting from above could only result in the puncture 

 of the dorsal vessel or heart — hence death and decomposition — the 

 very thing she guards against. However skilful the stiletto may be, 

 the caterpillar has not yet quite given up all hope of a struggle, the 

 effect of the paralysing operation is not yet wholly obtained, and this 

 is why the Sphex proceeds further by means of its powerful mandibles 

 to compress the cerebral ganglia. General paralysis is now obtained, 

 the bulky prey can now be dragged to the cell with comparative ease. 

 A feeble, very feeble, twitching denotes that the animal is still alive. 

 The egg of the Sphex is deposited on the ventral surface and the grub 

 will now be able to devour its prey at ease. 



Sphegidae do not always select caterpillars for storing their nests 

 with. Cerceridae use beetles. Phylanthus attacks the honey-bee, a 

 foe not to be despised ; Ammophila prefers caterpillars, but I have 

 seen one carrying young crickets. The very large group of Pelopceus 

 and Pompilus feed their larvae on spiders. But in each one of these 

 insects the nervous system has undergone a change ; the ganglia are 

 not disposed in the same manner, they are more or less distant, more 

 or less concentrated. In the bee we have a large complicated brain,, 

 an oesophageal ganglion, two thoracic ganglia instead of three, and 

 five or six abdominal ones. In the beetle they differ much in position, 

 but may be said to have agglomerated in the thoracic region, with the 

 exception of the cerebral one, of course ; in the spider, besides the 

 brain, there is a single ganglionic mass in the thorax, none in the 

 abdomen. But no matter where these ganglia are placed, the 

 fossorial hymenoptera know where to insert their stings with due 

 effect, and seldom fail. 



As I have already said, many Pompilidae select the spiders for 

 their prey. The Arachnid knows very well that it is as well armed 

 as its adversary, if not better. Its chelicerae are not only sharp and 

 strong, and articulated by powerful muscles, but they are also pro- 

 vided with a gland supplying a most virulent poison. The struggle 

 between a Pompilus and an Arachnid when it is a Lycosa or a My gale 

 is a very serious affair. The tactic of the spider is to seize the 

 Pompilus by the head and to pierce the cerebral ganglia with its 

 chelicerae ; she does not require any nutriment for her progeny, what 

 she wants is food for herself. The Pompilus again is very careful 

 not to thrust her head in the den of rapine and murder ; she knows 

 very well that the enemy must be got outside her shelter. I have 

 pever been able to witness closely the modus operandi, but I believe 

 it allows the spider to seize hold of its leg, and then by a jerk draws 

 it out. The spider may turn and face its foe now; it is too late, the 

 Sphex is already on its back, with a firm hold of the cephalathorax y 



