A Parasite of the Bembex 295 



nearer, some farther, in a geometrical line. If 

 the Bembex turns to thwart their designs, they 

 also turn, with a precision that keeps them in 

 the rear on the same straight line ; if she ad- 

 vances, they advance ; if she retreats, they 

 retreat, letting the Wasp set their pace all the 

 time, now flying slowly, now coming to a stand- 

 still, according to the behaviour of their leader, 

 the Bembex. They make no attempt to fling 

 themselves on the object of their cupidity ; 

 their tactics are confined to keeping ready, in 

 this rearguard position, which will save them 

 any hesitation at the critical moment. 



Sometimes, wearying of this obstinate pur- 

 suit, the Bembex alights ; the others instantly 

 settle on the sand, still in the rear, and do not 

 budge. The Wasp darts off again, with a shriller 

 whimpering, a sign no doubt of increasing indig- 

 nation ; the Midges dart after her. One last 

 method remains of throwing off the persistent 

 Flies : dashing off at full speed, the Bembex flies 

 far away, hoping perhaps to mislead the para- 

 sites by rapid evolutions across country. But 

 the wary Gnats are not caught in the trap : they 

 let her go and once more take up their positions 

 on the sand around the burrow. When the 

 Bembex returns, the same pursuit will begin all 

 over again, until at last the parasites' obstinacy 

 has worn down the mother's prudence. In that 



