HUNTERS OF LARGE ORTHOPTERA 191 



From the above observations we see that Stizus unicinc- 

 tits has two ways of locating her host: by inspecting all 

 breaks in the surface of the earth where Priononyx nests 

 are likely to occur, in order to locate the nest when 

 closed, and by shadowing the Priononyx while she is stor- 

 ing her prey and closing the hole. This evidence shows 

 that Fabre's 10 idea in regard to Ammophila, that the insect 

 is endowed with certain marvellous and mysterious powers, 

 an unknown sense, which draws her to her subterranean 

 prey, cannot apply to Stizus, although we are sure that, 

 from a literary standpoint, Fabre's chapter on An Unknown 

 Sense will live. True, her powers are wonderful, but it 

 seems to us after witnessing the above, that she finds her 

 host, not by magic, but by energy and persistence. Here 

 again, "genius is only the capacity for taking infinite pains." 

 We ourselves usually find Priononyx holes by examining the 

 piles of dust or earth-clips which look to us suspicious; so 

 does she. 



True, she may possess a delicate sense of smell or other 

 faculty, which may help her to detect the presence of the 

 Priononyx nest when near it, for she must be highly skilled 

 if she can inspect a mound of dust and determine, in five 

 seconds or less, whether or not a securely-covered Priononyx 

 hole lies beneath it. But in the case described above of the 

 Stizus opening up the parasitized nest, it seems incredible that 

 the scent alone could have attracted her to open up this spot. 

 It was natural that the Diptera should be attracted to the 

 hole after the earth that had lain next the decaying hopper 

 had been thrown out on top of the ground, all nicely satu- 

 rated with hopper scent. Since the flies appeared so 

 promptly when the tainted earth was thrown out, it is evi- 

 dent that they must have been plentiful in the field at that 



10 Chapter on An Unknown Sense, in The Hunting Wasps, 371- 

 384- ' 



