The Yellow-winged Sphex 69 



temporary abandonment of the victim to en- 

 trust their progeny to it. Some greater danger 

 still must therefore threaten the Sphex, since 

 her preliminary descent of the burrow is of such 

 imperious necessity. 



Here is the only fact observed by myself 

 that may throw a little light on the problem. 

 Amid a colony of Sphex-wasps in full swing, 

 a colony from which any other Wasp is usually 

 excluded, I one day surprised a huntress of a 

 different genus, Tachytes nigra, carrying one 

 by one, without hurrying, in the midst of the 

 crowd where she was but an intruder, grains of 

 sand, bits of little dry stalks and other diminu- 

 tive materials to stop up a burrow of the same 

 shape and width as the adjacent burrows of the 

 Sphex. The labour was too carefully per- 

 formed to allow of any doubt of the presence 

 of the worker's e^^ in the tunnel. A Sphex 

 moving about uneasily, apparently the lawful 1 

 owner of the burrow, did not fail, each time that 1 

 the strange Wasp entered the gallery, to rush I 

 in pursuit of her ; but she emerged swiftly, as \ 

 though frightened, followed by the other, who 

 impassively continued her work. I inspected 

 this burrow, evidently an object in dispute 1 

 between the two Wasps, and found in it a cell \ 

 provisioned with four Crickets. Suspicion al- \ 

 most makes way for certainty : these pro- / 



