VI THE YELLOW-WINGED SPHEX 87 



alone and returning to resume the prey left on the 

 threshold, does not the Sphex drag it into the 

 gallery, as she did in the open air, since the space 

 is wide enough, or take it with her while she enters 

 backwards ? The various predatory Hymenoptera 

 which I have been able to observe all drag their 

 prey at once to the bottom of their cells, holding 

 it underneath them by their mandibles and inter- 

 mediary feet. L^on Dufour's Cerceris does indeed 

 somewhat complicate her movements, since after 

 putting down her Buprestis for a moment at the 

 door of her underground abode, she instantly goes 

 backward into the gallery, seizes her victim with her 

 mandibles and drags it down ; but that is very unlike 

 the tactics adopted in a like case by the Sphex. 

 Why this domiciliary visit, which invariably precedes 

 the introduction of the prey? May it not be that 

 before descending hampered by a load, the Sphex 

 thinks it prudent to give a look round the bottom 

 of her dwelling to make sure that all is in order and 

 to drive out, if necessary, some impertinent parasite 

 which may have slipped in during her absence ? 

 Several Diptera, predatory flies, especially Tachinidae, 

 watch at the doors of all the hunting Hymenoptera, 

 spying out the favourable moment to lay their eggs 

 on other people's game, but none penetrate into the 

 dwelling, nor venture into the dark passages, where, 

 if by ill-luck the owner caught them, they might 

 have to pay dearly for their audacity. The Sphex, 

 like others, pays her tribute to the predatory 

 Tachinidae, but they never enter her burrow to 

 commit their misdeeds. Besides, have they not all 

 the time they need to lay their eggs on the cricket ? 



