TACHINIDAE 509 



Hymenoptera by a curious sort of indirect parasitism. They are 

 obscure little flies, somewhat resembling the common House-fly, 

 but they are adepts on the wing and have the art of ovipositing 

 with extreme rapidity ; they follow a Hymenopteron as it is carry- 

 ing the prey to the nest for its young. When the wasp alights 

 on the ground at the entrance to the nest, the MUtogramma 

 swoops dowai and rapidly deposits one or more eggs on the prey 

 the wasp designs as food for its own young. Afterwards the larvae 

 of the fly eat up the food, and in consequence of the greater 

 rapidity of their growth, the young of the Hymenopteron perishes. 

 Some of them are said to deposit living larvae, not eggs. Fabre 

 has drawn a very interesting picture of the relations that exist 

 between a species of MUtogramma and a Fossorial Wasp of the 

 genus Bembex} We may remind the reader that this Hymenop- 

 teron has not the art of stinging its victims so as to keep them 

 alive, and that it accordingly feeds its young by returning to 

 the nest at proper intervals with a fresh supply of food, instead 

 of provisioning the nest once and for all and then closing it. 

 This Hymenopteron has a hal)it of catching the largest and 

 most active flies — especially Tabanidae — for the benefit of its 

 young, and it would therefore be supposed that it would lie safe 

 from the parasitism of a small and feeble fly. On the contrary, 

 the MUtogramma adapts its tactics to the special case, and is in 

 fact aided in doing so by the wasp itself. As if knowing that the 

 wasp will return to the carefully-closed nest, the MUtogramma 

 waits near it, and quietly selects the favourable moment, when 

 the wasp is turning round to enter the nest backwards, and 

 deposits eggs on the prey. It appears from Fabre's account that 

 the Bembex is well aware of the presence of the fly, and would 

 seem to entertain a great dread of it, as if conscious that it is a 

 formidable enemy ; nevertheless the wasp never attacks the 

 little fly, l:)ut allows it sooner or later to accomplish its purpose, 

 and will, it appears, even continue to feed the fly-larvae, though 

 they are the certain destroyers of its own young, thus repeat- 

 ing the relations between cuckoo and sparrow. Most of us 

 think the wasp stupid, and find its relations to the fly incredible 

 or contemptible. Fabre takes a contrary view, and looks on it 

 as a superior Uncle Toby. We sympathise with the charming 

 French naturalist, without forming an opinion. 



' Souvenirs entomologiques, 1879, pp. 246-254. 



