98 HYMENOPTERA CHAP. 



attacks the larvae of several species of Cetonia, and S. (Colpa) 

 interrupta chooses the larvae of the chafers Anoxia villosa and 

 A. matutinalis. The mother Scolia enters the ground in August 

 or September, and having found a suitable larva stings it and 

 deposits an egg on the ventral surface of the prey ; the paralysed 

 larva is left where it was found, no attempt being made to place 

 it in a special receptacle. The egg is placed on the ventral 

 surface, well behind the feet, under a mass of matter in the 

 alimentary canal. Shortly after being hatched the young- 

 destroyer penetrates with its head the skin of the victim, and in 

 this position commences to feed ; it is necessary that it should 

 obtain its food without killing the Cetonia larva, for it cannot 

 prosper on decaying food, so that if the Cetonia larva die the 

 Scolia larva likewise perishes ; the latter, accordingly, does 

 not withdraw its head from the interior of the victim, but 

 remains always in the same position, as it grows larger extending 

 its head forwards into the front part of the interior of its victim ; 

 the internal organs of the latter are consumed in a systematic 

 order so as to delay bringing about its death till the last moment, 

 and thus all the interior of the Cetonia larva is appropriated till 

 nothing remains but an empty skin. By a series of experiments, 

 Fabre showed how essential it is that this apparently revolting 

 operation should be carried on with all details strictly en regie. 

 If the head of the Scolia larva be taken out from the victim and 

 applied to another part of the body of the Cetonia, the result is 

 that it cannot eat ; even if it be replaced in the original situa- 

 tion, after being taken away, it frequently happens that the 

 Cetonia larva dies, its death involving also that of the destroyer. 

 It is necessary, too, that the victim should be paralysed, for if an 

 intact Cetonia larva be taken and bound down in such a' position 

 that it cannot move, and if a small orifice in its skin be made in 

 the proper spot and a young Srolia larva be placed on it, the 

 little parasite will avail itself of the opportunity and commence 

 to feed on the larva provided for it, but the latter will speedily 

 die, and the Scolia necessarily perishes with it. Thus both the 

 paralysis of the victim and the special mode of eating are essential 

 to the life of the Scolia. The operation of stinging the larva, so 

 as to produce the necessary paralysis, or rather insensibility, is a 

 difficult one, and requires great skill and patience. The Cetonia 

 larva is of large size, and must be pierced in one particular spot ; 



