XXIII INSTINCT 541 



by patient work ; sometimes a quarter of an hom^ is sufficient for 

 the purpose, but in other cases three hours of uninterrupted 

 effort are required before the end is attained. Fabre expended 

 much time in watching this operation, and after the Insect had 

 completed it, he marked with a pencil the exact spot of the 

 masonry that was penetrated, and the date on which it was done, 

 and he states that he afterwards found that without any excep- 

 tion a proper spot had been selected, and a cell consequently 

 penetrated. Admirable as the instinct of the parasite appears 

 from this .point of view, it is nevertheless accompanied by a 

 remarkable deficiency in two other respects. The first is that 

 though the spot selected by the Leucospis invariably gives 

 entrance to a cell, yet in the majority of the cases the selected 

 cell is not a suitable one ; a large number of the cells of the 

 Chalicodoma are not occupied by living larvae on the point of 

 pupation though in that case only can the ^.gg of the Leucospis 

 hatch and successfully develop- but by dead and shrivelled 

 larvae, or by mouldy or dried-up food. And yet, in each case of 

 penetration, Fabre believes that an egg is deposited, even though 

 it may be impossible that it can undergo a successful develop- 

 ment. Strange as this may appear, it is nevertheless rendered 

 less improbable by the second deficiency in the instinct of the 

 parasite. The Insect has no power of recognising a cell that 

 has been previously pierced either by itself or by another of its 

 species. One bee larva can only supply nourishment for a single 

 Lirva of the parasite, and yet it is a common occurrence for a 

 cell to be revisited, pierced again and another Qgg introduced ; 

 indeed Fabre, by means of the cells he had marked, was able to 

 assure himself that it is no uncommon thing for this to be done 

 fom- times; four eggs, in fact, are sometimes deposited in a cell 

 that cannot by any possibility supply food for more than one 

 larva. The egg of the Leucospis is a curious object (Fig. 357, 

 A), very elongate oval, with one end drawn out and bent so as 

 to form a hook ; " it is not placed at random in the cell of the bee, 

 but is suspended on the delicate cocoon with which the Chalico- 

 doma larva is surrounded at the period of pupation. Faljre 

 allowed sufficient time to elapse for the hatching of the larvae 

 from the eggs, and then opened some cells where Leucospis eggs 

 had been deposited, in order to obtain the larvae ; when doing 

 this he was surprised that he never found more than one Leu- 



