PROVISION FOR REARING THE YOUNG. 1 33 



penetrate at the soft points; the two points attacked 

 are then rigorously determined by physical circum- 

 stances. But these arguments have no bearing if we 

 consider the method of procedure adopted by the 

 Ammophila} a hymenopterous insect related to the 

 preceding, which paralyses caterpillars. It is free in this 

 case to insert its sting at any portion of the body; yet 

 it knows how to turn over and arrange the captive so 

 that the dart shall penetrate both times at two points 

 where ganglia will be poisoned and immobility with- 

 out death be induced. It must then be agreed that 

 there is here an instinct much too sure to be called 

 mechanical; but these facts, which considered alone 

 seem simply marvellous, become much less so, and 

 lend themselves to evolutionary interpretation, when 

 it is recognised that they are related by insensible 

 degrees to other facts of the same order, much more 

 intelligent and at the same time less sure. 



Similar cases in which the specific instinct is less 

 powerful and individual initiative greater. — Here is, 

 for instance, the case of the Chlorion, where each 

 animal possesses more considerable initiative.^ It 

 attacks the Cockroach. These insects are of an 

 extremely varied size, according to age, and as they 

 are also very agile the Chlorion is not certain of 

 being always able to obtain victims of the same 

 dimension. The orifice of its burrow, which it 

 hollows in walls between the crevices of the stones, 

 is calculated on the average size of its victims. It 

 has also the habit of paralysing the cockroach by 



' Paul Marchal, " Observations sur V Ammophila affinis,'' Arch, de 

 Zool. exp. et genlr., ii. Serie, t. x., 1892. 



''■ Reaumur, Memoires pour servir i thistoire des Insectes, Paris, 

 1742, t. vi., pp. 2S2 284. 



