3o8 THE WONDERS OF INSTINCT 



chrysalid's needs. Among these spinners we see some 

 weaklings working listlessly at their carpet. Their ap- 

 pearance makes us deem them in the grip of a mortal 

 disease. I take a few of them and open their bellies, 

 using a needle by way of a scalpel. What comes out is 

 a bunch of green entrails, soaked in a bright yellow fluid, 

 which is really the creature's blood. These tangled 

 intestines swarm with little lazy grubs, varying greatly 

 in number, from ten or twenty at least to sometimes half 

 a hundred. They are the offspring of the Microgaster. 



What do they feed on? The lens makes conscientious 

 enquiries ; nowhere does it manage to show me the vermin 

 attacking solid nourishment, fatty tissues, muscles or 

 other parts ; nowhere do I see them bite, gnaw, or dissect. 

 The following experiment will tell us more fully : I pour 

 into a watch-glass the crowds extracted from the hos- 

 pitable paunches. I flood them with caterpillar's blood 

 obtained by simple pricks ; I place the preparation under 

 a glass bell-jar, in a moist atmosphere, to prevent evap- 

 oration; I repeat the nourishing bath by means of fresh 

 bleedings and give them the stimulant which they would 

 have gained from the living caterpillar. Thanks to these 

 precautions, my charges have all the appearance of excel- 

 lent health; they drink and thrive. But this state of 

 things cannot last long. Soon ripe for the transforma- 

 tion, my grubs leave the dining-room of the watch-glass 

 as they would have left the caterpillar's belly; they come 

 to the ground to try and weave their tiny cocoons. They 

 fail in the attempt and perish. They have missed a suit- 

 able support, that is to say, the silky carpet provided by 



