VI INSTINCT OF MASON-WASPS 279 



that of the mason -wasp (Odynerus parietum), and allied 

 predatory wasps. The mason -wasp makes a hole about 

 10 cm. deep in a bank of clay, moistens and softens the clay 

 she has removed with saliva, and probably also with water, 

 and builds w^ith it a tube leading from the mouth of the hole 

 and prolonging it. The tube at first stands out at right 

 angles to the bank, then bends downwards. Probably this 

 arrangement is chosen in order that the water may run off 

 more easily, just as the cells of the paper- wasp (Polistes 

 gallica), which are made of chewed wood, are turned down- 

 wards, so that the rain may be kept out as much as possible, 

 while the bees, contrariwise, build their cells upright, so that 

 the honey may remain in them. But the wasp casts out 

 some granules of clay from the mouth of the tube. Taschen- 

 berg ^ supposes that this is the material with which she after- 

 w^ards closes the tube. When the nest is ready, the wasp 

 brings into it larvae of beetles and other insects, which she 

 has paralysed by stinging them in the ganglia which govern 

 muscular action. This is one of the most marvellous in- 

 stincts that exist : since the wasp operates on various larvse 

 with nervous systems of various forms, she must effect the 

 paralysis in various ways, and even apart from this, she 

 makes a physiological experiment which is far in advance of 

 the knowledge of man. The wasp thus carries one motionless 

 but livino' larva after another into her tube until it is full, 

 and she rolls up the larvse and packs them so skilfully that 

 they take up as little room as possible. Finally, she lays her 

 egg in the store of living food, and closes the opening with clay. 

 Then she begins a new tube, and so lays one ^gg after another. 

 What a wonderful contrivance ! What calculation on the 

 part of the animal must have been necessary to discover it I 

 The larvae of the wasp require animal food. Dead food 

 enclosed in the cell w^ould soon putrefy, living active animals 



^ Brehm's Thierleben, second edition, vol. ix. p. 240. 



