THE INSECT AS A PARENT 267 



cism is disarmed. The large Scoliid wasps simply paralyse 

 their prey where they find it, and lay an egg on its body 

 — thus providing their grub with a store of fresh meat. 

 The true digger-wasps of the families Sphegidcc and 

 PompiUdas go further, laying up the food in a speeially 

 constructed nursery, which may take the form of a sub- 

 terranean chamber, a tunnel driven in the stem of a plant, 

 or an earthenware cell built up from clay mingled with 

 the insect's adhesive saliva. One of the best-known 

 Sphegid wasps is Annnophila sabulosa, whose behaviour 

 has been carefully watched by Fabre and other observers. 

 The female first sinks a vertical shaft into the ground 

 and excavates a single cell about two inches below the 

 surface. When the burrow is complete the wasp carefully 

 closes the entrance with a small stone. She then hurries 

 off, but returns sooner or later dragging a caterpillar 

 which she has paralysed with her sting — thereby rendering 

 her task more easy and preventing the victim's escape. 

 When the caterpillar has been stored an egg is laid, and 

 the cell is permanently closed. Thus, when the young 

 wasp-grub hatches it finds itself safely housed and amply 

 provided with food. 



Like so many other insects, these digger-wasps are 

 extremely conservative in their choice of food. Some take 

 caterpillars of a special kind, some two-winged flies, some 

 hard beetles. Certain of the smaller species prey exclu- 

 sively upon aphides, while at least one is known to take 

 " cuckoo-spit " nymphs from the midst of their frothy 

 surroundings. 



The Pompilids are spider-killers almost without excep- 

 tion, and some of them display no little temerity in their 

 hunting. A species of CaUcurgus, observed by Fabre, 

 does not enter the spider's den, for if she did so the owner 

 would destroy her with its poisonous fangs. She therefore 



