NATURAL HISTORY OF SOUTH AFRICA 



and the mother wasp or hornet captures small cater- 

 pillars, various other larvae, and spiders. These she 

 paralyses with an injection of venom sufficient to 

 render them comatose for a prolonged period, but 

 insufficient to kill them outright. The cell is filled 

 up with the victims and then sealed. The grub 

 which hatches from the egg feeds on the food provided 

 until it is adult. It then goes through the usual 

 change, and emerges a winged wasp or hornet. The 

 parent knows instinctively the exact quantity of 

 food to provide for her larva to last it until it is fully 

 grown. 



Hornets and wasps are generally claimed by ento- 

 mologists to be beneficial to man. This is only partly 

 so. A careful examination of the nests of the mason 

 wasp extending over a period of years has convinced 

 me the bulk of their victims are spiders. Spiders feed 

 on various insect pests, and render great service to man. 

 They capture large numbers of adult winged insects. 

 Each female of these victims of the spider would have 

 laid hundreds of eggs. Therefore one female adult 

 insect killed by a spider equals in economic importance 

 a hundred and sometimes a thousand larvas. 



The solitary wasps, however, which make burrows 

 in the ground, prey largely on caterpillars and other 

 destructive larvas. The wood wasps and saw-flies 

 puncture plants with their ovipositors or saws, and 

 deposit their eggs in the holes thus made. The 

 grubs burrow into the tissues of the wood, and 

 feed on it. 



Some grubs, notably those of the saw-fly, feed 

 264 



