272 



BENEFICIAL INSECTS. 



the hole is a narrow tunnel extending- perhaps one inch into the soil ; into 

 this hole the caterpillar is dragged, and laid at the bottom j the wasp 

 lays one egg upon it and comes out ; it then fills up the hole with small 



lumps of earth, smooths it off carefully 

 and goes away to repeat the process. 

 If the caterpillar is dug up and kept under 

 suitable conditions, it is possible to see what 

 occurs. The egg hatches after a few days 

 and the small white grub fastens on the 

 caterpillar, piercing the skin and pushing 

 in its head. It feeds upon the caterpillar, 

 which lies still and motionless, and as it 

 grows larger it stretches into the body of the 

 caterpillar, slowly devouring it. In time the 

 caterpillar is eaten out, only the skin remain- 

 ing, and the grub has grown into a large 

 cocoon of tough silk, within which 



It mates 



FIG. 328. 



Digger Wasp that stings cater* 

 pillars. 



white insect. It then spins a 



it turns to the pupa and eventually emerges as a wasp. 



and, if a female, does as its parent did, preying upon green caterpillars 



(fig. 328). 



The habits of this insect are similar to those of all the stinging 

 predators. The singu- 

 lar fact is that the 

 caterpillar is stung in 

 such a way as not to 

 kill it but to paralyse 

 it. If the caterpillar 

 were dead, it would 

 decay and the grub 



'&: 



PIG. 329. 



Lady-bird Beetle and its grub. (Magnified and 

 natural size.) 



hatching would find 

 no food ; if the cater- 

 pillar were alive and 

 could walk, it would 

 walk away with the 

 egg, which would be killed by exposure to sun and air. By paralysing 

 the caterpillar the mother ensures a supply of living food for her 

 young. Stinging predators are common in the fields ; some make 

 nests, others bury their prey in the ground, some are to be found 

 in our houses (fig. 327). They prey upon all manner of small insects, 

 upon spiders, and upon some of the larger insects. Their habits are 

 extremely diverse and display an ingenuity that has excited tjie admiration 



