282 INSECT ARTIZANS AND THEIR WORK 



the store of caterpillars. But there are various 

 species of Ruby Wasp, and they are known to differ 

 somewhat in their habits. Chrysis bidentata, for 

 example, looks out for a nest of the turret-building 

 Mason Wasp (Odynerus sfinifes), and if it can find 

 a chink in the masonry that closes the mouth of 

 the tunnel it gets its eggs inside. It was mainly 

 with the idea of keeping off this foe that the Mason 

 Wasp built the tower we have previously described 

 (page 71), from which she obtained the materials 

 to close the mouth of her nest. 



The remarkable point is that the Ruby Wasp is 

 said by some strange sense to ascertain at what 

 stage the Mason's grub has arrived. She desires a 

 grub that has reached full size and has spun its 

 cocoon. Having satisfied herself that she has got 

 an unseen victim in that condition, she deposits 

 several eggs, though only one hatches. Here again 

 there is a mystery. Why should six or ten eggs 

 be laid and only one hatch ? Yet it is said to be 

 so, and that the Chrysis grub attaches itself to the 

 skin of the Mason grub and sucks at it for about 

 eleven days. By that time it is an empty skin, 

 and the Chrysis grub having reached its full size 

 spins its own cocoon inside that of its victim and 

 remains there till the following spring. Then it 

 becomes a chrysalis, and about three weeks later 

 it comes forth as a brilliant Ruby W T asp to victimize 

 some other Mason — that is, if it be a female. 



Bembex ro strata is a solitary wasp that., instead 

 of filling up its cells with suff.cient food to last the 



