BURGLARS 281 



It is one of the Ruby-tail Wasps, ancTprobably the 

 species distinguished as Chrysis ignita. Although 

 it appears to have nothing to occupy its mind, and 

 is apparently spending its winged existence in an 

 easy-going manner, it is probably on the watch. 

 Possibly you have not noticed that on the wall, not 

 far from the position the Ruby-tail Wasp has taken 

 up, a Mason Wasp (Odynerus parutum) has half 

 finished the construction of her nest. 



As we have shown in an earlier chapter (see 

 page 77), the Mason Wasp provisions her cells with 

 little caterpillars, and when the cell is nearly full 

 the Ruby-tail watches the Mason go off for, per- 

 haps, the last caterpillar. Into the cell she then 

 drops one of her own eggs, and the Mason return- 

 ing, seals up the cell. What happens ? Dr. 

 Chapman watched this performance, and two days 

 after the cell had been closed he opened it. The 

 Chrysis egg had hatched and the grub that had 

 issued from it was already a quarter of an inch 

 long ; but there was no sign of the Mason Wasp's 

 egg or grub. The presumption is that the Chrysis 

 grub had eaten it. Thereafter the latter feasted 

 on the caterpillars that had been stored for the 

 sustenance of the Mason's offspring. In six days 

 all were eaten, and the Chrysis grub, after moulting 

 three or four times, had reached its full size ;■ so it 

 spun a cocoon and became a chrysalis. 



According to other observers it is usual for the 

 Ruby Wasp grub to wait until the Mason's grub 

 has grown, and to feed upon that without touching 



