CLEANING-UP TIME 283 



tit, no doubt the same one, hammering for many 

 minutes at something hard on the top of the May 

 tree. It is probably the very tough case of a 

 saw-fly grub, but we cannot say whether the bird 

 has yet won his way in or whether he will eventually 

 do so. Such perseverance ought to succeed. So 

 firmly does the saw-fly grub encase itself that the 

 grown fly has to have jaws of steel and extra- 

 ordinarily sharp, for the single purpose of opening 

 the cerement. For the rest of its life the jaws have 

 no use whatever. 



A far richer cache for the tits has been awaiting 

 them ever since the caterpillars crawled from the 

 cabbages, and slung their chrysalids under the 

 coping of the garden wall. For weeks and months 

 they hung there undiscovered, but at length a 

 party of great tits discovered them and cleared 

 them off in a single morning. If you think that 

 all the chrysalids are gone, wait till next April 

 and see if there are not just as many white butter- 

 flies as ever. We could point out to some soft- 

 billed bird another secret that ought to furnish 

 them with toothsome titbits. Under white silk 

 caps, about as big as a capital O, there are tiny 

 fat grubs that under the microscope turn out to 

 be immature bugs, as those insects that suck 

 plant juices with piercing trunks are technically 

 called. I think they are the mothers of next 

 year's aphides, though they are larger and fatter 

 than their daughters will be. There are twenty of 

 these white bed-chambers on the trunk of the 



