I20 OUR BIRD ALLIES. 
the turnip-moth (Agrots segetum), which, as every 
entomologist knows, work their way into the root 
during August or September, and there remain until 
fully fed, eating away a large chamber in the lower 
part. Now these turnips, when once attacked by the 
caterpillar, are doomed, and even if the rook were to 
cut them to fragments he could damage them no 
more, while in killing the larve he would prevent 
their conversion into moths, whose eggs in the fol- 
lowing season would produce a large brood of fresh 
caterpillars. ‘‘ Whenever I see a flock of rooks at 
work in a turnip-fieid,” writes Waterton, “which, in 
dry weather, is often the case, I know that they have 
not assembled there to eat either the turnips or the 
tops, but that they are employed in picking out a grub 
which has already made a lodgment in the turnip.” 
To destroy a rook while thus employed, indeed, 
would be about as rational as to shoot a policeman 
for following a noted burglar into a house which he 
had forcibly entered. 
Most of us, no doubt, have seen the rook following 
the plough, and picking up the grubs and worms as 
they are turned out of the ground. Sometimes quite 
a flock of the birds may be seen thus engaged, and 
there can be no question that the number of mis- 
chievous creatures which they at such times destroy 
must be very considerable. Save and except at seed- 
time and harvest, indeed, a rook in a field is a rook 
in his right place, and the farmer who most en- 
courages him will be the most likely to grow a suc- 
cessful crop. 
