82 FLASHLIGHTS ON NATURE 



and in another, close by, they will be very un- 

 common or quite unknown. It is probable that 

 this relative frequency or scarcity depends upon 

 the distribution of their proper food-insects. In- 

 deed, just as we all know that an " army fights 

 upon its stomach," so we are beginning to know 

 now that commissariat lies at the bottom of most 

 problems of animal life. I used to wonder on the 

 Riviera why trap-door spiders, with their long 

 tubular nests, were abundant in certain deep red 

 clay-banks, but wholly wanting in others, just as 

 sunny, just as soft, just as easy to tunnel ; till one 

 day it struck me that the spiderless banks were ex- 

 posed now and then to the cold wind, the mistral, 

 and hence were naturally almost flyless. As a 

 matter of course, the spiders went where the flies 

 were to be found ; and these open banks, though 

 sunny and warm, were from the spider's point of 

 view mere Klondykes or Saharas. 



It is just the same with the butcher-birds. 

 Beetles and bees frequent for the most part 

 warm, crumbling soils ; they are infrequent on 

 damp clays and chilly, marshy places. Sandstone 

 and chalk attract them ; on London clay or the 

 damp flats of the Weald they are few and far be- 

 tween. Hence, where the beetles are, there will 

 the shrikes be gathered together. They abound 

 (comparatively) in warm sandstone hills, but are 

 almost unknown in chilly clay districts. Not that 

 they mind the cold as such ; it is the question of 

 food that really affects them. So, too, with the 

 swallows and other long-winged insect-hawkers. 



