332 The Field Natw'alisfs Quarterly Nov. 



chap. ii. of Wallace's 'Darwinism,' and is as follows: "Two of our 

 common plants, the wild Heart's-ease ( Viola tricolor) and the Red 

 Clover ( Trifolium pratense), are thus fertilised by humble-bees almost 

 exclusively, and if these insects are prevented from visiting the flowers, 

 they produce either no seeds at all or exceedingly few. Now it is 

 known that field-mice destroy the combs and nests of humble-bees, and 

 Colonel Newman, who has paid great attention to these insects, believes 

 that more than two-thirds of all the humble-bees' nests in England are 

 thus destroyed. But the number of mice depends a good deal on the 

 number of cats ; and the same observer says that near villages and 

 towns he has found the nests of humble-bees more numerous than else- 

 where, which he attributes to the number of cats that destroy the mice. 

 Hence it follows that the abundance of red clover and wild heart's-ease 

 in a district will depend on a good supply of cats to kill the mice, which 

 would destroy and keep down the humble-bees, and prevent them from 

 fertilising the flowers. A chain of connection has thus been found 

 between such totally distinct organisms as flesh-eating mammalia and 

 sweet-smelling flowers, the abundance or scarcity of the one closely 

 corresponding to that of the other ! " 



C. R. G., Essex. 



Only one species of Swift, Cypsclus apus, is at all common in these 

 Isles, one of the last summer visitors to arrive and earliest to depart. 

 May and August being the periods of its migrations. The Needle- 

 tailed Swift is a straggler from Siberia, and has been once recorded in 

 Essex (' British Vertebrates,' Aflalo, p. 191). 



Salopian. 



You will find an account of the mammals of Shropshire in Forrest's 

 ' Fauna of Shropshire,' which may be obtained from L. Wilding, Castle 

 Street, Shrewsbury. 



T. N,, Wilts. 



Mr C. M. Rogers in 'Nature' (November 14, 1901) recorded the 

 finding of mice inside the ring snake on two occasions ; and also the 

 finding of birds which this species had swallowed on three occasions. 

 Some high authorities have restricted the diet of the ring snake {T. 

 natrix) to fish and amphibians, but we were never able to understand 

 the partiality of the snake for climbing bushes unless it had an eye to 

 some young birds. 



Bumpkin. 



See answer to " Ophis." Your letter savours too much of the style 

 of the champions of the side opposed to your view for us to insert it. 

 Are you really a bumpkin ? We agree with your argument but dislike 

 your mode of expressing it. 



