26 ANIMAL ECOLOGY 



cottonwoods colonise this ground, and another species of tiger 

 beetle (C lepida) then replaces the first one. In the old cotton- 

 woods, where conditions are different with grass and young 

 pine seedlings, C. formosa took the place of C lepida. Then 

 with the formation of a dominant pine community on the 

 ridges still another species, C. scutellaris^ replaces the previous 

 one and continues to live on into the next stage in succession, 

 a black oak community ; but it gradually becomes scarcer 

 with the change to white oak, until a stage is reached with no 

 tiger beetles at all. With the following red oak stage there 

 arrives C sexguttata^ which persists afterwards in clearings, 

 but when the climax association of beech and maple has been 

 reached tiger beetles again disappear altogether. Here there 

 can be distinguished at least eight stages in the development of 

 plant associations, and five different species of tiger beetle, 

 none of which come in more than two plant zones. 



12. It is important to note that we have to deal in this case 

 with a genus of animals which tends to form species which 

 are exclusive or confined to one or two plant associations. 

 In England there seems to be the same tendency among the 

 species of Cicindela. But this kind of strict Hmitation to 

 plant associations is probably rather unusual, especially among 

 carnivorous animals. Exception must be made in the case of 

 some of the great host of herbivorous animals (in particular 

 insects) which are attached to one species of plant only. But 

 even in these cases the plant itself, and therefore the animal, 

 is not usually confined to one plant association. In practice, 

 succession in animal communities is an infinitely more com- 

 plicated affair. One reason for this is the great lag of animals 

 behind plants, due to their different powers of dispersal. 

 Another reason is that the survival of only a few of the earlier 

 plants in the later stages will enable a great number of animals 

 to hang on also, and these of course cannot be separated in 

 their inter-relations with the newcomers. For instance, on 

 areas in the south of England where pine woods have grown 

 up over and largely replaced heather (Calluna), there are still 

 many patches of heather growing in the more open places, 

 and these have been found to contain the typical heather 



