BEHAVIOR OF SPIDERS AND OTHER INSECTS 419 



oak stage (the red oak associated with the black oak and white 

 oak in the earlier stages, and with shag-bark hickory, in the 

 later stages) ; (7) the beech and maple stages. In each of these 

 plant communities the animals live in five or more less distinct 

 strata: (1) beneath the ground (subterranean stratum); (2) at 

 the surface of the ground (ground stratum); (3) herbaceous 

 vegetation, low shrubs, etc., (field stratum); (4) shrubs and 

 young trees (shrub stratum); (5) trees (tree stratum). In con- 

 sidering different communities like strata should be compared. 

 Many animals invade several strata; they should be classified 

 primarily in the stratum in which they breed and secondarily 

 in the stratum or strata in which they feed or forage. Shelford 

 gives a rather exhaustive discussion of both communities and 

 strata, and gives tables showing the distribution of animal life 

 in both. The following epitome of his conclusions will be of 

 interest, not only to students of insect behavior, but to all field 

 zoologists. (1) The development of a forest on sand or other 

 mineral soil is accompanied by an almost complete change of 

 animal species and probably by a complete change of animal 

 mores. (2) Forest development is accompanied by marked 

 changes in the soil and in physical factors; animal distribution 

 is more closely correlated with differences in physical factors 

 than with the species of plants. (3) For animals dwelling in 

 the soil, the moisture equivalent or the wilting coefficient for a 

 standard plant is the best index of the moisture available to 

 the animals. (4) The evaporating power of the air is probably 

 the best index of the conditions of the atmosphere. (5) The 

 rate of evaporation, temperature, etc , varies much in different 

 communities and in different strata of the same community. 



(6) Land animals are comparable to small non-rooted plants. 



(7) The succession of all of the animals of a forest community 

 is comparable in principle to that in ponds; it is due to an 

 increment of changes in conditions produced by the plants and 

 the animals living at the given point. (8) The various animal 

 species are arranged in these communities in an orderly fashion 

 and the dominating animal mores are correlated with the domi- 

 nating conditions. (9) Taxonomic species usually have the 

 same mores, although the same species often has different mores 

 under different conditions, and different species may have the 

 same mores, (ro) Species and mores are not synonymous. 



