

INSECT ECOLOGY 



407 



preceding stage, but a greater number of species of small shrubs, with 

 a smaller number of individual shrubs. The trees close the overhead 

 spaces and make a dense shade, while the lower forest is open. Beech 

 and sugar maple are characteristic. These five stages are linked 

 together by transitional stages. 



Of the many species tabulated by Shelf ord, the tiger beetles and 

 grasshoppers may be selected to illustrate succession in relation to forest 

 development. The tiger beetles, Cicindela, breed in the subterranean 

 stratum and feed in the ground stratum. 



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TIGER BEETLES OF FOREST SUCCESSION (SHELFORD) 

 In these tables C signifies common; F, few; P, present 



With the tiger beetles the character of the soil, as regards suitability 

 for oviposition, is the chief factor that determines the presence or 

 absence of this or that species. C. sexguttata, which comes in with the 

 white oak- red oak- hickory forest, lays its eggs under loose leaves or in 

 little irregularities in the ground, which contain a little humus and are 

 slightly shaded; it is rare, however, in very shady situations, such as 

 those of the beech and maple forest. 



Of the orthoptera named in the following table, numbers i to 6 

 breed in the subterranean stratum and feed in the ground stratum; 

 6 feeds also in the vegetation strata; 7 breeds in the ground stratum, 

 feeds in the herbaceous; 8 and 9 breed and feed in the herbaceous; 

 10 and ii breed and feed in the tree stratum; 12 breeds and feeds in 

 the subterranean-ground stratum; and 13 in the ground stratum. 



The table indicates that the successive changes in vegetation are 

 accompanied by corresponding changes in the character of the orthop- 

 teran fauna. Other insects or other animals also illustrate the same 

 phenomenon of ecological succession. During the successive vegeta- 

 tional stages the numbers of a species increase until optimum conditions 

 of habitat are attained, and thereafter decrease. 



