406 ENTOMOLOGY 



growth. They also must find a location and deposit their eggs while 

 the wood is still soft and tender; otherwise they will be unable to 

 penetrate to a sufficient depth to protect the eggs from predaceous and 

 parasitic insects. The result is that we find that they, with a possible 

 exception, pass the winter in the egg stage, and have a single annual 

 generation. . . . A striking adaptation to a special period in a plant's 

 growth is shown in the life cycle of Micrutalis calva, the little shining 

 black seed-like tree hopper. The nymphs are found between the 

 branches of the blossom head of the Ironweed, Vernonia. This purple 

 flower appears only in the fall, so that the single generation of nymphs 

 comes on over 70 days later than its relative that lives in the tree. 



"In the case of Ceresa bubalis (the Buffalo tree hopper) and its 

 vegetation-feeding allies the need of haste is not so great as their food 

 plants, Composites, Legumes and others, grow all summer, so we find 

 the nymphal period both longer and later and the adults extending into 

 the fall." (E. D. Ball.) 



The time of appearance of the locust borer, Cyllene robinice, in the 

 fall coincides with that of the flowers of golden rod, on which the beetles 

 feed; the coloration of the beetles being protective, as Prof. H. Garman 

 has observed in Kentucky. 



Ecological. " Ecological succession of animals is succession of 

 mores over a given locality as conditions change. If species have rela- 

 tively fixed mores we have succession of species. When mores are 

 flexible we may have the same species remaining throughout, with 

 changes in mores. " (Shelford.) 



A few examples, from Shelf ord's Vegetation and the Control of Land 

 Animal Communities, will serve to illustrate this kind of succession. 



The stages of forest development are marked by the dominance of 

 certain species of trees which succeed one another in a rather definite 

 order. On the sand areas at the head of Lake Michigan, the sequence 

 is as follows (Cowles). i. Cottonwood Stage. Near the lake shore, 

 with the sand more or less shifting and rarely with more than a trace of 

 humus. 2. Pine Stage. With stable sand, considerably blackened by 

 humus, except in blowouts. 3. Black Oak Stage. With the sand much 

 darkened by humus and locally covered with a dry moss or with dead 

 leaves; grasses and a shrubby undergrowth occur. 4. Red Oak Stage. 

 Ground with a carpet of leaves and humus ; with a well marked shrubby 

 and herbaceous growth. Red oak, black oak, and white oak; often 

 hickory also. 5. Beech Stage. The mineral soil is covered with a 

 thick layer of leaves and humus. Fewer species of trees than in the 



