534 



THE COMMUNITY 



and the peak of population density were 

 reached in the same forests during May, 

 regardless of age of the particular fungus 

 involved. 



For many plant constituents phenologi- 

 cal correlation is the result of a direct 

 influence by physical factors, since their 

 photosynthesis (Chap. 27) is partially 

 dependent upon intensity of light. Animals 

 show direct behavioral response to such 

 influences as light, temperature, and pre- 

 cipitation, as well as indirect responses. 

 These latter are less easily studied. Many 

 indirect correlations occur with food plants, 

 and many contacts are made between com- 

 munity response and the rhythmic phe- 

 nomena of photoperiodicity (p. 121), in 

 which adjustments of plants and animals 

 are made to the relative lengths of day and 

 night (Garner and Allard, 1920; Kellerman, 

 1926; Rowan, 1926; Schick, 1932). Any 

 annual response by plants to physical fac- 

 tors is indirectly related to herbivores, and 

 still more indirectly related to parasites and 

 predators. 



This relationship was put nicely by Chap- 

 man (1920, p. 179): "Herbivorous beetles 

 . . . dependent upon growing plant tissue 

 for their food may be said to have the 

 factors of food and climatic conditions more 

 or less merged into one. Conditions which 

 favor the growth of plants favor the food 

 supply, and thus the growth and develop- 

 ment of the beetles." AppUed to the concept 

 under examination, this suggests that there 

 is a definite, although indirect, correlation 

 between light and the herbivores of a given 

 community, or series of communities at a 

 given latitude and altitude. Such indirect 

 relationships have been demonstrated be- 

 tween the flowering of plants and their 

 insect visitors (Robertson, 1889, 1928, 

 1929). Numerous indirect correlations are 

 found in such diverse phenomena as the 

 seasonal appearance of species of beetles in 

 the vicinities of Prague (Fritsch, 1851, 

 1851a), and Chicago (Park, 1930), in the 

 production of zooplankton off the coast of 

 Massachusetts (Clarke and Zinn, 1937), in 

 the seasonal fluctuations of algae, rotifers, 

 and cladocerans in Colorado lakes (Pennak, 

 1946), of rotifer productivity (Edmondson, 

 1946), of cyclomorphosis in Daphnia 

 (Brooks, 1946), in the seasonal distribution 

 of mosquitoes in Colombian rain forest 



(Bates, 1945), and in the accumulated 

 drift along the shores of large lakes. 



Under normal conditions, beach drift that 

 accumulates upon the sandy depositing 

 areas of Lake Michigan is concentrated in 

 particular reaches from central Wisconsin, 

 northeastern Illinois, northwestern Indiana, 

 to southern Michigan. This drift has a 

 seasonal periodicity that can be used as a 

 biological calendar. Parts of the faunas of 

 the inland communities are blown into 

 the lake, and eventually are deposited 

 upon the lower beaches in a dead or 

 debilitated condition. These animals are 

 chiefly insects, and since their appearance 

 in their native communities is seasonal, their 

 subsequent appearance on the beach, often 

 a few days after they have been observed in 

 their normal habitat niches, can be ana- 

 lyzed in quantitative terms. 



The biocoenose of the beach drift in gen- 

 eral is a complex and ever-shifting sea- 

 sonal phenomenon. It has been studied 

 often in the past (Wheeler, 1887; Need- 

 ham, 1900, 1904, 1917; Snow, 1902; 

 Herms, 1907; Shelford, 1913, pp. 218-221; 

 Park, 1930). Its matrix includes the car- 

 rion, just referred to, as well as dead fishes 

 and water birds washed ashore from the 

 lake community. 



Feeding upon this seasonal carrion are 

 numerous scavengers. These are chiefly bac- 

 teria, flies (Sarcophagidae), and beetles 

 (Silphidae, Trogidae, Scarabaeidae, Niti- 

 duUdae). These both feed and oviposit on 

 the drift. 



In turn the scavengers are preyed upon 

 by still other beetles (Histeridae, Silphidae, 

 Staphylinidae) that feed upon eggs, larvae, 

 pupae, or imagines of the eaters of dead 

 flesh. 



Most insects present, including these 

 predators, may be eaten by still other 

 predators, such as beetles (Carabidae, 

 Staphylinidae, Cicindehdae), spiders (Ly- 

 cosidae), and the toad (Bufo woodhousii 

 fowler i) . 



This food chain shows a marked seasonal 

 periodicity, as illustrated in Figures 181 and 

 182. The first of these shows the correlation 

 of the seasonal succession of beetles in 

 deciduous forest communities bordering on 

 Lake Michigan with the seasonal march in 

 air temperature, relative humidity, and 

 radiant energy in gram-calories. The second 

 figure shows the correlation of the seasonal 



