550 



rHE COMMUNITY 



cal influences operating and the relative 

 activity of the diurnal and nocturnal ani- 

 mals through the diel cycle. This was true 

 regardless of whether total vocalization was 

 measured (Figs. 189 and 190) or whether 

 locomotor activity was recorded (Fig. 

 191). 



The diel activity pattern of the whole 

 community is the sum of the diel patterns 

 of the individuals of all species populations 

 of the community. Therefore, whatever af- 

 fects a part aflEects the whole; whatever 

 affects the whole affects each part. In either 



Peckham, 1898) and flower- visiting mor- 

 delUd and cerambycid beetles and preda- 

 ceous coccinelhd beetles (Park, Lockett, 

 and Myers, 1931), whose periods of inac- 

 tivity are prolonged on overcast mornings. 

 Parallel modification of activity occurs in 

 the upper strata of aquatic communities, as 

 in the movements of planktonic crustaceans 

 in lakes (Juday, 1904). 



Influence of weather on activity is espe- 

 cially convincing when the same individ- 

 uals are observed under varying condi- 

 tions. Certain silphid beetles (Leiodes oh- 



Fig. 191. Recorded activity of four Panamanian forest lizards. Three of the species are diur- 

 nal; the fourth species is a nocturnal gecko (Thecadacttjlus rapicaudus) . (After O. Park.) 



case the effect depends upon the strength 

 of the influence operating, upon the part of 

 the community concerned, and upon the 

 time of the response, both seasonal and 

 with respect to the diel cycle. Such changes 

 may be immediate, or the complete reac- 

 tion chain may not be apparent until much 

 later. 



It is not surprising that local weather 

 may intervene to alter temporarily the nor- 

 mal diel periodicity. In general, the modifi- 

 cation of community activity by the partic- 

 ular weather of a diel cycle is differential 

 with respect to both nocturnal and diurnal 

 animals. For example, a strictly nocturnal 

 rodent, the springhaas (Pedetes surdaster) 

 of Africa, may be active on dark days 

 (Roosevelt, 1910), instead of going into 

 diurnal inactivity in subterranean burrows. 

 The reverse is true for such diurnal ani- 

 mals as many solitary wasps (Peckham and 



soleta) were studied in the field on two 

 nights a week apart (Park, Lockett, and 

 Myers, 1931). The first of these nights 

 was relatively cool and moist, and there 

 was a relatively large number of active 

 individuals (Fig. 192). The second 

 night was relatively warm and dry, and 

 there were almost no beetles active (Fig. 

 193). This difference in number of active 

 beetles is in apparent correlation with such 

 physical influences as relative humidity, 

 temperature, and rate of evaporation. 



Diel activities of the community may be 

 considered roughly in two major categories: 

 those concerned with reproduction, as, for 

 example, copulation, oviposition, and pupa- 

 tion; and those concerned with feeding. It 

 is interesting to note that the third primary 

 drive in the life of animals— namely, shel- 

 tering—has to do with protection in the rel- 

 ative security of a habitat niche or stratal 



