tlieir botlics ;ind by increased imisciilar activity, 

 l-'urthermore the compact cluster presents surface 

 area of lieat loss that is less than the total surface 

 area of the individuals separately (Mihini 1928). 

 When there is danger of overheating, the bees in the 

 hive spread out on the combs and fan with their 

 wings to create a circulation of air. They will also 

 carry water into the hive and place small quantities 

 both outside and inside the comb cells. The forced 

 air circulation evaporates the water and cools the 

 iiive. Bees also cool themselves by constantly moving 

 their tongues in and out of their mouths, exposing to 

 evafxiration tiie moisture that is i)resent on them as a 

 thin film (Lindauer 1953). Temperature regulation 

 is less well developed in other social Hymenoptera 

 (Himmer 1932). 



Coveys of bobwhite quail roost in close circles, 

 at night. Perhaps this enables detection of predators 

 approaching from any direction, but it is certain that 

 the birds can by that behavior tolerate lower air tem- 

 peratures and for a longer time than isolated birds 

 can (Gerstell 1939). Similarly, mice huddle in low 

 air temperatures, a behavior that reduces heat radia- 

 tion and consequent need for frequent feeding (Pry- 

 chodko 1958). 



Colloidal silver is toxic to fish. Ten goldfish were 

 simultaneously exposed to a liter of water dosed with 

 colloidal silver. They lived an average of 507 minutes 

 each. Fish individually exposed to a similar concen- 

 tration of silver in the same volume of water lived an 

 average of 182 minutes. The slime from the grouped 

 fish was sufficient to precipitate much of the colloidal 

 silver and render the solution less toxic (Alice and 

 Bowen 1932). Photosensitive animals survive longer 

 when exposed to excessive illumination in groups than 

 singly because of partial shading of one by another, 

 but fresh-water planaria exposed to ultraviolet live 

 longer in groups even when no shading is involved 

 (Allee and Wilder 1939). Marine flatworms Pro- 

 cerodes survive longer in fresh water in groups than 

 singly because the first worms that die from the 

 group release calcium into the water, conditioning it 

 and giving protection to the animals that remain 

 (Oesting and Allee 1935). 



A single muskox or bison may succumb to a 

 pack of wolves. When in a group, the males form a 

 circle facing outward with the females and young in- 

 side, whereby they are usually able to ward of? the 

 attack. By the same token, a single wolf has diffi- 

 culty killing a deer ; a single coyote, killing a prong- 

 horn antelope. But in packs the wolves can over- 

 power a deer, and by individually taking turns in 

 relay fashion, a pack of coyotes can chase a prong- 

 horn to exhaustion. 



Whether an animal occurs singly or in groups 

 may affect its learning rate and behavior. The com- 

 mon cockroach and the shell parakeet learn simple 



mazes less rapidly when other individuals arc around 

 than when alone, but goldfishes, minnows, and green 

 sunfishes learn mazes faster in groups ; phenomena 

 si)oken of respectively as negative and positive social 

 facilitation. Many animals are more active and alert 

 in grou])s than alone ; in groups, individual imitations 

 of others' behavior are common. Cormorants and 

 pelicans fish more proficiently in groups than alone 

 because group behavior is organized and each indi- 

 vidual jilays a certain role (Allee 195!). 



The beneficial effects of aggregation are lost if 

 the aggregation is either too small or too large. P"or 

 instance, the longevity of Drosophila is greatest with 

 a population density of iS to 55 flies per one ounce 

 culture bottle (Pearl, Miner, and Parker 1927). 

 Smaller densities are unable to control the growth 

 of the yeasts on which they feed ; greater densities 

 exhaust the food supply and excessive amounts of ex- 

 creta accumulate. Likewise an initial population of 

 4 Triboliitm beetles per i2 g of flour reproduces more 

 rapidly during the 25 days following than smaller or 

 larger initial populations (Park 1932). For all kinds 

 of animals, competition for food and other resources 

 of the habitat becomes more and more intense as 

 populations increase in size above an optimum. The 

 benefits resulting from an increase in the size of ag- 

 gregations up to the optimum represents coopera- 

 tion ; the harmful effects resulting from aggregations 

 that are too large is disoperation. 



The simplest animal aggregations exhibit little 

 social organization, for the individual organisms are 

 brought together more or less ephemerally by chance, 

 by sexual attraction, for reproduction, or because of 

 a similar response to environmental factors. An evo- 

 lution of organization may, however, be traced 

 through intermediate stages to the complex division 

 of labor found in some insect societies. Specializa- 

 tion occurs both in morphology and behavior. The 

 three primary castes of termites and ants are the 

 winged reproductive males and females, the wingless 

 sterile soldiers that possess large mandibles and irri- 

 tating glandular secretions, and the smaller, wing- 

 less, often sterile workers. The soldiers defend the 

 colony against predaceous enemies ; this function is 

 assumed by workers in bees and wasps, among which 

 a distinct soldier caste is lacking. In termites, the 

 soldiers may be either males or females ; in ants, they 

 are females. The worker caste in ants usually fe- 

 males, but in higher termites it may consist of either 

 males or females. In primitive termites the nymphs 

 of other castes substitute for the workers. The work- 

 ers collect food, cultivate gardens of fungi, take care 

 of domesticated aphids or coccids, feed the other 

 castes, and build shelters. The earliest organized 

 social life of primitive man was perhaps neither so 

 highly organized nor so far advanced in an evolution- 

 ary sense as these complex societies of insects, even 



Cooperation and disoperation 175 



