406 LAND ANIMALS 



are found simultaneously throughout the year; 96 in Java the lamelli- 

 corn beetles, Lachno sterna, Anomala, and Exopholis, likewise are 

 present in all stages of development at all times of the year. In Ascen- 

 sion, Dahl found the few spiders and insects both present in all stages. 97 

 This is also corroborated by the fact that the oft-described nocturnal 

 tropical concerts, the thousand-voiced chorus of the males of many 

 species of grasshoppers, crickets, and locusts, to which frogs also add 

 their music, lasts throughout the year. However, it is not the same 

 individuals that sing; the concert remains, the musicians change. The 

 limitation of certain insect colonies to one season, as in our bumblebees 

 and wasps, is not paralleled in the tropics. In Java, 98 as in Brazil, 99 

 perennial wasp colonies with persistent nests avoid too great an in- 

 crease in population by swarming, like honeybees in our latitudes. 



In many vertebrates the breeding habit is not associated with a 

 special season. The larvae of the toad, Bujo melanostictus, for exam- 

 ple, and apparently those of many other frogs and toads, are found in 

 Batavia throughout the year. 100 The nesting of the birds is also inde- 

 pendent of the season. In Cuba, for example, one may find eggs of the 

 finch Euethia cepida and of the hummingbird Biccordia 7'icordi, as 

 well as their young, in any month; 101 the booby (Sula) and the noddy 

 {Anous) breed continuously on the St. Paul Rock in the Atlantic, near 

 the equator. For that matter, the English sparrow breeds at every 

 season wherever there is a uniform temperature, as in factory hall- 

 ways. 102 Pregnant females of many, but not all, mammals may be 

 found at all times of the year. These include a number of South Ameri- 

 can monkeys, 103 the pigs in the Malay archipelago, 104 many of the 

 African antelopes, and the marsh deer and sloth of South America. 

 On the Galapagos Islands the breeding activities of the eared seals 

 {Arctocephalus) are continuous. 105 



Although the periodicity of the seasons with reference to tempera- 

 tures is lacking in the tropics, the daily cycles occur, but are much 

 more uniform here than in the higher latitudes; year in and year out 

 the day is approximately 12 hours long, while with progression into 

 higher latitudes the length of day increases in the spring and decreases 

 in the fall. This is important for the birds, which are essentially diurnal 

 animals and are directed principally by their eyes in their search for 

 food. Since the three or four hottest hours of midday are deducted from 

 the 12-hour day, there remain only 8 or 9 hours for the search for food. 

 This is enough for the birds so long as they have only themselves to 

 provide for, but the time becomes short when they must also provide 

 food for their young. It is different in the temperate belts. The farther 

 toward the pole, the longer the day becomes; at such latitudes there is 



