708 



NATURALIST'S GUIDE TO THE AMERICAS 



direction (85.7 per cent from the east) 

 are as constant as the rainfall is variable. 

 The mean daily variation in temperature 

 (24.9° to 29.5°), although small, is twice 

 that of the mean monthly records 

 (25.9°, January to March, to 28.3°, 

 September). 



II. BIOTA 



The flora is characterized by the 

 abundance of Croton. Commonly the 

 omnipresent thorn-trees are dwarfed 

 and distorted by the trade winds; the 

 foliage of the dividivi usually consists 

 of a flat, matted fan, which only spreads 

 out to the leeward of the trunk. The 

 giant, organpipe cacti are among the 

 most conspicuous features of the vege- 

 tation, while the flat-jointed cacti 

 (jOpuntia) are almost everywhere, and 

 the large "niggerheads" of Melocactus 

 and the spiked rosettes of Agave may 

 be about the only plant life near the 

 summits of the larger, limestone monad- 

 nocks. Nowhere can the vegetation 

 truly be called a forest, although, in 

 protected places, especially on the 

 leeward slopes of the higher hills, larger 

 trees {Bursera, Casearia, Bumelia, Ma- 

 chaonia, Guaiacum, etc.) do form small, 

 or even quite extensive, open groves. 

 Quite a few of the trees and shrubs shed 

 their leaves during the driest portion of 

 the year, although evergreen plants are 

 also prevalent. On the leeward slopes 

 of the highest peaklets (Sint Christoffel- 

 berg; 372.4 meters), are the most heavily 

 wooded valleys in the islands; especially 

 conspicuous are the large mats of Bro- 

 melia lasiantha, while a few epiphytes 

 (Tillandsia, Ficus, etc.) somewhat in- 

 crease the luxuriance of the arboreal 

 foliage. 



These islands are naturally without 

 large mammals, although deer have been 

 introduced on Curagao; the monotonous 

 avifauna is especially characterized by 

 the gray mockingbirds and shrikes, 

 although parrakeets lend a touch of 

 color in the more protected cliffs. A 

 large, nesting colony of flamingos lives 

 among the salt-pans of southern Bonaire. 



Ground lizards (Cnemidophorus) are 

 very abundant everywhere and the cliffs 

 are often infested by large iguanas. 

 Terrestrial molluscs are almost lacking 

 in the central region, but the limestone 

 rim, although poor in generic diversity, 

 support an individual abundance, of 

 such genera as Cerion and Tudora, 

 that I have never seen surpassed. 

 Due to the isolation of the islands, 

 practically all of the native species 

 (also the genera Stoastomo-ps and Cistu- 

 lops) are endemic, and the frequent 

 breaks in the limestone rim are coin- 

 cident with a remarkable diversity of 

 closely related species, subspecies and 

 local races. The affinities of this mol- 

 luscan population are with that of the 

 northern Antilles, rather than with that 

 known from the adjacent mainland, but, 

 as already indicated, the coastal fauna 

 of A^enezuela has been little studied. 

 Although the larger trees are cut for 

 charcoal, and the aloes fields of Aruba 

 have replaced the natural vegetation 

 of some of the limestone plains, the 

 aridity of these islands, and of the 

 coastal strip of Venezuela, has safe- 

 guarded the preservation of natural 

 conditions throughout these semi- 

 deserts. However, thriving coco-plan- 

 tations are maintained wherever the 

 ground water is near the surface or 

 irrigation is possible. A few springs 

 comprise most of the freshwater in the 

 islands, although sink-holes in the lime- 

 stone commonly form natural wells 

 with varying degrees of salinity. De- 

 spite the dry climate, protected embay- 

 ments are usually lined by mangrove- 

 thickets, both on the islands and along 

 the mainland; these are infested by an 

 abundance of large, burrowing crabs. 

 Another peculiar phenomenon of this 

 region is presented by the large armies of 

 "soldasjis" (hermit-crabs) which march 

 down from the highlands, during the 

 rains, to "wash their eggs" in the ocean. 



III. GUIDE AREAS 



Included in account of Venezuela. 



