2 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. «9 



enced, when the earth surface dries to considerable depths, except in 

 well-protected locations. The constant sea breezes cause rapid surface 

 evaporation, and in general the islands are so arid that many of the 

 plants are decidedly xerophytic in character. During the hurricanes, 

 which are a menace throughout much of the year, many of the smaller 

 islands are more or less inundated by sea water or drenched by spray 

 for periods long enough to have a serious effect on many small crea- 

 tures living in the soil. When it is understood that the delicate humus 

 animals, like most millipeds, require an environment with an unbroken 

 supply of food and moisture, and protection from the sun and flooding, 

 it will be realized that such animals have lived in these islands under 

 great difficulties. In the face of these difficulties it is astonishing that 

 these creatures have managed to maintain the unbroken continuity 

 through past ages that accounts for their presence on some of the 

 islands today. 



Unsatisfactory environmental conditions were found on many of 

 the small West Indian islands where collecting was done, such as 

 Beata and Saona Islands off the south coast of Haiti ; Barbuda, 

 Anguilla, and Saba in the northern Lesser Antilles ; and Bequia, 

 Cannouan, and Mayero in the Grenadines to the south. None of these 

 islands has high elevations where rain forest conditions are ap- 

 proached, with the possible exception of Saba. The single day spent 

 on that island did not allow a visit to the highest part, which is fre- 

 quently cloud-covered and is said to have considerable rainfall. At 

 the time of our visit Saba was rather dry, and few humus insects and 

 no millipeds were found during the walk from the sea up through the 

 town of Bottom to the still higher town of Windward at an elevation 

 of 2,500 feet. 



In the larger and more fertile West Indian islands, agricultural 

 activities, which include cutting down the forests, burning of brush 

 and grass lands, cultivation of various crops, pasturing of cattle, and 

 general denuding of the land by other means, have undoubtedly con- 

 tributed very greatly toward reducing the humus population. A strik- 

 ing example of these effects was found in St. Vincent, the most in- 

 tensively and generally cultivated island seen by the expedition. In 

 a trip over about half of the island few places were found where 

 humus insects might exist continuously, and no millipeds were seen, 

 although seven species have been reported, and one of these might 

 be expected to be rather abundant, as in other places where it is 

 known. There is little doubt that satisfactory conditions for milliped 

 life are more frequently met with in the higher parts of the island 

 than in the lower elevations, where the scarcity of forms may be at- 



