INSECTS AND ALLIES (ARTHROPODA) 



166 



We expect that, when fully studied, the arthropod 

 fauna of Enewetak Atoll will comprise 350 to 400 species. 

 This estimate takes into consideration that the 191 taxa 

 reported herein do not include many groups that arc 

 expected to occur in cryptic habitats, such as soil and 

 decaying plant materials and those associated with 

 vertebrates. 



In comparing the fauna of Enewetak Atoll with the 

 total number of species reported for the Marshall Islands, 

 we find about 32% (191 of 592) represented on Enewetak 

 (Table 3). Many of the exotic species carried to Kwajalein 

 and Enewetak in recent years are, of course, reflected in 

 this percentage, which would be lower if only the truly 

 indigenous and endemic elements were considered. We 

 estimate that around 43% (82 of 191) of the species 

 presently listed for Enewetak could be adventive elements. 

 The extent of transfer into neighboring atolls by these 

 adventives is not known. 



The percentage of species endemic lo the Marshalls is 

 certainly not high at 4% (25 of 592); we expect this figure 



to increase somewhat after future collections from cryptic 

 habitats are studied. These endemics are listed in Tabic 4. 

 The proportion of species endemic to Enewetak Atoll I* 

 very low at l'/2% (3 of 191); this percentage, too, ]» 

 expected to increase following future studies. Of the 25 

 species endemic to the Marshalls, 52% (13) are restricted 

 to the western or Ralik Chain, 24% (6) are restricted to 

 the eastern or Radak Chain, and 24% (6) are found on 

 both chains (Table 5). Present records indicate that 64% 

 (16 of 25) of these endemics are restricted to single atolls; 

 they represent only 2y2% (16 of 592) of the total Marshall 

 Islands' fauna. 



A rather low proportion, 9V2% (57 of 592), of the 

 Marshall Islands fauna is restricted to the central and east- 

 ern Carolines-Marshalls-Gilberts sector of the Pacific 

 (Table 6). This includes the most characteristic species to 

 be expected on atolls; they are listed in Table 7. About 

 half (31 of 57) are strictly limited to atolls and low islands, 

 and these include the taxa endemic to the Marshalls. The 

 others (26 of 57) also occur on high islands proximal to 



TABLE 3 



Numbers of Insects and Allies Reported for the Marshall 



Islands and Numbers for Enewetak Atoll Only, 



Including Counts of Endemic Taxa 



Group 



Marshall 

 Islands 



Enewetak 

 Atoll 



Endemic to 

 Marshalls 



Endemic to 

 Enewetak 



'Group is poorly surveyed, with Enewetak records accounting for most 

 or all Marshall Island records. 



