172 BULLETIN 66, UNITED STATES NATIONAL MUSEUM. 



Tropic of Cancer, India, Siam, and southern China, and also includes 

 Africa north of the Tropic of Cancer. The Ethiopian realm includes 

 Africa and Arabia south of the Tropic of Cancer. The Oriental realm 

 includes India, Siam, Burma, southern China, Sumatra, Java, Borneo, 

 and the Philippines. The Australian realm includes the remainder 

 of Malaysia, Melanesia, Polynesia, Australia, and New Zealand. A 

 map is presented herewith to show the delimitation of the subdivisions. 



Taking the host records as the only available criterion, it is found 

 that the parasitized species are distributed as follows: Nearctic 90, 

 Palsearctic 91 (Holarctic of Heilprin, excluding Mediterranean fauna, 

 162), Neotropical 19, Ethiopian 3, Oriental 14, and Australian 23. 

 It is probable that the low number for the tropical realms is due to 

 the fact that less collecting has been done, for it seems likely that the 

 tropical fauna should be most prolific in such forms. 



The following tables present the distribution of the known 238 

 species of host insects and show that the order is indeed world-wide, 

 yet not because of cosmopolitan host insects. The only regions 

 from which no hosts have been recorded are the boreal, the west cen- 

 tral African, Madagascar, and New Zealand. Only 13 of the 50 

 genera are found parasitized in two or more realms. These genera 

 are distributed as follows: 



Polistes in 5 realms and 9 regions; Sceliphron in 4 realms and 6 

 regions; Sphex in 4 realms and 6 regions; Proterosphex in 3 realms 

 and 5 regions ; Liburnia in 3 realms and 4 regions ; Vespa in 3 realms 

 and 3 regions; Andrena in 2 realms and 5 regions; Eumenes in 2 

 realms and 2 regions; Odynerus in 2 realms and 2 regions; Ancistro- 

 cerus in 2 realms and 2 regions; Parasphex in 2 realms and 2 regions; 

 Priononyx in 2 realms and 2 regions; Halictus in 3 realms and 3 

 regions. 



Only five of these genera are both Nearctic and Palaearctic with 

 regards to stylopization, namely, Liburnia, Polistes, Sphex, Andrena, 

 and Halictus. 



