NO. 3558 MALLOPHAGA—ELBEL 49 
occurring between hosts that happened to be nesting in close prox- 
imity; she stated that establishment on the new host might be facili- 
tated by the absence of a resident louse. 
It would appear that both lophocerus and acutovulvata species-groups 
shared a common ancestor of Chapinia on Tockus before the Indian 
and African Tockus became separated. Once separated, the Chapinia 
evolved as did the birds to the recognized species within each species- 
group. Natural straggling may have accounted for establishment 
on some of the hosts. 
Clay (1949b) mentioned that the chief factor influencing the 
production of allopatric species and genera of Mallophaga has been 
the successive splitting of the host populations during the evolution 
of the birds, thus leaving isolated louse populations. The louse 
population is considered as comprising all individuals that can inter- 
breed because their hosts can interbreed (Clay, 1958). Kellogg 
(1896) stated that with the spreading of the ancestral bird species, 
geographical races arose within the limits of the species. With time 
and isolation, these races became distinct species which were often 
distinguished only by superficial differences in color, etc. The 
Mallophaga remained practically unaffected since their environment 
was essentially unchanged. The environment of the Mallophaga, 
the physical and chemical composition of the feathers and blood, 
changes more slowly than do other factors leading toward speciation 
of the bird; until this environment changes, the Mallophaga would 
remain unchanged (Clay, 1949b). For example, in the acutovulvata 
species-group, the hosts Anthracoceros coronatus and A. converus are 
now considered to be full species distinct from A. a. albirostris, A. a. 
leucogaster, and A. marchei, yet all these hosts bear the same species 
of Mallophaga, Chapinia acutovulvata. Similarly, in the lophocerus 
species-group, Chapinia bucerotis infests eight subspecies in four 
species of Bycanistes, and C. lophocerus infests six subspecies in four 
species of Yockus. In the forcipatus species-group, Bucerophagus 
forcipatus infests three subspecies in three species and two genera. 
Although Anthracoceros marchei is restricted to the Philippines, it 
is host to Chapinia acutovulvata which infests other Anthracoceros 
species with wider distribution in the Oriental region. A. montani 
also is restricted to the Philippines, but its amblyceran parasite, 
C. hoplai, resembles most closely C. boonsongi from Rhyticeros undu- 
latus, which is distributed elsewhere in the Oriental region. Chapinia 
wenzel from Penelopides panini and C. traylori from Buceros hydro- 
corax both resemble most closely C. blakei from Rhyticeros leucoce- 
phalus. Although the host genus Buceros is not considered to be as 
related to Rhyticeros as is Penelopides, the host species from which 
C. wenzeli, C. blakei, and C. traylort were obtained are all restricted 
