50 PROCEEDINGS OF THE NATIONAL MUSEUM VOL. 120 
to the Philippines. Thus, C. traylori may have evolved as a result of 
natural straggling from the stock that gave rise to C. wenzeli and 
C. blakei and subsequently became established on the host B. hydro- 
corax. 
Chapinia lydae from Rhyticeros cassidixz has the characters of the 
acutovulvata species-group but superficially resembles members of the 
hirta species-group of which C. muesebecki, from Penelopides e. exar- 
hatus, like C. lydae, is restricted to the Australasian region (table 13). 
Chapinia hirta, the other member of the hirta species-group, infests 
subspecies of Rhyticeros plicatus in both the Oriental and Australasian 
regions. 
The hornbill genus Buceros is host to both Chapinia and Bucero- 
phagus (table 13); however, these Mallophaga do not infest the same 
hosts. Buceros hydrocoraz, the host of Chapinia traylori, is restricted 
to the Philippines, but B. rhinoceros and B. bicornis, the hosts of 
Bucerophagus forcipatus, are distributed elsewhere in the Oriental 
region. On the other hand, the mallophagan species, Chapinia 
waniti and Bucerocolpocephalum deignani, do infest the same host, 
Anorrhinus galeritus carinatus. 
In the productus species-group both Bucerophagus productus and B. 
africanus infest the two hosts, Bucorvus abyssinicus and B. lead- 
beateri. The population of each mallophagan species on each host 
could not be separated morphologically or statistically. Thus, only 
the two species, Bucerophagus productus and B. africanus, could be 
recognized. Similarly, Clay (1955) recognized only the one species, 
Bucorvellus docophorus, although specimens from Bucorvus lead- 
beateri showed a tendency to be smaller in size than specimens from 
B. abyssinicus. She further stated that it would be expected from 
Harrison’s rule (1915) that specimens from B. leadbeateri, the smaller 
host, would be smaller than specimens from the larger B. abyssinicus. 
However, Mackworth-Praed and Grant (1952) stated that B. lead- 
beateri was the largest of the Hornbills; they gave wing measurements 
for B. leadbeatert as 509-595 mm. and for B. abyssinicus as 495-595 
mm. 
Harrison (1915) stated the rule that bears his name: that in general, 
when a mallophagan genus is well distributed over a considerable 
number of nearly related hosts, the size of the parasite is roughly 
proportional to the size of the host. Chapinia camuri, the smallest 
species of Chapinia, infests the smallest hornbill, Zockus camurus, 
but Chapinia traylori, the largest species of Chapinia, does not infest 
Rhyticeros undulatus, the largest host for species of Chapinia. 
