ZOOLOGY 193 
Congo. One of these collected on the present Expedition is a new species (C. 
ninagongensis) (page 837). 
In relation to the occurrence of filariasis and elephantiasis in Liberia, it may 
be remarked that Culex quinquefasciatus (fatigans), as it is in many other tropical 
regions, is probably more commonly concerned in the transmission of Filaria 
bancrofti in Liberia. This subject is more fully discussed on page 231. However, 
Edwards has demonstrated that complete development of F’. bancrofti may also 
occur in Taeniorhynchus africanus, Anopheles rossi, A. costalis and A. algeriensis, 
as well as Culex pipiens. Of these A. costalis was found by Bequaert in Liberia. 
Culicoides grahami and C. austeni which, as has been shown, can act as an 
intermediate host for the filarial parasite Acanthocheilonema perstans, were also 
collected during the Expedition. This parasite, which produces transitory tumors 
known as Calabar swellings, is referred to particularly in Chapter XVII. 
In the British Cameroons, where infection of man with A. perstans is very 
common, Sharp found over seven per cent of the wild flies Culicoides naturally 
infected with this parasite. 
It seems probable that the scarcity of mosquitoes in parts of Liberia at certain 
periods of the year may be due to the excessively severe showers of rain which 
occur there during the rainy season, and which through the force of their heavy 
raindrops and the rushing torrents that the heaviest of them produce, destroy 
many of their larvae. 
Of the blood-sucking flies collected, twelve species of tabanids were encoun- 
tered in Liberia, four species of tsetse flies, one black fly (Simulium damnosum), 
five species of stable flies (Stomoxys) and six species of bird flies (Hippoboscidae). 
Both species of Chrysops (the mangrove fly), C. dimidiatus and C. silacea, which 
have been demonstrated by Leiper and by Connal to be the carriers of the 
filaria Loa loa, have been previously reported as having a wide distribution on 
the West African coast. In addition another allied species of Chrysops was 
found during the present Expedition by Dr. Bequaert in the Belgian Congo. 
Of the five species of tsetse flies in Liberia, four, Glossina palpalis, pallicera, 
fusca and nigrofusca were collected by Bequaert. Glossina medicorum has been 
previously reported by Austen as existing in the country. ‘Tsetse flies were 
not found to be very plentiful anywhere in Liberia. A trypanosome was found 
in the abdominal and head segments of one specimen of Glossina palpalis col- 
lected at Tappi Town, but no cases of sleeping sickness were discovered in this 
place. Simuliwm damnosum, a small species of black fly, was not encountered 
on the coast and was first observed in the interior of Liberia where at some 
ninety miles inland it was found in abundance. The breeding place of this fly 
was also discovered in a swiftly-flowing stream near this same locality, the larvae 
and pupae of the fly being found upon both dead and living leaves immersed in 
the water and exposed to the current, as well as upon the sides of stones beneath 
the water (see page 856). In contrast to the tsetse flies, only the females of 
Simulium bite, and they are voracious blood-suckers and bite freely at all hours 
of the day in shady places, but not in bright sunlight. This fly has been found to 
constitute an intermediate host for the parasite Onchocerca volvulus, which in 
