ASIATIC-PACIFIC COLLECTIONS 
33 
Comments on the Summarised Collections 
The relative poverty of deforested and settled areas. 
This feature, clearly illustrated by the data in Table i, is apparent in the following collec- 
tions (the numbers in brackets refer to the numbers in the tabulation on pp. 36-41): 
Mehta (2) in North India, trapped “only in dwelling houses and shops, both in the 
urban and semi-rural areas” and obtained 5 species from 2,451 hosts. 
Krishnan et al. (28) in the suburbs of Barrackpore and Calcutta obtained 9 species 
from 1,064 hosts. Their collecting area will have included open scrub. 
Gater (33) obtained 7 species from some 600 rats from around Kuala Lumpur ; but 
24 species from the same number of hosts from the forest edge a few miles away. 
Kalra (21-27) obtained only 3 species from 1,204 rats and shrews from the townships 
of Jubbalpore and Bangalore, but at least 18 species from 485 rats from North India. 
Jayewickreme (17-20) and Radford (16) in Ceylon got only 3 species from 252 hosts 
in Colombo, only 7 from the well-cultivated area of Nalanda, and 11 from 338 hosts 
from the moderately cultivated area round Embilipitiya. 
Nagayo and other workers in Japan (50), collecting thousands of voles in the restricted 
habitats of the infected fields in northwest Honshu obtained only 6 species, but four 
times this number have recently been obtained by collections (55) in a wider variety 
of habitats. 
A special example of this effect is found in the fauna of islands of an oceanic type — 3 species 
on Bat Island (84), 5 on Addu Atoll (33), 2 on Jarak (in 40), and 5-7 on islands such as Okinawa. 
Gater’s collection (33) of 7 species in Kuala Lumpur is particularly interesting as we would 
now find only 2 species in the tov/n proper, and only some 4-5 species in its suburbs. Gater 
mentioned Gahrliepia fletcheri as being fairly common on the house-rats but it has now practi- 
cally disappeared from the whole town area. These are reflections of the sophistication of the 
town during the intervening twenty years. 
The effect of bias in collecting host species 
Gunther (1940) reported that about 90 per cent, of some 2,000 chiggers collected by him 
in New Guinea were Trombicula wichmanni (reported as T. minor). T. wichmanni is essentially 
a bird-chigger, and he collected ten times as many birds as mammals. His findings contrast 
directly with those of Heaslip (1941) who reported that 90 per cent, of some 2,000 chiggers 
collected by him from mammals were T. deliensis. 
The late Dr. Consett Davies (No. 79) by collecting only reptiles yielded records of 4 species 
of Eutrombicula. A similar bias, in favour of two related groups of Schongastia and of Trombi- 
cula from reptiles, was evident in the studies made by Dr. R. F. Lawrence (1949) in South 
Africa. Dr. D. J. W. Smith (No. 64) appears to have collected 6 (new) species of Euschongastia, 
but none of Trombicula , from mammals in Australia but the reason for this has not been dis- 
covered. 
Boot-collections are well recognised as being biased. 
Bird-chiggers and the vectors of scrub-typhus are particularly likely to be introduced to 
oceanic islands, and the species recovered by the investigator will be influenced greatly by the 
inclusion or exclusion of birds. 
MALA YA, No. 26 , 1953 
