i6 
AUDY & HARRISON 
The Assemblage of Ectoparasites 
Preliminary check-lists of trombiculids were published in the Annual Report of the 
Institute for 1951 (pages 89-97). A tota l °f 9 2 species were listed from Malaysian sources, 
from material examined up to the end of 1952. The following species have since been added to 
this list, bringing the total up to 124 : Trombicula ( Leptotrombidium ), 6 ; T. ( Neotrom .), 1 ; 
Fonsecia, 1 ; Euschongastia sens, lat., 7 ; Doloisia sens, lat., 4 ; Walchiella, 1 ; Gahrliepia 
( Walchia ), 1 ; G. ( Schongastiella ), 2 ; G. ( Gahrliepia ), 1 ; G. ( Gateria ), 2 ; Whartonia , 2. 
Species in the check-list numbered 88, 89, 91 are provisionally to be ascribed to Whartonia not 
Hannemania. Species numbered 9, 10, 15, 33, 35, 46, 47, 48, 49, 53-55, 75, 76, 90, 92, have 
been described in the present collection of papers (Traub and Audy, 1953 Traub and Evans, 
1953, Womersley, 1953) while numbers 20, 31 and 77 have been described as E. dimolinae , 
E. revelae and Schongastiella hipposideros by Audy (1952). 
Table 2 gives a general impression of the degree of infestation of the various hosts by 
species or groups of trombiculid mites. The first three columns give the number of hosts 
examined from the three major habitat groups, but the mites from all these hosts have not been 
identified — the numbers for various hosts for which this has already been done are shown in 
Table 3. The relative abundance of infestation by various trombiculids is shown for the 
following : 
Subfamily Trombiculinae 
Trombicula and related genera 
Vectors of scrub-typhus : T. akamushi and T. deliensis (which have different distri- 
butions, as shown in Table 3). 
Other species of the subgenus Leptotrombidium , which includes several species 
(e.g. T. sylvestris ) closely related to the vectors. 
Species other than the above 
Euschongastia and related genera 
The E. indica group, of which E. indica is dominant outside, and E. audyi inside, the 
forest. Other species in this group occur, but rarely. 
The E. lacunosa group and the ( Walchiella ) oudemansi group. 
Species other than the above. 
Subfamily Gahrliepiinae (Walchiinae) (the genus Walchiella is excluded from this 
subfamily by us, being provisionally placed as a subgenus of Euschongastia.) 
The last five columns refer to major groups of parasites (trombiculid mites, parasitoid 
mites, ticks, lice, and fleas). The trombiculid mites and ticks remain attached for definite 
periods of time so that the mean number of these parasites per individual host is an important 
index of abundance (but see comments below). The parasitoids and fleas are however 
particularly prone to leave their hosts and actual numbers of these found on hosts in the 
prevailing conditions of collection are not particularly significant. For this reason, the 
infestations are here presented as a percentage of hosts infested. 
Table 3 gives details of the actual numbers of the commoner species of trombiculids on 
the commoner hosts which have been adequately studied. A similar but less accurate table 
was given by Audy and Harrison (1951, p. 377). In interpreting this table, three adjustments 
must be made. Firstly, the commensal rats — R. r. diardii in villages and towns, 
R. r. argentiventer in open fields and waste-land, and R. r. jalorensis in oilpalms and wooded 
waste land, as well as R. exulans and the several species on islands — all occur in large numbers 
which are not rivalled, and often not even approached, by the less dense populations of other 
species occurring in the forests. Therefore, any given degree of infestation of these rats is more 
significant as an indication of mite-population than it would be with the other more thinly 
STUD. INST. MED. RES. 
