MALAYSIAN PARASITES VI 
INDO-MALAYSIAN CHIGGERS OF THE SUBGENUS SCHONGASTIELLA 
(ACARINA TROMBICULIDAE)* 
By 
ROBERT TRAUB and THOMAS M. EVANS. 
During the war years intensive studies on scrub typhus were undertaken by the United 
States of America Typhus Commission in Assam and Burma. Postwar investigations on this 
mite-borne disease have been carried out in Malaya by the Colonial Office Research Unit and 
the U.S. Army Medical Research Unit, both headquartered at the Institute for Medical 
Research, Kuala Lumpur. As a result of these projects, quantities of trombiculid mites or 
chiggers have become available for study, including new and little-known species. 
The present paper includes descriptions of the larvae of seven new species of the subgenus 
Schongastiella (Hirst, 1915) of the genus Gahrliepia Oudemans, 1912, as well as records of 
G. (S.) punctata (Radford, 1946) and G. (S.) ligula (Radford, 1946). This group of mites is of 
potential medical significance, although its role has never been evaluated. The subgenus was 
regarded as wholly Indo-Malayan, but it has recently been reported in Africa (Andre, 1951). 
The fact that new species are currently being described by other workers, whereas other species 
are yet poorly known and inadequately collected, makes it impossible to prepare a revision of 
this subgenus at the present time. 
One of the Assam-Burma new species is described in detail. The other new forms are 
compared with the first, and only major differences are noted in order to save space. All these 
are illustrated in full. For purposes of ready comparison, a table is included which lists 
pertinent and significant data and measurements. In addition to the valuable measurements 
introduced by Womersley and Heaslip (1943), and which are now standard, new metric data 
and proportions, as well as terms and abbreviations, are included in the present paper. Among 
these are : (a) the pseudo-posterolateral setae (PPL) : the pair of abdominal setae encompassed 
by the enlarged scutum, and which at first glance appear to be the posterolaterals ; ( b ) PPW : the 
width in microns between PPL; (c) PP: the distance in microns between PPL and the posterior 
margin of the scutum; ( d ) A-PP: the distance between AL and PPL; and (e) DS: the length of 
typical dorsal setae. The ratio of PW to the scutal depth SD (=ASB— PSB), is a useful one, 
and serves to statistically equalize the apparent difference between the actual measurements of 
disproportionately large or small specimens of the same species. Important in this regard is 
the ratio of PW to the length of coxa II (see Traub and Audy, 1953, this Study p. 74). This 
ratio appears to be quite constant regardless of the size of the individual. The length of coxa II 
is measured as illustrated in fig. 3, i.e., from the base of the coxa (not the more contiguous plate, 
which is difficult to see in long-mounted specimens) to the tip of the apical spur on the anterior 
margin. The setation of the palpae is expressed by means of a formula after Audy (1952) e.g. 
N N BNB, in which the first letter refers to the seta on the palpal femur, the second to that of 
the genu, and the next three to the dorsal, lateral, ventral setae on the tibia, respectively. The 
letter N signifies the seta is nude, and B barbed. Where a bristle is mainly nude but lightly 
frayed or ciliated in one or two places the designation would be N (b). 
Gahrliepia (Schongastiella) liota n. sp. (figs. 1-9). 
Diagnosis of Larvae. — Near G. (S) ligula (Radford, 1946) (figs. 61-68) in that the scutum 
is constricted beyond PL, the portion of the plate posterior to these bristles being somewhat 
narrowed (Radford, 1946). Separable in that the hind coxae possess two bristles, not one; 
* Investigations supported by the Commission on Immunization of the U.S. Armed Forces Epidemiological Board 
and by the British Colonial Office Research Unit. 
MALAYA , No. 26, 1953 
