MALAYSIAN PARASITES VIII 
ON THE VALIDITY OF THOSE GENERA OF TROMBICULIDAE 
(ACARINA) WITH POSTEROLATERAL SETAE OFF THE SCUTUM 
By 
H. WOMERSLEY 
The number of Trombiculid genera characterised by having the scutum more or less 
reduced so that the posterior lateral scutal setae are placed off the scutum, has during the 
present decade been added to by many workers as our knowledge of this family of Acarina 
increases. 
No fewer than nine species* referred to seven genera have been described as follows : 
Ascoschongastia malayensis (Gater 1932) ... 
Tecomatlana sandovali Holfmann 1947 ••• 
Sauriscus ezuingi Lawrence 1949 ... 
Trisetica melvini Traub and Evans 1950 
Ascoschongastia hungerfordi Lipovsky 1951 
Pseudoschongastia hungerfordi Lipovsky 1951 
„ farneri Lipovsky 1951 ... 
„ diazi (Hoffmann 1947) Lipovsky 1951 
Anomalaspis ambiguus Brennan 1952 
Malaya 
Mexico 
S. Africa 
Burma 
Burma 
N. America 
N. America 
Mexico 
Venezuela 
(1) one AM and two AL scutal setae; 
All the above possess the following generic features 
(2) non-serrate chelicerae ; and (3) a more or less, and either longitudinally or transversely, 
reduced scutum so that PL lies distinctly away from the scutal margin. 
Other characters generally considered by acarologists as of generic or greater value are : 
(1) the leg-segmentation i.e., the division or otherwise of the femur, giving a 7-segmented or 
a 6-segmented leg; and (2) the form, filamentous, clavate, or globose, of the scutal sensillae. 
Wharton et al. (1950) have proposed a classification of the Trombiculidae (incl. Leeuwen- 
hoekiidae) in which the subfamily Gahrliepiinae (sic. Walchiinae) is denned on the basis of leg 
I being 7-segmented and II and III 6-segmented. In their key this includes two genera, then 
given unnamed as in MS rone to be, but as yet not, described by H. S. Fuller for the species 
Trombicula oudemansi Walch 1922, the other, since described by Lipovsky (1951) as Pseudos- 
chongastia. 
Both these, the species oudemansi and the genus Pseudoschongastia , possess an AM scutal 
seta, whereas all the other genera listed by Wharton et al in the Walchiinae lack this seta. 
Womersley (1952) confines the Gahrliepiinae (Walchiinae) to those forms not having an 
AM seta, a feature which from our present knowledge of the nymphal and adult stages is corre- 
lated with the occurrence of a dorsal stump-like process on the front tarsus in those later 
stages. None of the species placed in Pseudoschongastia have yet been reared to the nymph 
or adult, but the nymph of oudemansi was described by Womersley (1952) and this does 
not possess such a tarsal process. 
Thus while the Gahrliepiinae all appear, so far, to have the segmentation of the legs, 7-6-6, 
instead of the usual 7-7-7 in the Trombiculinae, the occurrence of odd forms with 7-6-6 in the 
latter subfamily is not of generic importance. In the reduction of the dorsal scutum with 
* This paper was written before the species to be placed in a new subgenus of Doloisia Ouds were found ( see Audy 1953 
this Study p. 159) 
STUD. INST. MED. RES. 
