TAXONOMY OF TROMBICULIDS 
153 
Remarks. — This is the globular e-g roup in Womerslev’s Key (1952 123 1). The dry-seasonal 
appearance of larvae of this group has been noted elsewhere (Audy, 1947; 1953, table 4; Audy 
et al. 1953). The writer has pleasure in naming this subgenus for his mite of a daughter. A 
revision of the subgenus is to be published with the description of further nymphal material. 
The inclusion of the two African species listed below is subject to confirmation. 
Old World species. — Africa: ? ? madecassa; ?“ SGH ” n. sp. Jad. & Verc., 1953 in press. Asia and 
Pacific: covelli, comata, globular e, kohlsi N, lanius N, miyagawai , mutabilis N, signata {N unpub.). 
Subgenus Walchiella Fuller, 1952, modified. 
Type. — Trombicula oudemansi Walch, 1922 :35, Geneesk. Tijd. Ned. Ind., 62 , 530-588. From mammals 
Malaysia and ? Australasia (type from Sumatra). 
Provisional Diagnosis (expanded). — Larval Euschongastia species close to those of the lacunosa- group 
(below) differing from them in having the femora of legs II & III undivided, these legs therefore 6-seg- 
mented instead of 7-segmented; chelicerae sometimes toothed or serrated, often simple, scutum well- 
chitinised and roughly rectangular but with posterior margin laterally rounded; bases of body-setae 
well-chitinised, generally conspicuous (DS set in platelets in heaslipi, traubi ), setae often fairly short with 
inconspicuous barbules, and a general tendency for the DS to vary in length according to position; without 
a mastitarsala III. Nymphs & Adults (known only for oudemansi and n. sp. undescribed) apparently 
with fine nude sensillae (cf. S'. vieta), sensillary area fairly broad relative to crista (ASL:SB ratio about 
1.9); not clearly distinguishable from those of other groups of Euschongastia. Not yet recorded outside 
Asiatic-Pacific area. 
Remarks. — The type species, E. oudemansi , is a dominant chigger on ground- dwelling 
animals in the Malayan forest (see Table 1) and it can now be recognised as the dominant 
member of a considerable and widespread species-group. E. oudemansi itself has, as originally 
described by Walch, a row of distinct teeth and typical Malayan material shows these clearly 
[not as figured by Womersley, 1952, fig. 32C, which is probably the chelicer of E. impar 
(Gunther, 1939)] Dr. D. J. Lee of Sydney University has kindly allowed the writer to study a 
paratype of Gunther’s impar , while Womersley has kindly lent a whole series of slides of 
material from New Guinea. From a study of these, it would appear that two distinct forms 
have been confused: one, impar , is without teeth to the chelicers (or perhaps with minute 
serrations ?) while the posterior dorsal-setae of the nymphs have very long subterminal setules ; 
the other, typical oudemansi , has recognisable cheliceral teeth and the subterminal setules are 
relatively short. The scuta appear to be shaped somewhat differently. Whether or not these 
two forms (which may occur in the same locality) are two species or only varieties or subspecies 
now overlapping, the writer is not prepared to discuss. Until the material has been studied, 
it would be advisable to regard impar as a valid species, or at least as a distinct form. 
E. oudemansi is a very small species, and in the small nymph the setation of the legs is 
simplified. This gives what may be false air of distinction to the chaetotaxy and it is hoped 
that a large species like some of those from Borneo may be bred in the near future. 
Although the writer believes that Walchiella is probably a good larval genus, it is not 
possible to separate it generically from the lacunosa- group and until the two groups have been 
studied closely it would appear best to treat Walchiella as a sister group, i.e. as a subgenus. 
World species (Asia & Pacific). — asonluca Traub & Audy, 1953 (this Study p. 84 ), calunosa Traub & 
Audy, 1953 {ibid, p. 84 ), heaslipi , impar , lewthwaitei , oudemansi , traubi , 5 species being studied (one 
species bred to nymph). 
Subgenus ( ? Walchiella): lacunosa-group 
Representative Species. — Neoschongastia lacunosa Gater, 1932:156, Parasitology , 24, 143-174. 
Common on ground-living rats in Malayan forest. 
Provisional Diagnosis. — Euschongastia species whose larvae differ from those of Walchiella in having 
all legs 7-segmented, but which otherwise share the following characters : scutum well-chitinised, punctate, 
roughly rectangular but PW often wider than AW ; anterior and lateral margins nearly straight, posterior 
margin characteristically flattened or slightly concave medially and convexly rounded laterally towards 
the PLs; sensillae clavate to lanceolate; bases of body-setae well chitinised; a tendency for scutal and 
dorsal setae to vary considerably in relative length from species to species; without a mastitarsala III. 
Nymph described for only one species {lacunosa): a typical Euschongastia. Not recorded from the New 
World. 
MALAYA, No. 26 , 1953 
