140 J. R. AUDY 
eyes. It would therefore appear that Ewing’s interpretation of the circles in the original 
drawings is correct. 
The following bat-chiggers are diminutive, similar in size to Euschongastia { Walchiella) 
oudemansi , and of the order of size of T. minor: T. minutissimum (Ouds.) (distinctive larva, 
from Europe, see p. 147); T. batui Philip and Traub (also distinctive); T. n. sp. R32181 Audy 
in MS (bred to the nymph, fig. 2). In addition to the last-named nymph, the writer recovered 
a single small nymph from bat-guano from a cave on Seletan Island. This cave had been 
occupied by tomb-bats, Taphozous melanopogon , from which Trombicula taphozous, T. insolli , 
and T. batui were recovered : the nymph is likely to belong to one of these species, and from 
its fairly small size it might even be batui. In fig. 2 the scuta of these nymphs have been 
drawn in outline for comparison with the reproduction of the scutum of minor , at about the 
same degree of enlargement. 
The writer concludes that the genotype of Trombicula is without eyes in the nymphs and 
adults and that although assumptions as to close larval relationships cannot yet be made by 
comparisons of nymphs, the nearest relations so far found are the above new species (R32181) 
and probably batui. 
Concerning the best way to stabilise this genus, Wharton and Fuller (1952:41) state that 
“ Berlese’s description and Willmann’s redescription of the type indicate that T. minor is 
congeneric with the adults of larvae that will key to the genus Trombicula in the above key.” 
This broad statement is acceptable but it must also be admitted that not enough is yet known 
of nymphs and adults to be confident of generic or subgeneric differences. The statement 
therefore does not exclude the possibility that any of the subgenera of Trombicula sensu lato 
may prove not to be congeneric with minor. These authors continue “ In order to maintain 
stability in the use of Trombicula as a generic name, the subdivisions of this originally large 
genus are here considered as subgenera. The only other alternative would be to consider 
Trombicula as containing only the genotype until additional information is obtained. Such 
a course would be entirely unjustified since, despite the plethora of generic names that have 
been proposed, Trombicula as here understood is no broader in its content than are such 
genera as Neoschongastia and Euschongastia. In handling nomenclatorial problems of this kind 
stability should be maintained if it at all possible to do so and still remain in agreement with 
the known biological facts.” The present writer agrees with the course suggested but would 
urge that a number of the subgenera should be recognised as genera whenever they can be 
clearly and unequivocally distinguished. Fonsecia is a case in point {see p. 148 below), while 
possibly Eutrombicula {see p. 145) may also justifiably be separated from Trombicula. 
Blankaartia { = Tragardhula ) is probably a valid genus but until the confusion of larvae of 
Blankaartia with some of those of Neotrombicula can be satisfactorily cleared it is probably 
best to recognise Blankaartia as a subgenus. 
Wharton and Fuller include in the subgenus Trombicula all the species which cannot 
definitely be grouped in the other subgenera, which they have in each case treated in a restricted 
sense (e.g., Leptotrombidium is practically restricted to the akamushi-growp). The usefulness 
of this course is doubtful to the present writer, who would prefer to expand the concepts of 
the present subgenera and to avoid as much as possible deliberately making a nomenclatorial 
dustbin. Even if this is done, many species must at present remain unallocated and it seems 
best to recognise them as such rather than to force them into existing subgenera. 
Subgenus Leptotrombidium Nagayo et al. 1916, sensu lato. 
Type. — Trombidium akamushi Brumpt 1910:506, Precis de Parasitologie, 2nd. ed., Paris (915 pp.). 
Common and widespread on mammals and birds, especially in triangle Malaya- Japan-New Guinea. 
Provisional Diagnosis (expanded). — Trombiculids whose larvae have roughly rectangular scuta, 
filiform sensillae with branches or barbs; palpal formula typically N/N/BNN(B) but setae on femur and/or 
STUD. INST. MED. RES. 
