TAXONOMY OF TROMBICULIDS 
127 
so that it might in fact be found to represent a link with the Gahrliepiinae ; nevertheless, it 
would appear that the proper place for this genus is at present also with the Trombiculinae. 
It would almost certainly be a mistake to raise a subfamily for these mites, at least at this stage, 
because it would be based on the division of the femora, a character of uncertain importance 
which has probably been independently acquired by Pseudoschongastia and the oudemansi- 
group so that there would arise a simultaneous demand for raising a second subfamily, which is 
certainly premature. Recent studies of the oudemansi- and lacunosa- groups have thus greatly 
strengthened the views expressed by Womersley (1952:12). 
4. Modification of setae. — This is discussed under Trombiculindns (p. 141) and Fonsecia 
(p. 148). Foliate expansions of setae are found in Trombiculindus (p. 141), the Eusch. foliata 
group (p. 154), and some Acomatacarus. Peg-like modifications or basal swelling of the setae 
may be noted in Fonsecia (p. 148), the dorsal setae of Eusch. causicola, the coxal 
seta on Trombicula consueta , and in several leeuwenhoekiines ( Nothotrombicula ; Audyana /). 
The setal bases of body setae are generally well-chitinised and conspicuous in species of 
Walchiella and the Eusch. lacunosa group (p. 153), and in the former subgenus they are further 
developed into platelets [in E.(W.) heaslipi , traubi] . Such platelets are also encountered caudally 
in Neoschongastia species ( entomyza , owiensis , retrocincta , yeomansi ), and in a different form in 
Guntherana. Anal plates are present in two species of Schongastiella ( arona , birella) described 
by Traub & Evans, 1953: 95. 
The post-larval stages 
1. Diversity of larval /post-larval stages. — Most species of trombiculids are known from 
the larvae, but the number of known nymphs and adults is rapidly multiplying. There appears 
to be very much less specific and generic variation in the non-parasitic post-larval stages than 
in the parasitic larval stage. For example, the nymphs of Heaslipia gateri, Trombicula hastata, 
and T. consueta are difficult to separate and appear to be closely related, but the larvae are very 
different. Similarly, the nymphs of Gahrliepia ornata and Walchia lewthwaitei are closely 
alike. This may to some extent be because a number of taxonomic characters of importance in 
nymphs and adults still remain to be recognised. On the other hand there is evidence that 
there may sometimes be more obvious differences between nymphs than exists between the 
corresponding larvae, an example from Malaya being the confusion of T. rara with another 
species (to be described) from pill-millipedes until differences in the nymphs led to a re- 
examination of the larvae (corrigendum on p. 427 of Womersley 1952 refers). At least two 
other examples have been found (Womersley in correspondence), but the best published 
examples are those of American species of Blankaartia ( =Megatrombicula Michener) and of 
Trombicula autumnalis in England. Michener (1946), in discussing T. ( Blankaartia ) attenuata , 
alleei, and velascoi , of which “ not every larva can be definitely placed in one species or another,” 
observed that the corresponding adult characters were conspicuously different. Richards 
(1950) described considerable variation (five forms) in larvae which were all considered to be 
T. autumnalis. Nymphs were reared only from one form of larva and they showed no 
particular variations. Womersley (1952:354, 365) considers that Richards was dealing with 
at least two species, T. autumnalis and T. inopinatum; but there were nevertheless 5 main forms. 
However, Jones (1952) has described two easily distinguished forms of nymph bred from a 
single form of larva of autumnalis. 
It is of course well recognised, e.g., in the Diptera Culicidae, that rigid ideas on the 
employment of either larval or adult characteristics are to be deplored. Certainly, species and 
subgenera based entirely on morphological larval characters may be fully acceptable though 
the free extension of this to genera (and even to subfamilies, as has been done) is debatable in 
particular instances. The Culicidae offer a number of examples of specific differentiation in 
MALAYA , No. 26, 1953 
