TAXONOMY OF TROMBICULIDS 
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(2) Sensu lato after Wharton and Fuller (1952:40-41): there is nothing controversial in the broad 
diagnosis given by these authors, who unlike Womersley recognise only one family of chiggers. 
Remarks. — Whether or not one accepts the single broad family or the two families 
Trombiculidae and Leeuwenhoekiidae, it is important to recognise that there are some relatively 
poorly studied “ leeuwenhoekiid ” groups of genera which appear to have a confusing number 
of affinities with the Trombidiidae. It may therefore help to add the following notes on the 
family Trombiculidae taken sensu stricto, so that comparisons may be made with the 
Leeuwenhoekiidae of Womersley (p. 163 below) and with the Trombidiidae (p. 166). 
Larvae with a dorsal plate (scutum), very rarely with accessory dorsal plates (caudal 
in Guntherana ; at bases of dorsal setae in a few species). Scutum posterior to gnathosome 
(apparently overlapping it only sometimes with extreme engorgement), without anterior 
median process or nasus (unless one is to include Hannemania on account of the constricted 
adults, see p. 164), usually with 5-6 scutal setae (2, 3 or rarely 4 setae anteriorly) but may 
be up to 20 ( Gateria species); always with one pair of sensillae, filiform (rarely nude, 
usually barbed or plumose) or expanded. Eyes if present usually 2+2, often on a distinct 
ocular plate. Seta on fused palpal coxa posterior to base of palpal femur, usually with 
long barbs or branches. Femora of legs usually divided (7 segmented legs), sometimes 
(and regularly in Gahrliepiines) undivided in legs II and III. All coxae usually i-setose; 
coxa I and/or II multisetose in typical Doloisia , otherwise i-setose; coxa III multisetose 
in several unrelated groups and frequently in the Gahrliepiines. Sternal setae 2 pairs, 
rarely 3. Larvae parasitic on vertebrates, very rarely on arthropods. 
Nymphs and Adults mostly small (1 mm or less); body constricted ( “figure eight ”). 
Scutum with one pair of filamentous sensillae (sometimes spatulate or mid-shaft thickened) 
arising from a subposterior sensillary area, ending anteriorly in a variously shaped, usually 
denticulate tectum (epistome) bearing a single seta (2 in Tr. Camilla ; in Ipotrombicula , 
known only from the adult, there is an accessory seta at the base of the crista). Eyes if 
present single, either close to sensillary area, or lateral to crista and away from scutum; if 
absent may be represented by pigment spots. 
Subfamily Trombiculinae Ewing 
Diagnosis (slightly modified). — Trombiculids whose larvae have a single median scutal seta (‘AM’), 
no anterior projection (nasus) on the scutum, and no stigmata or tracheal trunks; femora of legs II and III 
only occasionally undivided (all legs usually 7-segmented.) Nymphs and Adults without dorsal stump- 
like process to tarsus ; frequently with scutum relatively long compared with breadth. 
Remarks. — The writer prefers to distinguish two broad generic groups in this subfamily, 
related respectively to Trombicula (with unexpanded sensillae) and to Euschongastia (with 
terminally expanded sensillae), the latter group having a greater number of affinities with the 
Gahrliepiinae (=Walchiinae) in the presence of expanded sensillae, the presence of undivided 
femora in at least two different groups ( Walchiella and Pseudoschongastia ), the relative frequency 
of multisetose coxae, and in the shape of the scuta of the nymphs and adults (resembling those 
of the Gahrliepiines in the genera Guntherana and Doloisia sens. lat.). 
A. Trombicula group of genera — filiform sensillae 
Genus Trombicula Berlese 1905, expanded 
Type. — Trombicula minor Berlese, 1905:155, Redia, 6, 346-388. Adults from bat-guano, cave in 
Java (types now destroyed). 
Provisional Diagnosis (tentative broad genus). — Trombiculines whose larvae have 5 scutal setae, 
unexpanded sensillae (mid-shaft occasionally slightly thickened, e.g. in harrisoni- group), only coxa III 
ever with more than one seta and that exceptionally, tarsal claws normal with slender clawlike empodium. 
Nymphs and Adults with generally elongate scutum, sensillary area roughly diamond-shaped, with 
roughly dumb-bell shaped areola; eyes when present either placed close to sensillary bases or lateral to 
crista and away from the scutum. Sternum entire, precoxal plates generally absent, but in subgenus 
Leptotrombidium precoxal plate of leg I present and fused to form a longitudinally subdivided sternum. 
MALAYA , No. 26, 1953 
