J. L. HARRISON 
182 
Table 3 
A SUMMARY OF ESTIMATED FEEDING TIMES OF THOSE SPECIES FOR WHICH REASONABLY COM- 
PLETE DATA ARE AVAILABLE. 
Species 
Mean 
Maximum 
Trombicula wichmanni 
4 
5 
T. akamushi 
2.8 
6 
T. deliensis 
3.0 
8 
T. sp. nr. bodensis 
7 
10 
T. keukenschrijveri 
4 
8 
Euschongasta oudemansi 
10 
19 
Euschongastia lacunosa 
7 
18 
E. sp. nr. raui ... 
21 
40 
E. mutabilis 
6 
8 
Walchia lewthwaitei ... 
6 
10 
W. turmalis 
6 
10 
Schongastiella sp. nr. bengalensis 
14 
21 
Gahrliepia fletcheri 
5 
9 
Discussion 
Results such as those presented here are necessarily incomplete, since as long as work 
continues information is being added, giving more accurate estimations and increasing the list 
of species. If the results are ever to be used they must be summarised. They could be 
summarised for each species as they reach a predetermined level of accuracy, or they could be 
summarised for all species from time to time. The latter method is being followed here, so 
that this is likely to be the first of a series of such summaries. 
The results for Trombicula akamushi and T. deliensis suggest that the different methods of 
estimation used are reasonably in agreement, but indicates equally that too close an agreement 
is not to be expected. The method of estimating from wild-caught specimens by converting 
proportions to angles is found to give reasonable results when the records are evenly distributed 
from a number of rats, but when an unduly large proportion of the chiggers are recorded from 
only a few of the rats the estimates are liable to serious errors. 
These figures may be compared with the first approximations offered for certain species 
in India by Audy (1947) who however did not give detailed information in his unpublished 
report. Most of the observations were made in the cool dry season of Imphal (after November, 
1945). T. deliensis and T. longiseta (‘species L’) appeared to complete their feeding in 2-5 days. 
The “winter” species of Euschongastia (subgen. Helenicula , Audy, this Study p. 152) E. 
lanius (reported as E. mutabilis) and E. kohlsi, appeared to feed frequently for 5-10 days, and 
two gahrliepiines ( Walchia enode and Schongastiella ligula) for 4 or more weeks, after capture 
of their hosts. Michener (1946) observed in America that larvae of T. ( Eutrombicula :) batatas 
(very close to the T. wichmanni of Malaysia) fed for 2-10 days on chickens, the great majority 
detaching after 3-4 days. Wharton (1946) reported feeding-times of 10-32 days of Euschongastia 
indica in Guam, while Wharton and Fuller (1952) quote various similar accounts; several 
workers have observed that the feeding times of American scrub-itch chiggers vary according 
to the season and the host (warm or cold blooded). 
STUD. INST. MED. RES. 
