178 J. L. HARRISON 
4. Proportion of all T. deliensis from wild-caught rats recovered by the time shown. 
The time scale is logarithmic. 
is not an easy one to fit, and the problem is made much easier if the percentages are transformed 
into angles according to the relation, 
p=sin 2 0, 
when the sigmoidal curve will approximate to a straight line. Values of the angles are 
tabulated by Fisher and Yates (1942) and in practice percentages are converted to angles from 
the table, plotted on logarithmic paper, and a straight line drawn through the points 
by eye. Where this cuts the axis for day one gives the angle and hence the percentage for day 
one. The inverse of this is an estimate of the mean feeding time. Where the line reaches 90°, 
corresponding to 100 per cent., gives an estimate of the maximum feeding time. The data 
from Fig. 4 is shown plotted in this way in Fig. 5. 
Results 
Measurements are accumulating slowly for a large number of species at once. Some of 
the estimates are reasonably good, many are very rough indeed; but even a rough estimate is 
better than none at all, so all available information is presented here. Results are given in 
detail by methods of estimation in the lists below and are summarised in table 3. 
In the list, species of mites are given in the order of the Preliminary Checklist of Malaysian 
Trombiculid mites {Rep. Inst. med. Res. } 1951), but some of the names have been revised to 
STUD. INST. MED. RES. 
