38(5 Mammalian Trypanosomes of AIfrica 
of an hour would go by and only few of the insects take their fill. That they 
were hungry was obvious by their efforts to bite the fingers of the operator; 
directly they were placed on the reptile, however, they showed no further 
interest. Briefly, after much experimenting, the flies were found to feed well 
when housed in mosquito-net instead of wire-sided boxes, and placed on the 
lizard after exposure of the latter to the sun for a short time. The reptile 
proved extremely sensitive to sun heat, soon becoming very distressed, with 
protruded tongue and open mouth, and gasping for breath. The box of flies 
was placed on the reptile’s flank, and the upper netted side covered with a 
wet cloth to shut off the distracting effect of the operator’s hand. Now and 
then a cautious peep under the cloth revealed whether or not the flies were 
feeding, and if none were so engaged the box was lifted away and replaced 
again, if necessary gently stroking the animal’s skin under some conveniently 
situated empty fly to stimulate the insect to start feeding. With proper care 
and patience almost every fly will feed, and, with increasing familiarity, feeding 
becomes more rapid. The flies take as a rule longer to finish their feed on the 
lizard than on a monkey, the first part of the sucking act seeming the most 
difficult. It was noticed that once the flies in a box had fed well on the lizard, 
it was little or no use trying to feed them on the following day, whereas on 
monkeys the flies will feed readily day after day. Possibly the nuclear material 
present in the Varanus corpuscles accounts for this difference. 
Full-grown lizards do not appear to take the slightest notice of the flies, 
even when two boxes of flies are fed simultaneously on either flank; the first 
lizard employed, however, was a young animal, and it became increasingly 
restive until the insertion of a proboscis resulted in a general upheaval which 
eventually made feeding impossible. 
No trypanosomes were ever detected in the lizards employed in these 
experiments, nor were forms resembling T. grayi ever seen in the various 
flies fed upon them; dissection of 159 clean laboratory-bred palpalis fed for 
33 days on the experimental lizards failed to reveal any developmental 
flagellates. 
Reference to the pairs of parallel experiments in Tables V-Y1I will show 
that, although there is, perhaps, some indication that the number of flies 
containing flagellates is less on a diet of Varanus, than of monkey blood, yet 
it is possible, with the buck strain at any rate, for a fly to become infective 
on such a diet. 
For the paired experiments—devised so that the conditions of infective 
feeding were identical and the subsequent diet of the flies, reptile, or monkey 
blood respectively—the figures are: 
Varanus 
Total flies dissected after the 7tli day 
Containing flagellates 
.. 364 
.. 4(1-09%). 
Monkey 
... Total flies dissected after the 6th day 
Containing flagellates . 
328 
10 (3-04 %). 
