March 15 — Struck Lake Mlolo this morning — where Mevana was bitten. A hellish, green-scummed affair, full of crocodiles. Mevana has fixed up a fly-trap of fine wire netting baited with crocodile meat. It has a small entrance, and once the quarry get in, they don’t know enough to get out. As stupid as they are deadly, and ravenous for fresh meat or a bowl of blood. Hope we can get a good supply. I’ve decided that I must experiment with them — finding a way to change their appearance so that Moore won’t recognise them. Possibly I can cross them with some other species, producing a strange hybrid whose infection-carrying capacity will be undiminished. We’ll see. I must wait, but am in no hurry now. When I get ready I’ll have Mevana get me some infected meat to feed my envoys of death — and then for the post-office. Ought to be no trouble getting infection, for this country is a veritable pest-hole.
March 16 — Good luck. Two cages full. Five vigorous specimens with wings glistening like diamonds. Mevana is emptying them into a large can with a tightly meshed top, and I think we caught them in the nick of time. We can get them to M’gonga without trouble. Taking plenty of crocodile meat for their food. Undoubtedly all or most of it is infected.
April 20 — Back at M’gonga and busy in the laboratory. Have sent to Dr. Joost in Pretoria for some tsetse-flies for hybridisation experiments. Such a crossing, if it will work at all, ought to produce something pretty hard to recognise yet at the same time just as deadly as the palpalis. If this doesn’t work, I shall try certain other diptera from the interior, and I have sent to Dr. Vandervelde at Nyangwe for some of the Congo types. I shan’t have to send Mevana for more tainted meat after all; for I find I can keep cultures of the germ Trypanosoma gambiense, taken from the meat we got last month, almost indefinitely in tubes. When the time comes, I’ll taint some fresh meat and feed my winged envoys a good dose — then bon voyage to them!
June 18 — My tsetse-flies from Joost came today. Cages for breeding were all ready long ago, and I am now making selections. Intend to use ultra-violet rays to speed up the life-cycle. Fortunately I have the needed apparatus in my regular equipment. Naturally I tell no one what I’m doing. The ignorance of the few men here makes it easy for me to conceal my aims and pretend to be merely studying existing species for medical reasons.
June 29 — The crossing is fertile! Good deposits of eggs last Wednesday, and now I have some excellent larvae. If the mature insects look as strange as these do, I need do nothing more. Am preparing separate numbered cages for the different specimens.
July 7 — New hybrids are out! Disguise is excellent as to shape, but sheen of wings still suggests palpalis. Thorax has faint suggestions of the stripes of the tsetse. Slight variation in individuals. Am feeding them all on tainted crocodile meat, and after infectivity develops will try them on some of the blacks — apparently, of course, by accident. There are so many mildly venomous flies around here that it can easily be done without exciting suspicion. I shall loose an insect in my tightly screened dining-room when Batta, my house-boy, brings in breakfast — keeping well on guard myself. When it has done its work I’ll capture or swat it — an easy thing because of its stupidity — or asphyxiate it by filling the room with chlorine gas. If it doesn’t work the first time, I’ll try again until it does. Of course, I’ll have the tryparsamide handy in case I get bitten myself — but I shall be careful to avoid biting, for no antidote is really certain.
Aug. 10 — Infectivity mature, and managed to get Batta stung in fine shape. Caught the fly on him, returning it to its cage. Eased up the pain with iodine, and the poor devil is quite grateful for the service. Shall try a variant specimen on Gamba, the factor’s messenger, tomorrow. That will be all the tests I shall dare to make here, but if I need more I shall take some specimens to Ukala and get additional data.
Aug. 11 — Failed to get Gamba, but recaptured the fly alive. Batta still seems as well as usual, and has no pain in the back where he was stung. Shall wait before trying to get Gamba again.
Aug. 14 — Shipment of insects from Vandervelde at last. Fully seven distinct species, some more or less poisonous. Am keeping them well fed in case the tsetse crossing doesn’t work. Some of these fellows look very unlike the palpalis, but the trouble is that they may not make a fertile cross with it.
Aug. 17 — Got Gamba this afternoon, but had to kill the fly on him. It nipped him in the left shoulder. I dressed the bite, and Gamba is as grateful as Batta was. No change in Batta.
Aug. 20 — Gamba unchanged so far — Batta too. Am experimenting with a new form of disguise to supplement the hybridisation — some sort of dye to change the telltale glitter of the palpalis’ wings. A bluish tint would be best — something I could spray on a whole batch of insects. Shall begin by investigating things like Prussian and Turnbull’s blue — iron and cyanogen salts.