210 JAS. J. SIMPSON—ENTOMOLOGICAL 
to minimize this, some attempt should be made to clear an area so that embarkation 
might be made possible without, as at present, an accompanying swarm of 
tsetse. 
The Government steamer, the “ Mansahkillah,” has two decks, the lower for 
native passengers and crew, and the upper for Europeans. With the exception of 
one cabin and saloon on the upper deck, all the sleeping accommodation is below. 
During this tour in the Bintang Creek, Glossina palpalis swarmed in all parts of 
the vessel, not being restricted to the lower deck to so great an extent as one 
sees on the stern-wheelers which ply on the Niger. Never before have I seen 
G. palpalis in such numbers, and even on the upper deck saloon they were so 
troublesome that we had to have recourse to mosquito boots to protect our ankles, 
Though not to the same extent, this state of affairs obtains in many parts of the 
river, and the fact that a former master of this vessel died from sleeping-sickness, 
contracted on the Gambia, must not be overlooked. For this reason I should 
strongly recommend that every cabin and saloon be made mosquito-proof with 
wire gauze. As a marked contrast, from this point of view, I add a photo- 
graph (p. 226) of another Government steam-launch, the “ Rose,” which was 
fitted up for surveying purposes by Lieut. Spicer Simson, R.N., and which has 
been made mosquito-proof in the after part—a most admirable arrangement. 
A predatory spider, Plezippus payhulli, Aud., of the family ArTIDAE, 
inhabits the “ Mansahkillah” in large numbers. These do not spin a web but 
conceal themselves in dark corners, cracks, or crevices of the vessel, and dart 
suddenly on their prey. Although Glossina palpalis was most abundant, still, 
there were other non-biting diptera present in the saloon, but it was observed 
that these spiders ignored the other forms and devoted their whole attention to 
G. palpalis, stalked them, and eventually captured not a few. The attack was 
usually made from the rear, but was occasionally frontal, the spider always 
attempting to pin down the wings. When this attempt failed, the tsetse, by a 
rapid movement of the wings, generally managed to escape, but when once the 
spider got a fair hold, it hung on tenaciously sometimes for over an hour, at the 
end of which time the tsetse, though not actually dead, was in a state of 
collapse, at least in the case of those under observation. 
A very marked case of the effect of colour of clothing, in attracting or 
repelling Glossina, occurred during this trip. My companion, who in the earlier 
part of the day was wearing a white coat, and who was continually attacked by 
Glossina only in the legs and ankles, had occasion to change into a black coat. 
Soon after, he complained of being bitten on the back and arms, and at first 
thought that this was due to an increasing number of Glossina. After again 
changing his coat, he noticed that the bites on his back and arms decreased 
accordingly, and, to test the effect of this change of colour, he wore first one 
and then the other. In the same space of time, namely 10 minutes, I observed 
that whereas fifteen Glossina palpalis settled on the black coat, only two alighted 
on the white. The reason why one’s legs and ankles are the chief points of attack 
is that the flies alight and settle unobserved for a time under the seat of the chair 
or under the table, and then dart quickly out to the nearest unprotected part. 
It is pow known that Glossina can, and does, bite through moderately thick 
