Horse-Flies and Wasps 239 
we reached the dry bed of a river and crossed it several times, 
but could find no water to quench our thirst, whilst the sun 
shone down on us with pitiless heat. About one o’clock we 
came to some pools where the bed of the river was bare rock 
with rounded hollows containing water, warm but clean, as 
the cattle could not walk over the smooth slopes to get at it. 
Here we halted for an hour and had some tiste and maize 
cakes, and cut some Guinea grass that grew amongst the 
rocks for our mules. Over the heated rocks scampered 
brown lizards, chasing each other and revelling in the sun- 
shine. Butterflies on lazy wings came and settled on damp 
spots, and the cicada kept up his shrill continuous monotone, 
but not so loudly as he would later on when it got cooler. 
The cicada is supposed by some to pipe only during mid- 
day, but both in Central America and Brazil I found them 
loudest towards sunset, keeping up their shrill music until it 
was taken up by night-vocal crickets and locusts. 
We were returning parallel to our course in going to 
Segovia, but several leagues to the westward, and this made 
a wonderful difference in the climate. There we were wading 
through muddy swamps and drenched with continual rains. 
Here the plains were parched with heat, vegetation was dried 
up, and there was scarcely any water in the river beds. The 
north-east trade-wind, before it reaches thus far, gives up 
its moisture to the forests of the Atlantic slope, and now 
passed over without even a cloud to relieve the deep blue of 
the sky or temper the rays of the sun. 
The vegetation on the plains was almost entirely composed 
of thorny plants and shrubs; acacias, cacti, and bromeliz 
were the most abundant. Animal life was scarce; there 
were a few flycatchers amongst the birds, and armadilloes 
were the only mammals. Horse-flies (Tabanus) were too 
numerous, and drops of blood trickled down our mules’ faces 
where they had feasted. In some parts large, banded black 
and yellow wasps (Monedula surinamensis, Fabr.) came 
flying round us and had a threatening look as they hovered 
before our faces, but they were old acquaintances of mine in 
Brazil, and I knew that they were only searching about for 
the horse-flies with which they store their nests, just as other 
wasps do with spiders, first benumbing them with their sting. 
I noted here another instance of the instinctive dread that 
