Whistling Trees.
Schweinfurth, in his "Heart of Africa," describes what may be termed an insect organ-builder. In the country of the Shillooks, he says, the acacia groves extend over an area of a hundred miles square and stretch along the right bank of the stream. From the attacks of larvæ of insects, which have worked to the inside, their ivory white shoots are often distorted in form and swollen out at their base with globular bladders measuring about an inch in diameter. After the mysterious insect has unaccountably managed to glide out of its circular hole, this thorn-like shoot becomes a sort of musical instrument, upon which the wind, as it plays, produces the regular sound of a flute. On this account the natives of the Soudan have named it the whistling tree.