第66章

A strange kind of wood-cricket is found in this neighbourhood, the males of which produce a very loud and not unmusical noise by rubbing together the overlapping edges of their wing-cases.The notes are certainly the loudest and most extraordinary that Iever heard produced by an orthopterous insect.The natives call it the Tanana, in allusion to its music, which is a sharp, resonant stridulation resembling the syllables ta-na-na, ta-na-na, succeeding each other with little intermission.It seems to be rare in the neighbourhood.When the natives capture one, they keep it in a wicker-work cage for the sake of hearing it sing.Afriend of mine kept one six days.It was lively only for two or three, and then its loud note could be heard from one end of the village to the other.When it died he gave me the specimen, the only one I was able to procure.It is a member of the family Locustidae, a group intermediate between the Cricket (Achetidae)and the Grasshoppers (Acridiidae).The total length of the body is two inches and a quarter; when the wings are closed the insect has an inflated vesicular or bladder-like shape, owing to the great convexity of the thin but firm parchmenty wing-cases, and the colour is wholly pale-green.The instrument by which the Tanana produces its music is curiously contrived out of the ordinary nervures of the wing-cases.In each wing-case the inner edge, near its origin, has a horny expansion or lobe; on one wing (b) this lobe has sharp raised margins; on the other (a), the strong nervure which traverses the lobe on the under side is crossed by a number of fine sharp furrows like those of a file.

When the insect rapidly moves its wings, the file of the one lobe is scraped sharply across the horny margin of the other, thus producing the sounds; the parchmenty wing-cases and the hollow drum-like space which they enclose assist in giving resonance to the tones.The projecting portions of both wing-cases are traversed by a similar strong nervure, but this is scored like a file only in one of them, in the other remaining perfectly smooth.