130 LOWER AMAZONS—PARA TO OBYDOS.  Cuap. VI. 
which they enclose assisting to give 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. Other species of the family to which the 
Tanana belongs have similar stridulating organs, but in none are these 
so highly developed as in this insect ; they exist always in the males 
only, the other sex having the edges of the wing-cases quite straight 
and simple. ‘The mode of producing the sounds, and their object, 
have been investigated by several authors with regard to certain 
European species. They are the call-notes of the males. In the 
common field-cricket of Europe the male has been observed to place 
itself, in the evening, at the entrance of its burrow, and stridulate until 
a female approaches, when the louder notes are succeeded by a more 
subdued tone, whilst the successful musician caresses with his antennze 
the mate he has won. Any one, who will take the trouble, may 
observe a similar proceeding in the common house-cricket. The 
nature and object of this insect music are more uniform than the 
structure and situation of the instrument by which it is produced. 
This differs in each of the three allied families above mentioned. In 
the crickets the wing-cases are symmetrical; both have straight edges 
and sharply-scored nervures adapted to produce the stridulation. A 
distinct portion of their edges is not, therefore, set apart for the elabora- 
tion of a sound-producing instrument. In this family the wing-cases 
lie flat on the back of the insect, and overlap each other for a consider- 
able portion of their extent. In the Locustide the same members 
have a sloping position on each side of the body, and do not overlap, 
except to a small extent near their bases; it is out of this smail portion 
that the stridulating organ is contrived. Greater resonance is given in 
most species by a thin transparent plate, covered by a membrane, in 
the centre of the overlapping lobes. In the Grasshoppers (Acridiide) 
the wing-cases meet in a straight suture, and the friction of portions 
of their edges is no longer possible. But Nature exhibits the same 
fertility of resource here as elsewhere ; and, in contriving other methods 
of supplying the males with an instrument for the production of call- 
notes, indicates the great importance which she attaches to this function. 
The music in the males of the Acridiidz is produced by the scraping 
of the long hind thighs against the horny nervures of the outer edges 
of the wing-cases; a drum-shaped organ placed in a cavity near the 
insertion of the thighs being adapted to give resonance to the tones. 
I obtained very few birds at Obydos. ‘There was no scarcity of birds, 
but they were mostly common Cayenne species. In early morning the 
woods near my house were quite animated with their songs—an 
unusual thing in this country. I heard here for the first time the 
pleasing wild notes of the Carashué, a species of thrush, probably the 
Mimus lividus of ornithologists. I found it afterwards to be a common 
bird in the scattered woods of the campo district near Santarem. It is 
a much smaller and plainer-coloured bird than our thrush, and _ its 
song is not so loud, varied, or so long sustained; but the tone is of a 
sweet and plaintive quality, which harmonises well with the wild and 
silent woodlands, where alone it is heard, in the mornings and evenings 
