720 
RHYNCHOTA, 
sound appears to come from all round and is, unless one has much practice, 
extremely difficult to locate. The sound is produced by the vibration 
of a tense membrane situated in the base of the thorax ; there is a muscle 
attached to it which is supposed to produce vibrations, which are 
believed to be magnified by other membranes and by the operculum. A 
conspicuous feature of the process is the vibration of the abdomen 
which produces the trill, as apart from the vibration of the membrane 
producing the usual shrill high note. We confess to being unable to 
follow the descriptions of the mechanism as given by authors and it is 
not quite clear how the volume of sound is produced. The object of 
the sound is a mystery though, as it occurs only in the males ; it 
may be sexual or simply a diversion for the males which have no 
egg-laying to do. 
Cicadas are rare in the plains and but few species occur there ; they 
are characteristic of moist subtropical India ; it is unnecessary, therefore, 
to discuss the classification in detail. Distant’s volume III of Rhyn- 
chota in the Fauna of India enumerates 148 species as Indian, divided 
into three sub-families. The only species apparently really common 
outside hill localities is Platypleura octoguttata, Fabr., found in the hills 
and in the plains. P. mackinnoni , Dist., is found in Behar. 
SONG IN INSECTS. 
A large proportion of the sounds heard in the field are produced by 
insects and, while the motive that induces sound production is not 
always known, it is probably connected with sex, with simple forms of 
signalling and alarm giving, with protection from enemies, and finally 
with the simple expression of the emotions. The majority of the sounds 
heard are connected with sex, but it is by no means clear to what motive to 
attribute the loud continuous song of the Cicada, the most prominent 
of all insect noises. 
Sound is produced in insects almost always by the friction of one 
hard part of the integument against another. When one considers the 
hardness and beautiful jointing of the segments, the complexity and 
position of the limbs and wings, it is easy to realise that no very great 
structural modifications are required to enable one plate to rub against 
another in such a way as to produce rhythmical vibration. In a few 
species, sound is produced in other ways, by modifications of the spiracles 
so that the movement of the contained air may cause vibration, by 
mechanism connected with the wings and their vibration or by special 
