231 
May 31, 1912 The Queensland Natukalist. 
on the note a natural (five notes above rlie middle c at 
concert pitch), or on b fiat (half a tone higher). 
Having tested with a tuning-fork the songs of a^ number 
of specimens, and found that the full-cry did not in a single 
instance range above or below these notes, but was generally 
pitched exactly on the a natural or b flat, and, moreover, 
noticed that the majority of captured specimens consist 
either of large or decidedly smaller individuals, I am inclined 
to think that the males possibly constitute two classes, 
separated by a comparatively small grotip containing 
medium sized insects. 
The variation of a semitone between the full-cries 
of different males, is, therefore, very likely due to this 
inequality of size, and, assuming the lowest degree of tension 
of the drum-like membranes to be equal in all, the soUnd- 
organs of large forms, being proportionately wider in diameter, 
would naturally emit a deeper note than that produced 
by the same number of vibrations acting upon those of 
smaller specimens. 
The song begins on a lower pitch than that ultimately 
reached by the insect when in full-cry, so it seems reason- 
able to suppose that in addition to its ability to vibrave 
the membranes of the sound organs, it is also able to rlightly 
stretch, or to relax them. 
Taking the larger male, for exam])le, we find that it 
commences to sing on G natural (a tone below its maximum 
height) and repeats this note at intervals which in musical 
notation Avould be represented by a series of quavers occupy- 
ing from four to six bars of common time, and played at 
Allegro. In bars seven and eight (see illustration) these 
quavers are followed by semiquavers and demisemiquavers 
and before the termination of the ninth bar l)y semidemi- 
semiquavers and finally hemisemidemisemiquavers, the 
increase in rapidity being accompanied by a gradual rise 
of one tone, from the beginning of the seventh to the end of 
the ninth bar. The nine opening bars, vfiiich form a kind 
of short prelude to the cry, take about fifteen or tAventv 
seconds to perform, and usually precede the first song of 
the day, or may be heard during the glini])ses of sunshine 
in dull Aveather, when passing clouds have caused the insect 
to remian silent for a longer period than usual; but on hot, 
sunny days, after a veiy short interval of silence, it will 
often omit the prelude and suddenly start again at full 
speed on its to]) note. 
The various sounds and intervals composing the well- 
knov-nsong of this cicada are represented by the combination 
of notes in the following staves , but of course no attempt 
is made to illustrate the vibrations That give rise to them. 
To }>rodUce a natural for instance, the insect has to cause 
its drums to vibrate about 430 times per second, and 
