380 LIFE STORIES OF AUSTRALIAN INSECTS. 



Inside the body, just at the junction of thorax 

 and abdomen, towards the upper surface, the sound- 

 producing apparatus is situated. But the so-called 

 "drums," or flaps or dampers (Plate 48, Fig. 4 a), 

 are on the under side, and tliey protect the sound- 

 chambers below, which are circular. Across each 

 chamber is stretched a beautiful opalescent mem- 

 brane; this seems to correspond with tlie drum 

 parchment of an ordinary drum. But this mem- 

 brane does not produce the sound — it seems rather 

 to be a kind of sounding-board. Also when the 

 membrane is pierced by a pin the sound of the 

 cicada is not silenced. Powerful muscles work 

 certain internal plates, causing them to vibrate, 

 and by means of these the sound is produced. 



The eggs are laid in little slits made by the sharp 

 ovipositor of the mother-cicada, and so numerous 

 are these cuts that the twig is often rough with the 

 little "tags" of bark left by the slit. (Plate 48, 

 Fig. 3.) The eggs hatch in from six to eight weeks. 

 The larva is a queer-looking object with large 

 head and strong front legs. On leaving the 

 egg it drops or crawls down to the ground, into 

 which it cuts its way to a depth of one or two feet, 

 and there it lives, feeding on the roots of plants. 

 A distinct tunnel is made in the soil. 



The period passed in the larval stage varies with 

 the genus, but it may be from three to 17 years. 

 — the latter period was recorded in America. We 

 have noticed, on the coastal districts of New 

 South Wales, tlie appearance of cicadas in great 

 number at three or four year periods; hence it has 



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