204 Insect Music [FIFTH WEEK 



like those in the same group, so the independent tap- 

 pings play a sort of tune, each group alike in time, but 

 the tapping of the whole mass beginning and ending at 

 the same instant. This is doubtless a means of communi- 

 cation." 



The organ of hearing in insects is still to be discovered 

 in many forms, but in katydids it is situated on the mid- 

 dle of the fore-legs; in butterflies on the sides of the 

 thorax, while the tip of the horns or antennae of many 

 insects is considered to be the seat of this function. In 

 all it is little more than a cavity, over which a skin is 

 stretched like a drum-head, which thus reacts to the 

 vibration. This seems to be very often " tuned," as it 

 were, to the sounds made by the particular species in 

 which it is found. A cricket will at times be unaffected 

 by any sound, however loud, while at the slightest 

 "screek" or chirp of its own species, no matter how 

 faint, it will start its own little tune in all excitement. 



The songs of the cicadas are noted all over the world. 

 Darwin heard them while anchored half a mile off the 

 South American coast, and a giant species of that country 

 is said to produce a noise as loud as the whistle of a loco- 

 motive. Only the males sing, the females being dumb, 

 thus giving rise to the well-known Grecian couplet: 



" Happy the cicadas' lives, 

 For they all have voiceless wives." 



Anyone who has entered a wood where thousands of 

 the seventeen-year cicadas were hatching has never for- 

 gotton it. A threshing machine, or a gigantic frog chorus, 



