276 INSECT ARTIZANS AND THEIR WORK 



a loud, plaintive squeak, which has probably added 

 considerably to the awe which its large size and 

 grim ornamentation have inspired in nervous 

 persons. Various theories have been propounded 

 in explanation of this power ; but there can be 

 little doubt that Rossi's statement is the correct 

 one — that it is due to air being forced through the 

 short proboscis from special air-sacs, which may 

 be found by dissection of the moth. Similar 

 sounds are produced by the caterpillar and chrysalis. 

 A South American butterfly, Ageronia feronia, 

 makes a peculiar clicking noise, " similar to that 

 produced by a toothed wheel passing under a spring 

 catch," as Darwin described it in his Voyage of the 

 " Beagle." The Green Silver-lines (Hylophila prasi- 

 nana), of our own country, is also said to produce 

 " a sharp quick noise." Dr. Sharp says that " sound 

 production seems to be of more frequent occurrence 

 in Arctiidas than it is in any other family of Lepi- 

 doptera ; Dionychopus niveus produces a sound by, 

 it is believed, friction of the wings. In the case 

 of the genera Setina and Chelonia the process is 

 said to be peculiar to the male sex : Laboulbene 

 believes it to proceed from drum-like vesicles 

 situate one on each side of the base of the meta- 

 thorax." 



