78 



AN INTRODUCTION TO ENTOMOLOGY 



many jointed; while in others they are short and not segmented. 



The function of the cerci is different in different insects ; they are 

 beheved to be tactile in some, olfactory in others, 

 and in some males they aid in holding the female 

 during copulation. 



The median caudal filament. — In many of the 

 Ephemerida and in some of the Thysanura, the last 

 abdominal segment bears a long, median filament, 

 which resembles the many-jointed cerci of these 

 insects (Fig. 91); this filament is believed to be a 

 prolongation of the tergum of this segment and not a 

 true appendage like the cerci. 



The prolegs of larvae. — ^The question whether the 

 prolegs of larv^ee represent true appendages or are 

 merely hypodermal outgrowths has been much dis- 

 cussed. Several embryologists have shown that in 

 embryos of Lepidoptera and of saw-flies limb-rudi- 

 ments appear on all or most of the abdominal seg- 

 ments; and that they very soon disappear on those 

 segments which in the larva have no legs while on other segments 

 they are transferred into functional prolegs. If this view is estab- 

 lished we must regard such prolegs as representing primitive abdo- 

 minal appendages, that is as true abdominal legs. 



Fig. 91. — Lepis- 

 ma saccharina. 



V. THE MUSIC AND THE MUSICAL ORGANS 

 OF INSECTS 



Much has been written about music ; but the greater part of this 

 literature refers to music made by man for human ears. Man, how- 

 ever, is only one of many musical animals; and, although he excels 

 all others in musical accomplishments, a study of what is done by our 

 htmibler relatives is not without interest. 



The songs of birds command the attention of all observers. But 

 there is a great orchestra which is performing constantly through the 

 warmer portions of the year, which is almost unnoticed by man.. 

 Occasionally there is a performer that cannot be ignored, as: — • 



"The shy Cicada, whose noon- voice rings 

 So piercing shrill that it almost stings 

 The sense of hearing." (Elizabeth Akers.) 



But the great majority fiddle or drum away unnoticed by human ears. 



