26 INSECT A. 



way, nor did the amputation of these parts deprive the 

 insect of the sense of smell. The palpi of one species 

 of Staphylimis were cut off, and it ate. This same 

 insect was afterward set free in the garden, and sixty- 

 four days from the time of its liberation it was very 

 agile, and the palpi had begun to grow again, showing 

 that it had not materially suffered from the loss of 

 these organs. 



In a later article ^ Plateau concludes after many ex- 

 periments upon the air-breathing Articulates that the 

 palpi are not special organs of sense nor even indis- 

 pensable for introducing food into the mouth, but that 

 these appendages in the biting insects, female spiders, 

 and in the Myriopods belong to the category of organs 

 that are useless in the animals now possessing them. 

 In primitive ancestral forms they were doubtless use- 

 ful, but in the existing insects, according to Plateau, 

 they no longer perform important functions. While 

 this ' may be true of adult insects in a general way, it 

 is a sweeping statement, and should be received with 

 caution. In some larvae, like those of the dragon-fly 

 for example, the palpi have become highly specialized 

 and very useful as organs for procuring food, and it is 

 also very difficult to account for the almost universal 

 presence of these mouth parts in insects which take 

 food, if they are wholly useless appendages to the 

 mouth. 



Four pairs of appendages have been found attached 



1 See " Experiences sur le role des palpes chez les Arthro- 

 podes Maxilles. Palpes des Myriopodes et des Araneides," 

 Plateau, Bulletin de la Societe Zoologique de France, t. XL, 

 1886. 



