518 EXTERNAL ANATOMY OF INSECTS. 



tions of touch, or any other sense. The principal varia- 

 tions, as to form and structure, that occur in this part 

 will be mentioned in another place. I shall only here 

 observe, that in many instances the first joint of this part 

 is longer than the rest ; but in Tctyra pedicellata just 

 mentioned, it is by far the shortest, and shaped like the 

 pedicel of most insects. In the Libellulina, the Homo- 

 pterous Hemiptera, and those flies whose antennae ter- 

 minate in a bristle, the clavolet is represented by the 

 bristle. But in the flies which have a lateral bristle, on 

 the last joint, and those with triarticulate antennas that 

 have no bristle, the terminal joint represents it. The 

 clavolet often terminates in a knob, or in several joints 

 thicker than that which precedes them. This varies 

 greatly, not only in its form, but also in the number of 

 joints of which it is composed. Thus in Paussus, Platy- 

 pus, and many Calandr'ce, it consists of only a single 

 joint a ; in Anthrenus, JDitoma, &c. of two ,• in Nitidula, 

 Geoirupes, &c. of three b ; in Tetratoma, the Silphidte, of 

 four ; of Jive in Scaphidium d ; of six in one species of 

 Languria ; of seven in the common cockchafer [Melo- 

 lontha vulgaris e ); of eight in Diaper is Boleti, in which 

 the whole clavolet forms the club f ; of nine in Oenas ; and 

 ten in Cerapterus s. All the above, you will observe, are 

 beetles. In the other orders there are eleven joints in the 

 knob of some butterflies ; twelve in that of Ascalaphus h 

 and Myrmeleon ; and lastly, fourteen in Tracheitis '. 



• Plates XII. Fig. 28; and XXV. Fig. 13. m". 



b Plate XXV. Fig. % 5, 21. m". 



'• Plate XII. Fig. 10. m". <i Ibid. Fig. 4. m". 



c Plate XXV. Fig. 1. m". f Plate XI. Fig. 23. 



« Plate XXV. Fig. 24. n Ibid. Fig. 30. 



! Jurine Hymcnopt. t. \u.f. 3. 



