EXTERNAL ANATOMY OF INSECTS. 517, 
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, Pla- 
typus, and many Calandre, it consists of only a single 
joint ?; in Anthrenus, Ditoma, &c. of two ; in Nitidula, 
Geotrupes, &c. of three”; in Tetratoma and the Silphide, 
of four ©; of five in Scaphidium® ; of six in one species of 
Languria ; of seven in the common cockchafer (Melo- 
lonthe vulgaris*); of eight im Diaperis Bolet?, in which 
the whole clavelet forms the club‘; of-2zxe in Ocenas ; 
and ten in Cerapterus§. All the above, you will observe, 
are beetles. In the other orders there are eleven joints 
in the knob of some butterflies; ¢welve in that of Asca- 
laphus and Myrmeleon ; and lastly, fourteen in Cephusi. 
Under structure also, the number of joints of which 
antennz in general consist, should be considered. If 
you examine the insects belonging to the different or- 
ders, you will find remarkable variations in this respect. 
Let us run through them:—In the Coleoptera the na- 
tural number of joints is eleven; but this rule is not 
without many exceptions. Thus, many have fewer than 
the prescribed number : Paussus has only two", Clavi- 
ger and Platypus five, Dorcatoma and Calandra eight !, 
Geniates and Phaneus nme™, and lastly Melolontha 
i=) 
Pirates XII. Fic. 28; and XXV. Fic. 13. m’”. 
b Prare XXYV. Fre. 2, 5, 21. m”. 
* Prare XII. Fre. 10.m’. 4 [bid. Fic. 4. m’’. 
© Prare XOxVvy Bie. 1m’: f£. Prate XI. Fie. 23: 
® Prare XXV. Fic. 24. R Jpid: Kies 39: 
i Jurine Hymenopt. t. vii. f. 3. k Prate XXV, Fie, 28. 
Ibid. Fic. 15, Ticoskinaeners 
