EXTERNAL ANATOMY OF INSECTS. 519 



Under structure also, the number of joints of which 

 antennae 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 a , Clavi- 

 ger and Platypus five, Dorcatoma and Calandra eight b , 

 Geniates K. and Phanccus MacLeay nine c , and lastly 

 Melolontha ten d . Others, again, have more than eleven 

 joints : Cebrio Gigas, Chrysomela stolida, some Saperdcc, 

 and several others, have twelve. In Prionus imbricornis 

 the female has nineteen, and the male twenty e . Rhipi- 

 cera marginata has thirty-two ; and in a New Holland 

 species of this genus I counted thirty-eight. In the Or- 

 ihoptera I can trace no general law in this respect. In 

 Locusta Leach in some species you may count fourteen 

 joints, in others sixteen, and in others twenty-five. In 

 one, which appears to be a pupa, I found only thirteen. 

 In Mantis they exceed thirty ; but in Blatta, from between 

 thirty and forty, they reach nearly one hundred and fifty ; 

 often varying in number in different individuals of the 

 same species. The order Hemiptera exhibits two pecu- 

 liar types of antennae, which, with some exceptions, di- 

 stinguish the two natural sections into which M. Latreille 

 has judiciously divided it. In the Heteropterous section 

 they are without a bristle at their end ; and in the Homo- 

 pterous one, with the exception of Aphis, Thrips, &c. 



* Plate XXV. Fig. 28. " Ibid. Fig. 13. 



' Ibid. Fig. 5. '' Ibid. Fig. 1. 



e Plate XI. Fig. V2. * Linn. Trans, xii. t. xxi f. 3, 



