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Art. XLI. — On the Structure of the Aiitennco in the Order 

 Aphaniptera" of Kirby, with reference to the Propriety 

 of the Establishment of Genera tipon the Variations of 

 those Organs. By J. O. Westwood, Esq., F.L.S. &c. 



On looking at the head of the flea, for the purpose of dis- 

 covering its antennae, two organs are observed placed in the 

 ordinary situation of those members, and composed of four 

 joints, which, from their general appearance, situation, struc- 

 ture, and usage, have been regarded by most naturalists as the 

 true antennae. 



Latreille, however, from the philosophical manner in which he 

 had studied the organization of the whole of the annulose sub- 

 kingdom, had very early acquired a knowledge of the fact, that 

 in different groups the same organ is often employed in a 

 totally different manner, supplying the place, as well as the 

 use, of another organ which is either entirely obsolete, or 

 which has itself undergone an equally extensive modification : 

 hence, by tracing these supposed antennae to their place of 

 insertion, he was induced to consider them rather as palpi. 



Where, then, were the analogues of the true antennae? — 

 Behind the eye, on each side of the back of the head, a small 

 oval-oblong impression is perceived, which incloses a minute 

 organ, which in the living insect is kept in constant motion. 

 Respecting this apparatus, Latreille observes, in his Histoire 

 Naturelle et Generale, &c. : " Est-ce nn organe servant a 

 la respiration ? Seroit-ce line antenne ? Je ne puis pro- 

 noncer." 



Mr. Curtis, in illustrating the genus Pnlex, (Brit. Ent. 114, 

 April, 1826,) stated the Pulex irritans to be the type of the 

 genus, figured the P. TalpcB as an example, and gave an 

 admirable series of dissections of the mouth of P. Canis, with 



" I adopt Mr. Kirby's term, (Duges having proved its appropriateness,) in jirc- 

 ference to Suctoria, used by De Geer and Latreille, that name not being in 

 accordance with the other names of orders; to Aptera, as restricted to the flea by 

 Lamarck and MacLeay, considering it improper to apply to one group a term 

 intended originally to designate many very distinct groups, and which has been 

 employed by various naturalists in so many different ways ; and to Siplimiaptera, 

 proposed by Latreille (as being preferable "a celles trop vagues on trop gSnhales 

 de siiceurs et d'apth-es," and adopted by Curtis and Duges,) Mr. Kirby's name 

 having the priority. 



