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groups of animals, generally limited in extent, which exhibit in their 

 organization, with reference to the groups to which they naturally 

 belong, such anomalies as have constantly proved a source of per- 

 plexity to the systematists who have endeavoured to assign to them 

 their real place in the system of nature. In many instances the ano- 

 maly involves the transition from the structure of one group to that 

 of the adjoining ones; such instances constituting the osculant groups 

 of Mr. W. S. ?.JacLeay in his ' Horae Entomologicae'. Of these os- 

 culant groups some exist between the great divisions of the animal 

 kingdom ; others among the classes of which each of these great 

 divisions is composed ; others again between the -orders, the fami- 

 lies, and the minor subdivisions. The genus Nycteribia is thus os- 

 culant not between the families or even the orders of a class, but 

 between two of the classes themselves of the Annulose Sub-kingdom 

 — the Arachnida and the Haustellata. It is remarkable, moreover, for 

 being exclusively confined to a parasitic existence on that equally 

 anomalous group, the Chiroptera among the Mammalia. 



Notwithstanding the comparatively unattractive appearance of the 

 insects of this genus, the singular peculiarities of their structure have 

 drawn upon them the attention of LatreQle, Hermann, Dr. Leach, 

 M. L^on Dufour, and Mr. Curtis, who have severally contributed 

 much to the general stock of information respecting them. But the 

 minuteness of the objects themselves, their unfitness for accurate ex- 

 amination when dried and shrivelled as specimens usually are in cabi- 

 nets, their comparative rarity, and other causes, have rendered the 

 descriptions of those distinguished entomologists in some instances 

 unsatisfactory ; and it is with the view of fully elucidating the or- 

 ganization of the genus and of adding to its history such facts as he 

 has been enabled to ascertain, that Mr. Westwood offers to the So- 

 ciety his account of Nycteribia, to which he adds a Synopsis of the 

 whole of the species that have hitherto been observed, including the 

 characters of several not hitherto described. He enumerates the 

 sources from whence his materials have been derived ; and then pro- 

 ceeds to describe in great detail the structure of a new species brought 

 from Dukhun by Col. Sykes, — a species peculiarly adapted for the 

 purpose, both on account of its comparatively large size, 24- lines in 

 length, and of the fitness of the individuals for minute examination 

 owing to their having been preserved in spirit. Of this species he has 

 examined three individuals, all of which are females in different stages 

 of gestation. From the abdomen of the one which was most ad- 

 vanced Mr. Westwood extracted without difficulty a hard organized 

 white mass, nearly as large as the abdomen itself, of an oval form, 

 with traces of five articulations on the sides of the body, and having 

 at its broader end three small circular spots placed in a triangle, 

 with two smaller ones seated at a greater distance from them. That 

 this was the young of the Nycteribia in its pupa state cannot, he 

 conceives, be doubted : and it may consequently be regarded as 

 proved that these insects are pupiparous, as has indeed been conjec- 

 tured from their evident connexion with the Hippoboscidee. 



The whole of the external organization of Col. Sykes's Nycteribia 



